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      04-02-2018, 06:14 PM   #1
immortality
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Tire Change Side effect??

hi all,

i changed from oem tires (potenza re RFT 050a 255/35/18) to extreme contact DW06(255/35/18, not RFT) on oem wheel 18x8.5. only rear tire changed.
front is still oem.
now, i am undergoing side-effect or something not happened before.

car starts rolling very easily ... i feel i am not safe at all... and differential does not work properly when i accelerate at curve to put on highway. i mean inner side rear break comes almost at the end of corner then suddenly outer rear breaks come(1 time on the way to work)..which makes me scarred. i did drive same as usual...
I checked tire pressure and they're all good.

I asked semipro tuner he said extreme contact DW06 is not that bad to bring
all phenomenons. Maybe it is rear or front sway bar's problem.
but i never had same issues before i changed.

reason i changed to extreme contact is tread life. oem is great but only 100
tread life but extreme has 560 at half price..

do i have to go back to oem?
can you guys advise?
please help me..
i am so dis-pressed..
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      04-02-2018, 08:28 PM   #2
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The tires should be good and not cause these problems.

Investigate further
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      04-02-2018, 08:41 PM   #3
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Aside from running two different brand/style tires on either end of the car, which is not a great idea for several reasons, your main problem is the following:
With half worn tires on the front and brand new rubber on the rear, you're no doubt exceeding 3mm tread depth differential front to rear. That exceeds BMW's recommended limit and will confuse the traction control system in sweeping turns such as freeway on or off ramps. Mine did exactly the same thing and a persistent shop foreman at my dealer searched long and hard before he found the documentation that explained what was happening. The good news is that, since the rears wear 2x faster than the fronts on a Z4, the problem eventually resolves itself as the rear tire tread depth begins to catch up with the front. IMO though, you should have changed all four tires to totally rid yourself of those horrendous RFTs. But that has nothing to do with the issue you describe.
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      04-02-2018, 08:59 PM   #4
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Great response paris! That did not occur to meat all.
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      04-02-2018, 11:42 PM   #5
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thank you for all replies...
i could little understand thread gap between front and rear causing differential issue.

then is rolling issue from same gap issue? this makes me very nervous on highway...
do i need to change front too?
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      04-03-2018, 09:08 AM   #6
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Not a "differential" issue.

Paris says the problem may be the difference with the tread depth between the old and new tires. The traction control system measures wheel rotation and the different size of the tires is what may be causing erratic behavior in the turns.

Try getting new front tires of the same brand and see if this eliminates the problem.
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      04-03-2018, 05:31 PM   #7
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On top of what was said...you should never mix tires since they have different characteristics which would lead to unbalanced handling. Also you can tell us if all tires are all season, or summer tires, and what was the temperature at the time when you felt the tires break loose?
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      04-03-2018, 08:43 PM   #8
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Problem is not differential. It is DTC system being confused by tires of different outside diameter. As noted before you cannot run tires more than 3mm different in diameter.
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      04-11-2018, 11:23 AM   #9
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Really? The car's DSC is sensitive to a 3mm change in diameter? Wow.

3mm is .118", or roughly 1/8th (4/32nd) worth of tread depth. EVEN on a car that has squared tire sizes (same tires front and rear), in daily operation it is likely that the difference in tread wear will quickly exceed 1/8th of an inch difference between front and back on RWD platform. 1/8th inch in tire wear is about 1/3rd of typical tire tread depth (Conti DWS tread depth is 10/32")

Plus, if you could just humor me, the outer diameter of the 18" OEM wheel package and the 19" OEM wheel packages far exceeds 3mm. In fact, the front tire diameter of the 19" OEM wheel is .17", or 4.1mm larger than the rear. Are you guys suggesting that ALL Z4s with 19" OEM factory wheels have different DSC coding that eliminates that problem with different diameter tires?

This is the first I heard of this. Where is the technical documentation that says you can't have a diameter difference of more than 3mm?

There's a SIMPLER explanation than the DSC on the car is so sensitive that it can sense a 3mm difference in diameter. And that explanation is new tires come with MOLD RELEASE. As the tires are formed and molten rubber compound is injected in layers into a mold to shape the tread of the tire, each mold is coated with a thick layer of mold release to allow the rubber to separate from the mold as it's cracked open, otherwise hot, sticky rubber will stick to the mold and you can't form the tread pattern. that mold release is stuck on the top layer of tread, and brand stinking new tires can take between 200-500 miles to wear off that mold release off of the top layer of the rubber. Before that happens, all new tires tend to behave differently than their more worn-in brethren if you choose to only change 1 or 2 tires vs. 4.

If the DSC or the chassis dynamic is really sensitive to a 3mm overall diameter change, then you can't change from 18" to 19" wheels and vice versa.

By the way, as far as *I* know almost ALL BMW DSC/DTC/MDM/whatever chassis dynamic traction system allows for up to 3% difference in rotational speed differential from front to rear. On a 25-ish inch diameter (I say "-ish," because stock, OEM diameter can be as small as 25.02", and as big as 25.20") that allows for almost 0.75" of difference in diameter front to back.

All except for the E89 Z4, I suppose.
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      04-11-2018, 01:40 PM   #10
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Quote:
Originally Posted by The HACK View Post
Really? The car's DSC is sensitive to a 3mm change in diameter? Wow.

3mm is .118", or roughly 1/8th (4/32nd) worth of tread depth. EVEN on a car that has squared tire sizes (same tires front and rear), in daily operation it is likely that the difference in tread wear will quickly exceed 1/8th of an inch difference between front and back on RWD platform. 1/8th inch in tire wear is about 1/3rd of typical tire tread depth (Conti DWS tread depth is 10/32")

Plus, if you could just humor me, the outer diameter of the 18" OEM wheel package and the 19" OEM wheel packages far exceeds 3mm. In fact, the front tire diameter of the 19" OEM wheel is .17", or 4.1mm larger than the rear. Are you guys suggesting that ALL Z4s with 19" OEM factory wheels have different DSC coding that eliminates that problem with different diameter tires?

This is the first I heard of this. Where is the technical documentation that says you can't have a diameter difference of more than 3mm?

There's a SIMPLER explanation than the DSC on the car is so sensitive that it can sense a 3mm difference in diameter. And that explanation is new tires come with MOLD RELEASE. As the tires are formed and molten rubber compound is injected in layers into a mold to shape the tread of the tire, each mold is coated with a thick layer of mold release to allow the rubber to separate from the mold as it's cracked open, otherwise hot, sticky rubber will stick to the mold and you can't form the tread pattern. that mold release is stuck on the top layer of tread, and brand stinking new tires can take between 200-500 miles to wear off that mold release off of the top layer of the rubber. Before that happens, all new tires tend to behave differently than their more worn-in brethren if you choose to only change 1 or 2 tires vs. 4.

If the DSC or the chassis dynamic is really sensitive to a 3mm overall diameter change, then you can't change from 18" to 19" wheels and vice versa.

By the way, as far as *I* know almost ALL BMW DSC/DTC/MDM/whatever chassis dynamic traction system allows for up to 3% difference in rotational speed differential from front to rear. On a 25-ish inch diameter (I say "-ish," because stock, OEM diameter can be as small as 25.02", and as big as 25.20") that allows for almost 0.75" of difference in diameter front to back.

All except for the E89 Z4, I suppose.
Pretty sure you're right on the money here. I went from OEM RFT equipped 18's to stock size\offset 19's with no issues. Tires are also OEM size for BMW OEM 19" wheels. No DSC issues. I would FULLY expect the DSC to misbehave in the manner described by the OP if I was running Non-RFT's on the rear and OEM RFT's on the front. Probably not just different levels of grip but also a seriously significant difference in sidewall stiffness affecting the handling of the OP's car. I could see that setup causing all kinds issues with overall handling, let alone simply accelerating out of a corner. And you're absolutely right about new tires and the mold release coating. My MPSS' were slick as fuck right after install. The non-RFT's and accompanying wheel change on every car I've owned has been exactly the same experience. With my Z4, I coordinated my wheel and tire change with a 1000+ mile road trip I had coming up just for the purpose of wearing that off since it would've taken forever for me to do so in town because I drive so little these days compared to when I owned all my previous cars.

OP, get a matching set of tires for the front.
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      04-11-2018, 07:50 PM   #11
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HACK: Only fly in the ointment here is your 3mm tread depth difference actually grows to 6MM difference in tire diameter (there are two sides to the tire when measuring diameter). Using your math, that's 1/4" larger than the fronts and....
Davis449: How do you explain that I had the exact same problem as the OP when I replaced a worn out set of Bridgestone S-04 Pole Positions on the rear without changing the half worn S-04s on the front? Thus eliminating the different tire model argument.
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      04-12-2018, 02:14 PM   #12
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Quote:
Originally Posted by paris1 View Post
HACK: Only fly in the ointment here is your 3mm tread depth difference actually grows to 6MM difference in tire diameter (there are two sides to the tire when measuring diameter). Using your math, that's 1/4" larger than the fronts and....
Davis449: How do you explain that I had the exact same problem as the OP when I replaced a worn out set of Bridgestone S-04 Pole Positions on the rear without changing the half worn S-04s on the front? Thus eliminating the different tire model argument.
I agree this all sounds suspicious but the result you had gives it a lot of credibility.

Maybe the full answer lies in DSC adaptations? If so, the answer could be both:

Too large of a sudden change in diameter and the DSC doesn't know how to react. Over time, or via an adaptation reset, it gets sorted out.
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      04-12-2018, 06:33 PM   #13
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Quote:
Originally Posted by NoQuarter View Post
I agree this all sounds suspicious but the result you had gives it a lot of credibility.

Maybe the full answer lies in DSC adaptations? If so, the answer could be both:

Too large of a sudden change in diameter and the DSC doesn't know how to react. Over time, or via an adaptation reset, it gets sorted out.
Or...simply rear accelerated rear tire wear catching up with the loger lasting fronts!
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      04-13-2018, 09:46 AM   #14
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Quote:
Originally Posted by paris1 View Post
HACK: Only fly in the ointment here is your 3mm tread depth difference actually grows to 6MM difference in tire diameter (there are two sides to the tire when measuring diameter). Using your math, that's 1/4" larger than the fronts and....
Davis449: How do you explain that I had the exact same problem as the OP when I replaced a worn out set of Bridgestone S-04 Pole Positions on the rear without changing the half worn S-04s on the front? Thus eliminating the different tire model argument.
Honest question, did the problem eventually resolve itself?
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      04-13-2018, 10:12 AM   #15
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Quote:
Originally Posted by davis449 View Post
Honest question, did the problem eventually resolve itself?
As far as I know, yes. The car is my wife's DD and I don't drive it that much, but she hasn't mentioned it in the past year or so and it was during the rainy season that it was most noticeable. Our rains are just now ending, so I'm pretty sure one of us would have noticed it in that time frame if it were still an issue.
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      04-17-2018, 09:22 AM   #16
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Quote:
Originally Posted by paris1 View Post
As far as I know, yes. The car is my wife's DD and I don't drive it that much, but she hasn't mentioned it in the past year or so and it was during the rainy season that it was most noticeable. Our rains are just now ending, so I'm pretty sure one of us would have noticed it in that time frame if it were still an issue.
I just realized you misquoted me, origianlly, in the post I responded to with my honest question. I've never owned S04 Pole positions.
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      04-28-2018, 12:23 AM   #17
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Its all right here - you went from a soft to a very hard compound

"reason i changed to extreme contact is tread life. oem is great but only 100
tread life but extreme has 560 at half price"
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Last edited by scrammer; 04-28-2018 at 12:28 AM..
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      04-28-2018, 08:11 AM   #18
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Turn it off

Mold release plus hard compound plus different diameter plus different tire characteristics = confused DSC
What about turning that damned thing off and seeing what happens (hold down the sport+}
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      05-03-2018, 10:30 PM   #19
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hi all you guys,

i changed front tires too last week(extreme contact). now all problems have been solved. no more wired differential reaction, no more unsafe feelings at high speed. but i can feel lower grip and dull steering at high speed. alternatively i got more comfort below 60mh.

in addition, i follow oem tire size exactly(width,ratio,rim). the only difference is RFT and non RFT.
my tires are now all non RFT.
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      05-03-2018, 11:16 PM   #20
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Quote:
Originally Posted by immortality View Post
hi all you guys,

i changed front tires too last week(extreme contact). now all problems have been solved. no more wired differential reaction, no more unsafe feelings at high speed. but i can feel lower grip and dull steering at high speed. alternatively i got more comfort below 60mh.

in addition, i follow oem tire size exactly(width,ratio,rim). the only difference is RFT and non RFT.
my tires are now all non RFT.
Give the new fronts time to "scrub-in". It will sort itself out with some miles.
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      07-22-2019, 05:56 PM   #21
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Hello All,

Thank you to everybody who's contributed to this discussion.

I think I too may have this driving behaviour on my Z4 (e89 23i).
The behaviour was noticed immediately driving home with the new rear tyres, my wife has mentioned the driving behaviour too, so it's not just me! It's noticeable on uneven road surfaces and particularly exiting bends. The Z4 will feel like the rear-end is being pushed or pulled from one side to another.

Both rear tyres have been replaced from
Bridgestone Potenza 255/35 R18 90W RE 050A (OEM)
to
Continental SportContact 5 SSR 255/35 R18 90Y (non-OEM)

As it happens the Z4 was in at the BMW Dealership shortly after having the tyres replace, as part of a health-check the Dealership took the following tyre measurements (in brackets I've calculated the average):
NSF 5.0/4.2/4.6 (4.6mm)
OSF 4.6/3.9/4.3 (4.3mm)
OSR 6.5/6.8/7.1 (6.8mm)
NSR 6.4/6.5/7.1 (6.7mm)

The greatest difference in measurements is 7.1-3.8 = 3.3mm
The greatest average difference is 6.8-4.3 = 2.5mm

Does anybody think these measurements could point the driving behaviour cause being due to the difference in rotational speed differential from front to rear?

OR

Having traveled just 400m / 644km should I wait for the new rear tyres to "bed-in" i.e give the mold release a chance to wear off?

I've checked tyre pressures, wheel nut torque, tyres have been fitted correct with outside on the outside, additionally, balancing seems fine giving a smooth ride. The old tyres wore evenly so I don't suspect tracking.

THANKS, all comments appreciated.
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      07-22-2019, 10:53 PM   #22
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See my post #3 above. Your car is doing exactly the same thing mine did for exactly the same reason. It will rectify itself as the rears wear and, in the meantime, you can shut off the DSC if it bothers you that much.
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