Latex tubes.

If you are running latex tubes then you would have to pump them up the morning of the race as they lose air much faster than butyl tubes. Nothing wrong with making sure the pressure is right where you want it either :)

Slow leaks can happen at any time. This is one last chance to discover one. It also may be cooler in the morning than when you inflated the tires the day before. Yeah I know you could try to inflate them higher than normal the day before, but who does the math behind that??

apart from latex tubes - those of us that still run Tubulars - will always need a few lbs in the AM

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Graham Wilson
USAT Level III Elite Coach
http://www.thewilsongroup.biz

Because you never know if some lady had stopped by your bike and let the air out of your tires earlier in the morning.

Ahhhhhh well there you go!! Thanks everyone, knew there must have been some logical reason!

Mine drop 20lbs overnight at every race.

People let air out of your tubes after you check your bike in.

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Winner!

Stva: “Yeah I know you could try to inflate than higher than normal the day before, but who does the math behind that?? ”
Looks like I’m that guy. I run latex. Got tired of the pre race morning pump routine. So I studied rate of PSI loss over a 12-24 hour period. I pump to required pressure, put bike in car/rack bike night before race, and I’m done. One less thing to deal with on race morning.

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Blog: https://swimbikerunrinserepeat.wordpress.com

+1 (I reckon 10% per 24 hours if anyone is interested).

Even when I was running butyl, I figured the triathletes pumped their tires up race morning was because triathletes pump their tires up race morning, like some subgroup norm of behaviour. Or they were bored / nervous in transition and wanted something to do.

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Swim. Overbike. Walk.

Can't tell you how many times I've seen panicked people arriving on race morning only to find a tire flat from pumping up to capacity or over-inflating the day before and then rack the bike to sit in the hot sun the rest of the afternoon. I would think afternoon heat, humidity, how cold it gets sitting overnight all affect what kind of pressure reading you'll get the next morning. I pump to about 80-85 when racking and always check/pump race day am.

😀

In Asia we are advised to deflate upon bike check in as bikes will sit under the hot sun for several hours. I generally don't, but most people seem to follow the advice and pump up next morning.

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My race site: https://racesandplaces.wixsite.com/racesandplaces

Yes, some do it for this reason. At NYC race brief they suggested to deflate at check in and inflate in the morning.

Tubulars also have a tendency to leak air over time. MAYBE 5 psi over night.
Also some deflate the tires a bit when you have to check in your bike the day before and it sits in the sun all day at full pressure. Could pop a few tires.

I run clinchers and standard tubes and unless I have a hole, they keep air for weeks without needing inflated. BUT, I always make time to check on race morning in the event I need to air them up for some reason. Saved me at Tahoe in 2013. Little low. Aired them up and realize a spoke was busted and got a new wheel right before the race start from the techs. Would have been a disaster (maybe even a wreck) had I not checked pressure and aired up.

So, always check your tires race morning.

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Ryan
http://www.SetThePaceTriathlon.com
http://www.TriathlonTrainingDaddy.com
I got plans - https://www.trainingpeaks.com/...dotcom#trainingplans

Have you studied the loss of air rate due to atmospheric pressure and temperature? The rate of loss also isn't linear. I found it nearly impossible to come up with a formula, but I'd be interested to hear about your method.

I do this as well... mainly because my bike are in the house and inflating tires is one of the louder things in the morning hours.

I run tubulars and have tested just how much they lose over 18hours (ie: from bike drop off to race morning). I found mine lose 12-15psi at approximately 72 degrees air temp. At IMTX overnight, they lost 20psi due to the high afternoon heat at bike drop.

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Team Zoot-Texas, and Pickle Juice

Nickwhite, I haven’t considered temp and atmospheric pressure. I did my data in a 70 degree basement, not sure of barometric pressure. Pump to 110 psi, pressure 12 hours later 90, 24 hours later 80. 48 hours 70. I repeated this 2-3x over a few weeks. So I usually pump to 110-115 depending hours to bike start and duration of event night before.

Having said this, I was admittedly a bit nervous at IMCHoo last year when I realized my racked bike was in the sun from 3-7pm...maybe I’ll pump to 60 and bring pump to transition race morning this year at Choo😬.

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Blog: https://swimbikerunrinserepeat.wordpress.com

Can't tell you how many times I've seen panicked people arriving on race morning only to find a tire flat from pumping up to capacity or over-inflating the day before and then rack the bike to sit in the hot sun the rest of the afternoon.//


You would have to have one hell of a pump, and race at about 300PSI for that to happen. I don't know about youalls new fangled clinchers, but my old tubular contis burst pressure was like 350 lbs as I recall?And they were rated to about 160/170 psi for racing. I think people that have there tires burst overnight or at any time really, have another issue going on. If it is a clincher, probably a pinch, or some spoke poking out just enough to catch the tube, or just a weak spot in the tube. But getting past the burst pressure, well that would be very special indeed...

I pump up before all my rides. Plus I use latex. An old teacher of mine said once he pumped his tires the night before and left his bike in his car or had a long drive in during a cold day. I can’t really remember which. Just to pump his tires see his tire pressure low and repumped then. Sun came out and they burst. When I was a newbie I pumped the night before and even left my bike in my car before I had a rack to transport in. Ever since that story I deflate in transition during prep time and reinflate. Only takes a couple seconds and covers all my bases.

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I still lapped everyone on the couch!