[T67Regal]

Long story short, purchased a preowned 2020 M240i x with 40k miles(F22). The last 3 miles to home, on the first sharp bend I stayed the speed limit and my traction control went nuts. TC is Blinking on the dash entire way through the bend. it felt like the computer was trying to control a sliding vehicle but I was not sliding...hmm? next bend I stayed the speed limit again, same thing,...wth is going on!... not confidence inspiring at all!

Tire pressure is spot on for Pirelli P7 Run Flats. I then notice front tire is 225/40/18, HOWEVER rear is 225/45/18...WTH! I do some research and these are not the staggered set up at all. In fact, additional research says the overall diameter is about 23 mm difference and the circumference is about a 71 mm difference (about 4%)!! The front RF 40's look original and the rear RF 45's were almost new tires. With front worn down and rear almost new, I am guessing the front/rear circumference differential may have been as much as 5% at that point.

I am not well trained with the xdrive, but I researched about a years worth of posts on here and I believe a 4% circumference differential between front/rear is waaay too much. Not going into details here but open to your feedback on what the computer may be reading and doing to compensate for the circumference differential...?



Anyhow, once the dealer finally understood the circumference differential problem between the F/R, they agreed to reimburse me for replacement rear tires.

I have the stock 719M wheels (7.5x18 ET45) and I am NOT moving to wider wheel. My tire goals are: improved STRAIGHT line acceleration traction, and improved STRAIGHT line control at speed. (traction & control from a dig and a higher roll...will definitely need even more traction/control with a stage 1 tune).

Should I purchase:

1) 235/40/18 NON RF for all 4 OEM 719M wheels? Has anyone regretted installing a 235 on the OEM 7.5" wheel (instead of a recommended 225)?

2) 225/40/18 NON RF for just the rear OEM 719M wheels and keep the current Pirelli P7 225/40/18 RF on the front?

3) 225/40/18 NON RF on all 4 OEM 719 M wheels then add 12mm spacers? (this would improve my traction in twisties but not sure it would help with control on straight launches and rolls so much)

4) some other recommended setup for better traction/control during hard straight line acceleration?


Probably going with Conti Extreme contact DWS 06.... unless you suggest another favorite tire for straight line acceleration grip and control at speed?


Please LMK if I did not correctly communicate something. Not well trained with M240i x so please excuse any newbie errors too.

[who is this noob]

Start with a fresh set of non-runflat tires in stock, staggered size.

Get an alignment to make sure everything is in spec.

This will improve straight line stability and traction. And it’s a good baseline to learn the car.

[T67Regal]

Update: purchased 2 continental extreme contact 02 in 225/40/18, replaced incorrect size rear tires(225/45/18) with the new conti's. drove around first sharp bend going under the speed limit and there was not any traction control light blinking like crazy on the dash, no issues. Drove into next sharp bend with more speed, again not any TC light whatsoever, zero issues.

Contacted dealer, shared that the correct size square tires seemed to have stopped the TC light coming on during moderate bends. Dealer kept their word and are issuing me reimbursement for new contis. Kudos to the dealer!

Cliff: although it never crossed my mind, when purchasing a pre-owned x-drive, be sure to take the time to check all tire sizes! There can not be a 4+% circumference differential between the front and back.


BTW, The 240 REALLY grips with those contis, whew!

[SpencerC_6MT]

Originally Posted by T67Regal

BTW, The 240 REALLY grips with those contis, whew!

ExtremeContact Sport 02's are great tires. Now that my suspension setup is fully sorted out, I've struggled to induce understeer a single time on backroads. (They were very capable stock as well, but coilovers and sway bars made as much difference as I imagined the upgrade from 300tw to 200tw's would be - worth considering.) And if you don't spend your weekends trying to find the limits of your tires on backroads, they'll last a good while too

[Dantesboyz]

Great thread, not everyone is aware of this wear factor not just on our xdrive cars but a lot of awd cars, I've got subys too- same with those

Im typically a mps4s type guy but looking at maybe doing contis on a new set of summer only wheels. 🤔
Xdrive being a cheat code for grip and launch
The contis are more wallet friendly, adhd thoughts, wondering if you guys had more feedback

[SpencerC_6MT]

Originally Posted by Dantesboyz

Great thread, not everyone is aware of this wear factor not just on our xdrive cars but a lot of awd cars, I've got subys too- same with those

Im typically a mps4s type guy but looking at maybe doing contis on a new set of summer only wheels. 🤔
Xdrive being a cheat code for grip and launch
The contis are more wallet friendly, adhd thoughts, wondering if you guys had more feedback

I find ECS02 to be on-par with PS4S in every metric, you should look up Tire Rack's summer tire round-up for exact numbers. They're basically Michelins with a 10% discount as far as I'm concerned.

[MadLad]

Originally Posted by SpencerC_6MT

I find ECS02 to be on-par with PS4S in every metric, you should look up Tire Rack's summer tire round-up for exact numbers. They're basically Michelins with a 10% discount as far as I'm concerned.

I plan on going with ecs02 with the blackcircle discount and i was hesitating between going for 235 or 245 all around on my winter rims that are 8.5 or keep the staggered setup that came stock, 245 scares me from previous comments you made even if other commenters made it work all around like kernel kurtz https://www.2addicts.com/forums/show...0&postcount=39 but i plan on going with dinan springs next summer.
If i use the winter rims ill have to change rims on tires which adds more hassle than having a dedicated setup or rim too.
Understeer wise idk if its that much difference between 225 245 with the ecs2
Basically im lost so if you could give me a word of advice, on my current state would be appreciated. Thanks!

[SpencerC_6MT]

Originally Posted by coldbrosss

I plan on going with ecs02 with the blackcircle discount and i was hesitating between going for 235 or 245 all around on my winter rims that are 8.5 or keep the staggered setup that came stock, 245 scares me from previous comments you made even if other commenters made it work all around like kernel kurtz https://www.2addicts.com/forums/show...0&postcount=39 but i plan on going with dinan springs next summer.
If i use the winter rims ill have to change rims on tires which adds more hassle than having a dedicated setup or rim too.
Understeer wise idk if its that much difference between 225 245 with the ecs2
Basically im lost so if you could give me a word of advice, on my current state would be appreciated. Thanks!

235/40/18 square is a good middle ground to play it safe. The biggest reason I have rub issues it because I chose to go with 245/*40*/18 instead of 245/35/18, which are about 0.5" bigger in diameter than stock 225/40/18 fronts. That, in combination with lowering springs that dropped it 1.25", was simply too aggressive with stock fender liners.