Question for the tyre gurus,changing width 225 to 235

Montegojones41 · Post by **Montegojones41** » Wed Jun 03, 2020 9:12 pm

I have some new alloy wheels which are 8.5j front and 9.5j rear, fronts have 225/40/18 tyres fitted on the front currently but they look slightly stretched, will fitting 235/40/18 fit without affecting speedo too much and look more square on the wheel?
according to a tyre calculator see the pic,
thanks!

MACK · Post by **MACK** » Wed Jun 03, 2020 9:33 pm

Hi,

It wont affect the speedo at all as that's done from one of the rear wheels. It will look squarer/less stretched although I personally don't think 225/40 on a 8.5" looks bad at all, I have it on mine

Montegojones41 · Post by **Montegojones41** » Wed Jun 03, 2020 10:09 pm

Given the alloys it might give them slight rim protection also, was also hoping that as its very so slightly bigger in diameter that it wouldnt rub the arch liners, im on standard sport suspension currently, is yours lowered?

Mr Tidy · Post by **Mr Tidy** » Wed Jun 03, 2020 10:18 pm

I'd want a bit more rim protection too if possible - after all BMW fitted 255/35 tyres on the 8.5J rims on the rear with staggered 108s, MV2s, etc.

I can't see a 235/40x18 causing rubbing on the front - I've got 8.5Jx19 CSL Reps on mine with 235/35 x 19 tyres and have had no rubbing issues. Well not since I removed the spacers and got the coil-overs raised!

Montegojones41 · Post by **Montegojones41** » Wed Jun 03, 2020 10:56 pm

Pics should give you an idea , tyres on there are stretched think I’ll get away with 255 on the back but front can do 235 with some protection , just going from 255 to 265 the prices jumps a lot !
Does yours feel better now it’s raised a bit and no spacers ?

Pbondar · Post by **Pbondar** » Wed Jun 03, 2020 11:33 pm

I run 17” and 18” with 235/40 or 235/45 on msport springs with no issues apart from slightly heavier steering..but feel sure footed..

What offsets do you have?

Montegojones41 · Post by **Montegojones41** » Wed Jun 03, 2020 11:50 pm

Not sure on the offsets , I did trial fit the alloys to the car a couple of weeks ago and they sit perfect level with the arch edge , they came off a z4 e86 coupe owners car.
How come you run 17 on the front and 18 rear ? Never heard of that setup

Pbondar · Post by **Pbondar** » Thu Jun 04, 2020 9:50 pm

Montegojones41 wrote: ↑Wed Jun 03, 2020 11:50 pm Not sure on the offsets , I did trial fit the alloys to the car a couple of weeks ago and they sit perfect level with the arch edge , they came off a z4 e86 coupe owners car.
How come you run 17 on the front and 18 rear ? Never heard of that setup

Sorry for the confusion..

I have a set of 17” team dynamics pro race 1.2 running 235/45 17 and 255/40 17 and Zito 935 18” running 235/40 18 and 255/35

You should try and get the front offset down to 29mm ish if possible IMHO otherwise the steering may feel either twitchy or heavy..29mm is the E89 standard front offset, the E85 had quite different offsets about 17mm more..

Mr Tidy · Post by **Mr Tidy** » Thu Jun 04, 2020 10:47 pm

Montegojones41 wrote: ↑Wed Jun 03, 2020 10:56 pm Pics should give you an idea , tyres on there are stretched think I’ll get away with 255 on the back but front can do 235 with some protection , just going from 255 to 265 the prices jumps a lot !
Does yours feel better now it’s raised a bit and no spacers ?

To be honest it doesn't feel much different as the spring and damper rates aren't adjustable, but it does mean I don't have to clench my teeth waiting for sounds of grounding when I go over a speed bump!

M models had 9J rears with 245/40 tyres so a 255 tyre ought to work on a 9.5J rim, although there won't be much protection - as I found out with my 265s on 9.5Js.

Pbondar mentions heading towards E89 offsets. I had a set of staggered 18" E89 wheels on my 2nd Coupe and they were 18mm further out at the front, 10mm at the rear compared to the staggered E85/86 18s.

But your fronts are 8.5J not 8J so you need to take that into account too, although I don't think you have said what ET your wheels have (it's usually stamped on the back of the rim, but BMW call it IS).

Pbondar · Post by **Pbondar** » Thu Jun 04, 2020 11:14 pm

Mr Tidy wrote: ↑Thu Jun 04, 2020 10:47 pm
Montegojones41 wrote: ↑Wed Jun 03, 2020 10:56 pm Pics should give you an idea , tyres on there are stretched think I’ll get away with 255 on the back but front can do 235 with some protection , just going from 255 to 265 the prices jumps a lot !
Does yours feel better now it’s raised a bit and no spacers ?
To be honest it doesn't feel much different as the spring and damper rates aren't adjustable, but it does mean I don't have to clench my teeth waiting for sounds of grounding when I go over a speed bump!

M models had 9J rears with 245/40 tyres so a 255 tyre ought to work on a 9.5J rim, although there won't be much protection - as I found out with my 265s on 9.5Js.

Pbondar mentions heading towards E89 offsets. I had a set of staggered 18" E89 wheels on my 2nd Coupe and they were 18mm further out at the front, 10mm at the rear compared to the staggered E85/86 18s.

But your fronts are 8.5J not 8J so you need to take that into account too, although I don't think you have said what ET your wheels have (it's usually stamped on the back of the rim, but BMW call it IS).

Please ignore all my comments ..I thought you had an E89...I know zippo about E85s/E86s

Well apart from they are very nice cars

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