OK, I'll say up front that this is not another discussion of tubular vs. clincher. And this is not a discussion of this tread vs. that tread. This is simply about pressure.
A couple of us here at CXM are working on an article related to tire pressure for an upcoming issue. While we're reaching out to some of the gurus of our sport, mostly because it makes us feel cooler than we really are, we wanted to add another dimension to the article. Some of the best discussions and information I've seen has been relayed right here, through the beloved Cowbell forums. And since we are a community driven publication, here we go....
What's the method that you prefer for determining the appropriate tire pressure on a given day? Based on experience? Simply by feel during the warmup laps? NASA-Calibrated pressure gauge?
And whats the preferred method of inflation? Anyone else still use pumps? Or has everyone but me upgraded to the fancy electronic inflators?
Well, I've typically started out with a baseline pressure when I air up before warming up (like, for me, as just shy of 200 lbs) 35fr/38rear running most clinchers, and then see what that feels like. Sometimes I screw it up, and one race I made a horrible tire choice for the front and no pressure difference would have helped. For tubs, I usually start at a little lower and go from there with the same theory. But really, I think experience makes a huge difference, too...you'll start with lower or higher to begin with depending on course conditions...and THEN test pressure on warm-up.
Most of us amateur weekend warriors still use pumps, I'd say...although if they'd make a trainer attachment, I could be persuaded to set it up on one of my friends' while he's warming up...
I assume most riders take the same basic approach of they have pressure they start with (mine is 30 front/32 rear) then the unscientific add or remove air based on feel from a lap on the course. Of course I have seen other riders set their tire purely based on the recon lap and tire pressure of a more experienced teammate. On the other hand if I don't have my pump and am using someone elses I never trust the gauge and instead rely on the squeeze test. :-)
Now for my wife and who runs a pit bike we run same initial approach but often more test laps then use the gauge to set the second bike to be the same.
Sounds like we're all in agreement about starting off with a standard tire pressure. That is rad. I go by feel but I also know what my low end limit is based on my gauge.
I use a Craftsman cordless inflator. I am the only one in Pittsburgh with one and I only see a handful of them at races when I travel. Maybe one other one at MABRA, a couple in the MAC (Mcdaniel's being one of them)
I have tried to get really good at matching tire pressures via my thumb. You'll forget your pump or forget to charge the battery one time and then you're out of luck matching tire pressure across your other wheels.
Good point Chris.
I'm in agreement with you in regards to being able to "thumb it " . Like so many things in life these days we are so tied into recent technology and gadgetry that when these things fail to work for whatever reason we can become "crippled by technology" . Kinda like when you have an interval workout planned around specific wattage etc and your power meter craps out half way through..ughh! What to do ?!
As far as finding proper tire pressure I generally start at 28.5 front and 30 out back (175 lbs race weight) , running Tufo tubies and go from there based on feel during warmup etc. I use a digital gauge to make fine adjustments when needed. I do find that 90 % of the time my starting pressure works just fine. Sometimes it's not till after the race that I say to myself..hmm I coulda tweeked my pressure a bit.
I think it is important to distinguish between tubies, tubless, clinchers with tubes.
I run tubies on the A bike, and as most people, I start with a base pressure. Usually F30/R32, then some laps. If I feel the tire bottom once a lap, I'm good.
There is NO WAY I would use this method for clinchers. My B bike has clinchers and I usually just put 45 or so in and call it good. I always error on the high side for the clinchers, risk of pinch flat is just too high.
I still use a floor pump.
As for pressure, I run Michelin Mud2 Clinchers on tubeless rims. I've found that because the beads on the Michelins lock into the tubeless rims pretty well, this setup allows me to run pretty low pressures without pinch flatting (plus I'm too lazy/cheap to buy tubeless tires). I usually start at about 30 psi, and after a course preview I reduce air accordingly. Depending on the course, I'll end up with around 25 psi in front, and 28-30 rear. I also rely on the "squeeze test" more than a gauge. Keep in mind that I am around 130 lbs., so I can go pretty low on pressure, even with clinchers.
I will agree the baseline pressure is a good idea, but it's really about experimentation on non-race days that is the way to determine your approximate tire pressure for a given tread. Recently I've found the limit on back-tire pressure (clincher) after several pinch flats. I would say keeping a log of your pressures / treads / race conditions and thoughts is as valuable as your post-race training diary log.
My favorite method of getting the tire pressure just right is using my analog tire gauge which has an air-release button. This way I inflate to 2.5bar and then drop the pressure to the right pressure. I like this way much more than traditional gauges because you constantly have to inflate and deflate them to get them just right. I've checked the gauge against two other digital ones and found it reliable on it's readings. I inflate tires with my shop compressor to 2.5 or so when I'm dealing with a whole set of tires, which saves me a lot of time in just deflating at the course once I decide on the pressure.