How Wide is Right for Me?

open_corner

Our ideas of what is a performance bike have changed a lot in recent years! One of the most exciting bikes of the moment is the Open U.P. – a carbon race bike that accepts 50 mm-wide tires!

Not too long ago, every performance road bike had 700C x 23 mm tires. Now you have to choose not just how wide you want your tires to be, but – thanks to disc brakes – even which wheel size you want to use! For the Bicycle Quarterly test, we rode the Open with 650B x 48 mm tires, but our second tester, Nate King, raced his Open with 700C x 44 mm tires. Which is better? Or should you get several wheelsets for different courses? Is there a reason to switch tires and wheels on the same bike?

tire_test

Let’s first talk about some fundamentals: Wider tires don’t roll slower than narrow ones. Bicycle Quarterly‘s latest tire tests, published in the Winter 2016 issue (BQ 58), have shown this once again: In a real-road scenario, even 54 mm tires don’t roll slower than 32 mm – or any size in between. Before this, we already tested tires between 20 and 32 mm tires and found that the 20 mm and 23 mm were slowest, and all the others offered the same performance.

By the way, we tested at 22 mph, so this factors in the greater air resistance of the wider tires. It appears that wider tires have slightly lower rolling resistance, which cancels out the small increase in wind resistance. This means that at lower speeds, wider tires probably are faster than narrower ones. We tested on very smooth asphalt. On rougher roads, wider tires also are faster.

Yes, I know it’s not what we used to believe – we were quite surprised when we saw the results of our testing, but we’ve confirmed this time and again. And so have others in recent years.

To summarize all this research: Narrow tires (<25 mm) are slow. Above 25 mm, the width of your tires are won’t change your speed (at least up to 54 mm wide tires).

That doesn’t mean you can just slap any wide tires on your bike and expect it to go fast. What will change your speed is how supple your tires are: Tires with high-performance casings are faster, more comfortable and offer better traction, regardless of their width. If you choose heavy, reinforced ‘touring’ models when you switch to wider tires, you’ll likely to be disappointed – they’ll roll slower than racing tires because of their sturdy casings, not because of the extra width.

So we know that supple casings are key, and that width doesn’t matter. What size tires should we run then? Is wider always better? And what about wheel size?

open_paved_corner

Wider tires offer more cornering grip. This is true for racing cars and motorbikes as well as bicycles. On bicycles, there are two reasons for this: More rubber on the road gives you more traction. And wider tires are inflated to lower pressures, which means that they stay in contact with the road. If your tires don’t bounce over small irregularities in the pavement, they have even more traction than their width alone would suggest.

If you like to corner fast, you want the widest tires possible. Even on smooth pavement, the difference between 38 mm and 48 mm-wide tires is noticeable, and on rough surfaces or even gravel, it’s no contest.

WheelTest

Wheel size is another important consideration. The photo above shows three Bicycle Quarterly test bikes with identical geometries (head angle, trail, BB height, etc.), but different wheel sizes. What we found in that test: Wheel size greatly influence the handling of your bike. Larger wheels make the bike more stable, and so do heavier wheels – it’s the rotational inertia that matters, not the outer diameter.

Since wider tires are (slightly) heavier, you’ll want to decrease the wheel size to keep the rotational inertia – and thus the handling – the same. That means that your wheel size should be chosen based on your tire width and tire weight. That way, you can enjoy the nimble handling of a great racing bike even with wide tires.

Let’s a look at a few tire sizes that I enjoy riding, with their pluses and minuses:

ritchey_swissx

38 mm wide

  • To me, tires narrower than 38 mm don’t really make sense any longer. 38 mm tires still give you the “connected to the pavement” sensation that makes a racing bike feel so fast. Below 38 mm, all you gain is harshness. The bike doesn’t feel any better, just more jiggly.
  • 38 mm tires are great for pavement and occasional gravel riding.
  • To go with 38 mm tires, you have a choice of wheel sizes:
  • If you like the nimble handling of a racing bike, then choose 650B wheels for 38 mm tires.
  • If you prefer a bike that locks onto a cornering radius and won’t be deflected even if tense up in mid-corner, then use 700C wheels for 38 mm-wide tires.

hahn_shiretoko

42 – 44 mm wide

  • Adding 4 mm to the width of your tires gives you some added plushness – compared to 38 mm, you’ve increased the air volume by 22%.
  • In exchange for that added cush, you lose a little bit of connection to the road. To me, that isn’t a big loss, and I enjoy the greater traction and go-almost-anywhere capabilities of the wider tires.
  • For tires this wide, 650B is the optimal wheel size.
  • 42-44 mm tires are fine for most gravel riding. They have the advantage that good rim brakes (like our Compass centerpulls) fit over them – even with fenders. In fact, fender mounting becomes a compromise with tires wider than 44 mm (see below).

gravel_hairpin

48 – 54 mm wide

  • Now we are getting into some seriously wide tires for a road bike! A 54 mm tire holds twice as much air as a 38 mm tire.
  • Tires this wide change their feel depending on the pressure you run:
    • With the tires inflated to 38 psi (2.6 bar), our Open U.P. test bike felt like a road bike. The tires made more noise as they rolled over the pavement, but otherwise, the feel wasn’t all that different from narrower tires.
    • Letting out some air and reducing the pressure to 26 psi (1.8 bar) changed the bike completely. Now it was super-plush. The tires still had enough air so they wouldn’t collapse under hard cornering, but I could feel the ‘suspension’ when riding out of the saddle. At this pressure, the tires were ideal for rough gravel.
  • For tires this wide, I definitely recommend 650B wheels. With 700C rims, your bike will just plow straight ahead like a 29er mountain bike, and you’ll need suspension to absorb the bumps that you cannot steer around. On my Firefly (above), I went with 26″ wheels for a more agile handling. As a result, the bike feels remarkably similar to a good racing bike.
  • Fender mounting is an issue with tires this wide and road cranks: Ideally, a fender should be about 20 mm wider than the tire, but the chain will hit a fender that is wider than 62 mm when riding in the smallest gear! The solution is using a 62 mm fender that doesn’t wrap around the wheel very much and mount it a bit higher above the tire. It works, and we now offer a 650B fender specifically for 47-48 mm wide tires.

otaki_07

How about tires wider than 54 mm? That might be interesting, but you can’t really fit them between road cranks with narrow Q factor. 54 mm tires already are quite wide: They have the same air volume as 2.3″ mountain bike tires – it’s just that they don’t have knobs on the shoulders, so they measure out a bit narrower. Below is a comparison of the air volume of my three favorite tire sizes (to scale).

38-54-mm-tires

To summarize, if you want your bike to feel connected to the pavement like a good road bike, I recommend 650B x 38 mm tires. Compared to narrower tires, you get added comfort and speed on rough pavement, and more cornering traction, too.

I prefer a little extra rough-road performance and even better cornering traction, so for paved rides, my choice is 650B x 42 mm. You lose a little of the connection to the road, but during hard cornering, you actually get more, not less, feedback of how much traction you have in reserve, because the tires can really key into the pavement.

If my ride includes a lot of gravel, I’ll pick 650B x 48 mm or even 26″ x 54 mm. On pavement, the downside is that you get some tire roar – how much depends on the diameter of your bike’s frame tubes that provide the resonance chamber for the noise – and the tires’ feel is more sensitive to tire pressure. On the plus side, the traction in paved corners will blow your mind.

If you are using lightweight carbon rims and superlight tires, like our Compass Extralights, then it makes sense to go up one wheel size to compensate for the lighter weight. So for 38 – 43 mm tires, I’d recommend 700C wheels, and 44+ mm tires, I’d use 650B. Otherwise, your bike gets that ‘small-wheeled’ feel: The bike doesn’t hold its line on its own, but requires active input from the rider to go straight. It’s not a big deal, but we are talking about optimizing your bike here.

It seems that more and more riders are converging on these tire sizes: BQ‘s second tester for the Open U.P. recently received the latest model from his sponsors (above), and he spec’d it with 650B x 48 mm tires – like our test bike. And he tells us that he loves it!

With these suggestions as a starting point, I recommend test-riding a few bikes with different wheels and choosing the ones you like best.

Resources:

Photo credits: Toru Kanazaki (Photo 8), Natsuko Hirose (Photos 1, 3), Nate King (10).

About Jan Heine, Editor, Bicycle Quarterly

Spirited rides that zig-zag across mountain ranges. Bicycle Quarterly magazine and its sister company, Compass Cycles, that turns our research into the high-performance components we need for our adventures.
This entry was posted in Tires. Bookmark the permalink.

78 Responses to How Wide is Right for Me?

  1. Tom says:

    I’ve heard the “inertia” argument some times when it comes to 28 or 29″ wheels.
    But most people just don’t get the point that trail is affected by wheel diameter. So there is in fact a wheel diameter a frameset is (or should be) designed for.
    Running a bike with larger or smaller wheels will just mess up the handling.

    • The changes in trail are very small. I remember when I rode a 1952 René Herse designed for 38 mm tires with 32s – the only high-performance 650B tires at the time! – the bike no longer held its line in corners. Like you, I suspected that it was the reduction in geometric trail that caused this, but when I calculated this, I realized it wasn’t enough to affect the bike’s handling. That led to more experiments, and we discovered the importance of ‘pneumatic trail’ – wide tires make the bike inherently more stable.

  2. Peter says:

    Did you evaluate whether the weight of the rider has any effect on choosing tyre width? I can image a 60kg person being ok with 38mm @ 2.5 bar whereas a a 80kg would need 3+ bar, or a 42mm tyre for 2.5 bar>

    • MC says:

      I ride 32mm clements on my cross/commuter at approx 40psi give or take and weigh 78kg, and my tubeless cross tyres get run mid to low 30’s.

  3. Andrew Cohen says:

    I purchased an Open UP and am running 650×48 Compass Extralights and it is great on pavement and off. Like you I like higher pressures on pavement (32ish front and 35ish rear) and reduce pressure on gravel. I have been curious to try 26” wheels on the bike with your rat trap pass tires, but don’t have any such wheels around to try. Could you comment on this setup since you are familiar with the UP?

    • If you run carbon rims, the 650B x 48 Switchback Hills are the perfect tire for the Open U.P. I rode our test bike with them, and I really loved the way it handled. It’s only with heavier aluminum rims that you’d want a smaller wheel.

  4. MarkMin says:

    Like 32 mm Stampede Pass XL. Loved 35 mm Bon Jon XL (can’t fit them on my present bike). Would like to have had an affair with 38 mm Barlow Pass. But I’m looking forward to having a long relationship with the pair of 54 mm Rat Trap Pass(es?) I’ve got for the tandem I’m rebuilding. Which brings me to my question: what pressure should I run them at (155 kg/341 lbs bike & crew)? I’m assuming 35–40 psi, but I’d value any advice you have–and from any tandem riders out there.

    • I think that 35-40 psi sounds like a good starting point. Experiment from there to see what feels right.

    • Derek says:

      I had Rat Trap Pass tires on a tandem for 2k ish miles. Slightly heavier than you (360 total lbs) but 35psi was definitely too low for us. Cornering on pavement felt like we had a flat. They are still comfortable at higher pressures and handling is better.

      • Derek says:

        Adding to my earlier comment about RTP’s on a tandem, I measured tire drop at 45 psi and it was half an inch, which is almost 25%. Even the max, 55 psi, is fairly low for a tandem, unless you’re trying to ride through mud, sand, or snow, all of which I’ve done with 40-45 psi. On the road I run 45-50.

  5. John Collier says:

    I’m not an expert in these matters so I’d appreciate a little more detail on how changing wheel diameter affects handling. I have noted that wider tires (larger wheel diameter) on some bikes negatively affects the handling. I also happily ride a Moulton AM7 at very high speeds on curvy roads. I’m not advocating for narrower or smaller wheels. Just curious as to what is going on.

  6. jamey mcpherson says:

    2 thoughts to consider, the first is the suspension characteristics of a tire’s total volume. A 700×38 versus 650bX38, the 700 has a larger reservoir or “cartridge volume” and will have different suspension characteristics akin to longer travel for larger diameters.
    second consideration is that generally static friction (like most rolling) is independent of contact patch, but dynamic/sliding friction is not. I would suggest that the wider tire allows us time to correct our line out to a static friction state once we discover where the sliding state begins. This is testable with overhead cameras too. Basically, wider tires ease and slow the transition between static and dynamic friction during turns.

  7. Edwin says:

    Great article. I have learned a lot about tires from you.
    How do you see the frame size affecting these equations? I have been enjoying my 44-622 compass tires on my fairly large frame (I am 6’1″), but I am sure my son on his 48cm frame would appreciate smaller tires. At least smaller in radius, if not width.
    Does the difference between 26″ wheels and 700c wheels mean different things on our two frames. They actually both have 700c wheels, but I wouldn’t buy him a new bike with wheels that large on a frame so small.

    Thanks again.

  8. John Keiffer says:

    Lot’s of great info. I’m going to be getting a bike soon and running 650B x 48cm Compass tires. But this kind of article always seems incomplete without some talk about rims and internal widths. Otherwise the optimization aspect is not quite complete IMO.

    • John Keiffer says:

      Oh and I forget, is there a weight limit on the Extralight tires?

    • Rim width doesn’t make a big difference with supple tires. The sidewalls are too supple to hold up the bike, so you just run a slightly higher pressure – and yet the tires still are more comfortable and faster than stiffer tires at lower pressures.

      An extreme example of supple tires are tubulars. In that case, the tire is completely round, and how far the rim extends to each side doesn’t affect the handling at all. Mountain bike pros used to run 20 mm-wide 650C rims (intended for triathlon bikes with ultra-narrow tires), since those were the only rims that approached 26″ in diameter. They used custom-made 58 mm-wide tubular tires, with no apparent problems.

      From personal experience, I run 42 mm tires on 20 mm rims (outer width) and 54 mm tires on 25 mm rims, and the handling is the same as with wider rims. What does change is the tire width – tires are wider when mounted on wider rims.

  9. Dr J says:

    “How about tires wider than 54 mm? That might be interesting, but you can’t really fit them between road cranks with narrow Q factor.”

    You can. You just need to define what “road cranks” really means. My bike rolls on 650b x 56mm tires (with space for a bit more) and has “road cranks” with 145mm q-factor and 68mm BB shell. Of course, it’s limited to 44T largest chainring but that’s enough on “road” for me.

    • Absolutely, if you reduce the max. chainring size, you gain a millimeter or two. None of these ‘limits’ are set in stone. You can ovalize the chainstays or even replace them with flat steel bars, but I’m not sure what especially the latter does for the frame’s performance. In our experience, with round chainstays and adequate clearances all around, 54 mm is about the maximum.

  10. Mike Leary says:

    I’ve been using Compass tires since first reading your tire tests showing optimal performance with a 15% “tire drop,” about 8 years now. I’m not a competitive rider, but appreciate the ride, handling, and speed advantages of supple-sidewalled tires. Unfortunately as I’ve aged (I’m now 60) arm, back, and seat aches/pains have emerged that make riding my beloved Rawland Stag increasingly difficult. As a result, I recently purchased a recumbent and have been learning this new platform, as week as modifying it to my tastes. And there’s the rub. Compass does make 26″ tires that I want to try, but I can’t find anything other than Schwalbes for the 20″ front, and the better versions of those are quite narrow.

    So, any chance that Compass will come up with a 20″ supple sidewall tire? Failing that (which I expect will be the case), what about mixing a supple rear tire with a stiff front tire – any thoughts or guidance?

    Thanks,
    Mike

    • wrangle says:

      I’d suggest looking into 20″ BMX tires. While the majority of current ones are made for high pressures (110 psi), there are a few out there that have lower max pressures and are likely to be more supple. You’ll just have to hunt around a bit. Good news is a lot of them have great street tread designs and they’re cheap, so you could try out a few to see how you liked them.

    • wrangle says:

      I’d suggest looking into some wide 20″ BMX tires. The majority of current ones are made for high pressures (110 psi), but if you hunt around a bit, you can find some with lower max pressures and decent street tread designs. Not as good as having a Compass 20″, I’m sure, but it might be a good stopgap solution.

    • John C. Wilson says:

      Panaracer HP406. First quality Made in Japan tire. Longtime BMX staple, widely available.

    • Rien says:

      20″ Schwalbe Big Apple are wide an relatively supple

  11. Fred Lee says:

    I’ve been in the market for a bike like this. A few years ago, most bikes that met the criteria of taking a fattish tire while still being road-worthy had compromises of one sort or another. Specialized, for example, locked you into their proprietary hub design.

    It would be awesome if BQ would do a survey of Adventure Bikes with the inevitable pros and cons of each, across pricepoints. While looking at (more affordable) alternatives to the Open UP I came across the Mason Bokeh, which can be had fully built for ~$4K US and the Kinesis Tripster and G2 which are even more affordable.

    The Open UP looks like it ticks all the boxes but is probably out of reach for most of us. And in my perusal of my LBS I see precious little selection of wide tire capable bikes, even here in bike-crazy Portland. For whatever reason most of what I see is from the UK.

  12. Timothy Nielsen says:

    Lots to digest in this post! I’ve had the chance to put some miles on a set of your new Antelope Hill tires (700x55mm). I went with standard casing for the rear and ultralight on the front. On pavement I feel they provide a kind of “hovercraft” feeling as they float over cracked sections. I’ve had some issue seating the bead evenly, as at some particular combination of speed and pressure I feel a slight spontaneous bouncing…like when you are crossing an old bridge in a heavy truck. Notwithstanding this slight issue they provide confidence on rooted trails and gravel. On longer rides by the coast the strong crosswinds there affect me more than with the same bike and rims with narrower tires. Being a larger rider (112kg) I have found the need to keep the tires inflated at a higher pressure than most others might, to avoid sidewall collapse on aggressive cornering. Overall they are a true pleasure, many joyous, if vague, miles ahead for me!

    • I suspect the bouncing isn’t because the tire isn’t seated correctly, but because you are getting a resonance between your pedal strokes and the tire. Changing the air pressure will move that resonance to a different speed range. I’d increase the tire pressure a little and see whether the bouncing disappears.

  13. Sukho in PDX says:

    Jan this is great; thanks for synthesizing all your findings into one post. I’m sure folks will be referencing this for years to come. Thanks for all the work you’re doing; you’re really making your mark in a lot of great ways.

  14. I wanted to wear my Strada Bianca’s tires threads before installing the EL Barlow pass tires that i’ve been keeping in my bike parts stash for a long time, but after reading this I’m going to install them right away. 32mm tires certainly feel too narrow when you are accustomed to 54mm rubber.

  15. Colin Pinney says:

    Nice write-up Jan. Since you have calculated the volume of the different tire sizes, have you compared the volume and preferred pressure of the different tires to see if the amount of air molecules in the tires is the same or different as the casing width changes?

  16. zigak says:

    regarding “tire roar”, I recently bought a new bike specifically to be able to run wider tires. The old bike had 28mm conti gp 4000, and a new one has compass 32mm extralights (to ease in to the wider tires). The quietness of the old bike is remarkable! I thought the reason for the noise was the chevron thread. It would be interesting to compare it to the same tire with the slick thread.
    The old bike with 23mm or 28 mm contis was equally quiet, so I tend to think the width has nothing to do with noise.

    • Did you run the new bike with the old tires? What determines tire noise more than anything is the resonance of the frame. For example, my Firefly with its large-diameter titanium tubes is much louder than my Rene Herse with its small-diameter steel tubes, even when both run the same 650B x 42 mm tires. Carbon bikes tend to be louder still.

      Tire width also influences the noise the tires make, with wider tires being louder, but the effect is much smaller than that of different frame tubes.

      The chevron tread pattern can ‘sing’ on some road surfaces. I’ve only heard this once or twice in tens of thousands of miles. It’s not very loud and kind of charming, and it seems to occur only with tires inflated to high-pressures. (I used to get it more often when racing on narrow tubulars with a similar tread pattern.)

  17. Rick Thompson says:

    Should you make any adjustments for the size of the bike and rider? At 6′ 4″ and 200 lb, I’m very happy with 44 mm Snoqualmie Pass on 700c aluminum rims for road and gravel. Surely the optimum wheel and tire will scale to some extent with the rider.

    • The size of the wheel determines the handling. Unless you believe that taller riders want their bikes to handle differently from shorter ones, there is no reason to change the wheel size with rider height.

      What is different for different riders is personal preference. We assumed that you enjoy the nimble handling of a good racing bike, but without the skittishness of narrow tires. If you prefer a bike that ‘locks onto’ a selected line, then taller wheels may be a good idea. Most of all, if you enjoy your bike, then there is no reason to change!

      • Gert says:

        This is very difficult for me to understand. My intuition is that heigth of center of gravity, wheelbase, trail, and weight of rider also have an influence and that the influence the inertia of the wheels have would be relative to the other forces involved. And the difference between a 700-44 and a 650-44 will be less noticeable on a bike for 6-4 rider than for a 5-8 rider. At least a theoretical 12 foot rider would probably notice other handling issues other than the difference between 650B and 700C

      • I am sure there are other forces involved, but that doesn’t mean you should simply scale up the wheels with the rider. For example, a higher center of gravity makes the bike less reactive: getting it to turn requires more input, but balancing does, too. A larger wheel with more inertia won’t help with either of those.

        As to wheelbase, the way bikes are currently designed – with the chainstays being of almost constant length – wheelbase changes very little with rider size, but center of gravity moves rearward as the rider get taller.

        BQ Team rider Ryan is 193 cm (6’4″) tall, and he handles his 650B bike with much more confidence than his 700C one. Based on that experience, I’d recommend 650B over 700C for 40-44 mm-wide tires even for relatively tall riders.

  18. Scott Bontz says:

    Jan, none of what’s put here to consider in choosing tire and rim size addresses rider weight. Does that matter? Can a 130-pounder like me ride a proportionally narrower tire than a 180-pounder, to the same effect? Asked another way: Is what really matters not the tire size, but tire pressure? Because a 32mm tire and 42mm tire at the same pressure will have the same contact patch size. Will they have about the same cush? I know the contact patch shape will be different, but I don’t know it that would matter much. FYI, I ride Bon Jon Extralights, tubeless, usually at 32-35 in back, 24-28 in front, with a saddlebag. On lots of gravel.

    Also: If your tire is so supple that it needs higher pressure, what have you gained? If you could make tire casing tough enough, would you really want to take it to paper thin? In other words, might you want sidewall thickened up to a best compromise of suppleness and support? My Bon Jon sidewalls are cross-hatched. You told me before that this is OK, though it apparently indicates slight damage from lower than optimum pressure.

    Lastly, as I recall the early tests in your magazine were won by narrow racing tires, though wide tires were close to the top, and some narrow tires were indeed slower. For years you’ve said wide tires aren’t slower. Now you’ve claimed “narrow tires are slow.” I wonder if, from the necessarily limited number of tires tested, you should not make such a generalization.

    • Lots of good questions! You are right that weight goes into the equation. Most of us here weigh between 155 and 185 lb (70 to 85 kg), so if you are significantly lighter or heavier, you may go up or down a tire size.

      As to supple tires needing higher pressures, that doesn’t negate the advantages in comfort and speed that come with supple casings. Otherwise, we’d all ride airless tires, which run at the lowest possible pressure! A supple tire at 30 psi is much faster and more comfortable than a stiff tire at 15 psi.

      As to ‘narrow tires are slow’ that always has been true – in our very first tests, 25 mm tires rolled faster than 23s, and 20s were even slower. I clarified that I am talking about “<25 mm" tires when I say "narrow."

      • Scott Bontz says:

        But if I remember right, in the first tests the 25s — Vittoria? — were faster than anything larger. There was not a consistent increase in speed with tire width. The the fastest tires might’ve been so because they had the best casing. Apologies if I remember incorrectly. Thanks for your work.

      • The general take-home was indeed that casing quality is more important than any other factor. In our first tests, the fastest was a hand-made 24 mm tire, but the same tire in a 35 mm width later proved at least as fast. It’s only when you compare otherwise identical tires that width makes a difference between 20, 23 and 25 mm tires, with 25 mm being fastest.

  19. ken1putt says:

    This is fabulous information.
    I’ve been watching LeTour lately and on the stage into Roubaix with 15 (?) sections of cobbles, there were lots of crashes and even more flats among the GC contenders and their teams.
    Am I wrong in assuming that if you could somehow get an adventurous rider/team to switch to a ultralight gravel bike and run 650B LoupLou[ Pass or Bay Shoe Pass tires, they’d be able to corner MUCH faster, and almost eliminate flats.
    A couple of years ago Global Cycling Network took a road bike, a cross bike and a mountain bike to France and ran them on the cobbles of Paris-Roubaix. Despite “feeling” slower the mountain bike yielded the fastest times on their course.

    • There are lots of factors to consider, but our current thinking indicates that a road bike with ultra-wide tires, like my Firefly, would gain far more on the cobbles than it would give up on the paved sections. Our testing at 22 mph didn’t show any disadvantages for wide tires even on smooth pavement, but the pros are much faster, so there may be a slight aero penalty on smooth pavement. However, the gains on the cobbles are easy to quantify, and they are huge.

      Global Cycling Network’s ‘test’ was interesting: Despite putting out less power and running stiffer tires, the mountain bike was fastest simply by the virtue of the wide tires. Now imagine if you used a frame that allowed the rider to put out the same power as on the racing bike, and have supple tires…

      • ken1putt says:

        Thank you. I have a followup question. I know people who us “thornproof” inner tubes. Which are thicker than your tires.

        One of them switched to regular tubes and could immediately feel it on the bike. She thought it was the weight, but I am beginning to think that the stiffness might have been an even bigger factor.

        Does that make sense?

      • Yes, I suspect the stiffness of the tubes would be much more important than their weight. With every revolution of the wheel, you need to flex the tube along its entire length as the tire deforms at the contact patch with the road…

  20. Tom G. says:

    I think there is merit to the trend to wider tires but there will inevitably be a weight penalty to pay and/or the wider tire needs to be thinner and therefore more fragile otherwise.

    An apples to oranges comparison admittedly: I am running smooth tread Panaracer Parimoto Pacenti 38mm tires on my 27.5 gravel bike right now, and had the Babyshoe Pass tires on there for most of the winter and spring, The ride is nice and plush but the tubeless setup was a HUGE hassle (maybe just an unfortunate rim -tire combo?), but, truthfully, riding my older Lightspeed road bike with 25mm Continental Gatorskins gives me a sufficient ride over the same marginal roads and I worry a lot less about punctures and sidewall damage. I can make the same comparison to my old cyclocross rig which runs at most a 32mm tire.

  21. Jesse Hill says:

    What affect does tire width/weight have on acceleration?

    • We looked into that for Bicycle Quarterly, and the effect was much smaller than most people think. Bicycles don’t accelerate very fast, because our power-to-weight ratio isn’t that great. Even the slowest economycar has ten times as much power per kilogram as a pro racer.

      If wheel weight mattered for sprinters, they’d all race the smallest wheels the UCI allows – 550 mm. Many ave tried smaller wheels, but they’ve all returned to 700C, even though that’s 100 mm larger than the rules require.

      • Samuel Atkinson says:

        >”We looked into that for Bicycle Quarterly, and the effect was much smaller than most people think. Bicycles don’t accelerate very fast, because our power-to-weight ratio isn’t that great.”

        I think this runs counter to your point. If bicycles accelerate slowly, then hindrances to acceleration are going to be more significant than if they accelerate quickly. Much in the same way that a percentage speed up has more impact if it’s on climbs than descents, because you spend more time climbing.

        The main reason that wheel mass has less effect than some people expect is that the inertia differences just aren’t that big relative to the bike+rider system. With respect to acceleration, mass at the rim has roughly double the effect of mass on the frame… so adding an entire pound onto your rims should increase resistance to acceleration by somewhere in the neighborhood of 1% for most riders.

        >”If wheel weight mattered for sprinters, they’d all race the smallest wheels the UCI allows – 550 mm.”

        I mostly agree, although there are some complicating factors that combine to give 700c a lot of market inertia. At the top level of mass-start racing, racers generally like to use equipment compatible with what the support cars are carrying. And high-performance road racing equipment has much greater availability in 700c than other sizes, discouraging racing experimentation with other BSDs to begin with.

      • racers generally like to use equipment compatible with what the support cars are carrying.

        I’ve thought about this a lot. If you gain a significant advantage with smaller wheels, it’s worth the risk that you won’t get a wheel change when your support car isn’t available. After all, you’ll get a flat in less 5% of the races you enter. If you win 1/4 of the others due to the faster acceleration of the smaller wheels, you are still winning 24% of all races and beating the odds by a huge margin!

        The list of builders who tried smaller wheels is long. There was Cino Cinelli. Ernesto Colnago built a beautiful 650C bike for Guiseppe Saronni, but Saronni used an identical 700C bike instead (and still won the worlds). It seems that they tested the bikes and found that the advantages were not sufficient to adopt smaller wheels.

      • John C. Wilson says:

        Riders at 170# or 200# with ample power and considerable experience can shrug off a difference of a few hundred grams in wheel weight. They should shrug it off rather than obsess about it. For lighter riders and greener riders wheel weight can be a real issue. Even if you were to convince yourself that the physics say it is all inconsequential the psychological results of light wheels are massive. And light riders don’t wear out anything so they may as well have the light ones.

        Repetitiously confirmed by loaning good wheels to middle of pack light riders and watching them win their first race.

      • confirmed by loaning good wheels to middle of pack light riders and watching them win their first race.

        Assuming that the good wheels are shod with good tires, I’ll gladly believe you. When I switched from cheap tubulars to good ones (on the same wheels), I was astounded how much easier it became to follow moves in the pack and even make my own.

        Like you, I was convinced that my bike with its racing wheels accelerated way faster than it did with its training wheels. Now I think this was mostly because the lighter wheels made rocking the bike from side to side while sprinting out of the saddle much easier. In that case, the accelerations (side-to-side, not forward) are considerate: At a cadence of 90 rpm, the bike reverses direction no less than 3 times a second!

      • John C. Wilson says:

        Panaracer Comp 21 tubulars @180 grams. Most extremely supple. Wore thru to casing
        more often than they flatted. Also very low priced but no one would buy them so they are gone. Would Compass ever make a tubular?

        I was taught to sprint solid and motionless in saddle. It was only a rush, not a sprint, if the rpm were below 150. Rocking squanders energy and catches wind. Rocking exposes back muscles to injury.

      • I also enjoy sprinting in the saddle, starting with high rpm and feeling the bike surge forward. Like you, I find it no slower than sprinting out of the saddle. But then, nobody ever called me an ace sprinter.;-)

        Racers always have rocked their bikes when climbing out of the saddle. Rather than waste energy, it allows using your arms to propel the bike. Whether this makes up for the aero disadvantage probably depends on many factors, and it seems that the equation has changed in recent years, perhaps due to lead-outs being more common than in the past.

    • Andy Stow says:

      Shorter distance than a professional sprint, someone put on a competition bicycle “drag race” where the top prize was a brand new motorcycle. I think it was a promotional stunt before a motorcycle racing event. It was short, like 100 meters or something. Any bicycle could be used.

      All the top placers were on BMX bikes. It wasn’t even close.

      • Thanks for sharing that interesting anecdote. I suspect the biggest difference was how much power you could transfer into the bike. BMX bikes allow riders to use their upper body muscles much more than traditional racing bikes. The better aerodynamics of a racing bike are important when accelerating from 50 to 65 km/h at the finish of a road race, but when going from 0 to 40 km/h, aerodynamics are much less important. Similarly, rolling resistance is even more important at lower speeds, because it makes up more of the total resistance.

  22. Scott Emmens says:

    Jan, the timing of this post is perfect for me personally, thank you!
    I have been obsessing over Allroad bikes for some years, and lusting after an OPEN UP, but as someone further up mentioned these are out of financial reach for a lot of people, myself included.
    I have just built a Curve GXR “Allroad” bike and had intended running 700c and 650b wheel sets with different tyres but after reading this I think I’ll just stick with the 650bs, especially as the wheels I have had built aren’t exactly light, no Enves here unfortunately! The Curve is fantastic so far with the 700c wheels and 40c “gravel tyres” although I feel the tyres are dulling the feel significantly.
    My main requirement was to be able to squeeze 650b x 2.2 tyres for a 1100km bikepacking event I organise called the Kiwi Brevet. It has a couple of singletrack sections that are “proper” mountain biking, and New Zealand “gravel” is very very chunky. I’m also hoping to qualify, and ride, Paris Brest Paris next year on the same bike.
    Thanks again for you articles and research. I am impatiently awaiting my latest copy of Bicycle Quarterly in the mail, it kills me every issue as you tease us with what’s inside, then being in New Zealand, I have to wait an extra couple of weeks to receive it!
    Cheers, Scott

    • ryan giggs says:

      Can you fit a 2.2 in the back of the GXR?
      My ti Grovel barely fits a 650b x 2.1 ThunderBurt in the rear.
      Fork has plenty of room though.

  23. Matt says:

    Hello Jan,

    Informative article, as per usual. While it’s clear to me, having ridden Compass tires in all three wheel sizes, that overall diameter influences handling, I’m less clear on the speed/efficiency benefits of the different wheel sizes. It’s widely accepted that smaller, 26″ mtb wheels ‘spin up’ more quickly, and are more agile, than their larger brethren, while 29er wheels roll over obstacles more easily and are better for descending rough terrain. What I’m wondering is, has Compass tested its tires in respect to overall diameter and efficiency on the road? I’ve got a set of Switchback Hills, and while I love the ride quality, they *feel* slower on long, flat drags of road than the Snoqualmie Pass tires do. (So much so that I’m considering building a new 700c wheelset, with super-light Stan’s Crest rims, to install with Extra-light Snoqualmie Pass tires and compare myself. This specific wheel/tire combo yields an incredibly low rotating weight of less than 700 grams!) Is this a matter of ideal road tire width, as you allude to in this post as being ~42mm? Or does it have more to do with overall weight (the Snoqualmie Pass tires are noticeably lighter compared to the other 40mm plus tires that Compass offers)? Or something else entirely?

    Thanks,
    Matt

    • We tested how well different wheel sizes roll on smooth and rough roads – including our famous ‘rumble strip’ tests – and found no measurable difference between 700C, 650B and 26″ wheels, provided they ran the same tires in the same width at the same pressure. So wheel size doesn’t affect speed even on rough gravel roads.

      I don’t have enough experience on mountain bikes to comment. When I researched wheel size and speed, I was unable to find any studies that showed 700C (29er) wheels being faster. I suspect that it’s more the handling differences that make some riders faster. For example, a wheel that isn’t easily deflected may roll over obstacles better…

  24. André Ferreira Rocha says:

    currently using switchback hills, i have been trying to decided wether i should go for a smaller tire for the upcoming brevets i’m riding and as a prep for PBP next year. you mention 38mm as being optimal for road but later on you mention that wider tires can feel exactly the same if they’re more inflated.

    so… can i conclude from your article that, on 650b wheels, 48mm-54mm tires on 38 p.s.i. will make them feel and perform exactly as 38mm, with the “connected to the pavement” feeling, only adding a bit of tire roar?

    if that’s really true, i start to want a 26″ wheelset and rat trap pass tires instead… 😉

    • The feel of the bike will change with smaller wheels and narrower tires, but not its speed. So if you like the way your bike rides, go for the 48 mm tires even for a paved ride like PBP. You will be glad in the end – the last time I rode PBP in 2015, I found that some of the (paved) backroads were so rough that I was wishing for tires wider than my 42 mm Babyshoe Pass. It’s not a big deal when you are fresh and pedaling hard, but during those inevitable ‘rough spots’ you feel the vibrations much more…

  25. KaiS says:

    interesting article, would also be would be glad to hear your input and observations on different rim widths vs tire width.

    when you increase tire width, but not at the same time rim width, my experience is you need to compensate the too narrow rim for the wider tire with extra tire pressure, thus losing some of the wished-for plushness on rough ground. if you dont do that you are punished with spongy feel and increased self-steering.

    accordingly, if you are a heavy rider that would need a relatively high pressure anyway, you can get away with a narrower and lighter rim than would a lighter rider.

    my own observation of the matter indicate that a given tire combination roll faster with a wider rim; at the same time you can have less pressure and more plushness.

    if you have made observations on handling and rolling resistance of the respective tire widths in your article vs various rim widths i would be glad to hear about it!

  26. Alex Hales says:

    I think 650B x 42 mm are good for startup because it doesn’t matter which tire you choose first all depend upon’s how we handle the ride.

  27. bgddyjim says:

    Thankfully my Venge only takes 26mm tires… LOL.

    My old Trek won’t take anything wider than a 24.

  28. It seems like the tire pressure vs weight question comes up quite a bit in these discussions. In our testing with 110lb rider, 170lb rider, single bikes, tandems, and sometimes heavy luggage, I think we’ve settled on a conclusion. Each road or trail surface seems to have an optimum pressure. Certainly soft surfaces (dirt, gravel, mud, sand, snow) have a self-supporting pressure and your tires sink in if they’re pumped above it. Here’s a chart that we made with our pressure preferences for each type of surface, plotted versus total bike+rider weight. It assumes even weight distribution front/rear. As a corollary, we often use a slightly narrower tire in the front such that their inflation pressures can be the same at 15% tire drop. Here’s the chart for single bikes: https://docs.google.com/spreadsheets/u/2/d/e/2PACX-1vTA5EaYv-lwaBt5ZiSfcdpXfldWanA7IxQun7DEZp-Axedz83mmosu-Ug8J0B-aURHg25fsqcqRqxCJ/pubchart?oid=274554687&format=interactive
    And here’s one for tandems:
    https://docs.google.com/spreadsheets/u/2/d/e/2PACX-1vTA5EaYv-lwaBt5ZiSfcdpXfldWanA7IxQun7DEZp-Axedz83mmosu-Ug8J0B-aURHg25fsqcqRqxCJ/pubchart?oid=1950677175&format=interactive

  29. Naz H. says:

    Long-time reader and BQ buyer, first time commenter. I’ve been reading your posts for years, and this year I sold all my road-type bikes and things and went disc and gravel.

    I’ve been playing with tires a little bit not Compass yet. I had some Specialized Roubaix 2BR in that 30/32 designation but found that I was lacking both cush and volume for the terrain we have in the Marin Headlands/Tam and generally dirt/gravel of the Bay Area. I switched to the Panatacee Gravelking SKs (38mm tubeless) for some bite and love them on the dirt.

    Speed has definitely been sacrificed on pavement and am wondering about going to a non-knobbed tire at this size for some speed. But I’m unsure how much I’d lose interns of grip on the dirt here. A friend of mine rented an UP from Above Category to try the dirt thing (he loved it) and it was shod with some Snoqualmie Pass tires (IIRC – they were definitely Compass and fat!) and did some some traction loss when climbing on the dirt (as did I at the time as I was running the Roubaixs).

    My question is then: I loved this post and understand that this is generally on smooth/file tread tires, so how does some knobbys (like on the GK SKs or Schwalbe G-Ones) factor into speed, feel, etc?

    • It’s generally accepted that knobs slow the bike down, and as you’ve experienced yourself, most knobbies roll noticeably slower. For our ‘dual-purpose’ Steilacoom (700C) and Pumpkin Ridge (650B) tires, we’ve completely re-thought the design of knobby tires to maximize their performance and handling on pavement as well as in mud. If you need knobs on soft dirt, but don’t want to give up any noticeable speed on pavement, I suggest you give them a try. You can read an independent test of the Steilacooms here.

  30. Jon Blum says:

    Thanks for your guidance on tires. With respect to “there is no reason to change the wheel size with rider height,” I had thought this was a real issue for riders under 5’4″ (which includes a lot of women). Makers like Terry used smaller wheels (or a smaller front wheel) to avoid problems with frame geometry that occur when the frame gets too small for the wheels (toe clip overlap and some steering issues, if I remember right). I am not short enough to have personally experienced these issues, but some of my more petite friends were early adopters of 650b for this reason.

    • I am sorry my comment was easy to misunderstand. As you mention, fitting large wheels into small frames always has been a problem, and so it’s often inevitable to compromise the handling slightly to make the bike fit the rider. The original questions was about the other end of the scale, and with taller frames, there are no reasons to increase the wheel size beyond what is ideal for the desired handling characteristics.

  31. ryan giggs says:

    It took me a little while to get used to the smaller diameter of the 650b x 42 after initially trying the 48mm.
    I can feel the 42 rolls a little faster on the road / makes the bike a little more nimble in the ride, but I just like the rolling diameter feel of the 48 more. Spoiled for choice, I suppose.
    Using both on a 1200gm wheelset.

  32. Stuart Fogg says:

    I’ve often wondered why common bicycle wheel diameters run only from 559mm to 622mm (about 1.18:1). These ranges don’t seem sufficient for adults much below 5’1″ (female -1 SD from USA av) or above 6’1″ (male +1 SD from USA av). For example, every bicycle my 6’7″ friend has ever owned has looked comical in its proportions.

    Would it be possible to adjust stability with frame geometry rather than with wheel diameter in especially large or small frames?

    • We’ve thought about this a lot, but so far, we haven’t come up with a solution, nor have we ridden any bikes that handled great with wheels that were outside the ‘normal’ range. I suspect this is because wheel flop and trail are inversely proportional: a bike with more trail also has more wheel flop. What you gain with one you lose with the other. You can tweak the equation a bit by steepening the head angle, but most bikes already are close to the limit. Anything steeper than 74 or 75° doesn’t change the handling much, but it increases the propensity for judder under braking.

      Tony Foale did some experiments with motorcycles, and he came to similar conclusions. Interestingly, motorcycle wheel sizes also have tracked tire widths closely to maintain an ‘optimum’ rotational inertia: When tires became wider, wheel diameters decreased. More recently, low-profile tires have led to larger-diameter wheels again… It’s funny that bike makers still talk about keeping the overall diameter of the wheels constant, when motorcycle makers have known since the 1950s that it’s the rotational inertia that matters.

  33. David Reitz says:

    I am still confused about this wide, low-pressure supple tire thing. If this style tire is clearly faster and more comfortable than a narrower tire, how come the pros in a TDF stage like the Arras-Roubaix over the cobblestones aren’t riding bikes with +40 mm tires – it appears they were using 28 mm tires this year ?

    • That is a good question. We got that a lot way back, when our test results clearly showed that 25 mm tires are faster than 23s, even on very smooth roads. “Why do the pros use 23 mm tires, if 25s are faster.”

      I think the answer is simple: The pros don’t always use the fastest equipment. They face constraints of sponsorship, of available equipment (their racing bikes probably don’t fit wider tires), and simply of habit.

      There may be other constraints, too. How is the race won? Do racers break away on the cobbles, or do they ‘survive’ the cobbles to win in the final sprint on smooth pavement. At the power outputs of professional racers, wide tires at lower pressures may be too soft and bounce too much when sprinting with 1000+ Watts. It would be interesting to see a time trial that includes cobbles, as this would require top speed over the entire course, not just for a few seconds when the decisive move is made. Or a race that finishes on cobbles…

Comments are closed.