Anyone out there ever read Roadracing World? Of course you do, don’t be shy. John Ulrich publishes a pretty nice magazine based on one of our favorite pastimes. Yours truly has even written for ‘John’s World’ once or twice. Well, on page 31 of the December 2009 (Volume 19, Number 12) issue is a curious paragraph entitled “Tire Pressure Is a Big Deal Now”. The race is the FIM Moto GP World Championship at Estoril, Portugal, October 4th, 2009. Nicky Hayden refers to his tire pressure sensors revealing what he feels are erratic tire pressure readings and responds that he doesn’t know why? Really.

Perhaps as a former tire god I can educate the apparently hapless Hayden. Tire pressures are always taken cold, no exceptions. You are either ready to race or you’re not. No amount of hand wringing can change this. “Oh, but we use nitrogen in our tires so the tire pressures won’t change,” you say. Really.

Picture this, you employ tire warmers before the race to get your tires up to what you feel are race sensitive tire temperatures, you swerve back and forth to warm your tires (read National Privateer ‘To Swerve or Not to Swerve’ and ‘Quite Screwin’ Around and Just Go Straight’ by Timothy Kast), your brake rotors get so hot they glow neon cherry red and you wonder why your tire pressures are bouncing around all over the place. Really.

First off, you could have saved several pounds of dead weight by trashing the electronic tire pressure sensors on a race bike. They are absolutely worthless on a race-only motorcycle. I used to have a steady line of major manufacturer race teams on race day request that I grade their tires for concentricity, perfect balance and tire pressure BEFORE the race. Once the motorcycle goes further than 100 feet under its own power, the tire pressure could read just about anything. Count on it, Nicky. I don’t care whether you have one tire or a hundred and one; tire pressures are checked BEFORE the race on the bench or on the bike, then filed away in your head and in your notes for future reference. You are either ready to race when you go to the start line or you are the ill-prepared also-ran tripping up the leaders when they lap your nappy ass at the back of the pack. Your tuner sez, “Au contraire, Monsieur Tim, nitrogen (insert the proper techno-babble equation here) does not expand at the same rate as the ambient air temperature, so the tire pressure should remain a constant.” Ever touch a brake rotor with bare skin after your rider comes into the pits, Hidalgo? Hurts, doesn’t it? You probably have the scars to prove it, eh, Hidalgo? Well, it would seem odd that you could reach temperatures hot enough to roast a brake rotor, shred a tire, and boil brake fluid and fork oil all without altering the temperature of the nitrogen inside the aforementioned shredded tire. That would be pretty miraculous stuff, wouldn’t it? Nitrogen is a good race tool, but it’s not a magic elixir. What’s that, Nicky? I can’t hear you for all the guffaws in the background.

Tires will always be the greatest variable in racing and tire PRESSURES always seem to be the least understood of any variable in tires. What pressures were you running at the last race at that track? Don’t tell me, “That’s my tuner’s job, dude”. What if you change teams and you inherit a different tuner? Gee, that’s never happened before, has it? Can you say ‘Green Recruit‘? You should have recorded that information under Race Day Notes in your trackside notebook that you carry in your gear. You see, during practice and tire testing sessions it is important, no, mandatory, to either remember or record the race day tire pressures that you KNOW will work at every track and under every circumstance for your own edification and personal information. Don’t expect your tuner to do this for you, even though he or she should.

YOU are the nut behind the triple trees, you should know this, if you choose to call yourself a professional. The only thing those electronic tire pressure sensors were telling you were that they were indeed functioning properly, as they should. Street bikes ridden by some Nimrod that never checks his air pressure could actually benefit from something like that, but on a race bike they are simply a useless appendage. Remember, tire pressure sensors were invented to remove the liability factor from the manufacturer and the company insuring them, they are no substitute for the actual hands-on knowledge. When a tire loses its tread in large sections leaving only the carcass underneath, it is called ‘chunking’. Chunking is nearly always caused by high heat temperatures inside the tire carcass. The softer durometer rubber of the traction surface of the tire cannot dissipate enough of the heat generated by traction, power and cornering and this ‘unlocks’ the construction of the race tire. What happened to that nice cool nitrogen?

Reconfigure all of the conditions that we spoke of earlier (i.e. boiled brake fluid and fork oil, blistered brake rotors, chunking tires, not to mention ambient air temperatures and track surface temperatures) any way you please and you begin to visualize that there is virtually no freakin’ way that the pressure could NOT change in your tires as the race progresses. For this reason, tire pressures will ALWAYS be adjusted BEFORE your motorcycle leaves the pits and heads to the line. Don’t palaver or protest, just do it. It is the way it has been done since Eve was a contract rider for the Snake. Tire pressure has always been a big deal. Be a professional and go to the start line prepared.

Thank you.

See, and you thought I was just another pretty face.

Ride Safe.

Tim Kast

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