[Pol]

With reference to the German BMW forum (1erforum.de) and the findings of one of the forum fellows, I did a test with my recently mounted Michelin Pilot Alpin4 tires, front 235/40/18, rear 255/35/18
That fellow pretends that, accelerating from 140 to 180 km/h, DTC light is blinking all the time with instability as a consequence. He let the rear tires change to 255/40/18 and way the problems.
I did the test and indeed he is perfectly right. Only difference, no blinking DTC light.
My findings : vibrations on the rear axle who increase with speed. In my opinion, the stability systems indeed intervene and try to hold the rear wheels on track . Strange and scaring feeling, the car becomes less stable, but no lights blinking at all. Anyway the behaviour is completely different compared to the summer set. I do not understand BMW is not yet aware of that.
My rear tires don't have the BMW "star identification" while the front tires do. Tires have production week 35/16 (Aug/Sept).
On the other hand it seems productions from November, do have the "star identification". But what will be the difference in behaviour ???
What I know and what I think is that German test M2's, the ones we all saw circulating during last winter, had 235/40/18's all around. Didn't they test the 255/35/18's on the rear???
Anyway, during winter, accelerating from 140 to 180 km/h seems to be rather exceptional but it should be possible without those severe problems.
Comparing summer set with winterset :
245/35/19 - 265/35/19 : rear = 14mm taller than front
235/40/18 - 255/35/18 : rear = 10mm shorter than front
With 255/40/18 in the rear, rear is 16mm taller than front. Wouldn't that be the better choice ?

[quikM2]

Nice to hear they used a square setup when testing winters as that seems to be what most people including myself are going with. I personally would have preffered 235/40/18 all around but the option with the Apex wheel group buy was 245/40. Either way like you said the time in winter where you feel like you can or should go 140-180 should be far and few between and in my case never...

[chris719]

Originally Posted by Pol

With reference to the German BMW forum (1erforum.de) and the findings of one of the forum fellows, I did a test with my recently mounted Michelin Pilot Alpin4 tires, front 235/40/18, rear 255/35/18
That fellow pretends that, accelerating from 140 to 180 km/h, DTC light is blinking all the time with instability as a consequence. He let the rear tires change to 255/40/18 and way the problems.
I did the test and indeed he is perfectly right. Only difference, no blinking DTC light.
My findings : vibrations on the rear axle who increase with speed. In my opinion, the stability systems indeed intervene and try to hold the rear wheels on track . Strange and scaring feeling, the car becomes less stable, but no lights blinking at all. Anyway the behaviour is completely different compared to the summer set. I do not understand BMW is not yet aware of that.
My rear tires don't have the BMW "star identification" while the front tires do. Tires have production week 35/16 (Aug/Sept).
On the other hand it seems productions from November, do have the "star identification". But what will be the difference in behaviour ???
What I know and what I think is that German test M2's, the ones we all saw circulating during last winter, had 235/40/18's all around. Didn't they test the 255/35/18's on the rear???
Anyway, during winter, accelerating from 140 to 180 km/h seems to be rather exceptional but it should be possible without those severe problems.
Comparing summer set with winterset :
245/35/19 - 265/35/19 : rear = 14mm taller than front
235/40/18 - 255/35/18 : rear = 10mm shorter than front
With 255/40/18 in the rear, rear is 16mm taller than front. Wouldn't that be the better choice ?

What wheels are they mounted on? You may want to have them re-balanced on a Hunter Roadforce machine.

[Pol]

Originally Posted by chris719

What wheels are they mounted on? You may want to have them re-balanced on a Hunter Roadforce machine.

BMW 640M 18-8.5 / 18-9.0 as adviced by BMW itself. They are balanced of course. I wonder if a Hunter Roadforce balance machine might bring the solution.
I also e-mailed BMW BeLux about the problems. I wonder what they'll say.

[cento]

Hi together, i'm the one with problems on 255/35/18 in the rear.
Tyre was a Nokian, recomended by my tyre dealer.
With 255/40/18 the problem was solved imediately!

[Pol]

Originally Posted by cento

Hi together, i'm the one with problems on 255/35/18 in the rear.
Tyre was a Nokian, recomended by my tyre dealer.
With 255/40/18 the problem was solved imediately!

I sent also a mail to BMW BeLux to report the problems with the 255/35/18 Michelin Pilot Alpin4. I'm curious what will be there answer.
Anyway my dealer do not know what to do with it. First time they heard something about it.

[cento]

the same in austria. Nobody knows what to do but everything is ok for them.
i posted a vide in the german thread maybe you ar allowed to link it here....

[Pol]

Originally Posted by cento

the same in austria. Nobody knows what to do but everything is ok for them.
i posted a vide in the german thread maybe you ar allowed to link it here....

The embed code for the video seems to be invalid here.

[cento]

i found no video format in the attachmentlist....
it's an mp4
did you watch it?

[Pol]

Originally Posted by cento

i found no video format in the attachmentlist....
it's an mp4
did you watch it?

Yes I watched it and saw indeed the flickering of the DTC light.
And that one doesn't work with your video:


I put mine on Youtube.

[gmzanatta]

2 things:

1) I installed the set this past week, have not experienced any of the OP described issues.

2) Who in their right mind is going 140-180 km/h often in the snow during winter???

[Elwood74]

Originally Posted by gmzanatta

2 things:

1) I installed the set this past week, have not experienced any of the OP described issues.

2) Who in their right mind is going 140-180 km/h often in the snow during winter???

It's not going to be snowing all winter. Dry pavement will be around...

[gmzanatta]

Originally Posted by Elwood74

It's not going to be snowing all winter. Dry pavement will be around...

At the racetrack maybe unless you want a hefty ticket. Ours close for winter so the point it moot around here.

All I am saying is not many people will be doing the 140 to 180 pull during winter time.

PS: I did do the pull and had no trouble with traction control or wheels shaking.

[Pol]

Originally Posted by gmzanatta

2 things:

1) I installed the set this past week, have not experienced any of the OP described issues.

2) Who in their right mind is going 140-180 km/h often in the snow during winter???

You can easily continue with those tyres and stay under the higher speeds.
Latest years we rather exceptionaly had snowfall over here. And there are more and more periods in which weather conditions permit higher speeds on dry conditions.
Nevertheless I find those symptoms at least inadmissible especially on a tyre and rim set recommended by BMW.

[cento]

we are driving M cars, so why shouldn't we go on higher speed during winter? If the streets are dry there is no problem e.g. on german highways.
The problem occures also while overtaking - so its not realy fun if DTC starts flushing

[Pol]

Originally Posted by gmzanatta

PS: I did do the pull and had no trouble with traction control or wheels shaking.

Wheel diameter only seems to affect on the MDKG.

[gmzanatta]

Originally Posted by Pol

Wheel diameter only seems to affect on the MDKG.

Given that I am running the same winter set as described by the original post, wheel diameter should be the same, but I am not experience any of the shaking or DTC light issues.

[Pol]

Originally Posted by gmzanatta

Given that I am running the same winter set as described by the original post, wheel diameter should be the same, but I am not experience any of the shaking or DTC light issues.

Do you have the DKG?
MDKG must be very sensitive to wheel diameter as I feel a different behaviour of the gearbox since I put the wintergear on .

[gmzanatta]

Originally Posted by Pol

Do you have the DKG?
MDKG must be very sensitive to wheel diameter as I feel a different behaviour of the gearbox since I put the wintergear on .

No, 6MT.

[Pol]

Originally Posted by gmzanatta

No, 6MT.

Thanks! So as I said problems should be related to the DKG gearbox.

[Andycc]

Originally Posted by cento

Hi together, i'm the one with problems on 255/35/18 in the rear.
Tyre was a Nokian, recomended by my tyre dealer.
With 255/40/18 the problem was solved imediately!

Nokian's Hakka R2 are rated for speeds up to 170 km/h, so you were basically pushing them to and even past their designed limit. That might have had an effect on the traction too.

[cento]

Its the new WR A4