[blackcolor]

Hi, I'm newbie to here

May I know that if the stock size is "front 225/50/18", rear "255/45/18".

Due to michelin tyre don't have the rear size, if I change the tyre size to "front 225/45/18", rear "255/40/18"!

Apart form the real speed will be slower than the speedometer shown, and the car will become lower..........

What will happen if I make this change ? Or is it safe ?

Thank you very much!

[.BMW.]

You are correct, but your trip meter will show more miles than you have actually drive the car.

The difference in overall diameter is about 4%, i.e. you will add 4% more miles to the trip meter.

And also depending on the ride height of your car, the shorter tires may look small in the wheel housings.

[blackcolor]

Yes, the trip meter will become more.......

By the way, do you know will it be safe or stable if after changing that ?

[VMRWheels]

Your speedo will be off, but I don't think anything bad will happen aside from that. You'll just have slightly more wheel gap overall.

[Jack_DK]

What wheels do you have?

I have on order 400m (staggered 18) as part of my yet to arrive 320i + M Sports pack. The tires are 225 45 R18 Front / 255 40 R18 Rear, which is exactly what you getting in Michelin.

[blackcolor]

Originally Posted by Jack_DK

What wheels do you have?

I have on order 400m (staggered 18) as part of my yet to arrive 320i + M Sports pack. The tires are 225 45 R18 Front / 255 40 R18 Rear, which is exactly what you getting in Michelin.

My wheel is 400m too for my f34 m sport.
The stock wheels and tyre size is 18" 8J 225/50/18 (front) and 18" 9J 255/45/18 (rear) !

I wanna go for the michelin pss tyre, but the dealer said doesn't have the rear size. And I just worry about if I make change to 225/45/18 & 255/40/18, will it be safe or not !?

And I checked that if change the rear to 245/45/18 the difference in diameter is only 1.xx% ! (If changed to 255/45/18 is 3.xx%)

So, which solution is better and more safe as you think ?

[blackcolor]

Originally Posted by VMRWheels

Your speedo will be off, but I don't think anything bad will happen aside from that. You'll just have slightly more wheel gap overall.

Thanks VMR !

How about if I changed from 255/45/18 to 245/45/18 ?

[VMRWheels]

If you changed the rear size from a 255/45/18 to a 245/45/18, it will be a little narrower, and a little shorter overall.