Tyre Width Advice without rubbing

[sumotan]

Hi Gents,
Got a set of 19 inch 8.5 F & 9.5 R off set 35 mm all round. My tyre guy recommends to go wit 235/35 F & 265/30 rears confirm no rubbing.
Am gonna lower the car with Eibach Prokit. When I mentioned to my tyre guy that might be better if I go with 245/35 F & 275/30 R he says will rub. So question pls, is anyone here running the same combination without any issues ? Yes Im aware tyre is taller by 5-6mm but at the same time if my car is too low that 5-6 mm might just help with speed bums. lol

Many thanks again
Cheers

 

[Leek78]

I'm running 19" x 9" et35 F and 19" x 10" et38 R, with 235/35/19 F and 265/30/19 R tyres on my M sport e89, with no rubbing, and its close! IMO going any bigger will rub either the suspension or lip on some bumps.

 

[mr.tourette]

You'll need Mr Wilks expertise here, I'v just ordered 235/35/19 on et38 and 255/35/19 et35 wheel on his advice but my car is not lowered

 

[Nictrix]

Just to add a bit of info on ours
Front 8.5 et35 235/35/19 PS4s
Rear 10.0 et40 265/30/19 PS4s
No rubbing, standard Msport suspension
Would like to put 275 on the rear but not sure if anybody has done it and if this would introduce any rubbing.

 

[john-e89]

I’m on 235/35/19 fronts
275/30/19 rears on 30mm lowered springs than a standard M sport car, zero rubbing. Having said that I don’t know the ET tbh.

 

[john-e89]

Just to add a bit of info on ours
Front 8.5 et35 235/35/19 PS4s
Rear 10.0 et40 265/30/19 PS4s
No rubbing, standard Msport suspension
Would like to put 275 on the rear but not sure if anybody has done it and if this would introduce any rubbing.

No rubbing on mine on 275’s, M4 wheels Nictrix.

 

[Nictrix]

Just to add a bit of info on ours
Front 8.5 et35 235/35/19 PS4s
Rear 10.0 et40 265/30/19 PS4s
No rubbing, standard Msport suspension
Would like to put 275 on the rear but not sure if anybody has done it and if this would introduce any rubbing.

No rubbing on mine on 275’s, M4 wheels Nictrix.

Interesting. Offsets seem to be 29 front and 40 rear.
Probably be next year at least before needing new tyres.

 

[sumotan]

Thanks Gents,
I pretty sure that the fronts have no issues even on 245/35. Issue at hand is the rear cause offset is still 35mm had it be like 38-40mm offset,
problem would not exist. Unfortunately I love the looks of these wheel & they're light as well. Guess I would have to stick to my tyre man's advice.

Many thanks again
Cheers

 

[sumotan]

Just to share Gents & thank you again

 

[john-e89]

Just to add a bit of info on ours
Front 8.5 et35 235/35/19 PS4s
Rear 10.0 et40 265/30/19 PS4s
No rubbing, standard Msport suspension
Would like to put 275 on the rear but not sure if anybody has done it and if this would introduce any rubbing.

No rubbing on mine on 275’s, M4 wheels Nictrix.

Interesting. Offsets seem to be 29 front and 40 rear.
Probably be next year at least before needing new tyres.

I’ll check the et next time the wheels come off.

 

[mcbutler]

The people who make the Z4 spend ££ millions and many days if not months trialling tyre sizes in all sorts of conditions. The tyre they decide is the best option is the original size.
Mess with tyres at your peril, if you increase width you are reducing pressure on the tread contact patch and the ability of the tyre to pierce water film and reducing grip in the dry (unless you add a few sandbags of course).
No one will notice wider tyres, it wont change the look of your car either, safety first chum.....

 

[mr wilks]

The people who make the Z4 spend ££ millions and many days if not months trialling tyre sizes in all sorts of conditions. The tyre they decide is the best option is the original size.

Worth noting at this point the latest Z4 G29 come with proper sized tyres as do most of the other Bmw range like 3, 4 & 5 series ,
None run the rears 255 30 19 or 255 35 18 of previous models :wink: i don't see any issues whatsoever in changing tyre sizes if done with some sense & a little knowledge .
eg a 245 40 18 instead of a 255 35 18 on a 108 or MV2 ( 8.5j) isn't going to suddenly turn a car into a lethal weapon , you would in fact have a greater contact area , more comfort & better wheel protection .

 

[Nictrix]

a 245 40 18 instead of a 255 35 18 on a 108 or MV2 ( 8.5j) you would in fact have a greater contact area

Can you explain this bit as I dont quite understand it. It doesnt make sense in my head.

 

[mr wilks]

a 245 40 18 instead of a 255 35 18 on a 108 or MV2 ( 8.5j) you would in fact have a greater contact area

Can you explain this bit as I dont quite understand it. It doesnt make sense in my head.

I'l try here we go nice and slow
a 2 4 5 - 4 0 - 1 8 tyre fitted to a 8.5j rim will have a greater contact area on the tarmac than a 2 5 5 - 3 5 - 1 8 tyre .

 

[Nictrix]

a 245 40 18 instead of a 255 35 18 on a 108 or MV2 ( 8.5j) you would in fact have a greater contact area

Can you explain this bit as I dont quite understand it. It doesnt make sense in my head.

I'l try here we go nice and slow
a 2 4 5 - 4 0 - 1 8 tyre fitted to a 8.5j rim will have a greater contact area on the tarmac than a 2 5 5 - 3 5 - 1 8 tyre .

Oooohh you made yourself look all clever by trying to spell it out but really it just looks the same with no explanation. :thumbsdown:
It was a simple question that I thought you might have been able to explain.
Surely a 255 tyre has 10mm more tread across the width of the tyre in contact with the road than a 245, so how does increasing the sidewall by 5% increase the contact area of the tyre?

 

[Nictrix]

Can you explain this bit as I dont quite understand it. It doesnt make sense in my head.

I'l try here we go nice and slow
a 2 4 5 - 4 0 - 1 8 tyre fitted to a 8.5j rim will have a greater contact area on the tarmac than a 2 5 5 - 3 5 - 1 8 tyre .

Oooohh you made yourself look all clever by trying to spell it out but really it just looks the same with no explanation. :thumbsdown:
It was a simple question that I thought you might have been able to explain.
Surely a 255 tyre has 10mm more tread across the width of the tyre in contact with the road than a 245, so how does increasing the sidewall by 5% increase the contact area of the tyre?

Forget it, I searched the net and it seems it all rests on the width of the wheel.

 

[mr wilks]

I'l try here we go nice and slow
a 2 4 5 - 4 0 - 1 8 tyre fitted to a 8.5j rim will have a greater contact area on the tarmac than a 2 5 5 - 3 5 - 1 8 tyre .

Oooohh you made yourself look all clever by trying to spell it out but really it just looks the same with no explanation. :thumbsdown:
It was a simple question that I thought you might have been able to explain.
Surely a 255 tyre has 10mm more tread across the width of the tyre in contact with the road than a 245, so how does increasing the sidewall by 5% increase the contact area of the tyre?

Forget it, I searched the net and it seems it all rests on the width of the wheel.

Apologies if offended , it was meant with some humour
i can't give you the mathematical equation , i haven't the skills but basically the contact patch is bigger with 245 40 18 over 255 35 18 on 8.5j as it makes the patch longer so the patch area is larger but not necessarily wider , the same effect on 9.5j rims with 255 35 19 over 265 30 19 , you think wider is better but you actually decrease the amount of rubber on the road .
.
"mcbutler" also has a relevant point RE tyre pressures having effect on contact patch which isn't that surprising & no doubt manufacturers apply higher pressures when attempting to get better MPG that reduces contact area whereas lower pressure would achieve less mpg with a greater amount of tyre on tarmac

 

[engine killer]

a quick calculation, 245/40-18 vs 255/35-18 the circumference, 245 is about 55mm (2.68%) longer
255/35-19 vs 265/30-19, 255 is about 61mm (2.95%) longer

the percentage difference play a very very small effect on speedometer

 

[Nictrix]

Oooohh you made yourself look all clever by trying to spell it out but really it just looks the same with no explanation. :thumbsdown:
It was a simple question that I thought you might have been able to explain.
Surely a 255 tyre has 10mm more tread across the width of the tyre in contact with the road than a 245, so how does increasing the sidewall by 5% increase the contact area of the tyre?

Forget it, I searched the net and it seems it all rests on the width of the wheel.

Apologies if offended , it was meant with some humour
i can't give you the mathematical equation , i haven't the skills but basically the contact patch is bigger with 245 40 18 over 255 35 18 on 8.5j as it makes the patch longer so the patch area is larger but not necessarily wider , the same effect on 9.5j rims with 255 35 19 over 265 30 19 , you think wider is better but you actually decrease the amount of rubber on the road .
.
"mcbutler" also has a relevant point RE tyre pressures having effect on contact patch which isn't that surprising & no doubt manufacturers apply higher pressures when attempting to get better MPG that reduces contact area whereas lower pressure would achieve less mpg with a greater amount of tyre on tarmac

Not offended I was only looking for an answer
Now does this make a difference with the same tyres on a different width rim?
For instance the same tyres on a 9" rim would the 255 tyre have more in contact with the road than the 245 then?
Just thinking aloud about a 275 on a 10" rim, is it a better fit for the rim than a 265 which looks a little stretched?

 

[mr wilks]

@nictrix,
265 30 19 on 10j is as you point out "undersized" I would be on 265-35-19 or 275-30-19 either of which would increase contact patch over 265-30-19 & give rim protection + improve ride comfort