[Dex401]

I've got a lowered 23 M240I Xdrive without the ZTK package. The car is lowered with Eibach pro springs 20mm front and rear as well as a set of Bimecc spacers front 12.5 mm and rear 15mm with the 791M style wheels. I want to upgrade from the pirelli P zero's that come stock on the car to a set of michelin Pilot sport 4 S's. What size front and rear can we go to in our car? 225 front and 255 rear are simply too skinny for me hahahaha

[Wasp_Factory]

I believe your wheels will be 8J front and 8.5J rear.

Your best bet would be to go with 245/35/19 front and 255/35/19 rear. This stays within the 1% delta for xDrive and replicates the ZTK tyre sizes. 245 is the max tyre width you can put on an 8J wheel and these sizes are available in MPS4S.

Your scrub radius will already be outside of spec with the spacers, but at least you are keeping it reasonably close to BMW set up.

I run aftermarket fully forged 8.5J front, 9.5J rear with MPS4S* at 245/35/19 and 255/35/19. I can promise that grip and traction are more than adequate for fast road driving.

One last point - it is worth looking for the BMW star (*) MPS4S as the compound is slightly different to standard MPS4S. I also believe the rolling radius is very slightly different as well if you look deeply into the specs. There is a good comparative tyre test online somewhere.

[nype]

Originally Posted by Wasp_Factory

I believe your wheels will be 8J front and 8.5J rear.

Your best bet would be to go with 245/35/19 front and 255/35/19 rear. This stays within the 1% delta for xDrive and replicates the ZTK tyre sizes. 245 is the max tyre width you can put on an 8J wheel and these sizes are available in MPS4S.

Your scrub radius will already be outside of spec with the spacers, but at least you are keeping it reasonably close to BMW set up. Your front tyres will look a little stretched and you'll get little kerbing protection as a result.

I run aftermarket fully forged 8.5J front, 9.5J rear with MPS4S* at 245/35/19 and 255/35/19. I can promise that grip and traction are more than adequate for fast road driving.

One last point - it is worth looking for the BMW star (*) MPS4S as the compound is slightly different to standard MPS4S. I also believe the rolling radius is very slightly different as well if you look deeply into the specs. There is a good comparative tyre test online somewhere.

I was wondering I’m seeing “BMW Optimized” for certain tires when shopping online.

I have the 893-M wheels with ZTK package. Same 8.5 and 9.5 width as your aftermarket ones. Did you consider going 255/35/19 and 265/35/19 (bit more width / even less stretch / tiny bit more sidewall height)?

[Wasp_Factory]

I didn't - mainly because I didn't want to stray too far from the BMW ZTK spec size, because the rolling radius would change and therefore, so would the accuracy of the speedo, because the bigger tyres means more weight, because my wheels have a more aggressive offset and therefore already more poke than standard and given my car is lowered, didn't want to run the risk of rubbing with the wider tyres, because they don't make the BMW star rated MPS4S in 265 and because the car really doesn't appear to be under-tyred on the road to me and I am unlikely to track it.

I realised I made an error in my original response, which I've edited. 245s on an 8J rim will be a bit baggy, not stretched.

[JoeyJoeJo]

Originally Posted by Wasp_Factory

There is a good comparative tyre test online somewhere.

Is it this one? Really interesting.

[CTGT2005]

I am running 265 rear on 9.5 wheels and 255 fronts on 8.5 wheels. Doesn't look weird or anything. My speedometer also reads about 2 to 3 mph high at 45 mph.

[nype]

Originally Posted by CTGT2005

I am running 265 rear on 9.5 wheels and 255 fronts on 8.5 wheels. Doesn't look weird or anything. My speedometer also reads about 2 to 3 mph high at 45 mph.

Ya looks like it's -1.05% speedo error and 3.55mm ride height gain with tires that are 1 notch wider, on the stock ZTK package wheels.

[CTGT2005]

Originally Posted by nype

Ya looks like it's -1.05% speedo error and 3.55mm ride height gain with tires that are 1 notch wider, on the stock ZTK package wheels.

The takeaway is the speedometer is already calibrated to read a few mph high and any tires bigger than stock actually make it more accurate.

[Wasp_Factory]

Originally Posted by JoeyJoeJo

Is it this one? Really interesting.

Yep - that's the one. It is indeed very interesting

[jayritchie]

Originally Posted by Wasp_Factory

Yep - that's the one. It is indeed very interesting

Misha Charoudin mentioned in a recent video that the PS4S* are closer in performance to the Cup 2 than they are to regular PS4S.

They were originally designed for M cars in 19 and 20” but must’ve added the m240 ZTK sizes more recently as we’ve all got them.