15x7J ET13 with 205/50R15 Tyres.
The extremely sexy but rare MiM E30 wheels are of this size and fitment.
15" only? Why not bigger?
The only reason for bigger wheels is bigger brakes. E30's are super-light and don't need bigger brake discs. Aesthetically, 15" wheels beautifully compliment the E30's retro character, while still allowing plenty of performance tyre options. Yes, it's true that bigger wheels also allow lower profile tyres, but I will discuss that later on. For now, let me just say that bigger wheels add more unsprung weight. More weight in general can adversely affect acceleration, braking, handling, fuel economy.
7J? Why not wider?
When looking at your car, it's not very noticeable how wide your wheels are. If you want them to sit wide, you need only choose a lower offset. 7J wheels are the narrowest wheels that will ideally suit 205 width tyres (remember: wider wheels are heavier). You can go wider if you want wider tyres, but as discussed below, I don't think the E30 needs tyres wider than 205.
ET13? Why not lower?
At 7J width, ET13 will sit very flush, and when the suspension compresses, they will JUST clear the guards. With 7J wheels, ET13 is the widest fitment that will clear the guards. If you go for a more aggressive stance, you'll need guard work done (more $$$).
205 only? Why not wider?
Unless your E30 is HEAVILY modified, 205's will provide all the traction you need. Wider tyres will give better traction but they'll also add more unsprung weight. Also keep in mind that with a RWD car, breaking traction every now and then = FUN.
/50? Why not lower profile?
Lower profile tyres will provide you with more responsive handling due to reduced side-wall flex. However, at 205 width, the lowest profile you can get to fit 15" wheels is 50. Good quality performance tyres will perform very well, and you need not worry about side-wall flex destroying your lap times. You're better off worrying about your driving skills. More importantly, I believe E30's are such a pleasure to drive that they SHOULD be daily driven. If there are lots of potholes in your area, lower profile tyres mean you're more likely to damage or bend your wheels which means more $$$. Higher profile will give you that extra cushion for your precious wheels.
Other useful info:
All major tyre companies offer performance tyres in the 205/50R15 size.
If you wish to use a different wheel size, use the above numbers as a guide and put in your planned sizes into http://www.willtheyfit.com/. This will help you work out the offset you need to get a similar fitment.
E30 Wheel Fitment Sizes:
PCD 4x100, centre bore 57.1mm and M12x1.5 bolt thread.
Some 7J Wheel Choices:
PCD 4x100, centre bore 57.1mm and M12x1.5 bolt thread.
Some 7J Wheel Choices:
MiM's 15x7J ET13
Koya AE Tek 15x7J ET13
Work Meister S1 2P (O-Disk) 15x7J ET13 *Check Hub Bore
Koya AE Tek 15x7J ET13
Work Meister S1 2P (O-Disk) 15x7J ET13 *Check Hub Bore
If you really want wider tyres, you can go 15x8J ET22 with 225/45R15 Tyres. Be aware that running any higher offset than ET22 with 8J wheels may not clear the front struts. And you may need to do some guard rolling for them not to rub.
Some 8J Wheel Choices:
Rota Flush 15x8J ET20 *Check Hub Bore
Work Meister S1 2P (O-Disk) 15x8J ET22 *Check Hub Bore
Some 8J Wheel Choices:
Rota Flush 15x8J ET20 *Check Hub Bore
Work Meister S1 2P (O-Disk) 15x8J ET22 *Check Hub Bore
Work Meister CR01 (A-Disk) 15x8J ET22 *Check Hub Bore
