[RagaX3]

Hi everyone,

I've done what is considered a no-no and put Bridgestone Non-Run Flat tyres on the front of my F25 XDRIVE, while the rear maintain Dunlop Sport Run Flat tyres in good condition.

However, since doing so I have encountered 2 problems which I am unsure is related to the change, and I want to get an additional few opinions on the solution.


Problems:

1. Tyre Pressure Warning light activates for all tyres - Expected, likely needs reinitialising.

2. The car feels "bumpy", almost as if there is a traction or stability problem, when accelerating. It's very hard to describe, kind of like someone breaking on certain wheels occasionally. When coasting it feels smooth. - Could be diff related? but no warning lights.



Thoughts:

1. I believe the bumpy feeling and the warning pressure light is related to the mixed tyres, however I am open to other thoughts on this.


Solutions:

1. Change rear tyres to Non- Run Flats to match the front (Cheapest Option), but an I do this? or will the problem likely remain?

2. Accept a loss on the front tyres, and revert them back to Run Flats.


Any thoughts on this? I've done some searching, but I can't find much around this bumpy sensation I've been experiencing. So apologies if this has come up before.

[drukpa]

Change all non run flats, same brand and size.

Different tyres will damage your transfer case in the long run.

I have changed to non run flats, no problems, and much better ride quality.

[mwat]

Would you describe it as a tugging sensation?
I'm told that's the transfer-case needing new fluid and a recalibration.

My other suggestion would be to run a higher tire PSI all around.. 33/34/35

[RagaX3]

Tugging is certainly one way to describe it.

From what I can tell after more research it related to the new tyres.

I have 225/60/17 all round.

Th originals on the back are Dunlop Sport RFTs, the new ones are conventional non-run flats, Bridgestone Turanza T005.

What I am hoping to find out now before I buy any more tyres is:

1. Will making sure all tyres match with non-RFTs resolve it..

Because if I put new tyres on the back and the issue remains, I might rage destroy the car.

[mwat]

Originally Posted by RagaX3

Tugging is certainly one way to describe it.

From what I can tell after more research it related to the new tyres.

I have 225/60/17 all round.

Th originals on the back are Dunlop Sport RFTs, the new ones are conventional non-run flats, Bridgestone Turanza T005.

What I am hoping to find out now before I buy any more tyres is:

1. Will making sure all tyres match with non-RFTs resolve it..

Because if I put new tyres on the back and the issue remains, I might rage destroy the car.

I can tell you after changing from RFT's to Non-RFT's on all 4 corners I experienced a similar sensation. I brought it to two master tech's and they both said they couldn't feel what I was describing. In my research the answer is to change fluid and recalibrate. However, since I received a good bill of health from two different BMW master tech's I left it alone and bumped up my tire pressure in all 4 corners. That has definitely improved the sensation. I'm at right about 60k miles so I'll probably change the fluid anyway here shortly.

[RagaX3]

Originally Posted by mwat

I can tell you after changing from RFT's to Non-RFT's on all 4 corners I experienced a similar sensation. I brought it to two master tech's and they both said they couldn't feel what I was describing. In my research the answer is to change fluid and recalibrate. However, since I received a good bill of health from two different BMW master tech's I left it alone and bumped up my tire pressure in all 4 corners. That has definitely improved the sensation. I'm at right about 60k miles so I'll probably change the fluid anyway here shortly.

Interesting, also very concerning...

I believe it's the diameter that affects it, so increasing or decreasing the pressures could certainly improve or potentially fix it from what I've understood.

I'll attempt to measure my rear tyres vs my new tyres, as I've read some tyres are actually bigger or smaller than what's actually marked on the sidewall.

I have a friend with some BMW software, I can attempt a recalibration but was hit with a low voltage problem, I think I have an unrelated battery problem to resolve too.

[mwat]

Originally Posted by RagaX3

Interesting, also very concerning...

I believe it's the diameter that affects it, so increasing or decreasing the pressures could certainly improve or potentially fix it from what I've understood.

I'll attempt to measure my rear tyres vs my new tyres, as I've read some tyres are actually bigger or smaller than what's actually marked on the sidewall.

I have a friend with some BMW software, I can attempt a recalibration but was hit with a low voltage problem, I think I have an unrelated battery problem to resolve too.

Funny you say that, the master tech's that drove my car pulled my codes and saw under voltage and SWORE a new battery would fix it. Which it didn't, but that's okay I'm not gonna be stranded anywhere anytime soon.

[richardodn]

Rolling diameter is at best an approximation. I'd suggest going to the manufacturers' websites and look at the technical data for the tires you actually have. What you're looking for is the revolutions/mile or similar measurement.

[TEF]

Originally Posted by richardodn

Rolling diameter is at best an approximation. I'd suggest going to the manufacturers' websites and look at the technical data for the tires you actually have. What you're looking for is the revolutions/mile or similar measurement.

I agree with the rolling-diameter theory. Even tires of the same size from different manufactures can vary slightly in diameter. And this change in circumference is hard on the transfer case (because the rate of rotation varies from front to back). Another way to view this is that the price of another pair of tires is less than replacing your transfer case.

[mwat]

Originally Posted by TEF

I agree with the rolling-diameter theory. Even tires of the same size from different manufactures can vary slightly in diameter. And this change in circumference is hard on the transfer case (because the rate of rotation varies from front to back). Another way to view this is that the price of another pair of tires is less than replacing your transfer case.

This is true. However, I confirmed that the tires I replaced my runflats had identical rolling diameter and I'm still experiencing this on occasion. Here enters my tire PSI theory, but what do I know.

[TEF]

The factory label on my car's door jam already recommends different psi settings from front to rear (32 and 35 respectively), so how does one adjust this to conform to the "tire PSI theory"?

[mwat]

Originally Posted by TEF

The factory label on my car's door jam already recommends different psi settings from front to rear (32 and 35 respectively), so how does one adjust this to conform to the "tire PSI theory"?

My own personal theory that the TC likes higher psi on non run flat tires.