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      05-06-2015, 06:27 PM   #17
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Drives: M3
Join Date: Jun 2012
Location: Bay Area

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Originally Posted by Tinsta View Post
I'd like to get a set of wider Arc8's.. I have a 135i, currently running a set of Aero-7s (8j & 9j) but its got the 1m arches going on shortly, as rears were rubbing with kw v3s with camber plates. No spacers, and oem arches rolled.

Would a 8.5j et45 with 245 tyre and 9.5 et62 275 tyre fit, looking to get widest fitment are these available in possibly 9j and 10j sizes?
For our ARC-8s in 18x8.5" ET45 and 18x9.5" ET62 for the 1-series, we would recommend the 235/40/18 and 265/35/18 tire sizes. The 235/40/18 street tires are generally a direct fitment for the front of a stock car, and are a great improvement in width and grip over the stock 215/40/18 front tire size. Not all 235/40/18 tires will fit. R-compounds, slicks and some other tires may touch the strut tube, requiring a spacer to fit. This fitment is tight on both the strut tube side and on the fender side, so there is little room to play with on a stock car. If a 3-5mm spacer is used to clear the strut tube with some tires, then it would be ideal to dial in some negative camber into the front suspension to help clear the fender. 235/40/18 tires are tall and could potentially rub the plastic inner fender liner if the car is out of alignment. Plastic liner rubbing is usually considered acceptable by most owners, but it is something to look out for as the gills in the liner for the oil cooler can some times stick out towards the tire more than normal.

The rear 265/35/18 is a direct fitment on the 18x9.5” ET62 wheel. There is no need to roll or run additional negative camber for this tire size on this wheel. If you would like a wider tire, you would need to make some modifications to your 1-series in order to accommodate them. If a tire that is wider than 235/40/18 is being used a 3mm wheel spacer must also be installed, otherwise the tire will start rubbing the strut or spring perch. The 245/35/18 tire size would require either M3 front lower control arms, or camber plates, in order to achieve negative camber in the front due to how close the wheel and tire is in relation to the fender. For the 255/35/18 tire size, both the camber plates and the M3 front lower control arms are required to achieve enough negative camber in front in order for the front tires to clear the fenders. With coilover setups utilizing a cone shaped progressive front spring (KW, ST, or PSS9) a 235/40/18 tire is the maximum front tire width because the spring takes up too much room on the strut side creating rubbing issues once a wider tire is used.

The rears are limited to the 265/35/18 tire size with the ET62 ARC-8 unless you roll the fenders. Even then, there are other issues that arise when using the 275/35/18 size which is why we do not recommend it. This is because when one is running a 275/35/18 rear extreme performance (ie. Hankook RS3’s) or R-compound tires with the 18x9.5" ET62 then the tire will likely contact the rear sub frame. This sub frame rub is only when the suspension is drooping (lifted in the air for service). The tires do not touch the sub frame when driving, but because there is contact, we do not recommend 275 width tires usually. The ideal setup for no issues is definitely the 265/35/18. You may have read about using a 275/35/18 rear tire before we were aware of how significant this problem is in the rear of the 1- series. It may be possible to fit the 275/35/18 rear tire with the use of a 5mm rear wheel spacer but at that point you are pushing the wheel/tire out very far and fender rubbing will very likely happen without heavy fender rolling.