What size wheels do most run and why?
15,16,17 inch
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I'll answer this just to save you the heartache.
For best on-track performance with stock fenders, you want 225/45-15 tires on 15x8" wheels with an offset of ET25 or so. The smaller overall diameter will shorten your gearing a bit, which is good for acceleration.
If you want to drive around on the street (therefore care about keeping the speedometer reading accurate), then 225/50-15 will be better since the overall diameter is closer to stock.
If you can't find a good 15x8" wheel, then you can try 15x7" wheels. In that case, 225 mm tires are actually a little too wide, which makes the car feel a bit sloppy in transitions. In my testing, when I had 15x7" wheels on my E30, I actually had about the same grip with 205 mm tires. Again, in my testing, I found a 9"-wide wheel was necessary to really get the most out of a 225 mm tire.
205 mm tires also have the advantage of being lighter and usually cheaper (spec Miata size, so frequently on sale). So, I wouldn't rule out a 205/50-15 if you decide to run a 15x7" wheel. Grip levels will not be far different in either case.
As for larger wheel sizes, they don't make sense on the track for a typical E30 with stock fenders. Avoid 16" wheels at all costs, as the selection of race rubber is close to zero. You might think 17" is a good choice, but the overall diameter will generally be too big...which messes up your (already not-so-great gearing). Besides, you really don't need to go wider than 225 mm on an E30, so there's really no benefit to the 17" wheel. If you were running 245 mm or 255 mm tires, then you could argue that 17" makes sense. But you don't need that on a regular E30.
SUMMARY...
- Best performance for pure track use: 225/45-15 on a 15x8" (or 15x9") wheel
- Compromise for mixed street & track: 225/50-15 on a 15x8" wheel
- Good alternative in either case: 205/50-15 on a 15x7" wheel
- Do not buy 16" wheels for any reason
- Avoid 17" wheels unless you have a specific reason to do so
Last edited by Emre; 02-28-2016, 09:19 AM.sigpic
1987 Mercedes 190E 2.3-16: Vintage Racer
2010 BMW (E90) 335xi sedan: Grocery GetterComment
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I run 205/45/16 tires. Why because I can not run any wheels smaller then 16 due to my big brake setup.Current
99 328i (Sold)
91 318is M50B25TU
89 325ix (Parted out)
87 325is (Parted out)
95 525i (Parted Motor for 91 318is)Comment
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Since the OP didn't give the use going on about no 16" race rubber may or may not apply.
I run 16x8's with 225-45-16 ZII's,fits the looks of the car perfect and provides tons of grip for the street.Mine is just for the street and backroad burning.
I run the 225-45-15 race rubber on my track only Miata.Comment
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sigpic
1987 Mercedes 190E 2.3-16: Vintage Racer
2010 BMW (E90) 335xi sedan: Grocery GetterComment
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I LOVE my 16" SSR Type Cs, but wish I could find them in 8" width, for now Im running 205 in front and 225 in the back, probably going to have 225/45 all the way aroundSimon
Current Cars:
-1966 Lotus Elan
-1986 German Car
-2006 Volkswagen Jetta TDI

Make R3V Great Again -2020Comment
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Emre nailed it--ET25 sounds a bit high for a 15x8--my ET20 C1s don't have much clearance from the strut. But otherwise that's what you'll find is the best compromise, as well as most friendly to your wallet. I wouldn't go to 17s unless you strongly feel you've outgrown 205/225s and decide you want to step it up. Even then, there is the option of 15x10s and 245/40R15 RC1s or Hoosiers, but you'll want some real fender work first.paint sucksComment
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I ran 225/45/16 on my garage queen e30 with R888's on there and it was an animal. Agreed though, that the selection of 16" tires is next to nothing.
Now that I have a dedicated track e30 (we run 205/50/15's on it) I am trying to find a decent tire for the garage queen and it's proven relatively difficult. There's only 2 decent options outside of race rubber.Comment
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lol, that's why I just run race tires on the E30. I don't drive it in the winter anymore, and the non-race selection for small wheels is pretty awful anyway.I ran 225/45/16 on my garage queen e30 with R888's on there and it was an animal. Agreed though, that the selection of 16" tires is next to nothing.
Now that I have a dedicated track e30 (we run 205/50/15's on it) I am trying to find a decent tire for the garage queen and it's proven relatively difficult. There's only 2 decent options outside of race rubber.Comment
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Fitment is directly related to the offset, so you'll need to know what the offset is. You can google "offset calculator" to compare the stock wheel size and offset to the new wheels you are interested in.Comment

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