Wheel Offset / Rubbing Query

[jaedba2604]

Did put this in the BMW section but could do with some input sooner rather tan later and it's not really BMW specific so apologies but....

Evening,

I am after some advice regarding tyre compatability please.

I have just purchased a Z4 Coupe and the seller had 2 different sets of wheels, i didn't take both sets and have purchased the car with winter tyres on.

Initially I thought i'd just swap tyres, but given that a reasonable set of wheels can be had for not a huge amount of money and we seem to be enjoying ever more mercurial weather in this country, the luxury of being able to swap wheels at home is more appealing.

The winter tyres are on an 18" rim and i quite fancy going for some CSL style wheels for summer use. The seller had summer tyres on 19" rims (see sizes below) and experienced no rubbing, the car is lowered 20mm on eibach springs.

Given the sizes i state below, would my planned wheels rub if his old ones didn't? As far as i can see he was running a wider rear wheel with a more aggressive offset, so if anything my planned set up should be less prone to rubbing, but i didn't know if this was the case. The 'tyre man' has suggested 255/30 on the rear but this limits availability on the tyres - to either cheap or pricey!

sizes:

Existing 19"x8.5" et38 (tyre 235/35/19) front and 19"x9.5" et45 (tyre 265/30/19) rear

Planned 19" x 8" et34 (tyre 225/35/19) front and 19" x 9" et37 Deep concave (tyre 265/30/19) rear

Many thanks for any assistance.

[poo at Paul's]

Planned front should be about 8mm more sticky inny, the planned rear about 4 mm more sticky inny.
So check for clearance on the inside IMO, but should be fine.

[TVdinneR]

Once you know what wheel/tyre combination doesn`t rub, then you can start comparing your planned wheel/tyre combinations.
This will show you the comparisons between 2 wheels of differing width and offset:
http://www.1010tires.com/wheeloffsetcalculator.asp
The following will also show you the differences made by tyre sizes compared to your originals:
http://www.rimsntires.com/specs.jsp

It appears your planned front wheels give both more room inside and outside the wheel, whereas the planned rears will stick out a wee bit further on the wheel arch.
As far as tyres go, there is no need to step the fronts down to 225 unless you want to.
Its just the extra 8mm the rears will stick out with the 265`s
255`s will give you more clearance both sides but at the expense of the speedo being slightly out.

Edited by TVdinneR on Wednesday 7th March 12:29

Edited by TVdinneR on Wednesday 7th March 12:40

Edited by TVdinneR on Wednesday 7th March 12:48