We all know tyres should be checked and inflated when cold, however how much difference does this actually make?

I need to do the tyre pressures on the BMW before Scotland, and I’ve only got tomorrow to do it. It’s a pretty warm and sunny day, so doing it in the evening would obviously be best, but then I’d be doing it with the car packed!

I’m hoping to get up and do it early, but if not then - any ideas?

My car lives in the garage - the BMW is not as lucky!

38 minutes ago, OccyVRS said:

...but then I’d be doing it with the car packed...

Carrying a full load in the car doesn't increase the tyre pressures...even on a temporary basis while the load is being carried.

For example, the spare tyre will have the same tyre pressure whether it's off the car or fitted to the car carrying the weight of the car.

If the car's tyres are inflated when they are hot, simply add 3psi to the normal pressures and check again (adjusting the pressures if necessary) in the evening or after dark when the sun isn't heating the air in the tyres.

Air expands by about 10% when the temperature increases from 20 degrees Centigrade to 50 degrees Centigrade...so you might find that the tyre pressures increases by about 10% when they are measured at 50C compared to when they are measured at 20C...or about 3psi.

Edited 22 May22 May by Carlston

thread about tested standalone dTPMS kits

-> https://www.briskoda.net/forums/topic/434028-tire-pressure-monitoring-system/#comment-5895850

pumped 2.5 in the spring, later in the summer, can easily reach 3.0 bar

I can check mine in the morning after a cold night and maybe 2.4 Bar and later in the day 2.6 Bar, and after 5 miles driven 2.7. Today they will be at 2.8 Bar when the ambient temp gets to near 20*oC. But that is Air temp. The road surface / surface where parked will be much higher than the air temp with the sun heating it. Parked on Asphalt in the sun the pressures / temperatures can be a bit different than on red or grey pavers or on concrete / slabs. Try it, just move the car from one surface to another. Maybe only a matter of feet apart. Often where i park the drivers side are higher temp and pressure than the passenger side because sitting in the sun compared to the other side in the shade.

Edited 22 May22 May by Evolution13

I'd not rely on a VW or BMW computer system, though it might be right most times I'd confirm with indepedent equipment, a tyre pressure gauge. This doesn't have to be expensive, being consitent is very important, use the same reliable guage all the time as one reliable guage may vary slightly in its reading to another or other reliable gauges.

PSI -"Every 10°C change in temperature alters tyre pressure by 1-2 PSI." - https://www.national.co.uk/blog/hot-weather-tyre-pressure 

Edited 22 May22 May by nta16

Fixed with just a valve replacement not the sensor and better than mates rates, done for free gratis. Larry.