[HighlandPete]

Originally Posted by NISFAN

Try this, straight piece of ground, mark the bottom of each tyre and place a corresponding mark on the road. Roll the car forward a few revolutions of the tyres until the mark on one comes back to the bottom. See if they are all aligned. If not mark the road where the first tyre reached bottom dead centre, then continue to roll until the corresponding, front /rear reaches BDC. Measure from the start marks to finish marks respectively and calculate difference as a percentage.

Tyre pressures can be played with to balance the circumference, or my preferred method, remove the front propshaft

You beat me to it. ,

I was going to post what I'd do wearing my "R&D hat". Similar thing, roll the car and get some measurements.

I also suggest the OP plays with pressure to see what happens. Adjust the RC 'front to rear' with tyre pressure.

[ryanwarriors9]

Originally Posted by Tengocity

I ditched runflats on around 14000 miles, and have now done 108000 miles, the whole of that mileage on MPSS and then most recently on a set of MPS4S. Over winters I've been using non run flat Pilot Alpins.

I've not had any issues of any kind until very recently. On changing back to my summer tyres I noticed that one of my summer rears (MPS4S) has abnormal inner edge wear, yet the winter tyre that came off did not.

I did do one track day on that set of tyres last year, so wondering if that caused it, but that never caused me any issues on the MPSS sets I used, so I am booked to get the alignment checked on Friday to be sure. I have also noticed a slight vibration on that set of tyres now, so checking the wheel balance too.

A bit of a bizarre one if I'm honest, but who knows, maybe it's a thing with the MPS4S... or certainly when you're remapped, running quite low on coilovers, and 15mm spacers at the rear too.

If so then I'd go back to MPSS though, as they were great too, and I would never go back to runflats on that car.

Very interesting, Let me know how you get on mate because I’m about to order some going from RFT to non run flats

[B58 parts]

I am running 40f/42r in PSS 255/40/18 on 8.5 wide wheels all around. Anything less than 36 and the front starts to roll under itself in a hard corner. It's trial and error .. you have to try and find what feels right. I am still messing with them a bit.

If it breaks .. it breaks. You'll always have a weak point somewhere. They're not terribly expensive and it looks pretty easy to get at on jackstands. There is a super good diy on here where the guy even rebuilt one on the bench. That may be the best thread on this site. It sounds like the splines just weren't built strong enough for some.

Take the best runflat BMW approved tires and I bet we could still roast one in a few hours. I'd blame driving technique / launching over tires .. the clutch must absorb the initial load, not the axles.

[Tom Tallon]

I bought my 2016 330D msport xdrive fitted with Michelin Pilot SS by the factory ie a new purchase with normal tyres so BMW must think the combination works on 225/45 R18 front and 255/40 R18 back.

[HighlandPete]

Originally Posted by Tom Tallon

I bought my 2016 330D msport xdrive fitted with Michelin Pilot SS by the factory ie a new purchase with normal tyres so BMW must think the combination works on 225/45 R18 front and 255/40 R18 back.

They will be BMW approved, star marked tyres. It is not the run-flat or non run-flat specification that is in question, it's more centred on whether they are star marked tyres, or not.

[ryanwarriors9]

My mate at BMW has got back to me just laughing saying nothing to worry about change all 4 at once so even tread depths and get tyre pressure correct . . . get them ordered haha

[Oompah]

Originally Posted by ryanwarriors9

Sweet how long you been running them and what pressures ?

I took the original rft goodyears off after maybe 1500 miles. So I had mps4s for maybe 2500 miles.

[HighlandPete]

Originally Posted by ryanwarriors9

My mate at BMW has got back to me just laughing saying nothing to worry about change all 4 at once so even tread depths and get tyre pressure correct . . . get them ordered haha

Clearly you have the answer you want. Not every BMW garage will agree, some have no experience of xDrive issues, others have.

What happened to the guy you also quote....

Originally Posted by ryanwarriors9

....GRIP - this is where the problems started, had MPS4S non runflats fitted and the car immediately felt ‘bouncier’ still handled well but over big dips and general feel it felt ‘bouncy’... however the main problem was when fully warm every seven seconds or so the car would ‘surge’ for a second, a few hundred rpm ‘blip’. Not every time but around half the time.

Just put BMW starred 19” tyres Bridgestone Potenza S001 BMW starred tyres on and the car feels planted and no surging! Basically is this a rare isolated case or something else going on here? The Michelin MPS4S tyres are back on and have superb grip but the car feels bouncy again and the surging is back. I thought it was the Map but it wasn’t, DMS have been BRILLIANT In helping me source the problem. Question is, is the XDrive that sensitive to tyres....

Only change is the wheels and tyres... Coincidence, or the cause? Has he identified the cause and got a solution, other than the other wheel set?

[Lorcan]

Originally Posted by YuminNuman

If it breaks .. it breaks. You'll always have a weak point somewhere.

You sound like a drag racer

[ryanwarriors9]

Originally Posted by HighlandPete

Clearly you have the answer you want. Not every BMW garage will agree, some have no experience of xDrive issues, others have.

What happened to the guy you also quote....



Only change is the wheels and tyres... Coincidence, or the cause? Has he identified the cause and got a solution, other than the other wheel set?

Not sure yet waiting for an update hes changed the tyre pressures as everyone on the facebook page was running them at 36psi all round and they have had no issues. He changed them this morning so will update us tonight.

Thanks
Ryan

[B58 parts]

Originally Posted by Lorcan

You sound like a drag racer

Far from it

[Lorcan]

Originally Posted by ryanwarriors9

great stuff thanks. just sent my friend a message who is a BMW technician too see what he says

AC Schnitzer have confirmed that in their testing of 3 series xDrive cars with Pilot Sport 4S 225/40/19 front and 255/35/19 rear (and the AC Schnitzer performance upgrade) they have not encountered any such problems to date, but can't rule out problems with other products. For us, this tyre combination is still on sale.

Which doesn't take us much further forward

We do know though that BMW subtly change the specs of the cars during their model life and this can have a knock-on effect which then manifests itself in some cars and not others.

[James-335dx]

Hi All,

I also started a thread about switching to non run flats on my 335dx as my currently P Zero RF's are nearing their useable life. I assumed it would be a no brainer to swap over to MPS's and save myself £500 on the 4 as well as improve the ride quality. However all the above talk about the RC and Xdrive system has got me a little confused???
My car was just serviced at Sytners and their report showed uneven tyre ware, front edges bald (cornering too quickly possibly?) and the report was something along the lines of

OSF - 3.4
NSF - 3.3
OSR - 3.4
NSR - 3.0

So surely different RC already but no issues and they didn't mention anything to me at the time. Also as I'm running the 20" 405M wheels which were factory fitted I'm fairly sure that the front and rear tyre depths are different, 255/30/20 Rear and 225/35/20 at the front.

Any thoughts would be very welcome.

Also stock power currently but the car is booked into Durham remaps next month for a stage 1 rolling road remap via the OBD with patch so will be 400+ BHP

[HighlandPete]

Originally Posted by James-335xd

...So surely different RC already but no issues and they didn't mention anything to me at the time. Also as I'm running the 20" 405M wheels which were factory fitted I'm fairly sure that the front and rear tyre depths are different, 255/30/20 Rear and 225/35/20 at the front.

BMW will set up a car with tyres to a spec' which keeps within their design tolerances. This includes tyre logic, to accommodate a small percentage of variation in RC as the tyres wear.

Even the xDrive function itself is adding wear to the mechanisms, the central transfer clutch pack has to adapt to torque transfer conditions. It all comes down to tolerances.

When we move to tyres which are not approved, there is no data for how the tyres will perform within the design tolerances of xDrive. If the RC 'front to rear' is greater than BMW approved tyres (tyre and wheel combinations), then either the transfer box components takes the wear, or the tyres effectively scrub to compensate for the difference, or a bit of both. The RC difference has to be absorbed somewhere.

It makes sense to see that a tyre with lower grip will slip more readily than a really grippy tyre, one puts more load/wear on the transfer box than the other.

Reading static dimensions for the tyres doesn't help too much, we need the dynamic radius, or dynamic RC, of the tyre for the specific application, pressure, load, speed range, etc. Hence why BMW test and approve tyres to fit their design parameters.

[James-335dx]

Great, thanks. That helps a lot. So I guess if I can find a BMW approved tyre (Star marked) that is also non RF then that might be okay? Not sure I can find such a tyre but I'm sure you could opt for non RF when ordering the car from BMW

[Tengocity]

Originally Posted by James-335xd

Great, thanks. That helps a lot. So I guess if I can find a BMW approved tyre (Star marked) that is also non RF then that might be okay? Not sure I can find such a tyre but I'm sure you could opt for non RF when ordering the car from BMW

Pilot Super Sports are available as star marked tyres in those sizes.

I've had the alignment checked today on my car and it was way out, and hence the abnormal wear on the right rear, so looks like it was nothing to do with the tyre itself.

The badly worn tyre was actually showing cord in a few areas so I ended up replacing it, and also decided to just replace both rears to make sure I minimise these issues with differing tyre circumferences.

[mikeoz]

Originally Posted by Tengocity

Pilot Super Sports are available as star marked tyres in those sizes.

I've had the alignment checked today on my car and it was way out, and hence the abnormal wear on the right rear, so looks like it was nothing to do with the tyre itself.

The badly worn tyre was actually showing cord in a few areas so I ended up replacing it, and also decided to just replace both rears to make sure I minimise these issues with differing tyre circumferences.

That makes sense.
Who did you get the rears from? MP4s again I take it?

[Tengocity]

Originally Posted by mikeoz

That makes sense.
Who did you get the rears from? MP4s again I take it?

Yes, MPS4S again. I want getting the alignment done at wheels in motion in Chesham and they had the tyres in stock for a reasonable price at the associated Blackboots tyre business they have. I could have got them cheaper at Costco but not worth the extra time and fuel given I was there already.

[James-335dx]

Originally Posted by Tengocity

Pilot Super Sports are available as star marked tyres in those sizes.

I've had the alignment checked today on my car and it was way out, and hence the abnormal wear on the right rear, so looks like it was nothing to do with the tyre itself.

The badly worn tyre was actually showing cord in a few areas so I ended up replacing it, and also decided to just replace both rears to make sure I minimise these issues with differing tyre circumferences.

Brilliant, thanks. I'll have a look for the MPSS then and see how I get on

[Dr Forinor]

Originally Posted by Lorcan

Someone else on here had trouble with surging on a DMS remap, and had the remap removed I think.

Correct, that was me. Has been fine since DMS removed their remap & has been remapped by a local garage.

[Blueyzfr169]

Hello, I almost got to the bottom of this...

The DMS Map was causing the surging, a different quality map was put on and the surging was gone, much better power delivery and torque too.

The softness and bouncing is still there, 42psi tyre pressures helped a little but not much, there was also slight play in the front suspension bushes and the shocks were really soft, we suspect with the ACS spring drop it caused them both to wear prematurely very quickly.

I'm looking at Bilstein Coilovers for my next car, not just a spring change...

[Machinebuilder]

The issue with non runflat issue only seems to come up with staggard setups. If your car runs the same size on all four corners it should equalize the tires response. If it is a run flat or not isn't an issue from what I have read and heard. I recently ordered a non stock size 235/45-18 and talked to the service manager at my dealership to double check. He basically stated that square set ups have no problems. With staggard setups he has seen issues with x drive. In general staggard set-ups sizing was more critical. If you have rear wheel drive there are are no issues. With xdrive he recommended square setups for long term reliability.