quick tyres question

yipikayee · Post by **yipikayee** » Mon Jul 05, 2021 9:03 pm

Quote from the sticky guide:

"18” Tyre Sizes
Changing tyre sizes is also an option for those with 18” wheels. This could be because of a complex suspension and low spring set up, or simply to save some money on opting for slightly thinner tyres. The fronts can be changed from standard 225/40/18 to 215/40/18 (narrower) or 215/45/18 (narrower and for increased sidewall… comfort). Rear wheels as standard are 255/35/18 and this could be changed to 245/35/18 (narrower) or 245/40/18 (narrower and for increased sidewall… comfort)."

Now, i have order 245/40/18 on the rear, does it make a difference if i will go for 225/40/18 or 215/40/18 on the front?

Rears should arrive tommorow, want to change front tyres now, so wanted to double check vefore i would do a mistake.

Thanks

Mr Tidy · Post by **Mr Tidy** » Mon Jul 05, 2021 9:44 pm

With 245/40 tyres on the rear fitting a 40 profile on the front will make it sit a bit higher at the rear in relation to the front, compared to the standard tyre sizes - if that matters!

I'd probably stick to 225 fronts, even if only for a bit more kerb protection for your wheels. But possibly go for 225/45 fronts. That was the standard size for the M models, with 255/40 rears.

But there probably isn't a wrong answer - it all comes down to personal preference and what you want to achieve. Your choice for rears suggests you may be looking for a bit more compliance to help the ride - if that is the case I'd definitely go for 225/45 fronts.

Pbondar · Post by **Pbondar** » Mon Jul 05, 2021 10:43 pm

The key point is that the rolling diameter / circumference of the front and rears should ideally be within 1% tolerance ..

That’s why the fronts are always one size up in terms of aspect ratio over the rears..

This is for E85/E89 not necessarily for other BMWs..

sars · Post by **sars** » Tue Jul 06, 2021 8:21 am

If you could explain why you want to change from stock sizes?

Stock size for the front alloy width is 8” so ideal is 225 or 235, minimum is 215 but that will limit the amount of rim protection afforded.
Standard sizes were, excepting Z4M
16”& 17” 8 x 16/17 ET47, 225/50 R16 or 225/45 R17 all round (square set up)
18” fronts 8 x 18 ET47, 225/40 R18 & 8.5 x 18 ET50, 255/35 R18 (staggered)

yipikayee · Post by **yipikayee** » Tue Jul 06, 2021 3:21 pm

Thank you all for reply

Mr Tidy wrote: ↑Mon Jul 05, 2021 9:44 pm Your choice for rears suggests you may be looking for a bit more compliance to help the ride - if that is the case I'd definitely go for 225/45 fronts.

yes, more comfort and better grip. tyres i have now on are too stretched and its time for a change. Does 225/45 wont cause rubbing? i have standard suspension with fresh B4 bilstein

sars wrote: ↑Tue Jul 06, 2021 8:21 am If you could explain why you want to change from stock sizes?

i never had standard sized tyres on.
car came with awful setup of 19" rims, changed that in first two weeks to 18" staggered 8/8.5j style 32 , MASSIVE difference. so was happy with it for a long time but now i think its time for the tyres to go and want to do proper size this time.

Mr Tidy · Post by **Mr Tidy** » Tue Jul 06, 2021 7:07 pm

yipikayee wrote: ↑Tue Jul 06, 2021 3:21 pm yes, more comfort and better grip. tyres i have now on are too stretched and its time for a change. Does 225/45 wont cause rubbing? i have standard suspension with fresh B4 bilstein

I suppose each car has slightly different tolerances but the width is the same as OE so that won't be an issue, just possibly more sidewall depth although there is a fair bit of height in the arches.

I've got H & R coil-overs so my car is about 15mm lower than standard and my 225/45s aren't a problem.

yipikayee · Post by **yipikayee** » Tue Jul 06, 2021 7:27 pm

Mr Tidy wrote: ↑Tue Jul 06, 2021 7:07 pm
yipikayee wrote: ↑Tue Jul 06, 2021 3:21 pm yes, more comfort and better grip. tyres i have now on are too stretched and its time for a change. Does 225/45 wont cause rubbing? i have standard suspension with fresh B4 bilstein
I've got H & R coil-overs so my car is about 15mm lower than standard and my 225/45s aren't a problem.

thats great news, thank you

i actually found same tyres i bought for rear in said size and in great price as well so will order them today.

Thanks for help

mmm-five · Post by **mmm-five** » Wed Jul 14, 2021 12:46 pm

Mattex wrote: ↑Wed Jul 14, 2021 12:33 pm I'd go with 225 fronts just to give your wheels a little more kerb protection. 225/45 fronts, on the other hand, are a possibility. That was the standard size for M models, with 255/40 rear tires. It is very important to choose the right [url=https://*************.com/wheel-and-tire-packages.283376]wheels and tires[/url] for your car for your safety.

Mattex trying to spam again, with his bot-generated, nonsensical posts - at least the link has been auto-filtered out.

brillomaster · Post by **brillomaster** » Wed Jul 14, 2021 4:24 pm

i did wonder about Mattex and every post of his having some embedded link somewhere. so has he been deleted now?

mmm-five · Post by **mmm-five** » Wed Jul 14, 2021 5:24 pm

brillomaster wrote: ↑Wed Jul 14, 2021 4:24 pm i did wonder about Mattex and every post of his having some embedded link somewhere. so has he been deleted now?

I assume so, but you think they'd go to a bit of effort to check where the majority of users are from and spam forums that are from the US where a US link may generate some interest

Z4-forum.com

Z4-forum.com