Cyclocross Tires, Tubes, and Pressures
A couple weeks ago I was doing some research into various tire and tube options for cyclocross. As part of that research I contacted a number of tire companies with questions about the tires in their line ups such as if they have tubeless options and what sort of pressures they think they can run in various setups. I go this fantastic reply from Chris at Challenge Tire that covers basically everything you need to know about tires, tubes, and tire pressures. It was so helpful that I am sharing if with you all.
You recently sent us an email asking the following: “what sort of pressures you can run your open tubulars at with a latex and butyl tube?”
We don’t have an exact answer for that question as tire pressure is fairly nebulous. The pressure you run is based on rider weight, the rim being used and the conditions being ridden. For instance, the tire pressure I would run, with me being over 200 pounds, would be higher than riders who might be in the 150-170 pound range. Also, the conditions with roots at Cross Nationals in Austin would require me to run higher pressures than the fairly smooth conditions in Koksidje in Belgium where there are very few roots and no rocks.
There is a point at which the tire pressure is so low on a clincher based system that the tire will burp, or blow off the rim, while cornering. Clincher based system are based on the inner tube providing a certain amount of load against the tire pressing it against the rim. At some pressure the amount of pushing force caused by the rider and the pulling force from the ground during a turn will outweigh the tube and rim’s ability to hold the tire in place. And this changes depending again on the course, the rider weight and how the rider takes turns.
Our suggestion for new riders is to start their pressure around 35psi or 40 for heavier riders and those with less finesse. Ride the course and feel how the tires react. Then drop the pressure about 5psi and do the same. Continue to do this until you start to feel like the rim is bottoming out or the tire is folding over itself in corners. Then pump the tire pressure back up a couple psi. Do this for every course and you will start to get an idea of what you can ride pressure wise making it easier to fine tune at future events.
Deciding on the type of tire system to run depends on your budget, how much effort you want to put into racing and how serious you are about performance. Though we feel tubulars are best for those who truly want to be competitive in cross, we do offer a couple types of tires for clincher based systems. Both are less expensive than tubulars and are easier to swap out were conditions to change. Our open tubulars and vulcanized cross clinchers are designed to work with ETRTO clincher systems. This means they are intended to be used with an inner tube and run on ETRTO hook-bead rims with inner widths of 15-20mm (for 32 and 33mm tires, see attached chart). Our vulcanized clinchers and open tubulars were not designed to be run tubeless. Tubeless systems require a special bead to allow them to lock into a special rim which has a bead hook intended to lock the tire into place. Since there are currently four standards for tubeless, Challenge has opted to not offer a tubeless option as choosing the wrong combination could be lead to a tire coming off and a potential crash. We will reconsider as the industry hones in on fewer standards.
From our experience, tubeless systems with narrower tires (compared to mountain bike tires) need to be run at pressures slightly higher than those with inner tubes to help prevent burping. Higher pressures are slower than tires run at lower pressures. Also, most tubeless tires include additional butyl rubber applied to the casing to slow air loss through the tire. This makes for a stiffer tire which has less traction and tends to be less comfortable.
We feel open tubulars are ideal for those running clincher based systems as the higher thread count and natural rubber based treads are more flexible and offer more traction. You can run an open tubular at the same pressure as a vulcanized clincher and the tire will flex over obstacles as opposed to bouncing over them. This results in less shock being transferred to your body and allows you to ride deeper into corners and come out faster. At similar pressures, the open tubular will also have less rolling resistance than a vulcanized clincher.
In regards to inner tubes, the latex inner tube is more flexible (supple) than a butyl inner tube. This means that running a latex inner tube reduces rolling resistance and improves traction. This added flexibility also helps prevent punctures as the latex tube will flex away from smaller items that poke through the tire as opposed to a butyl inner tube which is fairly stiff and punctures immediately.
Challenge has athletes that run tubular tires as low as 1 bar (14ish psi) which we would not suggest on clincher systems. Also, tubular tires, if glued properly, can be ridden when flat with little concern for the tire coming off. Thus the rider can more quickly get to the pit for a replacement. This can’t be said for clincher based systems as a tire will most likely come off the rim leading to the rider with a flat having to do more running.
With regards to performance, here is how we compare some tire systems for cross:
- Good: vulcanized clinchers with butyl inner tubes and some tubeless systems
- Better: vulcanized clinchers with latex inner tubes
- Even Better: open tubulars with butyl inner tubes
- Much Better: open tubulars with latex inner tubes
- Best: tubulars with latex inner tubes
In regards to durability, ease of use and lower costs, read that list backwards as vulcanized clinchers with butyl inner tubes tend to be less expensive, are easier for most folks to install and the vulcanized casings and treads tend to be more durable. However, tubeless systems can be more difficult to install depending on the equipment and the users experience.
I realize this is a pretty long response. However, your comments and questions couldn’t be answered with single sentence response. Combined with tire tread selection, tire pressure is the most important aspect of cross performance affecting traction, speed, comfort, and more. Choosing the right tire system, the right tread and the right tire pressure can be the difference between first, second, last and not finishing.
Here are additional suggestions from Stu Thorne who runs the Cannondale/CyclocrossWorld team: http://www.bikeradar.com/us/road/gear/article/how-to-find-the-right-tire-pressure-for-cyclocross-35902/
The article is a few years old but the ideas and suggestions are the same.
Thanks for including us in your research for the upcoming article.