[speedbirdblack]

Hi Bimmers!

I have the M400 Staggered setup with 225 45 18, 255 40 18 tyres front & rear.

It has been fitted with Eibach Pro kit and I was pleased with improved aesthetics plus handling.

However, there are more room for improvement in my eyes.

Now it has come to the time of replacing tyres.

I fancy bit more wider setup. Specifically looking at 245 45 18, 265 40 18 front & rear.

Has anyone upgraded similar setup? I would greatly appreciate if you can share your experience, story and a pictures for reference.

Thanks in advance 🙏

[danb1979]

RWD or xDrive?

If RWD; 235/45s and 265/40s would make more sense IMO - one size wider and will sit perfectly on the wheels - 225/45 is slightly stretched, but 235/45 sits better, straighter sidewall, better rim protection

I run 18x8 405Ms all round for my summers with 235/45/18 Goodyear Assym6s all round



245/45 would be too big really

But use the tyre calculator on willtheyfit.com to see how they measure up

Need to keep the difference within the 2.5% +/- tolerances etc

[jmanB45]

Like dan says, 235/45 is the correct size to pair with 265/40, they will have exactly the same diameter. However, 265 width is too much for an 8.5" wheel, 9" is the minimum that's recommended. You can force it on, but the sidewall will bulge.

I would keep the stock tire sizes or get wider wheels if you really want a beefier look.

[BaconDouble]

I have a set of 18x8” square 400M wheels, but have an xDrive F34 (Gran Turismo). I haven’t fitted them yet, but I going to use 245/45-18 tires all around.

I’m downsizing from 225/45-19 wheels/tires as I want a bit more sidewall for a better ride.

The F34 has weird tire sizes to begin with (overall diameter is 27” vs rest of the F3X platform at 26”) but this size will surely work if you need a tire with more sidewall

[speedbirdblack]

Originally Posted by danb1979

RWD or xDrive?

If RWD; 235/45s and 265/40s would make more sense IMO - one size wider and will sit perfectly on the wheels - 225/45 is slightly stretched, but 235/45 sits better, straighter sidewall, better rim protection

I run 18x8 405Ms all round for my summers with 235/45/18 Goodyear Assym6s all round

[img]https://i.postimg.cc/9XdS48B7/405-Ms-fitted.jpg[/img]

245/45 would be too big really

But use the tyre calculator on willtheyfit.com to see how they measure up

Need to keep the difference within the 2.5% +/- tolerances etc

This is RWD.
Yes you are correct. 235 45s and 265 40s are the perfect combination as per willtheyfit.com.

225 45 Potenza S001 looks bit stretched on 8 inch wheel.

255 40 on the other hand, looks bit lost in the wheel arch even with Eibach Pro kit. This may be down to shorter sidewall compared to front 45.

265 40s will fix it according to willtheyfit.com.

So the maximum tollarance for RWD is 2.5%+/-?
405Ms 18s or 19s?
Cheers!

[alohasurftoad]

max width for 8.5" is 255. most 265 requires 9" width minimum. you can pinch/squeeze the 265 on 8.5" but performance benefit will only be for straight line "dig" traction. it is actually detrimental to handling when you over pinch the tire because sidewall support is reduced.

235/45/18+265/40/18 would be better on aftermarket rims 8.5" ET30-35, 9.5" ET40-45

[danb1979]

Originally Posted by jmanB45

Like dan says, 235/45 is the correct size to pair with 265/40, they will have exactly the same diameter. However, 265 width is too much for an 8.5" wheel, 9" is the minimum that's recommended. You can force it on, but the sidewall will bulge.

I would keep the stock tire sizes or get wider wheels if you really want a beefier look.

Keep forgetting the rears are 18x8.5.. You do wonder why they bothered haha

[jmanB45]

Originally Posted by speedbirdblack

255 40 on the other hand, looks bit lost in the wheel arch even with Eibach Pro kit. This may be down to shorter sidewall compared to front 45.

Spacers could be the solution for filling out the rear.

[speedbirdblack]

Originally Posted by jmanB45

Like dan says, 235/45 is the correct size to pair with 265/40, they will have exactly the same diameter. However, 265 width is too much for an 8.5" wheel, 9" is the minimum that's recommended. You can force it on, but the sidewall will bulge.

I would keep the stock tire sizes or get wider wheels if you really want a beefier look.

I will put M437 wheels at some point with coilovers but for now wider tyres would do.

As you correctly said, 265 will bulge a bit but I think it will fill the wheel arch nicely.

The rear wheel looks bit lost compared to the front possibly due to shorter sidewall and concave wheel.

So I'm expecting it to be filling the arch and wider tyre to give a beefier appearance from the back.

Swelling tyre and increased in height is the worry, not sure how it affects the overall handling? Steering response, breaking performance etc..

Cheers!

[speedbirdblack]

Originally Posted by BaconDouble

I have a set of 18x8” square 400M wheels, but have an xDrive F34 (Gran Turismo). I haven’t fitted them yet, but I going to use 245/45-18 tires all around.

I’m downsizing from 225/45-19 wheels/tires as I want a bit more sidewall for a better ride.

The F34 has weird tire sizes to begin with (overall diameter is 27” vs rest of the F3X platform at 26”) but this size will surely work if you need a tire with more sidewall

F34 generally have taller ride compared to rest of the F3X. Switching to 18s will lower the ride height fractionaly.

[speedbirdblack]

Originally Posted by jmanB45

Spacers could be the solution for filling out the rear.

15mm spacers on the rear is an option too.
Not sure whether they rub. It's on EIBACH PRO kit.

[speedbirdblack]

Originally Posted by alohasurftoad

max width for 8.5" is 255. most 265 requires 9" width minimum. you can pinch/squeeze the 265 on 8.5" but performance benefit will only be for straight line "dig" traction. it is actually detrimental to handling when you over pinch the tire because sidewall support is reduced.

235/45/18+265/40/18 would be better on aftermarket rims 8.5" ET30-35, 9.5" ET40-45

Your opinion is technically correct.

I don't fancy aftermarket wheels.OEM PLUS is the only way.

M437s are the ultimate solution but for now, I want to see wider tyres can do the trick without spending.

I will be replacing tyres soon anyways.

[jmanB45]

Originally Posted by speedbirdblack

I will put M437 wheels at some point with coilovers but for now wider tyres would do.

As you correctly said, 265 will bulge a bit but I think it will fill the wheel arch nicely.

The rear wheel looks bit lost compared to the front possibly due to shorter sidewall and concave wheel.

So I'm expecting it to be filling the arch and wider tyre to give a beefier appearance from the back.

Swelling tyre and increased in height is the worry, not sure how it affects the overall handling? Steering response, breaking performance etc..

Cheers!

Here is a post by johnung. 255/40 on an 8.5" ET40 rear wheel. Spacers used to get flush fitment. He is lowered too.

https://f30.bimmerpost.com/forums/sh...00&postcount=2