[mandar]

I have a bmw 2017 - 230i RWD convertible, rear wheel drive with 30k miles.

Tires: Pirelli cinturato P7 A/S m+s tubeless
225/40 R18 run flats

Front: 20k miles 36 psi
Rear: 300 miles 41 psi

I got it serviced at bmw dealership. about one month ago and they recommended that I change rear tires which they did.
I took the car thru some winding mountain roads and the rear end of the car was slipping and the car was not staying planted in the lane like it usually does

. I took it back and they did wheel alignment.
It has not really fixed the problem. The slip indicator turns on from time to time.
I had a auto cross colleague drive my car yesterday and he confirmed that he saw this behavior too.

I am in the San Francisco Bay Area.

[freakystyly]

Lots of questions to follow up, like... What size tires? What make/model of tire? What air pressure are you using? How many miles since you changed them? RWD or AWD? Has your differential fluid ever been changed? Do you have any wheel speed sensor codes? How are the brakes?

[mandar]

I appreciate your response .


I updated the original post with details too.

—-
Tires: Pirelli cinturato P7 A/S m+s tubeless
225/40 R18 run flats

Front: 20k miles 36 psi
Rear: 300 miles 41 psi
RWD

I don’t think diff fluid has been changed.
Breaks are good

“Wheel spin sensor codes” have not been checked. Dealership did not say that there were any codes, but I will inquire.

[Sportstick]

This does not sound like an issue involving the brakes. Did you change your tire size or perhaps have a typo for your size? Your tire size most closely resembles 225/40-18, not 255.

Your front tires are more than six years old, the usual expected life span for the rubber compound, regardless of mileage, as UV deteriorates the rubber. This can harden the rubber and cause loss of traction. However, you are noticing oversteer, not understeer, so the issue is elsewhere for now, but I would consider replacing the fronts as well regardless of remaining tread.

Did you have this same air pressure setup for the previous tires?

As you have a square set-up, the first thing I would try is to bring down the pressures of the rear tires to match the front at 36 psi which should reduce oversteer. If you are going by the door label, keep in mind those values are for a fully loaded car with passengers and cargo at the maximum capacity. Try this pressure setting with just you in the car and no cargo in the trunk and let us know the results.

[freakystyly]

Tires can be a bit slippy when brand new. It's from the mold release lube in the manufacturing processes. Just take it easy and drive normal for the first couple gas tanks worth of miles and things will improve.

Continental site if allowed to link has a good write up on breaking in new rubber: https://www.continental-tires.com/pr...ith-new-tires/

[mandar]

Yes typo indeed in tire size.
I will reduce pressure today and see what difference it makes. Thanks.

[goodness8]

Hello hi new here I need help I currently run 225/40/18 on my bmw 230ixdrive 2018 but I want to do a wider tire please I need good suggestions and the car is on a lowering springs

Thanks

[freakystyly]

Originally Posted by goodness8

Hello hi new here I need help I currently run 225/40/18 on my bmw 230ixdrive 2018 but I want to do a wider tire please I need good suggestions and the car is on a lowering springs

Thanks

The best place would be to check out the wheel and tire sub section over at https://www.2addicts.com/forums/forumdisplay.php?f=521

There's a nice thread by the folks at apex wheels with various sizes here: https://www.2addicts.com/forums/show....php?t=1393898

[Ajowhan]

If you have not break 500 miles or 1000 miles, I definitely would not want to take it to higher speed. Don't worry too much, it gets better as you break the tire in.

I had this exact same issue in the past. I was taking corners at the usual or slower than usual speed, and my traction start lighting up..

[mandar]

Update: after reducing the cold pressure in the rear wheels to 35psi (from 42), the car is driving significantly better.

After an hour of driving, the rear tire pressure was 38, and still the car was driving well.

Thanks for advise.

[leftoverture]

Originally Posted by mandar

Update: after reducing the cold pressure in the rear wheels to 35psi (from 42), the car is driving significantly better.

After an hour of driving, the rear tire pressure was 38, and still the car was driving well.

Thanks for advise.

This is exactly what I was going to recommend. These cars are hyper sensitive to tire pressure settings. More so than any other of the 60 or so cars I've owned.

[Shovelman]

Our cars are relatively light on wide tires. The tires will flex and put down a narrower contact patch if the pressure is high. Mine tends to understeer so I may try a couple less pounds in the front.

Wider tires are more sensitive to pressure/load. Just thinking about semi trucks that use many narrow tires under the places with varying loading, makes sense. The front wheels are single tires because the load is always the same. And it may steer a little funny with dual front tires.

[MarcoZandrini]

Bimmers have historically been sensitive to tire pressure changes.

[Sportstick]

Originally Posted by mandar

Update: after reducing the cold pressure in the rear wheels to 35psi (from 42), the car is driving significantly better.

After an hour of driving, the rear tire pressure was 38, and still the car was driving well.

Thanks for advise.

Glad it worked out. But, keep in mind that if you load up the car with people and cargo, adjust your tire pressures appropriately for that trip.

[SoftShoe]

OP
FWIW, I’m a neighbor with a 2019 m240i.
Installed an m-LSD shortly after buying the car, used, because it was so easy to have one wheel spin and the throttle dulled while turning onto 1 from a side road. And that’s on PS4S, not your all seasons.

I run 40 psi at the front and 38 at the back for even wear across the width of the tire. I find the grip much better at these pressures and with a little wear on the tires. It’s still relatively easy to break the rears loose, but it’s still usually between 45 and 65 degrees all year, too.

[goodness8]

Hi please would 225/40/r18XL Fit 230ixdrive 2018 bmw nitro slicks
Please kindly respond