Tubeless Cyclocross Tire Tips

Part of a series I'm calling Tires 101 with lots of great info to consider when looking for new tires.

GOT LESS (TUBES)?
There have been lots of comments back and forth between my readers about switching to tubeless for road and cyclocross. This is a guest post of sorts - an acquaintance was nice enough to write his thoughts down and share his info with us.

With cyclocross season right around the corner you might find this info helpful. There are tons of different combos of rims, tires, and tubeless products. We hope his insight into what worked for him last season for him will help with a few questions you may have. Here's what he had to say:

This year I have been racing cyclocross on road tubeless Shimano Dura Ace 7850sl wheels.  Just a quick search on Google will show that while Shimano is silent on using their road tubeless system wheels for cyclocross, there are plenty of others either talking it up, or talking it down.  What I will try to do here is describe the problem, tell you what has worked for me, and perhaps more importantly, tell you what hasn’t worked — and the lessons I learned from the experiments.

Why is this Difficult and What Are Your Options?

• Cyclocross puts tires under incredible stresses.  In addition to providing forward and lateral traction, your tires must provide a degree of suspension — ability to conform to the terrain, in order for you to be fast.  And at the same time the tire needs to fit in a road bike style frame with adequate mud clearance — typically a 32-34mm tire.

• In order to provide this suspension and “suppleness”, you need to run relatively low pressures and your tire should have compliant sidewalls (high thread count and thin rubber).
• The traditional solution to this puzzle is to use tubular tires.  And frankly, this is what almost all of the best cross racers do.  But tubulars have their drawbacks — they are expensive, are messy to deal with, require multiple wheelsets for different conditions, and hard to fix if they flat.   That’s not to say they aren’t a good choice, but these problems open the door for other solutions like tubeless.
• Another option is to run tubes with clincher wheelsets.  The problem with this is that in order to get adequately low pressure, you run a high risk of pinch flatting.  And the tube/clincher combo can be heavy.  The advantage of this setup is it is the easiest to maintain and switch — one set of race wheels and a set of pit wheels will get you going and switching tires for conditions is very easy.
• So how do you eliminate the pinch flats on clinchers?  Run them without the tubes! If only it were that simple …

What You Need to Know About ‘Cross Tubeless: Some Basics

• Tubeless is unlikely to ever provide the abosolute performance of the best tubulars, but definitely will involve less tire cement and toxic solvents
• It’s a “system” with changing variables — so no single component (rim, tire, rim strip) is going to guarantee success with all other options.
• Hutchinson is currently the sole manufacture of tubeless specific ‘cross tires.
• Use regular clinchers in a tubeless system at your own risk.

What I Learned the Hard Way About Setup

• Some tires are better for tubeless than others.  Early reports are that the new 2010 version of the Hutchinson Piranha and Bulldog tubeless readies are much improved, with a tighter carbon road -tubeless bead can handle any PSI you throw at it.  In my experience, the older models, without using Stan’s rim strips and a layer of velox tape below the rim strip, is extremely prone to burping at any pressure below 40psi on the 7850sl’s.
• Use sealant — I’ve had good luck with Stan’s and Cafe Latex.
• To get the best seal you need to have a tire bead that sits tightly against the channel of the rim.  This may mean you need to build up your rim, either with a rim strip, with tape or both.  Google your rim model and “cyclocrosstubeless” to see if others have specific setups that have worked.  You can build up the rim with velox tape, electrical tape, or strapping tape.  Strapping tape or Stan’s yellow tape is the best because they both do a great job of sealing the spoke holes, but with the low pressure in cross you can get away with electrical tape.  Of course all of this stuff goes under the Stan’s rim strip.  And don’t let the tape creep up the sidewalls — it should stay in the channel or else you could compromise your seal.
• The idea is to build up the channel so that two things happen.  First, when you put the uninflated tire on the rim the bead sits tight against the floor of the rim.  This makes it easy to inflate — you should be able to inflate your setup with a floor pump.  Second, you should have a tight interface between rim and bead (what Stan calls a “bead socket”) — meaning the distance between the “floor” of the rim and the hook on the top of the sidewall.
• I found that with the 2009 Hutchinson tires I NEEDED Stan’s cross specific rim strips unless I was to  build my own rim strips. Not worth the effort IMO.  With the rim strips and a layer of Velox tape my setup became virtually unburpable at 30 psi on the roughest, driest courses in Oregon.
• If you aren’t using the Hutchinson tubeless models, start with new tires, or at least tires you have never inflated above 40 psi.  Too much pressure can stretch the bead making it harder to get that tight seal in the channel of the rim.

Getting It Done

• After you have built up your rim sufficiently and have your rim strips in, or your valve stem if you don’t need them, remove the valve core and hook up your floor pump.  You should be able to inflate the tire without any sealant and get the bead to seat — hopefully with that familiar “popping” sound.  I tried running Easton EA90SLX’s tubeless, they didn’t pop though and they seem to be working fine — until the burped under some “scrimmage” cross conditions.   If you are having problems check to make sure the bead of the tire is as well seated around the valve stem. If it still won’t inflate try sponging on the rim some soapy water.
• Once inflated, remove the pump and let the air out.  If you have a stan’s syringe put 1.5 oz of sealant in the tire through the valve.  If you don’t have the syringe, remove one bead, use a scoop and a half of sealant and carefully remount the tire and pump it up.  You may be able to pump it up with the valve core in or you may have to remove it to get that higher air flow.  Do NOT exceed 40 psi unless you have the Hutchinson tubeless ready tires — I pump it to 35.  Shake, rotate, shake rotate.  Let the tire sit flat on each side a few minutes between shakes so the sealant can seal the sidewalls and beads.
• Ride it around the neighborhood.  Do some tests.  Ride off some curbs.  Can you make the tire burp at 35 psi simply by pushing on the sidewall?  At that pressure you ought to be able to deflect the tire off the rim in a huge way and still have the seal hold.  Go find a field with some off hills and ride off camber.  Apply the brakes, corner hard.  Get comfortable with the pressure you want to run.
• I found that I was able to bond my Hutchinsons to the Stan’s rim strips by lowering the pressure and making small burps around the rim with my fingers.  The sealant acted as the glue.  And after that I think when ever the bead pulled away from the rim the rim strip stayed with it and the tire stayed sealed.
• If it’s working, go race.  Your ideal pressure depends on your weight, the course, the tire and your riding style.  In my experience if you ahven’t bottomed out your tire at least once during a race your pressure probably was too high.   But unless you are in the clydesdale realm, don’t go over 40 psi.  Besides, if you are over 40, you might as well use a tube.
• The other day I was riding on a gravel road downhill and got a small cut in the sidewall.  The tire went almost flat.  I gave it some air and it leaked a bit more, then I shake the sealant around at the cut and badda bing, it sealed it.  Pumped it back up and finished my ride and the tire is still holding air. So for all my efforts I am sure I avoided at least one tube change!

What I Will Do Next Year

Get the new Hutchinson tires!  With the tighter bead I hope that this will allow me to ditch the rim strips and velox tape — that should shave 100 grams off my wheelset weight.  By all accounts this works well on the Shimano wheels.  But apparently not on some other wheels — such as Stan’s 340 rim and certain Mavic’s.  Apparently the bead is so tight on the 340 that people have been breaking it, putting their wheels out of true or been unable to seat the bead.  So the story continues to be that, for better or for worse, cyclocross tubeless is a multi variable experiment.  Best of luck with yours!

Share your thoughts, questions, and experiences in the comments...