Choosing Your Tires

We’ve experienced a profound revolution in road bikes in recent years: It used to be that to go fast, you rode narrow tires and pumped them up to the maximum pressure. If you wanted more comfort, you used wider tires and (maybe) lower pressures, but you knew that you’d be slower.

Now we know that comfort and speed aren’t opposed, but inextricably linked: A bike that absorbs shocks better rolls faster. Narrow tires don’t have any speed advantage, and inflating your tires to the maximum often makes your bike slower.

But what does this means in practical terms, when it comes to choosing new tires for your bike? Do you need to get a new bike with clearances for ultra-wide tires? Or is there a way to benefit from the “tire revolution” on your existing bike?

The simple guidelines below are based on more than a decade of research into the performance of tires, and they’ve proven themselves on the road time and again.

Supple Casing

The most important part of the “tire revolution” is the supple casings. In the past, we thought that supple casings and wide tires didn’t go together well, because supple, wide tires have to be run at relatively low pressures. Now we know that lower pressures don’t make tires roll slower. And that makes a supple casing better in the two important areas of tire performance: A supple casing has less resistance as it flexes (hysteretic losses) and it transmits less vibrations from the road (suspension losses). It’s a win-win scenario.

Compared to the casing, all other factors – width, tread thickness, weight, etc. – are of minor importance. In Bicycle Quarterly‘s tire tests, the five fastest tires ranged in width from 24 to 36 mm, but they all had one thing in common: a supple casing. In practical terms, this means that a supple 25 mm-wide racing tire will be more comfortable and faster than a 42 mm touring tire with stiff sidewalls.

So don’t fret if your bike can only fit relatively narrow tires. Just get the best, most supple ones you can find, and enjoy most of the benefits of the “tire revolution”.

Width

When in doubt, use wider tires. At least up to 42 mm, wider simply is better. More grip, more comfort, same speed, fewer flats. What about the aerodynamics of wider tires? In our testing, both in the wind tunnel and on the test track, we found the effect too small to measure. And when you factor in the greater shock absorption (lower suspension losses) of the wider tires, it’s likely that any small increase in wind resistance is made up by the smoother rolling of the wider tires. On smooth roads, it comes out the same, on rough surfaces, wide tires are demonstrably faster.

Of course, you’ll have to work with the clearances of your bike. Don’t try to squeeze the largest possible tire in there with just a hair’s breadth of clearance. Your tire may “grow” with age or your wheel may go slightly out of true. I recommend a minimum of 3 mm clearance all around the tire. When in doubt which tire will fit, go with a slightly narrower one. If you find that you have more clearance than expected, get the bigger size the next time around.

Wheel Size

When you get a new bike, wheel size is an important consideration. Smaller and/or lighter wheels will be more nimble, larger and/or heavier wheels will be more stable. Ideally, your bike is both stable and nimble: It should stay faithfully on a chosen line, but it shouldn’t resist if you want to change its trajectory. How do you achieve that?

The forces of trail and wheel flop cancel each other, especially on a bike without a front load. That is why the wheel size plays such an important role – you can’t really compensate for a front wheel that is too large or too small.

The bike industry is only slowly waking up to this. Too many gravel bikes still come with the same 700C wheels that you find on racing bikes with much narrower tires. Smaller 650B wheels are a better choice for wide tires – from 40 to 50 mm –  and for even wider tires, I prefer 26″ wheels. That way, you can enjoy the nimble feel of a good road bike and the surefootedness of wide tires…

If you use ultralight carbon rims and superlight tires (like our Compass Extralights), you can go up one wheel size. The larger diameter compensates the light weight to keep the rotational inertia in the “optimum” range.

My “dream bikes” are equipped with either 650B x 42 mm tires (left) or 26″ x 54 mm, depending on whether they will see mostly paved or mostly gravel roads. But in practical terms, I am perfectly happy on a bike with 700C x 32 mm tires (right), provided the tires are supple performance models and not sluggish “touring” tires.

The importance of supple casings isn’t a new discovery. For almost a century, professional racers have ridden supple, handmade tires, no matter whether the fashion was for 30, 20 or now 25 mm-wide tires. In fact, tires are the only thing that hasn’t changed significantly on pro racing bikes during the last 70 years. You could put Fausto Coppi’s tires on Christopher Froome’s bike, and he’d never know the difference.

Outside the pro peloton, the importance of supple tires was largely forgotten as riders became more concerned about flat resistance than the joy of gliding along on a cushion of air. Only recently, supple clinchers have become available that offer the feel and performance of great racing tubulars, but in much wider widths.

Speaking of flats, that is the one drawback of staying with narrow tires. Since they run at higher pressures, they are more likely to puncture. And yet, in my experience, the fear of flats is often overstated. On the beautiful backroads that offer the best cycling experience, flats are relatively rare.

Debris accumulates where cars don’t go, hence you get so many flats when riding on the shoulders of busy highways. On backroads, you ride in the traffic lane (but with little traffic, you don’t bother anybody), so there isn’t much debris that could puncture your tires.

downhill

To summarize, you don’t need a new bike to enjoy the “tire revolution”. For your existing bike, choose tires with supple casings, and use the widest model your bike can fit with safe clearances. And when it’s time to get a new bike, consider getting a bike designed for wider tires and perhaps smaller wheels to get the performance of wide tires with the nimble handling that makes a good racing bike so much fun. It’s that simple!

More information:

Photo credit: Goggles & Dust / Brett Horton Collection (classic racers).

Posted in Testing and Tech, Tires | 43 Comments

Berthoud Saddles and Spare Parts

Berthoud saddles are among the most comfortable in the world. What’s even better, they are fully and easily rebuildable. Every part for the saddles is available from Compass Cycles, and you can replace all parts using standard tools. Berthoud saddles are designed to be easy to work on, even though it is rarely necessary:  The 10-year-old prototype saddle I am using on my Urban Bike shows no sign of wearing out.

The most important spare parts are probably the leather tops (above). After a few decades of hard riding, you may need a new one. Or if you want to change the color of your saddle, it’s easy enough to do. Simply unbolt the top and install a new one.

All the other parts are available as well. If you want a lighter saddle, you can replace your stainless steel rails for titanium ones. A friend once lost one of the bolts on his Berthoud saddle – easy to fix. The front and rear frames have never broken before, but just in case your saddle is involved in an accident, we have the parts in stock. It’s all part of Compass’ commitment to customer service. And if you prefer to have your bike shop service your Berthoud saddle, we wholesale all these parts, too.

In addition to the spare parts, we now have Berthoud’s women’s models, the Marie-Blanque (stainless rails) and Agnel (titanium) in stock. The names are inspired by the high mountain passes where these saddles were developed: The stainless steel models take their names from the Pyrenees, while the titanium-railed saddles are named after passes in the Alps. The women’s models have shorter noses than the men’s saddles. On all Berthoud saddles, the extra “give” of the flexible underframes makes them more comfortable than leather saddles with metal frames.

Berthoud also makes leather handlebar tape, in colors matching those of the saddles (except the “cork” finish). It’s one of the best handlebar tapes you’ll find anywhere.

We enjoy working with Berthoud, because everybody there has many years of experience. Above you see company owner Philippe Marguet (left) and Vincent Crétin (right) examine the hides that will be turned into saddles. Before starting production a decade ago, Gilles Berthoud tracked down employees from the long-defunct French saddle maker Idéale to learn about the craft of making leather saddles.

The same applies to the bags and panniers. For the last 20 years, they all have been made by one woman: Véronique Durand. And she in turn was trained for three years by a seamstress from Sologne, the bag maker that pioneered these bags in the 1950s. All this experience shows in products that are among the best in the world.

Last summer, we cycled across beautiful backroads to Pont-de-Vaux in France, where Berthoud’s workshop is located. We spent a day learning how saddles, bags and other parts are made. We met the dedicated employees, and even had Véronique sign the panniers she made for me 17 years ago (below). We ate a great lunch at a traditional French brasserie and enjoyed a day filled with fun and laughter.

We reminisced about the story behind the bags on my bike: I had to wait six months for these panniers while Véronique was on maternity leave. Gilles Berthoud apologized at the time, but I was glad that she could spend time with her daughter. I think of that every time I use the panniers – and now they even have Véronique’s signature on them. I plan to use them at least for another 17 years!

It’s one of the many fascinating parts of the Gilles Berthoud story. For a detailed feature on the company, with many photos, check out the Summer 2017 Bicycle Quarterly.

To find out more about Gilles Berthoud products, click on the links below:

Posted in Saddles | 13 Comments

Riding My René Herse

In recent months, I’ve been traveling and testing so many bikes for Bicycle Quarterly that I my “main” bike, the René Herse, hasn’t seen much use. But now the Summer BQ is out, and I am back on my favorite bike. We built it six years ago as a prototype to try new ideas – wide, supple tires; superlight tubing; centerpull brakes; low-trail geometry; and even some special 1940s derailleurs: the front is operated by a direct lever, while the rear is a Nivex with desmodromic actuation and constant spring tension.

To some, the Herse may look like a classic from a bygone time, but its performance is totally modern. I choose it when I want to go far and fast, so I’ve ridden it in 2 Paris-Brest-Paris, 2 Raids Pyreneen, the Oregon Outback, many other brevets and adventures, plus our usual fast-paced rides around Seattle.

Check out the video above to see what it’s like to ride the bike, and how those derailleurs work. (Make sure to view it in “Full Screen” mode.)

What the video can’t convey is how the bike feels. It’s quite different from riding the modern machines: If I had to summarize it in a single word, it feels light. Not because it weighs very little (although at 11.3 kg / 25 lb, it is lighter than most fully equipped bikes). BQ‘s recent test bikes didn’t have fenders, racks and lights, so they weighed even less. The Herse feels light and small to the point where it almost disappears underneath me.

The narrow tread (Q factor) of the cranks lets my pedal stroke flow easily, whether I’m just spinning along or racing uphill at maximum speed. The low-trail geometry requires only a light touch to direct the bike where I want to go. The thin handlebars, wrapped only in cloth tape, invite this light touch. The brakes don’t require manhandling either, yet they aren’t as grabby as some hydraulic discs. Even the derailleurs’ action is light – they feel lighter than even Di2 paddles. And all these controls have similar weights – which is very important to me, because it makes every action on the bike feel completely natural.

I find it interesting to compare the Herse to the other bikes I’ve ridden in recent months. The closest in feel is my Firefly. This may come as a surprise, as the Firefly is a modern titanium bike, but both frames respond similarly to my pedal strokes. The Campagnolo Ergopower feels similar to the Nivex, too: Shifts require only small hand movements, but both derailleurs respond best to decisive shifts. Punch the levers home, and you get quick shifts. If you are hesitant, the gears may not engage cleanly.

Both bikes have low-trail geometries, and the inertia of the wheels is similar, too: The Firefly has wider 54 mm tires, but smaller 26″ rims, whereas the Herse runs 650B x 42 mm tires. That means their handling is similarly intuitive. Where the two feel different is when riding out of the saddle: The Firefly has less inertia to rocking the bike from side to side, since it doesn’t have fenders nor a rack. So I enjoy the Firefly as a racing bike, for fast-paced rides that don’t require carrying much in terms of supplies. The Herse is a bike that can traverse entire states without stopping. And since their frames allow me to reach my maximum power output, their speed is exactly the same.

How about the Mule? Outwardly similar – it’s also a 650B randonneur bike made from steel – it feels quite different. Due to its oversized down tube, the frame responds differently to my pedal strokes. Designed to carry a heavier front load, the Mule also has a little more trail. As a result, the Mule feels more planted – more “modern”, if I dare say so – than the Herse. The Mule is a great bike that especially comes into its own when carrying heavy front panniers on the low-rider rack.

I greatly enjoyed our last two test bikes, the Open (above) and the Boo. Made from carbon and bamboo, they had stiffer frames and a completely different feel. They required me to be more on top of my game, to think more about pedaling smoothly and with power. Their geometries had more trail, which makes them better suited to riders who grip the handlebars firmly. I prefer to guide the bike with a light touch – like a good horse – so I enjoy low-trail geometries for the precision (not much trail) and stability (not much wheel flop). Don’t get me wrong – these are great bikes, but for me, they’d work better if they had more frame flex and less trail.

In the end, I enjoy the Herse so much because it feels like an extension of my body. When I ride it, I don’t think about the bike. And that let’s me enjoy the ride even more.

As to the prototype parts that I’ve tested on this bike, many now are available from Compass Cycles: Supple, wide tires that combine speed with comfort. Handlebars shaped for comfort even after ten hours on the bike. Centerpull brakes that are superlight in weight and offer great stopping power and modulation. René Herse cranks that allow you to choose gearing suited to your riding style. Supple fork blades for a little extra suspension.

What about those eye-catching derailleurs? I put them on the bike because I was curious about them. I like them a lot, but I don’t think they change the riding experience as much as the parts mentioned above. I’m perfectly happy with the “standard” derailleurs on my Mule, and I also enjoy the Campagnolo Ergopower on my Firefly. That said, the Nivex rear derailleur in particular does point out areas on modern derailleurs that could be improved, but that is a story for another day…

Posted in Rides, Testing and Tech | 20 Comments

Expert Discussion on Frame Stiffness

“I no longer believe that the ultimate rigidity defines the ultimate bike!” That revolutionary statement came from Damon Rinard, Road Engineering Manager at Cannondale, in a recent Cyclingtips.com podcast on frame stiffness and “planing”.

For many decades, stiffer frames were thought to perform better. Frame flex was equated with wasted energy. And yet there were some who had doubts about this. I recall Peter Weigle telling me many years ago, when I complained about a test bike that just didn’t seem to perform: “Perhaps it’s too stiff for you?”

Back then, the idea that frame stiffness could negatively affect performance seemed far-fetched, but the more we researched it, the more we found that some frames performed better than others. And for us, more flexible frames – as long as the flex was in the right places – performed better. We coined a term for this: “Planing” took the image of a boat that rises out of the water and goes faster with less energy than when it was fully submerged.

Even though the concept wasn’t entirely new, “planing” went against decades of accepted wisdom in the bike industry. Our double-blind studies (above) were carefully designed, but at first, they were met with incredulity or even derision. After all, bike makers spent significant resources figuring out how to make their frames stiffer, and magazines determined the “stiffness-to-weight ratio” as the ultimate measure of a frame’s performance. How could all this be wrong?

Recently, James Huang, technical editor of the popular web site Cyclingtips.com, asked me whether I could participate in a podcast on frame stiffness with Damon Rinard from Cannondale. Cannondale! The company’s bikes are famous for their stiff frames, and Damon is one of the foremost researchers on frame stiffness. I was bracing for a heated discussion!

But Damon is a smart guy, and rather than accept the conventional wisdom that frame flex is lost energy, he has tried to quantify these losses. And he came up empty-handed. It appears that no energy is lost when the frame flexes. There is no doubt that bike frames flex, but apparently, that energy is returned to the drivetrain, so it powers the bike forward.

That formed a fascinating basis for our discussion. We both agree that frame flex doesn’t rob energy. But could it be beneficial? Click here to listen to the podcast and hear the entire discussion.

Further reading:

Posted in Testing and Tech | 53 Comments

Compass 700C x 35 mm and 38 mm Back in Stock

The long days of summer see us heading far into the mountains. Often, our ambitious plans push the limits of even the longest days… Above, Natsuko descends the incredible chain of passes in the Cevennes mountains of France. This amazing tour is featured in the latest Bicycle Quarterly.

Just in time for the adventures of the summer, our latest shipment of Compass Barlow Pass 700C x 38 and Bon Jon Pass 700C x 35 mm tires has arrived. We appreciate your patience while demand outpaced supply during the last few weeks. All of us at Compass Cycles work hard to keep all our products in stock at all times. Because for us, excellent tires are essential supplies for great rides.

Click on the links below for more information about:

Posted in Bicycle Quarterly Back Issues, Tires | 8 Comments

Exploring a Foreign City by Bike

Unpublished photos are fun, especially when they tell a different story from the one featured in Bicycle Quarterly. When I was cleaning out old photo files, I was reminded of our trip to Mexico City a little over a year ago. The main reason to visit Mexico with our bikes was to cycle across the Paso de Cortès (BQ 56) and around Cuernavaca (BQ 59). In between these trips, we were based in Mexico City, and we used the opportunity to explore this fascinating city on our bikes. Part of the reason for our early-morning exploration was to photograph the Firefly test bike for the magazine… but as it turns out, the photos talk as much about the setting as they do about the bike.

Most of our rides were in the morning, before the city woke up. As our tires pattered over the ancient stone pavements, we rolled by the stalls of the shoe-shine people, still folded up and waiting for the day’s work.

The stores were still closed, too. From the signs, we could tell that each street specialized in one product, making shopping easy. If you need a wedding dress, you come to Calle Honduras (Honduras Street), where you can choose among at least a dozen stores with bridal gowns and dresses.

We could not figure out what the “Fancy Moustache” store sells. Whatever it is, the shutters say: “For connoisseurs only…”

The streets were empty. Except for the early-morning deliveries. Many came by bicycle, like the ice delivery on this ancient-looking bicycle with a sidecar. At each shop, the man chopped off a block of ice and dragged it into the shop with his special pliers. Then he continued to the next store, leaving behind a faint trace of water as his giant ice cubes slowly melted.

Mexico City is incredibly colorful…

…but also full of ancient history. The colonial architecture is amazing, with beautiful old woodwork…

…and many of the old buildings reuse stones from the great pyramids of Tenochtitlan, as this city was called before the Spanish conquered it. Seeing all this in the magic early morning light was special.

By the time we returned to the main square with its giant cathedral, the city was waking up. We visited during the Semana Santa (Easter Week), so the main square was closed to cars. Every day, a different festival was taking place: a rock concert on the night we arrived; a baseball game the next day…

Cyclists joined the many pedestrians that were beginning to crowd the streets. The sun was getting too high for photography. Time to return to our hotel for breakfast.

From the rooftop terrace of the hotel’s restaurant, we saw the small volcanos that dot the Valley of Mexico. In the distant haze, we could see the giant peaks that were the destination of our cyclotouring adventures. But in the mean time, cycling in Mexico City was worth the trip by itself.

During future travels, I plan to do more exploring by bike. It’s a unique way of seeing a city. You cover ground more quickly than on foot, yet it’s easy to slow down or stop to take in the sights. In many cities, you don’t even have to bring your own bike, since there are excellent bikesharing programs, like Mexico’s Ecobici. I hope this summer will take you exploring to great places!

And if you missed the Bicycle Quarterlies with the stories about Mexico (BQ 56 and 59), back issues are available. Or order the complete set of the last year’s four issues, which includes these and many other exciting articles.

Posted in Rides | 9 Comments

The Trouble with “Road Tubeless”

It’s always interesting when bike industry people talk among each other, off-the-record. On the ride from the airport to Paul Camp a few weeks ago, one bike tester was still visibly shaken when he related: “My tubeless tire blew off the rim yesterday. I almost crashed.” Worried that this might have been one of our tires, I asked about the brand. He mentioned a big maker, known as a pioneer of  “Road Tubeless”. The tester continued: “I had it inflated to 90 psi, well under the max. I was just riding along, when suddenly – bam!”

Tubeless tires are becoming popular these days. Using inner tubes inside your tire almost seems like a throwback to the 1950s. Cars have not used inner tubes in over half a century, and mountain bikes have gone tubeless, too. Many of us have been riding our Allroad bikes, with their wide tires, tubeless for years.

Finally, road bikes, with narrower tires, are going tubeless, too. But it hasn’t always been smooth sailing: There are more and more reports of tires blowing off the rims. What is going on? Why are tires with inner tubes safe at high pressures, but the same tires sometimes blow off the rim when mounted tubeless?

An inner tube doesn’t just hold air, it also reinforces the joint between the tire and the rim. Air pressure pushes the tube against the tire so that it no longer can move independently. For the tire to blow off, a very small section of the tube must stretch tremendously, so the tire can climb over the rim’s edge. As flexible as inner tubes are, they get to a point where they don’t stretch any farther – pull on a tube, and you’ll notice this. That makes it very hard for the tire to blow off the rim.

Without an inner tube, there is nothing reinforcing that joint. If the fit between rim and tire is even just the slightest bit loose, the tire can slide upward, and – bam! In fact, even with a perfect fit, there is a point at which a tire blows off the rim: Tire beads can stretch a little, and the higher you inflate the tire, the more force there is stretching the bead. That appears to be the root cause of the problem: Road tires typically are run at relatively high pressures.

Thinking about this, I realized that “Road Tubeless” is a bit in uncharted waters: Usually, tubeless tires run at much lower pressures. Tires for cars and motorcycles are generally inflated to less than 45 psi. (The exception is airplane tires with up to 200 psi, but those are a very special design.)

All these tires also are much stiffer than bicycle tires, which helps them stay on the rim. A supple tire can move in just one small spot, which makes it much easier to climb over the rim’s edge. I was surprised at Paul Camp to hear about the tester’s experience with a tire that isn’t even known for its supple casing. But compared to car or motorcycle tires, even stiff bicycle tires are supple…

There have been a few isolated reports of our 700C x 35 mm Bon Jon Pass tires blowing off the rims, too. We’ve wondered whether perhaps there was a manufacturing error. We mounted one of the tires from that production run on a wheel with a Reynolds carbon rim that we had measured carefully to make sure its diameter was exactly to spec. We inflated the tire to its maximum pressure of 90 psi (6.2 bar) – without problems. The pressure has already gone down to 85 psi by the time I took the photo – there was no sealant in the tire for reasons that will become apparent in the next paragraph.

I then inflated the tire further. 100 psi was fine. 105 psi, no problem. A few more pump strokes, about 108 psi, and – bam! The tire blew off the rim. I was wearing ear protection, and there was no sealant inside the tire, so no damage was done.

Of course, few people would inflate a 35 mm tire to 108 psi (7.6 bar). Even with tubes, the Bon Jon Pass is rated to a maximum of 90 psi (6.2 bar). And as long as everything is perfect, you can run them tubeless at this pressure, too. But in the real world, not everything is perfect. The diameter of different rims can vary considerably. Panaracer’s engineers found that the rims on many production bikes are a bit smaller than spec, because that makes it easier to mount the tires on the assembly line. Of course, this also results in a looser fit of the tires.

This also explains why the few instances of Compass tires blowing off the rims have mostly been with Bon Jon Pass tires: They are our narrowest tubeless-compatible tire – 35 mm wide – and people tend to run them at higher pressures. On the other hand, the gravel racers love this tire and report zero problems despite the often brutal riding conditions. But they run their Bon Jons at 60 psi or less…

Over the last year, I’ve been testing every model of tubeless-compatible tire in the Compass program. I’ve mounted them without tubes on a range of bikes, both Bicycle Quarterly test bikes and my own machines. I’ve experienced zero problems, but I also run them at pressures of 60 psi (4 bar) or lower. I remounted the Bon Jon Pass that blew off the rim and inflated it to 60 psi, put in some sealant, and took it for a couple of rides. As expected, it was fine.

Based on this experience, we recommend: Do not exceed 60 psi (4 bar) when running Compass tires tubeless. If you need higher pressures, please use tubes. Since the problems with running tubeless tires at high pressures are not limited to Compass tires, I’d recommend this for all tubeless tires – and especially for high-performance tires that are relatively supple.

BJPASS_result-750x481

However, you also don’t want to run too low a pressure with tubeless tires. If the tire flexes excessively, this will break down the casing until it starts to leak (above). With a narrow tire, you have a narrow window between “too high” and “too low” pressures. On a 35 mm tire, 60 psi (4 bar) still is plenty for most riders. (I usually ride my Bon Jons at about 35-40 psi.) But if we were to offer a 26 mm-wide tubeless-compatible tire, 60 psi isn’t enough even for a light rider. Yet going higher than 60 psi would risk blowing the tire off some rims.

With wider tires, you don’t have that problem. I run the 54 mm-wide Rat Trap Pass tires on my Firefly at 40 psi (2.8 bar) on smooth roads. At such a “high” pressure (for tires this wide), the bike feels like a racing bike. On gravel, I can go down to 22 psi (1.5 bar) without risking damage to the casings. I run them tubeless now, after suffering two pinch flats during the Otaki 100 km Mountain Bike Race in Japan (above). As I found out, riding over really rough ground at very high speed will pinch-flat even 54 mm tires!

I feel that for riding on rough gravel, tubeless really is the way to go. Choose tires that are wide enough, run them at low pressure, and you shouldn’t have trouble. (Unless your rims are way out of spec.)

For road riding, the advantages of tubeless tires are less clear. Pinch flats are much less of an issue on the road, unless you still ride ultra-narrow tires. All the testing I’ve seen – including our own – indicates that the rolling resistance of tubeless tires is no lower, and perhaps even higher, than using thin, lightweight inner tubes. That isn’t surprising: You replace an ultra-supple inner tube with a liquid sloshing around inside your tire.

What about flats? One nice feature is that the sealant inside the tubeless tire automatically seals small punctures. But it appears you don’t have to go tubeless for that: Some riders use sealant inside their tubes. They report that it also seals small punctures in the tube – provided you use it from the start, when you mount a new tire. (With an old tire, during a puncture, the air may not escape through hole that is right above the puncture in the tube, but through a bigger hole from a previous puncture that is elsewhere in the tire. Then the sealant flows into the space between tire and tube, creating a mess without sealing the tube.)

Based on all of the above, we concluded that at this time, running high-pressure tires tubeless isn’t worth the risks. Can these issues be resolved? It’s difficult to say. Perhaps “Road Tubeless” is the way of the future, or perhaps it’ll be like radial tires for bicycles. Cars have used radials for decades, but for bicycles, they never caught on.

What needs to happen to make tubeless tires safe even at high pressures? Clearly, the interface between tire bead and rim must become more standardized, and manufacturing tolerances must become tighter. With a “perfect” rim, it’s already fine to run our 35 mm tires tubeless at 90 psi, but how do we get all rims to be perfect?

It might also help to increase the size of the interface between rim and tire bead. Modern cars have rim flanges that are 17.5 mm tall – three times as tall as most bicycle rims. However, that means a complete redesign of the tire/rim interface, with the result that the new tires would not be compatible with old rims, and vice versa.

The tire bead also might have to become less stretchy, but there are downsides to this. Tubeless-compatible tires already have stiffer beads than “standard” models. There aren’t any stiffer materials than what is being used, so making them even stiffer means adding weight and bulk. We haven’t given up hope yet: Together with Panaracer, who make our Compass tires, we continue to research tubeless technology in the continuing quest to improve our tires further.

For now, here is the take-home message for running tubeless tires:

  • For tubeless, we recommend a maximum pressure of 60 psi (4 bar).
  • If you are riding on gravel or rough stuff, tubeless eliminates pinch flats. And you’ll be running less than 60 psi anyhow.
  • If you ride on the road and need more than 60 psi, use inner tubes. Not just with Compass tires, but with other brands as well.
  • Even on smooth roads, Compass’ wide tires roll as fast as our narrow ones. Getting wider tires and running them at pressures below 60 psi is a good way to use tubeless on the road.
  • When mounting a tire tubeless, first inflate it 20% higher than the pressure you’ll be riding. Let it sit for a while to make sure it will not blow off your rim. Then decrease the pressure before you ride the bike. That way, you know that you aren’t at the upper pressure limit for that particular tire/rim combination.

Tubeless technology holds great promise, but like everything, it should be applied where it makes sense and where it is safe. In a future post, we’ll talk about tips on how to set up Compass tires tubeless.

Photo credits: Nicola Joly (exploded tire), Cyclocross Magazine (damaged casing), Toru Kanazaki (Otaki 100 km Race)

Posted in Testing and Tech, Tires | 131 Comments