Bike checkin - leave tire pressure low

The science says you don't need to.  

That said, I always pump up my tires in the morning anyway so no harm in doing so.

No.  You don't need to.  It's another one of those things triathletes do because people tell them to, not because it makes any sense.

YMMV.

I agree that you don't need to reduce pressure.  I read the science on it before, but it's something like a few hundred degrees of increased temperature in order to increase about 5 psi in your tires.

There are people that blow tires in transition, but my guess is that probably has more to do with the following.

1.  People who are misinformed about more pressure being faster.

2.  People using pumps with faulty pressure gauges.

3.  People who simply had a sidewall cut in their tires...often not realizing it because they don't ride on their race wheels/tires that often.

4.  The simple fact that you might have hundreds, or even thousands of bikes in one area...all pumping up their tires around the same time...so the chances of you hearing a blowout increases.

All that said, I have only heard one blowout while in transition.  And that was about 30 minutes after bike check in opened...so it had nothing to do with increased temperatures...unless the guy pumped up his tires in a walk in freezer or something.

If this *phenomenon* was actually true, people would be blowing out tubes while on the bike leg of IM all the time.  Being that they top off their tires in the morning and won't finish the bike till the hottest part of the day.

And that increase to 130 only results in a 10 psi increase.  so assuming you started in 90 degrees at 110 psi and it rose to an effective 130 degrees, you'd be looking at 120 psi.  Still don't see how that is going to cause a blowout.

I think there is a much greater risk -having seen, or actually heard, it at every race as I race in a colder climate- of nervous triathletes pumping their tires race morning and having issues then, whether that's related to a bad bead setting, or overinflation, or an unfamiliar pump, or......  I saw people doing this (deflating  tires in T1) at IM Canada where it was forecast to be 55 degrees overnight.

Anyway, I invite all those in my AG to continue the practice  

Then the answer is butyl.  Latex tubes don't come with the bike.

Good luck at St Anthony's, looks like we finally will be getting some decent weather here in FL for the race.  My business partners nephew will be there attempting to get his pro card or whatever its called.

The bike check in for St A's is Saturday from 12-6p which is the hot period of the day with a current high forecast of 86⁰F.   If anything the temps will start dropping in mid-afternoon after you drop your bike off.  Unless there is some other latent problem, then I don't see much risk of heat causing a flat. 

The biggest temperature increase will be actually be between the time transitiion closes at 6:45am on Sunday and the time you get back to T1, especially if like me, you're starting in one of the later waves.

I'm planning to drop my bike off at about 1pm Saturday and will probably top the tires off then to about 110 psi.  My normal routine is to then top them off again in the morning befiore the race.

Mark

So they aren't flat when I walk or ride my bike to check in? 

I'll be doing a short check ride at home Saturday morning before I drive to St. Pete for check in, so I'll pump them up for that if nothing else. 

Regardless, I'd expect the pressures to be a few pounds lower on Sunday morning after sitting out all night.  I might need to top them off, or adjust based on other factors, i.e., rain, wet roads, etc. 

Worst case would be showing up Sunday morning and finding an unexplained flat.

Mark

With a butyl tube you aren't going to lose much but you really should be prepared for the possibility of walking into the transition area on race morning and finding a flat tire that will need to be replaced.  It's not a likely scenario but if you are prepared for it, you won't be scrambling if it does happen.