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Technical FAQ: ’cross tire woes

  • By Lennard Zinn
  • Published Nov. 3, 2009
  • Updated Feb. 23, 2011 at 12:44 PM EDT

Cyclocross season is in full swing, and it came to Boulder over the weekend in the form of the Blue Sky Velo Cup and the Boulder Cup.

For some reason, I’ve got more of a ’cross bug this season than I’ve had since 1981. While one of the things that totally cooled my jets on ’cross back then was getting burned out on how much work I constantly had to do on my bikes, I now get a special kick out of that part, since I care a lot less about my results now and more about having fun. And working on bikes is not a chore when it’s an end in itself, rather than only a means to an end. Also, it is a lot more fun working on nice equipment available today than the cobbled-together junk I raced on back then.

I think by the end of the 1980-81 season, I had patched my four crappy Wolber ’cross tubulars each around 20 times and ran into my own stitching whenever I peeled back the base tape; I had rebuilt my wheels probably five times, each time with another weak Super Champion rim destined to a short life, and I had straightened my fork so many times that I no longer used a jig and did it with care. With the fork still on the bike, I would just stand on the fork crown on the ground at the end of each race and yank up on the blades to bring it back into shape.

But in spite of the improvements in equipment, and they are massive, some of the same things that plagued us then still do now. Even though my bikes are probably five pounds lighter now than they were back then, they’ve still got cantilever brakes and tubulars. People still get lots of flats and roll tires, and plenty of riders are still bedeviled by a fork that shudders violently under hard application of the front fork. It is these and other things that I plan on addressing in this and upcoming weeks. In this one, I’ll focus on flats.

Next week or the week after, depending on the VeloNews editorial retreat, will be on rolled tires and gluing tubulars. The week after, I’ll take up front brake shudder. So, if you have problems or solutions on those topics, send ’em in to me at veloqna@comcast.net.

I worked the pits during the muddy Blue Sky Velo Cup and saw an amazing amount of carnage on tires, especially given how muddy it was. Our own speedy Matt Pacocha came through the pits the first time in fifth place among the pros, only to flat shortly thereafter and lose lots of places as well as exhaust himself before coming back around to the pit for a new bike. There was no saving his tire with Hutchinson Fast’Air latex foam in a can, he had pinched it in so many places by then it was unusable.

There were piles of wheels with flat tires in the pits by the end of the pro race. But one would not expect to see so many flats on such a soft course; there must have been a lot of thorns in that mud. Same with the race I did in Castle Rock the day of VeloSwap the prior weekend; it was also very muddy and soft. The slippery descents encouraged people to ride off into the weeds searching for traction, which could have been where they found thorns. I did, but I don’t worry about flats (see below). Jonathan Baker won the pro race but flatted in the process.

So the big question I have is, why aren’t people putting sealant in their tires? Or are they and still getting flats? I know Matt was not, because I asked him.

I have six sets of cyclocross wheels – four tubular sets and two clincher sets. I run 25-30ml of Caffélatex (http://www.effettomariposa.com/caffelatex_en.html#caffelatexinjector_en) in all of my tires. On the tubulars, I remove the valve core and stick the hose of the syringe injector over the valve. On clinchers, I use the bigger 700 X 35-42C inner tubes so that the tube is not stretched very much inside, which would open a puncture hole bigger. And I just stick the hose of the syringe injector right over the valve and shoot it right in through the valve core. The valve works fine afterward.

I chose Caffélatex because of the demos I’ve seen at bike shows in transparent tires where the sealant stays foamy. It would seem to me that this would give a measure of protection in the case of a snake bite (pinch flat), where usually you could be certain that a sealant would not seal the hole of the snake bite pair that is toward the rim. And any sealant will fill most small holes on the circumference (thorns, etc.).
I have come back from training rides on both clinchers and tubulars where there were goat’s head thorns sticking out of my tires all over the place, and I never even knew it. No air loss in subsequent days, either. It was as if I never even hit a thorn in the first place.

By definition, water weighs 1 gram per milliliter, and the density of liquid latex sealants is bound to be similar to water. So you would add 25-30 grams per tire, and, indeed, this is the weight difference I measure. To me, this extra weight with absolute confidence of not getting flats is worth a lot. Last weekend I was running my tires at 24 psi, and I weigh 175 pounds! The weekend prior, I raced both races at 28 psi. Tubulars feel great on rough courses at this pressure, and they hold really nicely on the turns and side hills. But if you’re afraid to run them low for fear of flats, what’s the point in having them in the first place?

Mark Taylor, who rides in my age group, got three flat tires on Sunday at the Boulder Cup and one on Saturday at Blue Sky. His last flat was on a tubular with latex sealant in it, but the tire was many seasons old (and silk; what a shame).

I still believe that if you drain the sealant out at the end of each season and re-do them, that your tires will last until the tread wears out.

Next week: gluing tires.


Lennard

Dear Lennard,
I have tried and failed to use tubeless technology for cyclocross, and before I give up totally on it I thought I would write to you and ask if you knew of any secrets to successful setup.

I have the tubeless ready Shimano Dura-Ace WH-7850 wheels, Hutchinson Tubeless Ready Bulldog CX and Tubeless Ready Piranha CX tires, and I have used Hutchinson’s Fast’air sealant (and I tried their Protect’air in an early, also failed attempt).

I have used Hutchinson tire levers to apply soapy water to wet the tire bead/rims during setup.  (I very likely did not use 50% liquid soap however, as I read today on the instructions on the back of the tire lever packaging; and I can’t recall whether I applied the water/soap to the wheel rim or tire bead?)  I believe I was able to push the tires on the rim without the use of the levers.

When using this setup I get burping of air if I run anything close to low tire pressure (below the sidewall recommendation of 43 psi), which is the whole point of trying tubeless for cross, right?

I have tried this wheel/tire setup with a tube, but it just seems really heavy (because of the tire, both thickness of the wall and volume of the shape).

Do you have any suggestions on how to best use this tubeless setup for cross, without getting the burping of air that I and others that I know have had problems with?  I was wondering if the large size of the tire (700 x 34) might be part of the problem, putting a lot of lateral, “roll off” torque on the tires in corners, when running low tire pressure?
Greg

Dear Greg,
I have not used them, but everybody I know who has, has told me the same thing. They burp at low pressures, making them useless for racing cyclocross. I personally love the Hutchinson road tubeless tires, and I have them on all four of my road bikes (including one with your same wheelset), but they’re smaller tires (as you said), and I’m running them at high pressure. Furthermore, the cyclocross tubeless tires do not have the carbon bead of the road tubeless tires but instead have an aramid (a.k.a. Kevlar) bead, which could be prone to stretch more and will certainly not be as small and lock into such a tight space as the carbon bead. By spring 2010, Hutchinson promises to have the carbon bead on the tubeless ’cross tires as well.

And you’re right, there is not point to running them with an inner tube, because they become heavy and overly stiff. It’s best to find some different tires (and run inner tubes with latex sealant in them).
-Lennard


Dear Lennard,

I’m currently riding a cross bike that fits me perfectly, except for the significant toe overlap (close to an inch).  I have taught myself how to do low speed tight turns without jamming my foot into the front wheel.  Never the less, its still remains a potential hazard. The fork is 1-1/8 threadless with a 45 or 46 mm rake.  I’m very long legged, 6’4", and have size 49 shoes with the SPD cleats set all the way back for touring and commuting.  I’m currently running 35mm tires as well.  Do you have any suggestions for eliminating the toe overlap without eliminating the bike?
Adam

Dear Adam,
I’m having a very hard time imagining how a bike that fits a 6’4" rider could even have pedal overlap at all, given how long the top tube must be, no matter how long your legs are, what your shoe size is and how far back your cleats are.
We build a lot of bikes for riders your height who also have large feet, sometimes far-back positioned cleats and, almost always, cranks on the order of 200mm and longer, and they don’t have pedal overlap. I’m assuming you’re using something like a 175mm or so crank length, so that gives you at least an inch less forward extension than with a 200mm. A 6’4" rider generally needs at least a 62cm top tube length (maybe 60-61cm for the really long-legged), which, unless the seat angle is extremely shallow and the head angle extremely steep (which would certainly not be something you’d expect on a ’cross bike!), there would normally be plenty of room for the feet not to hit the tire.

My concern is that the builder tried to reel in the wheelbase and gave you a steep head angle (74 degrees or more—I have seen many tall frames with head angles as steep as 76.5 degrees), in which case, substituting a fork with a lot of rake (offset) in order to reduce pedal overlap would be a big no-no, because the fork trail would be so minimal that it would be super unstable.

Otherwise, if you want to keep that frame, the rest of the options for reducing overlap I’m sure you’ve thought about and I don’t even need to tell you — move your cleats further forward on the shoes, shorten the cranks, get smaller tires. Of course, all of those things probably rob you of some performance…
-Lennard

FILED UNDER: Bikes and Tech / Cyclocross / Technical FAQ TAGS: / / / / /

Lennard Zinn

Lennard Zinn

Our longtime technical writer joined VeloNews in 1987. He is also a framebuilder, a former U.S. National Team rider, and author of many bicycle books, including Zinn and the Art of Mountain Bike Maintenance and Zinn and the Art of Road Bike Maintenance, as well as Zinn and the Art of Triathlon Bikes and Zinn's Cycling Primer: Maintenance Tips and Skill Building for Cyclists. He holds a Bachelor’s degree in physics from Colorado College. Readers can send brief technical questions to Ask LZ.

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