Tyre size and pressure

[Waftycrankers]

Hi all
Looking for some advice on the sizes of my Tyres, I have 225/35/19 on the front and 225/30/19 on the rear. Is difference in profile usual?
Also, what pressure should I be inflating to?
Thanks for any advice in advance….

[B21]

Rear should be 255/30 19 not 225/30

225/35 19 and 255/30 19 are standard sizes on factory 19”rims

36/42 psi is the factory figures for oe runflats

If you don’t have runflats different pressures apply

[KennyP]

On Michelin website you can enter all your car details(mark model, engine, wheel and tire sizes) and it gives you recommended tire pressures.
for 19 inch stock tire sizes on a 35i it recommends 2.3 bar front and 2.8bar rear.
The sticker in the drivers door jam/gap says 2.4 bar front and 2.9bar rear, thats the same as B21 said in psi.

[Waftycrankers]

Thanks for the replies this far. My error, the rears are 255/30/19 not 225.
Mine are not run flats.
Unfortunately the sticker on the door jam is half torn. Not sure why.

[B21]

Originally Posted by Waftycrankers

Thanks for the replies this far. My error, the rears are 255/30/19 not 225.
Mine are not run flats.
Unfortunately the sticker on the door jam is half torn. Not sure why.

Yiu may find for non run flats that pressures in he range 32/34 through 36/38 are more beneficial..

[Waftycrankers]

Thanks. I’ve found a couple of links online, state that non run flats pressure should be 33psi in the fronts and in the rears.

[KennyP]

Hmm i wouldnt go too low from stock pressures at the rear... on 19 inch rims you can risk developing cracks on the inside edge of the wheel.
That edge is already lower than the outside edge because of negative camber.
now if you lower tire pressure aka deflate tire you diminish the sidewall even more and risk banging that edge up.

I remember years ago there were threads where people even suggested inflating rears past stock pressure to keep cracking from happening... 33 in the rear seems too low to me.

My suggestion is to try it yourself... start with stock figures and slowly deviate from them and test. See what you prefer. For me i even notice from driving that tires are 0.2-0.3 bar low...

Couple illustrations that were posted on this forum in 2010...

[Waftycrankers]

Oops, just realised I missed a little info from my last post, the site I found states 33psi (2.3bar) in the fronts and 41psi(2.83bar) in the rears.

[B21]

For non run flats there’s no specific pressures…as discussed it’s best to experiment to see what works for you …personally I find 32/34 to 34/36 works for me..be that on 18” and 19”…

[Steve Jarvis]

I run 34psi all around, but B21's recommendation looks good to me. His lower front pressures helps negate some of the understeer. These cars need way more rear bar. I'm on H&R springs right now, but the balance is similar to stock.

[Marcoose]

I'm on M4PS. 34 front, 38 rear. KWV3 and other suspension upgrades too. It's tits.