Tire pressure - why my tires look so flat?

[G30M]

I see that these racing people with high volume tires set tire pressures at 21, 24 something like that

I have 255/35/19 RFTs and i am to set it at 39-50 COLD!

I tried 35PSI and the tire looks so flat

Even at 39 it still looks flat

What gives?

M340i is about 4000lbs with me in it

[G30M]

second question - maybe i need higher volume tires?

255 40 18 is exactly yhe same size i am after performance first second comfort looks not important

any advice?

[DanG]

Originally Posted by G80M4

second question - maybe i need higher volume tires?

255 40 18 is exactly yhe same size i am after performance first second comfort looks not important

any advice?

If you are performance first, get rid of those run flats. Try Michelin PS4Ss in stock size. I run at stock pressure and tires look fine.

[Westside Guy]

Originally Posted by DanG

If you are performance first, get rid of those run flats. Try Michelin PS4Ss in stock size. I run at stock pressure and tires look fine.

At the very least the OP should consider the Michelin Pilot Super Sports. They come as standard equipment when you order the 19 inch wheels on the Z4 M40i. BMW recommends 32 psi when the tires are cold and they look perfectly fine.

That being said I will probably get the Pilot Sport 4s tires when it is time to replace my SS ones as the 4s is a fabulous dry and wet performer and perfect for where I live in South Florida.

[HighlandPete]

Originally Posted by G80M4

second question - maybe i need higher volume tires?

255 40 18 is exactly the same size i am after performance first second comfort looks not important

any advice?

Got to ask, what is the problem? If the pressure is in the working range, you have the performance first, comfort second. How it looks is simply a case of "that is how it is", looking flat is not a problem.

Smaller diameter rims give higher sidewalls and performance gives way to more comfort. That's what you'd be doing with a higher aspect ratio on your current rims.

[Tommysalami]

Pics?

I ran a (non-performance all season) tire at too low pressure during an autox a long time ago and think I destroyed the sidewalls inner construction. After that no matter the pressure, the sidewalls sagged out a bit and they looked flat.

[G30M]

the issue is that performance track cars run high(er) volume tires [eg 265 35 18] and low pressures [24 psi] - but hey it was a stripped out F series M4 ... so perhaps very light

when i look at mine it's low volume and high pressure!

maybe a storm in a teacup ... 255 35 19 is probably same volume as 265 35 18 if not more ...

will do some more reading ....

yes that's why i'm asking questions, will be ditching RFTs on my next set

[HighlandPete]

Originally Posted by G80M4

the issue is that performance track cars run high(er) volume tires [eg 265 35 18] and low pressures [24 psi] - but hey it was a stripped out F series M4 ... so perhaps very light

when i look at mine it's low volume and high pressure!

maybe a storm in a teacup ... 255 35 19 is probably same volume as 265 35 18 if not more ...

will do some more reading ....

yes that's why i'm asking questions, will be ditching RFTs on my next set

A lot of variables and different requirements when we compare a track/race car. The M4 road setup is not on those sizes, if running 18" wheels. (255/40 ZR18 95Y / 275/40 ZR18 99Y on 9.0J x 18 / 10.0J x 18). The track setup you mention means the sidewall height is less than the road car. BTW, was the M4 running a square setup, or are you talking front or rear sizing?

You'd also need to know rim widths for those sizes, that also has an influence, besides the pressure. I'd say the key thing to consider is, a stripped out track/racing coupe is far different for weight and chassis balance than a road going, load carrying wagon.

[G30M]

hmm my car recommends (255 35 19) 39 psi min

whereas the G80 recommends 32 psi min for the same tire

https://www.carsguide.com.au/bmw/m-m.../tyre-pressure

[G30M]

M3


3 Series