You don't need to be an 'investor' to invest in Singletrack: 6 days left: 95% of target - Find out more
Probably dumb question alert.
Now, I know that you're supposed to check your car tyres regularly, and you should do it when they're cold. I will be honest and say that I probably don't check them enough, but do when I have a longish journey to make, which I do on Thursday.
Thing is, they're not just cold at the moment, they're cold. Like probably just about freezing. So, do I have to take that into account? The temperature means that they'll doubtless be showing a lower pressure than they otherwise would, but if I top them up to the right pressure will they not then be over-inflated once they get up to temperature? Or am I overthinking it?
You're overthinking it.
Temperature is measured relative to absolute zero, or -273.15 deg C.
So the difference between now (say, 0C), and an early start in June (say, 10C) is going to be <4%, or about 1psi, or within the likely margin for error between guages.
More accurately than that, yes there will be an additional impact from water condensing inside the tyre, but we're still probably talking about margins about as thick as the needle on the guage.
I'd pump them upto whatever the sticker in the door says. Either they'll have lost 2-3 psi by themselves by the time its 40C again, or you'll check them once a week between now and then and let it out yourself.
Mine are usually all 42psi, today with the cold they’re all 38psi, I’ll leave them as is for now as they with creep back up with the temperature, as long as they all show about the same I’m happy enough.
Variation in load will make a bigger difference. If in doubt, slightly higher pressure is better than under pressure for braking.
Mine are usually all 42psi, today with the cold they’re all 38psi, I’ll leave them as is for now as they with creep back up with the temperature, as long as they all show about the same I’m happy enough.
unless you live in Braemar that reduction in pressure was not caused by the effect of temperature change.
Cheers all, I'll just stick in whatever's on the door sticker. If I can defrost the door to open it..
Yeah, I have never understood this.
As in, my mental calculations with respect to Absolute Zero agree with yours and that even with a 30deg swing, they shouldn't vary by more than about 3psi (10%), but the variation with temperature always seems to be more than that.
Apart from a vague curiiosity, I don't give it too much attention though.
@gonefishin Braemar is just over 60 miles away so not that far, good guess!
They won't get as warm as they do in summer, so it'll even out.
Set the pressures in a sort of typical temperature for the time of year. When the weather changes, re-check them again. Mine are ok now - set to the recommended pressure on a -1C morning, but if the weather breaks and we get to 12C I'll do it again. Likewise in summer if there's a heatwave I'll be sure to check before and after.
Yes, you are overthinking it to a degree...
However... Given you're not likely to drive as hard in current conditions, and that lower pressure does generally equal more grip (to a point obviously), then I'd err on the side of slightly lower pressures than slightly high.
Tyre pressure recommendations are made assuming a typical 15-20deg ambient temperature, and a "cold" tyre (that is to say one that hasn't yet been warmed up through use)... Drop the temps by 20deg, and the pressures will drop a little anyway. If your "cold" recommended temp for your car tyres is 42psi, then in 0deg temps, I'd say 38psi is probably about right (the tyre will lose maybe 2psi due to temp, but then running it 2psi lower to aid with grip won't hurt either)... Similarly if temps in summer are as high as they were this summer, over inflating by 2-3psi won't hurt either especially if you don't want to overheat the tyres too soon.
slightly higher pressure is better than under pressure for braking
Ignoring extreme pressures, why would, say, 40psi be better than 30psi on a car that has a recommended pressure of 35psi? My brain suggests it's the other way around
Make sure you adjust for altitude too.
And the current high pressure weather system we have. You'll need to let a little bit out when a low pressure system comes in.