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Why is my F40 M135ix tramlining and wearing its tyres out?

76K views 364 replies 75 participants last post by  Kierond 
#1 ·
BMW have suggested ridiculously high tyre pressures for the M135ix in order to reduce it's emissions. However, this massive over-inflation can lead to central tyre wear (particularly on Bridgestones), poor grip, poor ride quality, tramlining, etc. All bad, basically. The only upside to over-inflation is MPG.

For a lightly loaded F40 M135ix, people have found dropping to roughly 2.5 Bar/36psi front and 2.3 Bar/33psi rear a noticeable improvement (or even slightly lower). Well worth an experiment as air is basically free at your local petrol station.

Tyre pressures should be set cold, using a decent pressure gauge like a RaceX. Don't forget to reset the TPMS to the new pressures afterwards.
 
#3 ·
I reckon 1 psi difference on the rear axle won't make all that much difference...

BMW's recommendation for the front axle is way too high though (clearly to achieve their claimed efficiency figures rather than comfort/drive ability).
 
#9 ·
marco_polo said:
2.5 Bar/36psi front and 2.3 Bar/33psi rear
I put my pressures back to 36psi front and 33psi rear and (as I already suspected) I no longer have to use the grip of death on the steering wheel in anticipation of the wheel being pulled back and forth randomly, it's a shame I put the pressures back up a while ago as the central tyre wear is significant after only 3600 miles, new tyres will be needed soon unfortunately! 🥴
 
#11 ·
imba said:
Does TPMS throw an low pressure warning when we lower it to 36 and 33 psi?
Mine didn't, I reset the TPMS straight away so it didn't get chance as it needs some wheel rotations before it realises.
 
#12 ·
Carlosfandang0 said:
imba said:
Does TPMS throw an low pressure warning when we lower it to 36 and 33 psi?
Mine didn't, I reset the TPMS straight away so it didn't get chance as it needs some wheel rotations before it realises.
Mine didn't either and haven't yet worked out how to reset the TPMS.
 
#17 ·
What tyres are you running Wrex?

I'm on just shy of 8k miles, and still have a minimum of 5mm all round (on Conti Premium Contact 6, 19").
 
#20 ·
Wrex said:
5000 miles and on 3mm
Mine were the same after 5000 miles. S005's with factory pressures.

Currently running the CPC6 at 2.6bar front and 2.3 rear and after 2500 miles there's no evidence of centre wear.
 
#23 ·
M135i20 said:
Braeburn2010 said:
7000 miles and just over 5mm on the front about 5.4
Not too bad 👍
Yeah I thought that was OK. And that is following the recommend pressures off 2.7 bar front and 2.2 rear.
I have lowered the front to 2.5 bar which around 36 psi but the fuel economy doesn't seem as good now. So I'm wondering what I do now
 
#25 ·
Braeburn2010 said:
M135i20 said:
Braeburn2010 said:
7000 miles and just over 5mm on the front about 5.4
Not too bad 👍
Yeah I thought that was OK. And that is following the recommend pressures off 2.7 bar front and 2.2 rear.
I have lowered the front to 2.5 bar which around 36 psi but the fuel economy doesn't seem as good now. So I'm wondering what I do now
I think the Bridgestone Potenza's are more sensitive to the over inflation & tramlining issues that most are experiencing. The continentals haven't generated the same level of complaints that I've read about & the wear seems much better. Whilst reducing pressures will soften the ride on both tyres it will naturally have a negative effect on the cars efficiency. It all depends on whether you prefer seeing slightly higher mpg no's over experiencing a more compliant ride with slightly better traction. Depends on the roads where you live, your driving style, the types of journeys you regularly do & how the tyres are wearing.
 
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