Tyre pressures for 18" wheels?

[GorillaPie]

Morning morning!

Seeking advice on recommended tyre pressures for non-standard wheels...

My recently-acquired Z3 3.0i is fitted with what I assume to be aftermarket 18" M-branded alloys - currently running Conti 225/40s at the front and 255/35s at the rear.

Obviously the PSI numbers stipulated in the owner's manual are for the original rims, so I'm not sure what I should be aiming for in terms of tyre pressures on these aftermarket rims?

Any advice from other 18" owners much appreciated - thank you!

(loving the car otherwise - notwithstanding all the usual gripes about it not handling as sharply as an Elise, yawn, etc, etc - M54B30 remains a peach, even if it gives the car more of a torquey GT character than, say, the S2000 with its VTEC motorbike engine)

 

[andyglym]

Morning morning!

Seeking advice on recommended tyre pressures for non-standard wheels...

My recently-acquired Z3 3.0i is fitted with what I assume to be aftermarket 18" M-branded alloys - currently running Conti 225/40s at the front and 255/35s at the rear.

Obviously the PSI numbers stipulated in the owner's manual are for the original rims, so I'm not sure what I should be aiming for in terms of tyre pressures on these aftermarket rims?

Any advice from other 18" owners much appreciated - thank you!

(loving the car otherwise - notwithstanding all the usual gripes about it not handling as sharply as an Elise, yawn, etc, etc - M54B30 remains a peach, even if it gives the car more of a torquey GT character than, say, the S2000 with its VTEC motorbike engine)

Hi mate, I run staggered 18's on my 2.8, I played around and settled on 32psi all round. Does the job.

 

[GorillaPie]

Thanks for the super-quick reply! People seem to be so helpful on this forum - clearly Z owners are a nice bunch?!

Let me try 32psi and see how I get on - have read in some places that Z3 handling is unusually dependent on running the optimum tyre pressures, not sure how true this is but also hard to know what 'standard' handling is even supposed to feel like when I don't yet know if other mods have been made to the bushes etc.

Obviously I know about the larger wheels and front strut-brace but will have to wait and see on all the other stuff. Generally I've been pleasantly surprised by the ride quality given tyre profiles etc, steering feel is not exactly telepathic but what can one expect with the chunky aftermarket wheels etc... Anyway thanks again for the quick advice!

 

[andyglym]

Thanks for the super-quick reply! People seem to be so helpful on this forum - clearly Z owners are a nice bunch?!

Let me try 32psi and see how I get on - have read in some places that Z3 handling is unusually dependent on running the optimum tyre pressures, not sure how true this is but also hard to know what 'standard' handling is even supposed to feel like when I don't yet know if other mods have been made to the bushes etc.

Obviously I know about the larger wheels and front strut-brace but will have to wait and see on all the other stuff. Generally I've been pleasantly surprised by the ride quality given tyre profiles etc, steering feel is not exactly telepathic but what can one expect with the chunky aftermarket wheels etc... Anyway thanks again for the quick advice!

Just for note, the tyre pressures are one of many factors that impact on handling, if some/many/all bushes are past their prime this will impact heavily. All mine are done and runs sweet as, zero tramlining.

 

[t-tony]

I run those sizes on my Z4 at 33 front and 36 rear. These are my summer (dry weather) wheels.

Tony.

 

[milsford]

Last month, I bought 225/40's and 225/35's from 4wheelonline for my 2.8 and I run them at 32 psi. Ride is good so far.