Bike tyre v car tyre

[Markymark]

Sorry, probably dumb question but...

My car tyres kepp pretty much the exact pressure over 1year + whereas my bike I am pumping them up every couple of weeks. I do roughly the same mileage and on the same roads. Obviously there are difference in the tyres and the weight distribution, but the valves don't seem that different.

Why is that?

 

[ianrauk]

Bike tyres are pumped up to a far higher pressure the car tyres, double, triple the amount in a smaller amount of space so the air inside the tube is under far greater pressure to escape.

 

[Jon2]

It's probably the rubber being much thicker in a car tyre. The air escapes slowly through the thin rubber of a bike tyre.

 

[Markymark]

ok, both of those make sense.

 

[tyred]

Your car tyre also has a hell of a lot more air pumped into it so the tiny loss over time will take much longer to register on a typical simple tyre pressure guage.

 

[02GF74]

if your bike tyre has a shraeder type valve i.e. car type then it is probably on a cheap inner tube. Cheap inner tubes ten to have thick walls so are heavy so they should nbot leak. Some lightweight inner tubes- and I habre only come across presta valved ones, ok, there may be shraeder too but I do not recall seeing them and certainly would not have been looking for them since I do not use that type of valve (queue post as to which is better: shraeder or presta!!) and they achieve lightness by using different thin walled material - the result is less weight but bein more porous, they will go noticealby soft after say 1 or 2 weeks.

so basically, what I think I am saying is if your shraeder bike tyres are going soft in that sort of time (1-2 weeks) then either you have a slow puncture are the valve is not sealing properly.