[Coastali8]

     Featured on BIMMERPOST.com

Just finished mounting new tires.
Wanted to make the tire size issues perfectly clear.

Put 245/40X20 Bridgestone Potenza S001 on the front.
Put 275/35X20 Bridgestone Potenza S001 on the rear.

Tire diameter and sidewall dimensions stay nearly the same as original equipment tires but width increases by slightly more than 1 inch front and rear.
Factory wheels, no spacers.

Absolutely no issues. Everything clears over rough roads and tight turns.
Probably still about 1/4 inch clearance in the tightest spots.

Although putting narrow tires on wide rims can have safety issues. Placing slightly wider tires on narrow rims the only real issue can be uneven tire wear. That can be mitigated with proper monitoring of tire pressure.

The car looks better.
In my opinion the original tires didn’t match the aggressive look of the car.

These tires give you slightly more protection from curbs for the wheels and fill the fender wells just a bit better.

The car feels just a tiny bit heavier with steering and understeer disappears.

I feel it’s a improvement in looks and handling.

[RichTimpa]

Have any pictures?

[Coastali8]

Attached photos.

[Coastali8]

Attached one more

[363ny]

Looks great! Job well done!

[wanesso]

I'll try this— maybe my rear tires won't wear out so fast...

[RichTimpa]

Originally Posted by Coastal i8

Attached one more

Really like how well it looks and really want to know if there is any down side like rubbing.

I think I might have to do this when tires need replacing.

[jcpca356]

looks great! i installed spacers to achieve the flush look on mine

[JasH]

Originally Posted by jcpca356

looks great! i installed spacers to achieve the flush look on mine

Be aware this will impact the aero negatively. Specifically the air curtain design over the wheels won't work as intended.


Wider wheels will do the same.

[BanjoPaterson]

Originally Posted by Coastal i8

Just finished mounting new tires.
Wanted to make the tire size issues perfectly clear.

Put 245/40X20 Bridgestone Potenza S001 on the front.
Put 275/35X20 Bridgestone Potenza S001 on the rear.

Tire diameter and sidewall dimensions stay nearly the same as original equipment tires but width increases by slightly more than 1 inch front and rear.
Factory wheels, no spacers.

Absolutely no issues. Everything clears over rough roads and tight turns.
Probably still about 1/4 inch clearance in the tightest spots.

Although putting narrow tires on wide rims can have safety issues. Placing slightly wider tires on narrow rims the only real issue can be uneven tire wear. That can be mitigated with proper monitoring of tire pressure.

The car looks better.
In my opinion the original tires didn’t match the aggressive look of the car.

These tires give you slightly more protection from curbs for the wheels and fill the fender wells just a bit better.

The car feels just a tiny bit heavier with steering and understeer disappears.

I feel it’s a improvement in looks and handling.

Looks good, but my only question is how are the original rims able to handle wider tyres? I admit, I think the current tyres are a joke, but I didn't think you could actually put wider tyres on rims designed for smaller ones?

[wanesso]

Originally Posted by BanjoPaterson

Looks good, but my only question is how are the original rims able to handle wider tyres? I admit, I think the current tyres are a joke, but I didn't think you could actually put wider tyres on rims designed for smaller ones?

Yep, a bit nervous about the wider tires on stock rims...got some follow up yet? I need to replace tires asap. They look good, seem good so far

[jojo]

I just put Michelin Pilot Sport 4s on original rims.
245/40/20 front
255/40/20 rear

Drives great. Better handling to me it seems. And better milage wear than the S001.

[wanesso]

Originally Posted by jojo

I just put Michelin Pilot Sport 4s on original rims.
245/40/20 front
255/40/20 rear

Drives great. Better handling to me it seems. And better milage wear than the S001.

Tire rack?

[Coastali8]

I purchased the 245/40X20 and 275/35X20 from Tire Rack (not Tyre Rack)

They will email you and tell you that the tires are not standard sizes. Just respond “okay “you know.

Local tire shop mounted them up with no issues.
Factory wheels, no spacers.
Everything fits, no clearance issues.

Just for reference... many vehicle manufacturers have put wider than tire manufacturers recommend tires on narrow wheels as original equipment. Both BMW and Porsche have done this.

Because the wider tire has a higher load carrying capacity at a lower inflation pressure.
You can reduce front and rear tire pressure by around 3 psi to carry the same weight as the original equipment tire to coincide with what BMW decided to use. By reducing the inflation pressure a couple of psi that will also help compensate for a wider tire on a narrow wheel wanting to bulge in the center and give you a more even tire wear.

Original tires
Front 215/45X20 load index 95XL @32psi=1227 lbs
Rear 245/40X20 load index 99XL @32psi=1371 lbs


New tires
Front 245/40X20 load index 99XL @28psi= 1243 lbs
Rear 275/35X20 load index 102XL @29psi= 1388 lbs


I decided on running 30 psi in the front and 30 psi in the rear. (The tire pressure monitoring system is happy down to -25% or 24 psi.) Just as a starting point, and see how it feels and how the tires wear.

So far, so good.

Tire size vs inflation pressures for the same load capacity chart.
https://www.toyotires.com/media/2125...s_20170203.pdf

Tire size comparison chart.
https://tiresize.com/comparison/

[jojo]

Originally Posted by wanesso

Tire rack?

I just went to my local Tire Kingdom. Was the same price as Tire Rack.

[BanjoPaterson]

Originally Posted by jojo

I just put Michelin Pilot Sport 4s on original rims.
245/40/20 front
255/40/20 rear

Drives great. Better handling to me it seems. And better milage wear than the S001.

Thanks... and very interesting that they should fit.

[jojo]

The traction control is less invasive now. The light flashes but the car does not bog down as it searches for grip.