#Cyclocross Sizing Tires Like Carry-on Bags

A 33cm Clement PDX Clincher Too Fat for UCI

Even that spiky haired Food Network culinary star Guy Fieri will tell you a cup of flour is not necessarily a cup of flour.  It depends on how it’s measured.  The UCI device for measuring width of cyclocross tires is the heaping tablespoon of baking.  The maximum legal width for a cross tire is 33mm.  It says right there on the sidewall.  I'd assume someone probably measured it before it was stamped and stickered, but you know about assumptions. 

Regardless, last time I checked at my local shop they didn’t sell 33.1, 33.2 or 33.5 tires.  They did have quite a selection of 32’s, 33’s and even 34’s.  So we all brought tires to the Masters World Championships with a number of 33 or less written on the sidewall.  No one wanted to risk getting DQ’d for something silly at Worlds.  Personally, I smartly left my 34 Griffo mounted on a carbon Zipp at home and instead brought a 33 Clement PDX mounted on a old Ritchey WCS wheel.  Coincidentally, one tire that was getting flagged by officials as being too fat was the Clement PDX 33 clincher.  You’ll recognize it by the World Champion rainbow stripes on the sidewall.  I brought three to the venue, two on the pit bike and one on a back-up wheel.  I had to scramble.  

Like a cup of flour, there’s air inside a tire.  When you’re baking a cake, do you pank down the flour in the measuring cup to get the maximum amount inside?  Maybe you do, if you want a thicker batter.  Do you leave it slightly heaped or leveled off with the edge of a knife?  Do you use the cup measure made out off stiff stainless steel, or does the OXO brand plastic one your wife bought on her $200 shopping spree at Target do in a pinch?  

Rider: "We Can't Hear Back Here."  UCI Official: "Listen!"

I’m sure a Clement PDX Clincher 33 can in fact measure 33mm wide, maybe less, on a submarine.  It may measure 40mm on the moon or Breckenridge.  While the distance between the two sides of the UCI measuring jig may be an exact 33mm, it is quite possible to fit the device over a tire that measures slightly fatter.  The real problem is that there’s air inside of tires, sometimes inner tubes.  The more stuff inside the tire, the more unyielding it will be.  There's stuff on outside of tires too, like morning dew or peanut butter mud.  On a cold day, rubber can be stiff.   In effect, a pliable tire that passed the test on a rainy warm October afternoon at the Cincy3 Cyclocross Festival may not pass the test on a frozen mud morning in January.  After a few hours of hearing about riders being sent back from the start line with too fat Clement PDX’s, we learned that rim width also played into the equation.  The 33 PDX mounted on a wide rim skinnied up the sidewalls and passed the officials measuring jig test.  Mounted on a skinny rim, the 33 PDX plumped up and measured too fat.  I scrambled to borrow a set of wheels for the pit bike; coincidently pit bikes weren’t being checked.

Now what was originally intended to be an exact measurement of 33mm becomes an opinion.  Riders with flagged tires told me the official said the jig didn’t go on and off the tire smoothly.  It's like the Seinfeld parody of the Simpson trial.  Maybe the official had wimpy biceps, we joked.  You would think either the jig goes on or it doesn’t.  Either it comes off or it doesn’t.  Is the jig stuck to my tire permanently or not?  Should we smear a little Vaseline on the sidewall and try again.  The UCI is measuring millimeters like airports measure bags for the overhead bin.  Believe me, there’s not a bag I own that I can’t stuff into that metal frame.  Now and then, I still have to check it.  Go figure.  It’s the opinion of that bitchy flight attendant, not exact science.

A Nice Addition to Your Toolbox

Obviously I’m in no position to make suggestions such as actually using a device that measures width in actual millimeters, so I won’t do that.  Maybe there’s an App for that.  I will suggest that the UCI come up with a better place to measure tire width than at the start line of the World Championships with 5 minutes till the gun goes off.  It was sad to hear riders with what they thought were 33mm tires have to run back to their team compound (ie: back of their 2001 Honda Civic packed like a Jenga game) in the 5 minute window and risk losing their call up for likely the most important race of their lives.  I will also suggest that we all put a caliper in our toolboxes and practice a little more riding mud on 32mm tires.  I heard Sven Nys once said a 34mm tire makes muddy descents child’s play.  We all can get better.  So can the UCI.  Maybe there could be a tire width checking station where riders could report to at their leisure before their event and get a tire pre-approval sticker.  I’d suggest one with rainbow stripes.