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      12-13-2023, 07:21 AM   #1
Novel
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245/40/17 or 255/40/17 square fitments on non-M

Hi,

I'm thinking about R17 square setup for the next season. I think I'll go with 9" wide rims with offset around 30. However, I'm not sure about tyre size.

Apex's fitment guide suggests 235/40/17 for square setups and that's the widest what they recommend either for square or in front.

However, for Z4M it suggests various sizes, up to 275/40/17 on 9.5" ET35 rims. So I'm wondering if I'm missing something, and what's the difference between Z4 and Z4M that allows Z4M to have larger and wider rims fitted?

From what I can see, part numbers for the front fenders are the same between 3.0si and Z4M. Fender liners are different, but I guess that's only because of the cooling ducts in the Z4M bumper. IIUC, front arms also have the same geometry and the only difference is Z4M arms have a stronger ball joints and different castor due to different rear bushings...

On the other hand, I'm running 235/40/18 on 8.5" with ET35 (those are basically 4 rear OEM ET50 wheels with 15mm spacers all around) and I don't really understand how 275 could fit... I'm also somewhat lowered with ST X suspension and have around -2.7 front camber. Even with that setup I have a slight rubbing in the inner fender liner, around the place where the bumper connects the fender, closer to the outer edge.

So I'm curious to know what's the experience on running setups like 245/255 on the front? Does it maybe need some stiffer suspension to fix potential rubbing issues?
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      12-20-2023, 11:32 AM   #2
ctdriver86
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What is the diameter and length of your front spring? I have JRZ RS PRO coilovers and can confirm that 18x10 +25 with 265 fits in the front with about -3.5 camber. I think 17x10 with a 255 will fit in the front if you don't mind more camber. 255 on a 10 will be better in terms of performance handling than a 275. I can also confirm this. I tried 275 on a 9.5 and then switched to a 265 on a 10.5 and the car was faster on the track. The tires load up better giving you more confidence to have faster cornering speed.
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      12-24-2023, 03:40 AM   #3
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Quote:
Originally Posted by ctdriver86 View Post
What is the diameter and length of your front spring? I have JRZ RS PRO coilovers and can confirm that 18x10 +25 with 265 fits in the front with about -3.5 camber. I think 17x10 with a 255 will fit in the front if you don't mind more camber. 255 on a 10 will be better in terms of performance handling than a 275. I can also confirm this. I tried 275 on a 9.5 and then switched to a 265 on a 10.5 and the car was faster on the track. The tires load up better giving you more confidence to have faster cornering speed.
My front spring length is 170mm and diameter is 81.5mm.
However, after I've started this thread, and after doing some some research, I came to a conclusion that I actually need to start with the suspension upgrade before touching wheels/tires. ST X is a cheap street suspension, with soft springs (50 N/mm front), I'm not sure building anything on top of it makes sense...

It's nice though that there are options to moving to a wider tire, thanks for sharing that info. I'm curious though how did you managed to get -3.5 camber, is that just camber plates?

Looking at my camber plates, it doesn't look like I have too much space for camber increase.

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      01-11-2024, 03:52 PM   #4
ctdriver86
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Oh yea not sure if 18x10 will fit with that suspension setup. My JRZ runs 60mm ID 5 in Length springs and there's enough room to fit 18x10.5 with -3.5 camber on camber plates.

Camber plates usually have about up to -4 in adjustment.
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      01-13-2024, 11:35 AM   #5
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Quote:
Originally Posted by ctdriver86 View Post
Oh yea not sure if 18x10 will fit with that suspension setup. My JRZ runs 60mm ID 5 in Length springs and there's enough room to fit 18x10.5 with -3.5 camber on camber plates.

Camber plates usually have about up to -4 in adjustment.
I see, thanks.

I decided to get rid of ST X for a proper suspension, and then I'll start re-iterating on the wheel/tyre combos.
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