Bon Jon Pass Review: “An Exceptional Tyre”

“An exceptional tyre that will make you faster and happier.” That was the verdict when the British web site http://www.road.cc tested our Bon Jon Pass tires recently. When we hear positive feedback, whether it’s from a professional tester or a customer, it makes our day.

I smiled when I read the calculation of the weight savings. It appears that, on average, spending a British pound ($1.28) will make your bike 1.91 g lighter. Based on that metric, the tester explained that choosing “the Compass Bon Jon Pass Extralight over the Schwalbe G-One Speed was ‘worth’ £157 of savings elsewhere. Ergo, at £67 RRP, the Bon Jon Pass is a ridiculously cost-effective weight saver.” I’m not sure about the math, but it does show that lightweight tires are the easiest way to shed significant weight, especially with wide tires where the weight differences can be quite large.

More importantly, the tester liked the supple casing and the excellent grip and comfort in the real world of the Scottish Highlands: “I hardly noticed broken patches of chip seal, or small gaps and lips of manhole covers. I found myself thinking up tests for what I could and couldn’t feel through the bike’s contact points.”

Negatives? Tubeless setup with supple tires is inevitably a bit trickier – the fit between tire and rim must be ‘just right’ and the thin casing is more likely to leak air until it seals. And his riding partners apparently weren’t always happy: “I realised I wasn’t signalling road surface irregularities as much as I should be to my sub-30mm-shod brethren following behind.” Until they switch to supple, wide tires, too…

No bike test would be complete without commenting on performance – “These are fast tyres, period. World-beatingly fast.” – and price – “I believe they are worth every penny.” 

There isn’t much we can add. We developed our tires because we wanted faster and more comfortable tires for our own bikes. When others enjoy them as much as we do, it makes us happy, too.

Further information:

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Ultralight Handlebar Bag Pre-Order

How do you make an ultralight bag? That was the first question when the Concours de Machines announced that the weight of the bikes included the bag.

Peter Weigle worked very hard to get his fully equipped bike down to just 20.0 lb (9.07 kg), and we wanted to make sure the bag was also as light as possible.

Gilles Berthoud bags already are among the lightest bags available today. Even so, we knew savings were possible without compromising its size or performance. The result is on the left in the photo above, with the standard bag on the right for comparison.

Together with our friends at Gilles Berthoud, we decided to use the same canvas fabric and leather as on the standard bags: Thinner materials wouldn’t last as long.

The first step was to remove the outside pockets. We gave up a little capacity and convenience, but gained significant weight savings. Next, our friends at Gilles Berthoud reduced the leather reinforcements to an absolute minimum.

They examined every part of the bag to see where weight could be saved. Above are studies for the attachment to the rack backstop. In the end, they replaced the strap with a short sleeve that slips over the rack backstop and also anchors the hook for the closure. It’s by far the lightest and simplest solution.

We thought about eliminating the map pocket, but I felt that it was essential. The goal with this project wasn’t to create the lightest bike at all cost, but a no-compromise machine that will be ridden hard for many years. How about reverting to the older style of map pocket that is open on the side, rather than using a Velcro closure? That is a small compromise, and it saves valuable grams. There are a few other weight-saving details, but we also added a little piece of leather with the Gilles Bethoud logo to the front of the bag. It may weigh 3 grams, but those who created this amazing bag deserve credit.

The result? The entire bag weighs just 266 g. That is less than half the weight of the standard bag (which is already very light). And this is the GB28 – the largest size – which holds a whopping 13 liters. I can’t think of any other adventure-sized handlebar bag that comes close to being this light.

The bag has lived up to its promise. I’ve used it quite a bit in all kinds of weather – that is why it no longer looks brand-new in the studio photos. Since the fabric and leather are the same as the standard bags, it should last as long. (My very first Berthoud bag, which I bought in 2000, is still going strong.)

And it’s as waterproof as the standard bags – the cotton fabric swells when it gets wet, and even after hours in the rain, there is no water inside. (I place my notebook and other moisture-sensitive items in a Ziploc bag as a precaution.)

There is one other modification we made compared to the standard bags: Since there is so little leather, the ultralight bag is less stiff than the standard model. So we made a very lightweight aluminum stiffener that attaches to the decaleur and to the small inner flaps with Velcro. (The large flaps keep the contents in the bag on really rough terrain, so we kept them, too. The flaps also allow you to overstuff the bag, which is useful during long events. Plus they keep out the rain.)

Does a superlight handlebar bag make sense when its contents will weigh more than the bag? Like the trunk of my car, my handlebar bag rarely is filled to the brim. It just gives me options. I can start a ride before sunrise, dressed for chilly temperatures, and then shed layers as it warms up. I can bring a camera and take photos when the mood strikes. I can even swing by the farmers’ market on the way home and pick up some fresh vegetables for lunch. A superlight bag makes sense in the context of a fully equipped bike that offers the performance of a racing bike with the versatility of fenders and lights.

In addition, I want a bag like this for long-distance events like Paris-Brest-Paris or the Raid Pyreneen, where I count every gram before the start. I plan my stops carefully, and I carry enough supplies to limit my off-the-bike time to the absolute minimum. A superlight bag is among the easier ways to save weight on my bike. (For cyclotouring where a few minutes make no difference, I definitely recommend the standard bags.)

We are now offering the ultralight Concours de Machines bag in a limited, one-time production run. It will be available in three sizes, and it will incorporate a few small changes based on what we’ve learned from the prototype. It will include the stiffener that is designed to attach to a decaleur. The rear sleeve fits on a rack with a backstop no wider than 48 mm – perfect for our Compass/Rene Herse racks.

If you would like one of these bags, please pre-order by January 15. The bags will be delivered in March, so you can use it in this year’s 1200 km Paris-Brest-Paris.

More information:

  • Pre-orders will close on January 15 at midnight, Pacific Time.
  • Bag includes aluminum stiffener.
  • Available in three sizes: GB22, GB25 and GB28, with gray fabric
  • Bags will be delivered in March.
  • Click here to pre-order ultra-light bag.
  • Peter Weigle’s ultralight bike for the Concours de Machines
  • Click here for more information about all Gilles Berthoud bags.
Posted in Racks/Bags | 17 Comments

Remembering Lyli Herse’s Birthday

Today would have been Lyli Herse’s 91st birthday. And last Friday has been a year from her passing…

… and the 111th birthday of her father, René Herse. They continue to inspire us in so many ways. Today, we just want to remember their smiles and their passion for cycling in all its forms.

Lyli was a friend for so long that it’s hard to believe she’s gone. Until the very end, she rode her home trainer, but she told us that she dreamt of cycling in the mountains.

We miss her! She passed on her family’s legacy to us, and she told us that her father would have been happy to see so many people passionate about rides and adventures again. Together, let’s keep their spirit alive!

Posted in Uncategorized | 5 Comments

Myth 16: Higher Tire Pressure is Faster

This used to be one of the first things you learned as a cyclist: If you want to go fast, make sure your tires are pumped up to the maximum pressure. The harder your tires are inflated, the faster they roll.

We now know that this isn’t true. The realization that tire pressure does not affect performance is the key to the revolution that has swept through the cycling world in recent years. Without this new-found knowledge, all-road bikes and their supple, wide tires would make no sense at all. Here is how it works.

Tire resistance is determined by two factors:

Hysteretic Losses: With each turn of the wheels, the tires flex. You can see that in the photo above: Both tires flatten where they touch the road. Flexing the tires takes energy – imagine squeezing a tennis ball. Energy on a bike can only come from one source: the rider’s power output. Reduce the energy lost to flex, and you’ll go faster.

The easiest way to reduce this energy loss: Inflate the tires more, and they’ll flex less. Less flex means less energy is converted to heat as the tire casing deforms under the weight of bike and rider.

You can also reduce the losses by making the tire casing easier to flex. A supple casing is easier to flex than a stiff one, so it absorbs less energy for the same amount of flex. Imagine squeezing a marshmallow instead of a tennis ball.

So we want a tire that is supple and runs high pressures. That means we have to make it narrow. Why can’t a wide tire be supple and run at high pressures?

Pressure is force per surface area. For example, PSI stands for Pounds per Square Inch. The larger the tire’s circumference (more inches), the more force will act on it (more pounds). Imagine the casing as a chain, with the pressure as an elephant standing on each link. If the chain is ten links long, it has to support the weight of ten elephants. Make the chain twice as long, and you’ll have twenty elephants standing on it. The chain has to be twice as strong. Or you have to reduce the weight of each elephant. Back to tires, this means that a wider tire either needs a stronger (read: stiffer) casing, or you need to reduce the pressure.

Summary: The best way to reduce hysteretic losses is to use supple tires, make them narrow, and inflate them hard. With wider tires, you either can have a supple casing or high pressure, but not both. Either way, wider tires will have more hysteretic losses. If you only look at hysteretic losses, ‘wide high-performance tires’ seems like an oxymoron.

That was the accepted wisdom when we started looking at tire performance way back in 2007. It’s not incorrect, but it overlooks a second factor that also affects how fast a bicycle rolls – and tire pressure works the opposite way there.

Suspension Losses: As the bike vibrates, energy is lost. Most of that energy is absorbed in the rider’s body, as soft tissues rub against each other. Decades ago, the U.S. Army studied tank seats and found that the discomfort we feel from vibrations is caused by friction between our body’s soft tissues. This friction consumes energy that is turned into heat. (Rub your hands against each other to see how friction creates heat.) The more uncomfortable the vibrations, the more energy is lost.

Mountain bikers have known for a long time that bouncing makes your bike slower. The fastest mtb is the one that absorbs shocks best. Road cyclists used to think that we had to ‘tough it out’ to go fast. We endured the discomfort of narrow high-pressure tires because we thought that they rolled faster. We thought that pavement was too smooth for suspension losses to matter.

At Bicycle Quarterly, we started to test the performance of tires on real roads in 2007. At first, we also assumed that higher pressures rolled faster. However, as long-distance cyclists, we suspected that there was a point of diminishing returns. Our thinking was this: In a short race, we may endure all kinds of discomfort if it makes us faster. But we can endure discomfort only for so long before it affects our power output. In a ride as long as the 1200 km (750 miles) of Paris-Brest-Paris, we might give up 5% in rolling resistance if we gain 20% in comfort. What we wanted to know: Where is this point of diminishing returns?

Back then, tire resistance was tested on steel drums that measure only the hysteretic losses. On steel drums, there is no doubt that higher pressures produce better results – as shown by all tires in the table above. Take the Vittoria Rubino Pro (second from bottom): At 60 psi, it requires 40% more energy than at 120 psi. I mention this tire, because later on, you’ll see how it performs under real-world conditions.

Drum tests also suggest that high pressure is more important than a supple casing: In the table above, the slowest tire at 120 psi has less resistance (13.4 W) than the second-fastest tire at 60 psi (13.9 W). That is why tire makers used to make their wide tires with stiff casings, so they could withstand high pressures. A wide, supple tire – limited to a low pressure rating of, say, 60 psi – would perform poorly on the steel drum. That is why they didn’t exist – who would want to make a slow ‘high-performance’ tire? It all made sense – if you test tires on steel drums.

Imagine our surprise when we found that in the real world – on real roads – tires perform very differently. We tested numerous tires, with two different methods (roll-down and power-meter), and always found the same: Higher pressures don’t make tires faster. And the advantages of supple casings are much larger than the steel drum tests suggest.

Why? Because the suspension losses are significant even on very smooth roads. And both lower pressures and supple casings reduce the vibrations of the bike and thus the suspension losses. But you cannot measure suspension losses unless you have a rider on the bike. That is why earlier studies (and many since) failed to give meaningful results…

Above are the real-road results for three Vittoria 700C x 25 mm tires, including the Rubino Pro. We tested on brand-new, ultra-smooth asphalt. For the Rubino, there is no difference in speed between 80 and 11o psi. It’s clear for all tires: Higher pressures don’t make them faster.

(Note that the Watts are for the entire bike and rider, not just for one tire. That is why the power measurements is so much higher than in the drum tests.)

What happens is this: As tire pressure increases, the tire flexes less, and the hysteretic losses go down. However, the tire also vibrates more, and the suspension losses increase. The two roughly cancel each other, and that is why there is no clear trend in the table above.

Before we continue, it’s important to mention that we made sure these results are statistically significant. This means that we are seeing real differences in performance, not just ‘noise’ in the data.

The graph shows a few more things:

  • Really low pressures make a tire slow, because it flexes way too much: the hysteretic losses are huge. The extreme is a totally flat tire – very slow. At some point, the tire has enough air to avoid excessive flex. Above this ‘break point,’ hysteretic and suspension losses start to balance each other.
  • Hysteretic and suspension losses are non-linear, so they balance differently for different tires and different pressures.
  • CX Tubular: A tubular tire sits on top of the rim, so it can flex around its entire circumference. It can run at very low pressures without excessive flex. The break point is low (80 psi).
  • CX Clincher: A clincher rim constrains the tire around about 1/3 of its circumference, so higher pressure is needed to avoid excessive flex. The break point is a bit higher (87 psi).
  • Rubino Clincher: The Rubino’s stiffer casing is harder to flex: The hysteretic losses for the same amount of flex are higher. The stiffer casing also transmits more vibrations, so low pressure doesn’t reduce the suspension losses to the same amount. This means that the break point is higher than for the more supple CX (95 psi).
  • All three tires roll slowest at moderately high pressure: The tire is already too hard to absorb vibrations, so suspension losses are high. However, the casing still flexes, so hysteretic losses are also high. It’s better to run low or very high pressures, at least on the very smooth asphalt of our test track.

Summary: On real roads, even smooth ones, higher pressures don’t roll faster.

We tested many tires – above from our first tests in 2007 that measured the time for a roll-down on a carefully chosen test hill – and we always found the same: Above the break point, increasing the tire pressure doesn’t make you faster. The break point is higher for stiffer tires. For the tubulars, the break point is lower than the pressures we tested.

I wish we had done this testing when I was still racing. Back then, I ran 21.5 mm Clement Criteriums at a bone-rattling 130 psi. I would have been faster – much faster – on 28 mm Campione Del Mondos at much lower pressures.

The above results were on ultra-smooth pavement (Vittoria) and relatively rough, but not bumpy, pavement (others). Does the road surface affect a tire’s break point?

To test the extreme, we ran various tires on rumble strips, which are a good stand-in for cobblestones. (Unlike real cobblestones, rumble strips are very regular, so we could obtain repeatable results.) We also tested each tire on the smooth pavement right next to the rumble strips.

On the smooth pavement (left), the Compass 26 mm tires roll as fast at 75 psi as they do at 95 psi. This confirms what we’d found before: Even on smooth roads, tire pressure makes no difference.

On the rumble strips (right), higher pressure was slower: The 26 mm Compass tires used 20% more energy at 95 psi than they did at 75 psi.

Summary: On really rough surfaces, higher pressures roll slower. Wider tires roll faster on rough surfaces because they can handle lower pressures.

So now we know that higher pressures don’t make your bike faster – whether on ultra-smooth asphalt, on rough surfaces like cobblestones, or anywhere in between. For supple tires, the break point – even on smooth surfaces – is close to the point where the tire becomes unrideable, because the sidewalls collapse under hard cornering. On rough surfaces, it’s hard to reach the break point – the tire pinch-flats before its performance deteriorates.

Conclusion: If you want to go fast, you need supple tires. That is all. Pumping them up harder won’t make you faster. On rough surfaces, it actually makes you slower.

When we saw these results, we realized that this could revolutionize bicycles: If we didn’t need to high pressure to go fast, we could make wide tires with supple casings, run them at low pressure, and still roll as fast as we did on narrow ‘racing’ tires. With these wide, supple tires, we could go on roads and trails that wouldn’t be much fun on a traditional, narrow-tire racing bike.

We envisioned a new breed of bike – racing bikes with ultra-wide, supple tires – and we called them ‘Allroad Bikes’ (still without a hyphen). That was way back, in 2007.

The first step was to make the tires needed for these all-road bikes. First we worked with other manufacturers, but in order to get exactly the tires we wanted, we introduced our own Compass tires in truly wide widths (above). It’s taken the bike industry a little while to get on board, but now our ideas are generally accepted: all-road bikes are the most important segment in the performance bicycle market.

All-road bikes are more than a passing fad, because they finally correct one of the shortcomings of traditional performance bikes: the need to trade comfort for speed. Now we know that discomfort not only is unpleasant, it actually slows you down. Put more simply:

Comfort = Speed

Cycling has become much more fun on all-road bikes that combine the fun of riding a performance bike with the comfort and go-anywhere ability of wide tires. They are the bikes of the future, and they are here to stay.

As Compass becomes Rene Herse Cycles this year, we will continue to push the envelope beyond what most people think possible. The latest development are our dual-purpose knobbies that roll as well on pavement as many racing tires and offer great traction in mud and snow. It’s going to be a fun ride!

Further reading:

Posted in Testing and Tech, Tires | 35 Comments

Happy New Year

We are looking forward to another great year! We wish all our readers joy, happiness and many great rides in 2019. See you on the road!
—The BQ and Compass/Rene Herse team

Photo credit: Ryan Francesconi

Posted in Uncategorized | 3 Comments

What Makes a Good Winter Tire?

Winter riding is fun. The crisp air, the clear skies and the beautiful views. Getting out and breathing fresh air. There are many reasons to enjoy it.

Winter riding requires preparation. The most obvious is clothing – which we’ll leave for another post. Today, let’s talk about what makes a good winter tire.

Cold temperatures make rubber less grippy. There is no way around this. In theory, it should be possible to formulate rubber compounds specially for optimum grip in cold conditions. In practice, many ‘Winter Compound’ bicycle tires offer less grip in cold conditions, rather than more.

With all tires, you need to consider the reduced grip when it’s cold. Especially on familiar routes, it can come as a surprise when the grip suddenly bleeds away, at speeds that are well within the limits when the temperatures are warmer.

Having ridden many tires in cold conditions, I can say with confidence that the rubber compound of our Compass tires is among the most grippy you’ll find anywhere, cold or warm, wet or dry.

The chevron tread of Compass road tires helps to improve traction by interlocking with the road surface – which works regardless of the temperature. Even so, take it easy during cold days!

What about snow? Snow is surprisingly grippy. How much tread you need depends on the temperature: Cold snow requires only a chevron tread, like that of our road tires, to hook up. (You’ll see an imprint of the tire tread on the snow surface.) But when the temperatures are around freezing, the slushy snow is slippery, and you really need knobs to get good grip. (The knobs don’t hurt when it’s colder, either.)

Should a snow tire be wide – to float over the snowpack? Or narrow – to cut through the snow and try to find grip on the ground underneath?

Rally cars use narrow tires in snow. They are heavy and powerful, which allows their tires to dig down to a firm surface underneath the snow.

Snow cats use the opposite approach: Their wide tracks allow them to travel on top of deep snow without sinking in.

For bicycles, wide tires seem to be a better choice. Compressing the snow takes energy, and the less you sink in, the easier you roll. And cyclists don’t have enough weight and power to dig through the snow into the firm ground below.

What about ice? Under most conditions, only studded tires grip on ice. They punch holes into the ice that allows them to interlock with the surface. However, studded tires aren’t much fun to ride on dry roads. I suspect that a supple tire with studs wouldn’t work well – you probably need a stiff tire to push the studs into the (hard) ice.

There is one other issue: When it snows, many communities spread fine aggregate on the roads for better traction. Often, that aggregate contains freshly crushed rocks that can be very sharp and cause flat tires. In our area, we’ve found that the crushed rock will puncture worn tires – probably both because they are thinner and because aged rubber is easier to cut. Running relatively new tires has eliminated that concern for us.

If you live in a place that sees snow, but also dry roads, our dual-purpose knobbies are hard to beat as all-round winter tires. They roll as fast on dry roads as most racing tires. They corner as well as most road tires (above). And yet on mud and snow, they offer the grip of the best knobbies. Available in 700C x 38 and 650B x 42 mm, they are a great choice for rides where you may encounter all kinds of conditions.

Click here for more information about our tires.

Posted in Testing and Tech, Tires | 35 Comments

Happy Holidays!

All of us at Compass Cycles and Bicycle Quarterly wish you Happy Holidays!

Posted in Uncategorized | 1 Comment