Changing tire profile

[BDO]

Hi all,


I have a Z4M Roady, and need to change the tires. The stock sizes are RIDICULOUSLY expensive (255/40/18 and 225/45/18), and the sales dude suggested that I go to 255/35/18 and 225/40/18. The price difference is about 60%.

I understand that the speedometer will over read by about 4%. The diameter difference is about 4% smaller too.

Will there be any other adverse effects (other than the speed overread)?

Thanks!

 

[M@r]{]

It'll handle better, slightly harsher ride, you'll have a larger gap in the arches (excuse to buy some Eibach lowering springs) and accelerate better

If it were me I'd do it

 

[BDO]

Thanks mate!

 

[M@r]{]

BTW I'm no expert so wait for other advice before taking the plunge, thats just my take on it and what I'd do

 

[ga41]

I wouldn't, partly because I think my speedometer is already not that accurate but mainly because I think it would make the tires look too skinny in the wheel arches. If it was a track set of wheel/tires then I wouldn't care but not for a daily driver.

The pictures below work?

 

[geepee]

the sales dude suggested that I go to 255/35/18 and 225/40/18.

I thought that these are the stock sizes?

Thats what mine are anyway.

 

[ga41]

the sales dude suggested that I go to 255/35/18 and 225/40/18.

I thought that these are the stock sizes?

Thats what mine are anyway.

Stocks are 225/45/18 and 255/40/18

 

[Dav the wheel nut]

the sales dude suggested that I go to 255/35/18 and 225/40/18.

I thought that these are the stock sizes?

Thats what mine are anyway.

So did I :?

 

[WLH]

225/40-18 front and 255/35-18 rear are the stock size for non ///M E-85 roadster with staggered size tire setup. Stock size for the ///M is 225/45-18 front and 255/40-18 rear.

 

[BDO]

I wouldn't, partly because I think my speedometer is already not that accurate but mainly because I think it would make the tires look too skinny in the wheel arches. If it was a track set of wheel/tires then I wouldn't care but not for a daily driver.

The pictures below work?

Yep the pics work, but I don't think that they are very accurate, since the rim itself is smaller in the second pic. Don't think the difference would be quite as dramatic visually.

 

[ga41]

Well go by the pure numbers then, there's a 1.2cm difference in sidewall height...

 

[M@r]{]

If the OP is ok with a 4% inaccuracy in his speedo, which he has already mentioned he is, the only other thing imo is the gap in the arches, nothing a 10-20mm drop wouldn't sort out.

A 60% saving in tyre cost can't be ignored.

Could put it like this; whats better, going for premium band tyres with a lower profile, or going for a higher profile but on a budget tyre?

 

[Dreamer]

I have the lower profile rubber on my M wheels and they look much better. The car sits lower too remember. Go for it.