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      11-06-2012, 03:31 PM   #4
Lieutenant Colonel

Drives: M3
Join Date: Jun 2012
Location: Bay Area

iTrader: (2)

Originally Posted by robertm View Post
So I've pretty well decided I'm switching to a square setup. 18x10 25et all around. I'm doing this for a myriad of reasons. First I love the way the car handles with this setup. Second, the ability to rotate all tires to all corners will greatly increase tire life. Third, 18s are cheaper than 19s.

The question though is how wide can we go up front. A few people are already running 275/35/18s with stock susp (don't know if they are using camber plates -anyone?). I've got 295s on the back now and I'd like to stay as wide as possible. So, can we get 285s up front and what's it going to take?

Here's some background info:

Front: 245/35/19 Sect Width 9.8" Dia 25.8"
Back: 265/3519 Sect Width 10.7" Dia 26.3"

18" Options:
275/35/18 Sect Width 10.9" Dia 25.6"
285/30/18 Sect Width 11.4'" Dia 24.8"
285/35/18 Sect Width 11.4" Dia 25.9"

One thing to note is the front stock size section width is misleading as itís based on a 8.5" wheel and we are running 9" wheel. So maybe change that section width to 10.3".

Looking at the difference between the 285/30 and 285/35 the thing that stands out is the overall dia. The 285/35 would be a much nicer looking fit as the dia more closely matches stock. I'm afraid 285/30 may create a pretty large wheel gap with the fender.

It doesn't end there though. Here are a couple other data points:

285/30/18 Tread Width 10.5"
285/35/18 Tread Width 10.1"

So the 285/30 is shorter (dia) but it has a seemingly larger contact patch. This would be good where rubber meets the road but what effect will that have inside the wheel well?

Basically compared to each other:
285/30 short and wide
285/35 tall and narrow

So what will it take to make one of these work? Camber plates seem like a given. Will spacers be required too? One requirement is they still need to fit within the fender or at least not make contact with the outer fender under track loading conditions.

Thoughts, ideas, opinions!
With Camber plates you can definitely fit a 285/30/18 front tire and 18x10" ET25 in the front of your 1M. Strut clearance will be very close but you should be able to clear on an oem set up and coilover set up as long as attention is paid to the spring perch location relative to the wheel/tire. This is the maximum width for the front of your 1M. The 285/35/18 is way too tall and even with an extreme amount of negative camber it will definitely rub on the fender liners with any kind of steering angle. Also the 285/35/18 would look quite odd with that tall of a tire in the front of the car. We have 18x10" ET25 wheels available in both the ARC-8 and EC-7 models as well as camber plates for your 1M!