Ristov_

Hello,

I purchased a used car from my friend whom I knew he had this issue. Basically when accelerating hard or moderate, there was a pushing force from the front wheels just like the car was hesitating for a split second… Car is 78,000km and he is the first owner of the car.

He drove it for 3-4 months with the tyre underinflated most of the time due to air hissing out and he kept adding pressure it every day or so at the gas station. 2 weeks ago he changed the front right tyre with a used one who wasn't hissing air and the pushing force dissapeared. Car was running fine!

Now I made a big service, oil and filters (castrol and mahle), zf original 8L + zf filter, disks and brakes with water pump. Basically a service which would at least get me 50,000 km without issues.

I ordered new tyres to replace the old one. The car had OEM bmw wheels 19" with 9j at the back and 8.5j at the front.

Old tyres were 245/40/19 with 275/35/19 Pirelli + 1 Michelin (front right that was replaced)

New tyres are 245/40/19 with 275/35/19 Dunlop

And the car is doing the same pushing force from the front, like hesitation for a split second and if you keep the pedal to the floor it does it X times. 10+

Basically when the transfer case is working to distribute the force.

How can NEW, SAME TYRE SIZE cause the pushing effect, but old USED tyres with low threads not cause this?

I switched today to the old tyres and problem is GONE. The moment I switch to the new tyre set, problem comes again… tried calibrating the transfer case at my local bmw guy, no use.

Will change the fluid inside the transfer case tomorrow… What else I should try? Or am I doomed driving with used tyres all my life

seanjordan20

Although they were the OE tires at one point Dunlops are the worst tires you can put on the car. They received many complaints across all the BMW series. This is why BMW no longer uses them. I would suggest you go with the Michelin Power Sport 4s or Continental Extreme Contact DW06

Ristov_

Yeah, I’d change them if it is the last resort.

Old tyres are 3 pirelli runflats with 1 michelin non run flat, and Transfer Case has no problems….

How do you explain this? I guess Dunlop are not approved by BMW, but 4 new tyres with even thread in them within the tyre size as noted on the door which is 245/40-19 and 275/35-19, non-runflats and still problems…

seanjordan20

They were approved tires until they had a lot of issues with them. This could very well be one of the issues they had. Was anything else done to the car before you bought it. I'm not seeing that anything else would cause this issue unless something suspension wise was done and even then it's a stretch.

Ristov_

Basically he drove it for 3 months with a bad tyre that was hissing air from time to time, so the pressure was uneven with the other front tyre, and he was feeling this knocking or pushing effect.

He bought a michelin tyre used one, which was not hissing air and problem was solved.

Now I bought 4 non run flat tyres, identical sizes to the old ones 245/40-19 and 275/35-19 and it starts to do this pushing effect when accelerating…

I will change the Transfer Case fluid and do adaptation of the VTG… something inside tells me that it’s not that problem.

Old, uneven tyres 3 runflats pirelli + 1 non runflat michelin with low threads left = NO PROBLEMS

Brand New, non run flats, same brand Dunlop Sp Sport Maxx 245/40-19 / 275/35-19 = PROBLEMS

Same OEM wheels.

go figure, all of my local mechanics are having ???? In their minds.

seanjordan20

Another thing could be the alignment.

Ristov_

Alignment? Tyres were properly balanced and inflated, sizes are the same as old ones.

You are saying that rolling diameter of Pirelli is within the 1% but rolling diameter of Dunlop is above the approved % by the transfer case?

Do you think it matters manufacturer to manufacturer about the rolling diameter and tyre circumference?

I thought all 245/40-19 and 275/35-19 had the same rolling diameter and tyre circumference?

seanjordan20

No that is what's confusing. You shouldn't be having the issue you're having but you do and the only difference is the tires. To me it just makes since that the tires are the issue but I'm not there to actually see it. Do you have a shop that can do a radial and lateral runout test. That would definitively answer the question on it being a tire or hub issue

seanjordan20

Wrong test suggested. Im thinking of something different

Ristov_

Back left and front left tyre have 1-2mm difference in rolling diameter (circumference)… well within the limits