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      10-12-2012, 10:54 AM   #1
can128
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18 x 8.5 Front / 18 x 9.5 Rear Max Tire Size

So I need new tires, and I'm hoping I can go as wide a 275 on the rears with my 9.5" wheels. Has anyone done this or know if it's possible?
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      10-12-2012, 11:00 AM   #2
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It all depends on the offset of the wheel and the actual running width of the tire. Plenty of people have fit 275/35/18 Michelin Pilot SS on the rear with a 18x9.5 ET58/62 from Apex in the EC-7 and ARC-8 wheel models. When you get into VMR fitments (18x9.5 ET45/50) it gets significantly harder to fit that wide of a wheel in the fenders without a serious roll/pull. I have been told that, if you have the right offset wheel, you could even go 18x10 and get a 285 in there, but then wheel diameter differences start to get a little screwy.

Fronts max out at about 235/40 with an 18x8.5 ET45 both inboard and outboard AFAIK without serious camber adjustments.
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      10-12-2012, 11:03 AM   #3
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Quote:
Originally Posted by b1aze View Post
It all depends on the offset of the wheel and the actual running width of the tire. Plenty of people have fit 275/35/18 Michelin Pilot SS on the rear with a 18x9.5 ET58/62 from Apex in the EC-7 and ARC-8 wheel models. When you get into VMR fitments (18x9.5 ET45/50) it gets significantly harder to fit that wide of a wheel in the fenders without a serious roll/pull. I have been told that, if you have the right offset wheel, you could even go 18x10 and get a 285 in there, but then wheel diameter differences start to get a little screwy.

Fronts max out at about 235/40 with an 18x8.5 ET45 both inboard and outboard AFAIK without serious camber adjustments.
Thanks for the useful info. My VMRs are 8.5 ET40 Front, and 9.5 ET45 Rear.
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      10-12-2012, 12:27 PM   #4
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Originally Posted by b1aze View Post
I have been told that, if you have the right offset wheel, you could even go 18x10 and get a 285 in there, but then wheel diameter differences start to get a little screwy.
it's worth noting that in terms of outer rolling diameter, 285/30-18 is a far better choice than 275/35-18, actually. 275 is about as "screwy" as diameters get, since it should be a 275/30-18, but that's a nonexistent size. you don't get into the correct 30% aspect ratio until 285 and wider. that's not to say that 285/30-18 will be a breeze to fit width-wise... just thought i'd note that 275/35/18 is about as far off as i've seen anyone use with respect to diameter. way too tall in my opinion, especially for a car that already has very tall gearing.
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      10-12-2012, 12:42 PM   #5
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Originally Posted by can128 View Post
Thanks for the useful info. My VMRs are 8.5 ET40 Front, and 9.5 ET45 Rear.
if you're sticking to your VMR wheels at 18x9.5 et45 in the back, even 255 is goint to be a tight fit and will likely rub (depending on all kinds of factors). 265 would be a disaster. you're basically looking at 245/35-18 or 255/35-18 in the back unless you want new wheels.
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      10-12-2012, 12:47 PM   #6
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Quote:
Originally Posted by fourtailpipes View Post
it's worth noting that in terms of outer rolling diameter, 285/30-18 is a far better choice than 275/35-18, actually. 275 is about as "screwy" as diameters get, since it should be a 275/30-18, but that's a nonexistent size. you don't get into the correct 30% aspect ratio until 285 and wider. that's not to say that 285/30-18 will be a breeze to fit width-wise... just thought i'd note that 275/35/18 is about as far off as i've seen anyone use with respect to diameter. way too tall in my opinion, especially for a car that already has very tall gearing.
It depends what your motivation is. I know some people who will use a taller tire all around to "fill the gaps" in the fenders. The 275/35 does a pretty decent job of that, but in turn, increases your rolling diameter, which is actually harder for the car to turn than a smaller diameter of the same weight. A taller sidewall, all things else equal, will give a cushier ride, but sacrifice a bit of turn in sharpness.

Quote:
Originally Posted by fourtailpipes View Post
if you're sticking to your VMR wheels at 18x9.5 et45 in the back, even 255 is goint to be a tight fit and will likely rub (depending on all kinds of factors). 265 would be a disaster. you're basically looking at 245/35-18 or 255/35-18 in the back unless you want new wheels.
Pretty much this. If you wont even consider taking an eastwood roller (or baseball bat) to your fenders, the 245 will be your only option. Considering the OEM tire is of the same width, you have gained yourself essentially nothing in tire width, aside from a stretched tire

The only VMR i would consider is the 701 with 19x9.5 ET50 in the rear, and thats still barely a 255 tire for proper fitment.
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      10-12-2012, 01:07 PM   #7
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It depends what your motivation is. I know some people who will use a taller tire all around to "fill the gaps" in the fenders.
that's just silly. taller tires lengthen effective gear ratios, like a final drive adjustment. this car has very long gearing to begin with, which really doesn't need to be even further lengthened.

for example, the 275/35-18 pilot super sport has an outer diameter of 25.6". the oem size (245/35-18) of the same tire has an outer diameter of 24.8". this is an increase in rollout of 3.2%. in a stock car with 300 ft-lb of torque, that's an effective reduction of 9.68 ft-lb of torque applied to the road across the curve in every gear! in other areas of the forum you'll find people spending thousands on fancy little carbon fiber bits and bobs that add less torque than that.

Last edited by fourtailpipes; 10-12-2012 at 01:13 PM.
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      10-12-2012, 01:32 PM   #8
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ive got 245/35/18 pss's on 8.5 VMR VB3's up front. I have to run 15mm spacers up front to keep the tire off the shock, but i also have E46 rotors, so i think that screws with offsets a bit. It does rub on the track, but im kinda low, my vorshlags are maxed out and i have m3 front control arms, i think im at -4.5* camber in the front
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      10-12-2012, 06:57 PM   #9
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Quote:
Originally Posted by ezeedee
ive got 245/35/18 pss's on 8.5 VMR VB3's up front. I have to run 15mm spacers up front to keep the tire off the shock, but i also have E46 rotors, so i think that screws with offsets a bit. It does rub on the track, but im kinda low, my vorshlags are maxed out and i have m3 front control arms, i think im at -4.5* camber in the front
Do you have a picture of -4.5 camber? I might be going with that much camber but I need to see it first! Thanks!
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      10-12-2012, 07:51 PM   #10
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Quote:
Originally Posted by b1aze View Post
Plenty of people have fit 275/35/18 Michelin Pilot SS on the rear with a 18x9.5 ET58/62 from Apex in the EC-7 and ARC-8 wheel models. I have been told that, if you have the right offset wheel, you could even go 18x10 and get a 285 in there, but then wheel diameter differences start to get a little screwy.
As noted.

I have Apex Arc 8's and last season ran 275/35-18 PSS rear, this season am running 285/30-18 AD08's. Both work fine even on the 9.5" wheel width, but as listed in the forums, the 285's are closer to the right diameter, which I think is part of the reason I prefer them.

However, with VMR's you're looking at 245 rear max. It's just the wrong offset to fit rubber.
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