[E91d325]

Hi all,

Might have made a mistake here... bought some 437m wheels off an M4.

Fronts are 255 35 19
Rears are 275 35 19

I hadn't thought it would be an issue I've fitted them and only done 5 miles.

But checking the tyre pressures are realised that the sticker doesn't account for those sizes?

So I'm assuming that I'm gonna have to change the tyres?

They have only done about 5k miles....so will I nee to change all the tyres or just 2?

Feeling very stupid.

[alexonahurry]

they are perfectly fine mate, no issues - size is recommended for the wheel set

[E91d325]

Oh really? Ive been under the impression it's going to throw the Rolling circumference out?
And then will cause my 435xdrive issues?

Someone's said I should swap too
235 40 19
And
265 35 19

Thanks

[alexonahurry]

Originally Posted by F32435d

Oh really? Ive been under the impression it's going to throw the Rolling circumference out?
And then will cause my 435xdrive issues?

Someone's said I should swap too
235 40 19
And
265 35 19

Thanks

It fits a normal F3X, not sure about XDrive. Is your car already showing any errors?

[Tommi_Mav]

I have the same car with you (F32 435dx) and I also use a set of 437m off of an M4.

To begin with, according to BMW this tyre combo is not recommended for our car. Additionally, rolling circumference exceeds 1% difference. Nevertheless, I used them for almost 1 year and a half without any problems until they were worn out. I even drove a total of 10 laps in the Ring. Only when it was time to put new shoes on, I changed the rears to 265/35 (kept fronts as 255/35 again) to keep the difference close to 1%. Didn't want to put 255 wide in the rears, fearing of stretching the tyres on a 10" wheel.

I initially wanted to put 245/40 front, 275/35 rear due to lower total cost, but there was no non-RFT version for the fronts in MPSS line.

Regarding tyre pressure, I use 2.6 bar front and rear. My tyre pressure sticker on the car's column (probably yours too) has an indication for 2.6 when using 255/35/19 on the rears, so I went with that.

I know a lot of people say you may put x-drive system under stress when exceeding 1% rolling circumference difference, but unless you do hard accelerations, I don't think you'll have any problems with your combo until it's time to change tyres. Otherwise, if you want to keep your head free of worries, you can change only one set of tyres (front or rear) to match their rolling circumference. IMHO, I wouldn't go to 235 wide in the front due to stretching the tyre on a 9" wheel, but at the end... it's up to you.

[E91d325]

Originally Posted by Tommi_Mav

I have the same car with you (F32 435dx) and I also use a set of 437m off of an M4.

To begin with, according to BMW this tyre combo is not recommended for our car. Additionally, rolling circumference exceeds 1% difference. Nevertheless, I used them for almost 1 year and a half without any problems until they were worn out. I even drove a total of 10 laps in the Ring. Only when it was time to put new shoes on, I changed the rears to 265/35 (kept fronts as 255/35 again) to keep the difference close to 1%. Didn't want to put 255 wide in the rears, fearing of stretching the tyres on a 10" wheel.

I initially wanted to put 245/40 front, 275/35 rear due to lower total cost, but there was no non-RFT version for the fronts in MPSS line.

Regarding tyre pressure, I use 2.6 bar front and rear. My tyre pressure sticker on the car's column (probably yours too) has an indication for 2.6 when using 255/35/19 on the rears, so I went with that.





I know a lot of people say you may put x-drive system under stress when exceeding 1% rolling circumference difference, but unless you do hard accelerations, I don't think you'll have any problems with your combo until it's time to change tyres. Otherwise, if you want to keep your head free of worries, you can change only one set of tyres (front or rear) to match their rolling circumference. IMHO, I wouldn't go to 235 wide in the front due to stretching the tyre on a 9" wheel, but at the end... it's up to you.

That's good to hear,

I was looking at replacing the front with 245 40 19 but they are not made in Michelin SS.
So looked at 235 40 19 and it seems that pilot sport 4s are the only ones available but then I'm mixing the patterns.

Obviously BMW have said either is not good.

Your set up is 3.5mm difference, how's that been? I thought it was a 3mm max.

I'm mapped and zf gearbox tune, maybe I'll just keep the acceleration light for now and then change at a later stage.

I would like to ideally change the front, but I would have to change to pilot sport 4s... And then I'm running different tyres! What a nightmare

[Tommi_Mav]

Originally Posted by F32435d

Your set up is 3.5mm difference, how's that been? I thought it was a 3mm max.

255 has a circumference of 2076.9mm, whereas the 265 has 2098.9mm.
So the actual difference is 1.06%.

[J555]

Originally Posted by Tommi_Mav

255 has a circumference of 2076.9mm, whereas the 265 has 2098.9mm.
So the actual difference is 1.06%.

Unfortunately, the real difference needs to be measured, as it depends on more factors (as the real physical tire sizes, tread wear or the stretch). That's part of an answer, why some circumference difference works fine for some, but not for others...

See below, what Michelin claims for their tires:
>> The sizes shown are average design values for tires measured on specified measuring rim widths. Some tires may vary from this value by +/-3% of the section height (affecting overall diameter), and +/-4% of the section width.
>> Section width varies approximately 0.2" (5mm) for every 0.5" change in rim width.

[Tommi_Mav]

Originally Posted by J555

Unfortunately, the real difference needs to be measured, as it depends on more factors (as the real physical tire sizes, tread wear or the stretch). That's part of an answer, why some circumference difference works fine for some, but not for others...

See below, what Michelin claims for their tires:
>> The sizes shown are average design values for tires measured on specified measuring rim widths. Some tires may vary from this value by +/-3% of the section height (affecting overall diameter), and +/-4% of the section width.
>> Section width varies approximately 0.2" (5mm) for every 0.5" change in rim width.

Totally agree with you. But unless you measure each tyre, you have to do calculations at least with the given dimensions by the factory.

In my case, the 265 (rear) are very close in width with the 255 (front). So, since the rear rims are 1" wider compared to the fronts, the 265 tyre is theoretically more stretched than the 255 => 265 has less rolling circumference than factory stated => closer to the 255 circumference => the difference is even less than 1.06%.

But the worst case scenario is that both tyres have the factory stated dimensions, so the difference in my case can't be more than 1.06%.

[E91d325]

Driving to work this morning, had to accelerate abit on the slip road, didn't kick down so not hard at all ... Definitely felt some different vibrations.... Unsure if it's the tyre or just the size of them?
I guess it could be diff / prop

I think I'll switch back to my old wheels until I can sort it out.

Do we think that Michelin SS on the rear and then PS4s on the front will be ok?

Planning to switch to fronts to 235 40 .. will give a 2.25mm difference but different tread patterns.... Do we think this is less likely to cause issue than having match tyres but the wrong size?

Cheers

[alohasurftoad]

255/35/19 & 265/35/19 is a 1.0% and another combo you may want to consider. 255/35/19 up front has a bit of poke at stock height and looks better if lowered with some negative camber to reduce the poke at the top shoulder.

https://f30.bimmerpost.com/forums/sh...&postcount=257

https://f30.bimmerpost.com/forums/sh...&postcount=265