Rim Weight

At Compass Bicycles, we are not obsessive gram counters, but none of us want to carry extra weight on our bikes. A few grams here and there add up quickly to a couple of pounds, and that can make a difference not only in how the bike performs, but also how it feels when you ride it.

There are some components where you cannot save weight without undue compromises, and rims are a very good example. A well-designed clincher rim weighs about 450-500 g (650B) and 480-530 g (700C). To reduce this weight further, you only can remove material in four ways:

  • Thinner sidewalls. Example: 1.3 mm instead of 1.6 mm. Savings: 30 g.* The rim sidewall abrades as you brake. You need at least 0.7 mm of sidewall thickness to keep the tire from exploding. With the thinner sidewalls, your rim can lose only 0.6 mm until it is worn out, instead of 0.9 mm. That means your rim will last only 2/3 as long.
  • Narrower rim: Example: 20 mm instead of 23 mm. Savings: 24 g. On the down side, the rim no longer supports wide tires well.
  • Thinner rim “floor” (the side facing the hub): Example: 0.9 mm instead of 1.0 mm. Savings: 11.4 g. Now there is less material to counter the stresses imparted by the spokes, and the rim is more likely to crack.
  • Bottom of the well (the side facing the tire): Most rims already have the bare minimum here, so there are no further savings possible.
  • Rim shape: A more triangular shape can save material over a traditional box section, but the brake tracks are much shallower. You will have to adjust your brake pads frequently as they wear, otherwise they will cut into the tire (with sidepull and centerpull brakes) or dive under the rim (with cantilevers).

None of these weight saving options are very appealing. In the end, a good rim has a certain weight, and there is little you can do about it.

If you really must have a lighter rim, just ride it, and it will get lighter every time you brake. Of the two rims shown above, one is 70 grams lighter. Both rims started out from the same extrusion (Mavic MA-2/MA-40). The rim on the left is brand-new. The rim on the right has been used for a few years. The abrasion of the brake pads has removed 0.7 mm from each sidewall. The rim has lost 70 g of weight, but it is close to the limit where it becomes unsafe to use.

Even if you are willing to compromise durability and tire support to save weight, all the potential savings add up to only 65 g per rim. If you use a disc-only rim, you save another 30-40 g, but the separate brake disc weighs more than you save on the rim. (And using “disc-only” rims with rim brakes is a bad idea for obvious reasons: the brake tracks are worn out from the onset.)

Here are a few better ideas to reduce the weight of your wheels:

  • Folding tires: A Kevlar bead saves about 70 g per tire. Such a tire performs the same as one with a wire bead.
  • Superlight Tubes. On a 650B x 42 mm tire, using a superlight tube saves about 45 g. The down side is that you’ll have to inflate your tires every couple of weeks, as the air leaks out of the thinner tube more quickly.

Together, the weight savings from lighter tires and tubes are more than you’ll ever get by using a “pre-worn” rim. Light weight components have their place, but they should not come with undue compromises.

* The circumference of a 650B rim is 183 cm, the sidewall is about 1 cm tall. The aluminum removed by making the sidewall 0.03 cm thinner is 183 x 1 x 0.03 = 5.49 cm3. There are two sidewalls, so you remove 9.98 cm3. Aluminum has a specific density of 2.7 g/cm3, so the savings are 9.98 x 2.7 = 29.6 g.

About Jan Heine, Editor, Bicycle Quarterly

I love cycling and bicycles, especially those that take us off the beaten path. I edit Bicycle Quarterly magazine, and occasionally write for other publications. One of our companies, Bicycle Quarterly Press publishes cycling books, while Compass Bicycles Ltd. makes and distributes high-quality bicycle components for real-world riders.
This entry was posted in hubs/rims, Testing and Tech. Bookmark the permalink.

52 Responses to Rim Weight

  1. RJ says:

    You overlook one other way to save weight at the wheel – remove the tube entirely. Some tubeless rims are even designed to eliminate the need for tape. There’s a reduction of an easy 100g.

    • You are right – you can eliminate even the superlight tube (a savings of 95 g) – but you add some sealant and perhaps a heavier rim tape. Even so, the potential for savings is significant. There are some drawbacks – the need of compressed air to seat the tire, and the issue of the sealant all over your hands if you ever have a flat tire.

      • RJ says:

        I understand what you’re saying Jan. But you really should give it a try. The only time I typically need compressed air is the first mounting of the tire (when it’s shape is irregular from being packaged). After that a floor pump usually works just fine because the tire has settled into a nice round shape.
        I actually carry a pair of Safe Grip latex gloves (size large <40g) with me so getting stuff on my hands is a non-issue. I do that not because I'm concerned about sealant, I find the chain grunge much more difficult to clean off. And the gloves can add a little extra warmth if the weather changes unexpectedly.

      • I am totally open to tubeless. We hope to try it soon. Since I posted the disadvantages of lightweight tubes (slight air leak), I felt that the disadvantages of tubeless should be mentioned as well.

  2. Bubba says:

    Your sliding Singer brakes don’t dive at all. You could get away with tiny brake tracks on the rims with those brakes. :)

    We’ve seen some early prototypes of the new Pacenti 650B road rim on the web, including JPW showing they weigh 387g. Do you know which of the above compromises was made to get there? Regarding the lifespan of rims, 2/3 of the life sounds pretty bad, but it’s hard for me to put that into context. I’ve seen you post that rim x would be dead after a single Seattle winter, but I also think your Singer might have 50+year old rims. I know the real answer is “It depends” but how long do you consider the life of a rim? For example, if that 390g Pacenti rim will last 24 years, and your 500g rim will last 36, then I’d consider them both to have a fairly long life expectancy. How many years or miles do you get out of a wheel before the rim is worn out?

    • The MA-2 rim that was worn out lasted me about 4 years in Seattle. It was on the front wheel, and I don’t brake very much. The MA-2 has very thick sidewalls (1.6 mm), which is why it is so heavy. Most modern rims have sidewalls that are only 1.4 mm thick. If you use your rear brake, you can wear through a rear rim in one winter…

      50 years for a rim means that the bike hasn’t been ridden much, or only on flat country roads, where you rarely need to brake. Like everything, rim weight is a compromise, and I certainly don’t want 600 g rims, even if they last twice as long. Since you need to keep a wall thickness of 0.7 mm to contain the tire pressure, it’s a case of diminishing returns. If you make the wall thickness 0.8 mm, you get half as much life as you would with a 0.9 mm wall, while saving just 10 g.

  3. Steve says:

    Mavic and Campagnolo machine off material from the rim “floor” between spoke holes on their rims, leaving the full depth of the extrusion around the holes and a thinner section where presumably, (hopefully?) there is less stress transferred from the spokes.

  4. Neil says:

    I’ve never been too concerned with weight, having my own fair share to lose before being concerned with a few grams on my wheels, but in the spirit of the article, what do you think about eyelets vs no eyelets? Any thoughts on the cost-benefit of this option?

    • You don’t need eyelets if you have a very thick rim bottom, like aero rims have. On the other hand, eyelets make it easier to turn the nipples.

      Double vs. single eyelets: I used to think that it didn’t matter, but after thinking about it and discussing with some rim makers, I think that a well-designed rim with double eyelets can be better. The trick has to be to make both eyelets load-bearing, and that requires some very close tolerances. Otherwise, only one eyelet bears the load, and you could just as well leave out the other one.

  5. RodneyAB says:

    Interesting subjects. . .at NAHBS I saw the Pacenti rim prototype, with it’s wear indicator dimple, which I had to ask about. . .and I want a set. jPW has the rim with a tubeless shaved Hetre set-up.

  6. Garth says:

    One aspect of wheel weight left out of this discussion is Jan’s research on the gyroscopic forces created by the front wheel to create a well-handling bicycle. It seems to me that if you have an ideal weight to maintain, if you can save weight in one area, you would want to increase the weight where it’s more useful – a fatter tire.

  7. Sim Richards says:

    All this talk of rims exploding after only one season gives me the heebee geebees! As someone who’s ridden every possible bicycle for great distances over the years I have to conclude that rim brakes are for places where it doesn’t rain / OR / for people who don’t go riding when it is raining.
    The old argument that disk brakes are heavier than rim doesn’t hold true any more; a Formula R1 caliper & lever weigh in at 270g + 85g for a 140mm rotor = 355g. Versus 210g for a Diacompe 610 + 160g for a brake lever = 370g. I know frames and forks have to be beefed up a bit for disks and this won’t suit classic bikes but if buying new you’d be a fool to ignore the sharp consistent braking afforded by disks not to mention never having to rebuild a blown rim ever again.

    • Rims should not explode – you want to catch the wear before that happens! I know that it can be tricky.

      Your point about disc brakes is a good one. I don’t know about your weights, but a Mafac Raid mounted to braze-ons weighs less than 130 g, and a nice lever about 120 g, so you get 250 g, not 370 g, but that is splitting hairs. The disc is only marginally heavier, and no enough to make a big difference in performance. You’ll have to replace the disc rotors eventually, but at least you can see how thin they are.

      Right now, I can see two major issues about disc brakes on road bikes:
      1. No drop handlebar levers available for hydraulic brakes. Cable-operated brakes simply have too much flex in the system. Either the calipers rub, or the brake lever bottoms out against the handlebars if you brake really hard.
      2. You need to beef up the fork, which reduces the shock absorption of the forks. Ideally, you’d use a stiff fork with secondary suspension, but that adds more weight and complexity.

      • msrw says:

        I have an Avid BB7 cable actuated disk on the rear wheel of my tandem (with a 203mm rotor and it works exceptionally well–great modulation, excellent stopping power without undue pressure on the lever, no caliper rub, no bottoming out of the lever etc. I had used two different hydraulic brakes before going with the Avid and both were fussier and less effective. Honestly, there is something to be said about simple bicycle components.

      • On the rear of any bike, even a tandem, you have less traction when braking, which limits your brake power. So even a mechanical disc will be OK. On the front wheel, you have more traction, and can use more brake power.

        I remember testing a Civia with mechanical Avid discs: Approaching a red light in downtown Seattle on a steep descent, I pulled the lever all the way to the bars, and the bike still didn’t slow down appreciably. Fortunately, the light turned green before I arrived. Then an expert bike shop adjusted the brake, and it did brake better, but it also annoyingly rubbed on the disc with every wheel revolution.

    • Bill says:

      Fork blades may have to be beefed up for disc brakes, but the rim should be able to be significantly lighter when there’s no need for a braking track. I suspect that could be a good trade-off. Carbon fiber rims, anyone?

  8. Steve Palincsar says:

    How strong is strong enough surely must vary with the rider and the load. At 0.1 tons, I’m confident I need a stronger rim than someone who weighs only 110 or 120 lb.

    I don’t use ultra-light anything (except those Maxxix 558×1.75 ultralight tubes, which work great in 650B applications) but I’m well aware there’s a great range in rims. Among roadies, the Open Pro used to be the rim of choice for everything up to and including 35-38mm wide tires, even though the manufacturer sternly warns against using tires that wide. As light rims go, how light are Open Pro’s, and how heavy a rider+load does it take to become too heavy for that rim?

    In the 650B world, I recall back in the beginning someone commissioned a special run of Velocity Aeroheads, which I believe were lighter than the other 650B rims available at the time (chiefly the Synergy). Anyone know how they worked out? I don’t recall hearing anything about failures of the Aerohead (unlike the Synergy OC, of which I’ve personally had several crack).

  9. Conrad says:

    Nice article- I wouldn’t have thought that a worn out rim could save so much weight!
    I build up my commuter wheels with Velocity Synergy rims. I did crack one or two at the eyelet- I have found that the maximum spoke tension you want with a box section rim is about 100 kgF. I can build up an Aerohead or A23 with a lot more tension with no problems. A rear Velocity Synergy can make it through 2 Seattle winters for me, and I sort of push my luck with rim wear. Not too bad, but I am intrigued with the idea of discs. Especially if you’re heading down hills with cargo or kid trailers when it is wet. I’m waiting for the hydraulic road discs.
    One other thing you can do to decrease weight is use aluminum nipples on the front wheel and non drive side of the rear. I use linseed oil on spoke threads and while I hardly ever have to touch up a wheel, when I have there has not been any seizing or serious corrosion issues.

  10. Phil Miller says:

    Anybody had any experience putting Nitrogen into those ultralite tubes? Nitrogen is supposed to be less permeable and so need ‘topping off’ less, if at all. Set it and forget it. It’s also less susceptable to temperature changes, though on a bike that’s not going to be a tremendous advantage. Of course, if you take a flat you are going to have to pump with Air or CO2 and then you’re back where you started. If Nitrogen did solve the 50-85g tube leakage, then the problem would be finding 12/16g threaded/unthreaded cartridges… :-)

    • The leakage is so little on my bike that it isn’t a bother. I should check my tire pressure every month anyhow, in case there is a slow leak from a minor puncture…

    • Bubba says:

      Here’s an article about the theory with empirical results.

      http://home.comcast.net/~prestondrake/N2_FAQ_Q04.htm

      The punchline is that O2 leaks about 4x as fast as N2 through butyl rubber. Air is about 79% N2 and about 21% O2. As a result Air leaks about half again faster than N2. So if you ‘top off’ your tires once every two weeks with Air, you could get the same effect by topping off with pure Nitrogen every 3 weeks.

  11. Phil Miller says:

    Good article, especially this:
    “Note also that if you fill and top off with air, the percentage of N2 will gradually increase over time; at first you lose about half O2 and half N2, but you top off with a mixture of 78% N2 and 22% O2. So if you fill your tires with air and they initially lose about a psi a month, then after a year of this, it’s down to mostly N2 inside the tire, and the leakdown rate should slow down.”

    This squares with what I’ve observed, although I’ve always given a different reason. Brand new tubes do leak more than old ones. I always attributed it to some kind of hardening/curing effect in the interior rubber. I think this explanation is better.

    • Whatever it is, the leak rate does seem to slow down over time. When we first tested superlight tubes, we had to inflate almost weekly. Now it’s been a month since I inflated the tire with the superlight tube, and the pressure hasn’t dropped measurably.

    • RodneyAB says:

      Admittedly I’m not from the modern bike world, and therefore know little about modern rims, or tubeless systems, so if you put a sealant inside a tube, does that slow down the leak rate?

  12. HillDancer says:

    It’s a shame you had a poor experience with a mechanical disc brake system Jan. The symptoms you describe are not indicative of a properly equipped and adjusted BB7 kit. I can brake on my BB7 kit from the hoods to a complete stop with my little fingers behind the levers and not contact them, and that’s with a shifter lever in the way also. Straightening a rotor with a pair of flat faced parallel jaw pliers is all it takes to eliminate an annoying pad rub. Appropriate size rotors, a pad compound matched to intended use, and correct bed-in procedure, will yield valuable tactile feedback for accurate modulation, and strong braking power with less lever effort & travel needed for rim brakes.

    Small diameter weight saving rotors are OK for flatland riding and off road/gravel, but for steep descents on dry pavement where traction is abundant, large diameter heavy rotors are a must to disperse increased heat, especially so with a tire contact patch the size of Hetre’s. The moment of inertia for a brake rotor is far less than tire or rim, I don’t think its weight should be considered in the same context.

    BTW, my rims approach 600 grams in weight, their unyielding mass serves valuable functions, well worth to me what others would call a penalty.

    • I am glad the mechanical discs work fine for you. I think a big difference is how hard people brake. I am talking about descending a 15% slope at 30 mph, and then trying to come to a complete stop. The type of braking where you shift your weight all the way back, lock your elbows, pull on the front brake lever as hard as you can, and when you come to a stop, you can smell burnt brake pads, if you use Kool-Stop salmon-colored pads. But being able to brake that hard can make the difference between avoiding an accident or not.

      The disc brakes on our test bike were fine-tuned by an expert mechanic, who also claimed that these work fine.

      Disc brakes, because of their smaller diameter, need to clamp the disc much harder than rim brakes. That means that parts are more likely to flex. That is where hydraulics shine: They transmit the hand force without flex or compression, straight to a piston that pushes the pads against the disc. The mechanical brake has many parts that flex. For similar reasons, cars still use drum brakes for the handbrake, which is cable-operated, in addition to discs for the main, hydraulic brakes. (Many cars have small drums for the handbrake inside the rear discs.)

      There also may be a difference between the mountain bike Avid BB7 and the road-bike Avid BB5. The road bike brakes may be a particularly poor design. They have more mechanical advantage than necessary – you don’t need much lever force – which means that they use more cable travel than necessary. I was thinking of trying the brakes with non-aero levers with less mechanical advantage, but a near fatal component failure on the Civia test-bike put me off any further experimentation with that bike.

      Hydraulic discs, on the other hand, work very, very well, but alas, they do not work with the flexible fork blades that we have found so important for mid-size bump absorption.

      • HillDancer says:

        “I am talking about descending a 15% slope at 30 mph, and then trying to come to a complete stop. The type of braking where you shift your weight all the way back, lock your elbows, pull on the front brake lever as hard as you can, and when you come to a stop, you can smell burnt brake pads”
        My downhill braking requirements exceed those grades and speeds often. Scary rim brake fade is the main reason I chose disc brakes, accelerated rim wear was secondary.

        Modern automotive parking brakes apply force via the rear disc brake caliper using a mechanical screw mechanismsim on the, piston(s) just like BB7 & BB5 brakes.

        BB7 & BB5 road calipers are short-pull versus long-pull on the mountain versions. BB5 pads are smaller than BB7, and lack an adjustment knob on the moving pad side. Criticism could be made BB7s are overbuilt, certainly not a poor design. Brake cable housings designed for disc brakes like Ripstops allow little cable travel loss; I don’t know the other flex characteristics you mention.

        I have no doubt your disc brake experience could be greatly improved upon without depending on hydraulic actuation. Hydraulic disc brakes have there own limitations.

  13. Willem says:

    I ride Schwalbe xxlight tubes on my loaded tourer, and the topping up problem really is not a isue with these tubes. I see no or almost no difference with heavier tubes.
    Willem

  14. David G says:

    I just received a wheelset with denodized and polished 650B Stan’s ZTR 355 rims. I’m not sure how accurate my scale is, but the spare rim that I ordered with the wheels weighs less than 350 grams! In light of your post that is a bit scary. I mounted Hetres with no tubes and a scoop of Stan’s sealant per tire this morning and pumped them up with a standard high-volume floor pump, no problem. We’ll see how they work on the road…

  15. Daniel says:

    While perhaps a tangent, I’d love to hear your opinion: What do you feel are appropriate spoke counts and gauges for the rando-scene. If you need the specifics, let’s say a tall drink of water like yours truly (6’2″) with a total load of 200lbs (engine and cargo). I plan to build a new set of 700C wheels later this year.

  16. Mike V says:

    One item that wasn’t addressed with regards to rim weights is the lifespan of the rim extrusion. Many rim manufacturers, including Mavic back in the MA2 production days (I don’t know what they are today), have a rim weight tolerance of +/- 10%. This could mean a swing of 90g on a targeted 450g rim.

  17. Rob Johnston says:

    What are smart tube choices for GB Hetre 42mm? 270 pound tandem duo.

    • The Schwalbe SV12 really works well. If you want lighter weight, we have had good experiences with Maxxis Flyweight 26″ x 1.75″ tubes, but they appear to be unavailable right now.

      • Steve Palincsar says:

        Based on the pictures of the boxes, I’m confident it was the Ultralight 26×1.5-1.75 you tested, not the Flyweight, which in my experience is every bit as good as you said in your review. So too is the Schwalbe SV12, although of course it’s much heavier and bulkier.

      • We tested the Flyweight – the box said “Flyweight” and the weight matched the specs for the “Flyweight.” We have been trying to get the Flyweight tubes, but according to Maxxis, no distributor in this country stocks them.

      • neilsen says:

        I don’t see Maxxis listing a Flyweight tube in a 26″ x 1.75″. I do see on their website a Flyweight in a 26″ x 1.9-2.1″ that is available through BTI. Since Maxxis lists this tire as having a .45 mm wall thickness, would this then be comparable to the Bontrager XXX Lite tube made in 26″ x 1.75/2.1″ that is also listed as .45 mm wall thickness?

      • Maybe Maxxis discontinued the tube we tested. One issue with superlight tubes is that they must be of good quality. Less expensive tubes often have uneven wall thicknesses, which is OK with thicker tubes, but not so good with superlight ones.

  18. BBB says:

    Just my 50cent ;-)

    1. TUBELESS
    I’m surprised that some clever and open minded folks like you haven’t managed to embrace the tubeless nirvana or perhaps give it a go and e.g. doing some comparison rolling resistance tests . Tubeless isn’t entirely about the weight but about PUNCTURE RESISTANCE, rolling and comfort. You really have to try riding some trimmed or shaven lightweight XC or CX tyres (on the road) to fully appreciate the benefits.

    2. BB7s
    !! I use BB7s both on a “road” and on a mountain bike. I’m quite heavy and carry some work stuff in my panniers and they have PLENTY of stopping power and modulation. E.g. on a mountain bike I never use more than one finger for braking. If they are spongy and they don’t stop you, you are certainly doing something WRONG!
    They need Jagwire or similar compression-less casing with good quality SS inners and alu or metal ferrules, as straight as possible cable routing and it’s also a good idea to back off with the caliper arm tension or even remove the brake lever return spring. It’s all about details.

    The truth is that even with frictionless cables lasting forever and mech brakes being as light, people would be still choosing hydraulic brakes because “hydraulic” sounds sexier and superior.

    Hydraulic systems have their own problems and the main one is temperamental sticky pistons and random rotor rub… which your brakes will develop sooner or later ;-)

    • Which brake levers do you use with the BB7 on drop handlebars?

      My main concern about disc brakes is the need to beef up the fork blades, which reduces their ability to absorb shocks. The difference in ride quality between small-diameter fork blades and stiffer large-diameter blades is very noticeable.

    • RJ says:

      1. Sold on tubeless and I’ve been a certifiable “tubeless evangelist” for some time now.
      2. Tried BB7s on my MTB and really didn’t like them at all. Too much fiddling around for such lack luster modulation. Sold them and went back to XTR V-brakes until I could afford nice hydraulics. When I built my 650B MTB I went with XT hydraulic discs. It’s been a couple years now and they have been the most low maintenance and trouble free bicycle brakes I’ve ever had, period. Once I was past the first few rides (initial setup and break-in) I’ve had to do absolutely nothing more than wash my bike normally.

  19. BBB says:

    I used to use 105 ST-5600 levers and now I have Cane Creek SCR-5s (road) which I prefer.

  20. HillDancer says:

    I use SRAM integrated road levers on my drop bars with BB7 road brakes, and I also use the brake lever only model on my rim brake bike with downtube shifters. A bonus feature is adjustable lever travel for finger reach. I use one finger from the drops and two from the hoods with a 200mm rotor up front, 180mm rotor in back, and preferred pad compound cocktail.

    I preload the lever arm to reduce lever travel, and fine tune with an in-line adjuster. Another comment about pad rub, some pad springs are weak to begin with or loose their resiliance after numerous heat cycles and fail to return a pad corner. For my use, increased spring tension works for the better.

    I agree ride comfort diminishes with stiffer fork blades, and will add straight versus curved shape. Dave Kirk is exploring a longer IS bracket approach to spreading the brake load on a curved fork’s lower leg that looks promising for retaining some tube flexibility higher on the fork.

  21. rodneyAB says:

    I’ve been looking at TRP parabox, a master cylinder placed under the handlebars, that would maybe interfere with a bag, but the unit permits use of drop-bar brake lever cables in, and hydraulics out. Seems that cross bikes are moving away from canti’s to discs.

    • David G in Madison WI says:

      In the next few years I think we are going to see Shimano and Sram and other companies release hydraulic disc brakes for cyclocross and road (and rando) bikes with integrated brifters, etc. Then carbon fiber clinchers, which currently are limited by safety concerns related to rim-braking on long descents, among other issues, will be a more viable option. I’d love to try a go-fast lightweight rando bike with really good hydraulic disc brakes, sub-300 gram 650B carbon fiber clincher rims, and tubeless Pari-Moto tires with sealant for flat protection. The Shimano XTR disc brakes on my new MTB are phenomenal. I would be surprised if any experienced mountain biker would say that cantis or V-brakes are better from a braking performance perspective (cost, reliability, ease of setup and maintenance, and aesthetics are different matters). Of course, the downside of utilizing products that push the envelope is that the rider may be more vulnerable to ride-ending mechanicals compared to more simple tried-and-true designs like 500 gram aluminum rims and cantilever and centerpull brakes.

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