Tram lining?

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InvertedPanda
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Tram lining?

Post by InvertedPanda »

Hey guys,

I have an xDrive BMW M135i and during the summer, I run my OZ Ultraleggera’s. The specs are as followed:

18x8j ET40 all round.

Front tyres: Michelin Pilot Super Sports 225/40/18 with the BMW * on the sidewall

Rear tyres: Michelin Pilot Super Sports 255/35/18 without the BMW * on the sidewall

I’m aware that the standard spec is 245/35/18 on the rear but the xDrive system can’t handle the difference in rolling radius, which causes the car to judder fairly violently under acceleration.

That’s why I run the 255’s on the rear.

However, I’ve noticed that my car often “tram lines” or wobbles a little bit at the rear. Not too violent but enough for me to notice. This usually happens during lane changes over the lane stripes, for example.

I was wondering whether this is because the car is over tyred at the rear?

Therefore, I got thinking. How about 245/35’s all round?

Would they fit on the front? I don’t want to run 225/40’s all round because it looks a tad “skinny” then. I run 225/40’s all round for winter.

Looking forward to your input.

Thank you!
MHD "Stage 2+" tuned 2013 BMW M135i xDrive F21
Instagram: @insta_hamz

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marco_polo
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Re: Tram lining?

Post by marco_polo »

255mm is to too much tyre for an 8" rim really, I'm not surprised it feels a bit wobbly at the back.

I run 245/35 all round on 8" ET40, I don't know if they'd also fit on the front of an xDrive, possibly?
Silver F21 M135i - ManBox - HK - Adaptive + Eibach Pro's - BBS CH-R's - BMWP Drexler LSD - M4 LCA's

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InvertedPanda
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Re: Tram lining?

Post by InvertedPanda »

Do you have any pics of how yours sits?

I’m pretty sure that even with the xDrive system, the wheels sit identical to a RWD variant.
MHD "Stage 2+" tuned 2013 BMW M135i xDrive F21
Instagram: @insta_hamz

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Re: Tram lining?

Post by marco_polo »

I've been messing about with mine, longer front wishbones. They would sit fine though, there's loads of room inside the front arches as standard. I'll try to dig up an old photo later.

If you offered up a rear to your front axle temporarily it would give a pretty good indication of how it would look/fit?
Silver F21 M135i - ManBox - HK - Adaptive + Eibach Pro's - BBS CH-R's - BMWP Drexler LSD - M4 LCA's

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50pence
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Re: Tram lining?

Post by 50pence »

If staggered I'd stick with standard BMW fitment on an X-Drive, and ensure that the tyres are fairly evenly worn all round. The only change I'd consider would be to all square.

--
F20 M135i LCi, auto, adaptive suspension, adaptive LED h/l + HB assist, h/seats, c/pack, elec folding mirrors etc
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InvertedPanda
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Re: Tram lining?

Post by InvertedPanda »

50pence wrote:
Sat May 23, 2020 8:47 am
If staggered I'd stick with standard BMW fitment on an X-Drive, and ensure that the tyres are fairly evenly worn all round. The only change I'd consider would be to all square.

--
No can do, I’m afraid. The standard staggered fitment that BMW recommend causes xDrive judder.

If I have 225/40 front and 245/35 rears in the Bridgestone RFT’s, there’s no judder.

If I put the equivalent tyres on in MPSS’s, I get judder under acceleration. Trust me, I’ve been through this topic. In fact, there’s a thread that I created on it about 2 years ago.

I will try and put one of my rears on the front to see how much rubbing there is (if there is any).

Next summer, I’ll run a square set of 245/35’s if possible.
MHD "Stage 2+" tuned 2013 BMW M135i xDrive F21
Instagram: @insta_hamz

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Re: Tram lining?

Post by marco_polo »

With a 255 at ET40, I'd expect the tyre to just kiss the damper, I wouldn't try driving it. Or simply measure up from your existing front tyre, imagining it's 10mm wider both sides.

Here's mine, including the 1/2" longer M4 wishbones:

Image
Silver F21 M135i - ManBox - HK - Adaptive + Eibach Pro's - BBS CH-R's - BMWP Drexler LSD - M4 LCA's

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InvertedPanda
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Re: Tram lining?

Post by InvertedPanda »

Cheers! I will measure it up next time I have the car on a ramp or something.

Looks like I will be opting for a square 245/35 setup next summer!
MHD "Stage 2+" tuned 2013 BMW M135i xDrive F21
Instagram: @insta_hamz

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