Cycling UK Forum

simonhill wrote:tyre pressure increases by 0.1 bar for 10 degrees C (1 bar = 14 psi)

Tyres pumped to 6 bar (=90psi) at 17°C, pre-ride in the early morning.
Bike left parked in the sun over a lunch stop, with black tyres getting up to 75°C (say).

That's a pressure of 6*(273+75)/(273+17) = 7.2 bar

Hey thanks everybody for some really interesting information and I'm learning a lot from you all
I had never thought about the heat on the tyres previously even though the same thing happened to an old sports car of mine that is only used in the early spring and autumn and left in the sun in the summer because its too hot. I always cover the soft top car up but forgot about the wheels and one year all four tyres had sidewall issues due to the sun melting them, but never thought of that issue with the bike, yes it is covered up and it does have black sidewalls on the current tyres. I will ensure that the when I put the cover on I also cover the wheels.
Will get some normal tyres and see how it goes
Thanks again
Amazing stuff

Worth mentioning that using rim brakes a lot creates heat and can make tyres explode, I had that happen in Wales

Schwalbe marathon plus are great for puncture resistance but I prefer something with better ride quality (and still having excellent puncture resistance) is a Schwalbe marathon supreme.

Another vote for the Marathon Supreme. I've been using for the last few years.

Hardly ever have a puncture and have regularly ridden in temps of 30° and sometimes over 40.

When getting new tyres, it could be an idea to have the rim tape replaced. Won't cost much.

andrew_s wrote:

simonhill wrote:tyre pressure increases by 0.1 bar for 10 degrees C (1 bar = 14 psi)

Tyres pumped to 6 bar (=90psi) at 17°C, pre-ride in the early morning.
Bike left parked in the sun over a lunch stop, with black tyres getting up to 75°C (say).

That's a pressure of 6*(273+75)/(273+17) = 7.2 bar

7.2 bar isn't that excessive - I think most modern tyres will withstand a pressure of that magnitude.
Didn't CJ suggest pumping a tyre well above normal levels to test the integrity of a rim?
IME during at least 70 years I have never observed a tyre exploding from being left in the sun.
I did hear some explosions when riders were inflating tyres when preparing for the Paris-Roubaix randonee but that was at 4 in the morning probably due to not fitting tubes correctly.
OTOH on a long descent I've sometimes had to stop to let the rims cool - the rim can get hot enough to burn the hand - that will cause an inner tube to explode- not happened so far.