Tyre Pressures At Altitude.

[bikeman66]

Hi all,

This may seem like a dumb question. I like to run the tyres on my road bike at maximum pressure, partly to decrease any rolling resistance and partly to minimise the risk of pinch flats on the awful roads down here on the Isle of Wight. With a trip to Mont Ventoux coming up in April 2015, I was wondering if there might be any issue with pressure at the summit? The reason I ask is that when I was on holiday in Provence in August, we drove up Ventoux. One of my kids had an unopened pack of crisps on the back seat of the car and we noticed that as we got higher up the mountain the bag was actually expanding, to the point where it did actually burst just as I was parking the car at the summit. I know a bike tyre is a lot more resilient than a crisp packet, but obviously I would prefer not to have a sudden blowout when rounding the hairpins on the descent. Would I be better off dropping the pressure in the tyres and potentially increasing rolling resistance on an already challenging route, or do you guys think the tyres will be fine even if I have them at maximum pressure at the bottom of the mountain? Anyone had any concerns like this before, or is it a complete non issue?

 

[ianrauk]

The pro-peleton seem to manage ok.

 

[User33236]

The difference in atmospheric pressure between sea level and the top of Mont Ventoux (1912m) is typically just over 2.8 psi so nothing worth worrying about.

 

[bikeman66]

The difference in atmospheric pressure between sea level and the top of Mont Ventoux (1912m) is typically just over 2.8 psi so nothing worth worrying about.

Thanks for the reply User33236.

 

[slowmotion]

Here's a thread about bike tyres at altitude.......very high altitude!
http://www.cyclechat.net/threads/th...ut-letting-bike-tyres-down-when-flying.93013/
Someone suggests that your tyres would only be 15 psi over-pressure if you took them into Space. I don't think Mt Ventoux is going to be a problem.

 

[TheDoctor]

Complete non-issue. Enjoy the ride

 

[boydj]

I'd question the need to have tyres at maximum pressure anyway. There have been lots of articles in the last couple of years highlighting research showing that very high tyre pressures are actually slower with higher rolling resistance, have less grip and give a worse ride because the tyres will be bouncing and losing contact with the surface rather than deforming and maintaining contact.
http://triathlete-europe.competitor.com/2011/05/03/facts-figures-myths-optimum-tyre-pressure
http://road.cc/content/forum/89867-right-tyre-pressure
http://janheine.wordpress.com/2010/10/18/science-and-bicycles-1-tires-and-pressure/ (interesting chart in this one)

Personally, I ride with 90 / 85 psi on 25mm tyres and I don't get pinch punctures.

 

[oldfatfool]

I have had cans of red bull explode traveling through the alps, made quite a mess of the carpet in the car, however no issues whatsoever either on a loaded tourer running 80 psi, nor a 'racing' bike at 130 psi. hth

 

[Drago]

Atmospheric pressure is only a little over 14PSI ASL. You'd be dead from apoxia before you needed to worry about changing tyre pressures due to altitude.

 

[Donger]

Complete non-issue. Enjoy the ride

I guess tyres can take that amount of extra pressure - but it is quite a cool thing to see. The same thing happened to my wife's crisps in the Alps last year and I had exactly the same thought.... I have a photo for every occasion ....thought I'd share this one:

 

[Drago]

I've had a bottle of Pepsi explode in my kitchen for no discernable reason whatsoever, and I'm pretty sure my house wasn't being driven up a mountain at the time.

 

[TheDoctor]

I've seen the crisps-inflating-themselves thing on a plane before (Handy Hint - there's a reason that airlines sell Pringles-inna-tube rather than crisps-inna-bag), and I can advise that leaving a can of lemon Fanta in a car in a ski resort overnight is a Very Bad Idea.
I don't know if it was the reduced air pressure at 1600 m, or the coldness, but the following day the inside of the car was coated in lemony badness...
But I've taken a bike to the top of Ventoux, and the tyres were fine
For that matter, I've taken a car to Val Thorens at 2200 m, and the tyres were fine also

 

[slowmotion]

I left a 2.5 litre can of emulsion paint in my rusty Fiat Panda on a very hot day. I returned to find that Jackson Pollock seemed to have visited.

PV=nRT

or something

 

[TheDoctor]

Well, a paint tin lid isn't designed to hold any pressure at all...

 

[sreten]

Hi,

Riding bike tyres at maximum pressure is just simply wrong,
unless your heavy and the tyres are skinny so your in the right
ballpark for tyre drop, then even so the front should be lower.

The practicalities for bad roads are simple, fit the fattest
tyre that will fit the bike and run at optimum lower pressure.
They will be more comfortable, faster and won't pinch flat.

Overinflating tyres from optimum makes you slower.

rgds, sreten.