Prospeed_Motorsport

I have searched and read many on the threads on this topic already....

I'm trying to understand how you determine wpacer size and other than telling you want to use, none of the threads really explain how spacer size is determined.

For example I note several threads suggest a 21 mm spacer front and a 28 mm spacer rear, however couldn't you just do the math to determine spacer size? i.e. if the factory/base offset is 23 mm then to fit a ET55 wheel wouldn't you need a 32 mm spacer? (55 - 23 = 32) And wouldn't that work for front and rear if the new wheels are ET55 front and rear?

Getting ready to order spacer/adapters for the 86 951 for the winter wheels/snow tires that are coming.

zblowfish

Depends on the width of the wheel too so post the widths

Prospeed_Motorsport

The fronts are 7.5 x 17 ET52 and the rears are 9 x 17 ET47

racer

As to your original question, with 4 same sized wheels with the same offsets of 55, then yes, it is just a matter of doing the math (new ET 55 - old ET or 23 = 32mm specer/adaptor).

kenkawai993

Subtract the wheel offset from the cars offset. So early car 23.3 minus 55 = size of spacer. Later cars have the larger offset so its "bolt on".

Prospeed_Motorsport

So then the spacers I want are 29 mm for the front 7.5" ET52 and 24 mm for the rear 9" ET47? Can anyone confirm this? As in they have done this before. As I'm having custom spacer/adapters made I don't want to screw this up.

racer

One thing to consider is well.. if you want the wheels pushed "out" to fill the fender wells, you might go a little larger.. or if you are worried about rubbing (based on camber and ride height settings) maybe just stay "stock" as it were. You don't mention much about how the car is currently set up.

If running winter tires, to be fair, I don't think I'd want 9" in the rear.. Maybe an 8 or maybe 7's all around (running maybe a 205 front, 225 rear). Tall/Skinny is good for snow tires, not wide

kenkawai993

Yeaa, I concur. Skinny and tall is good for winter. At the most, I'd go 215 all around for winter|snow tires.

And yes, you are correct about your calculation in your above post.

But keep in mind, different tire sizes are different for all tires. A 205 on tire "A" might be 215 on tire "B" and vice versa. Some run wider or skinnier then others. I mention this because if you buy the spacers, the tires might rub or not fit as well in the fender the way you want.

Prospeed_Motorsport

Yep I know what is best for winter tires but the wheels and tires are coming at a GREAT deal and the budget is limited.... In a perfect world I would have found 7 and 8 x 17 with 205 & 225 but....

The car is lowered about an inch front and rear. There are currently 7.5 & 9 x 17 on the car right now with the summer tires. Other than that, camber etc is set for factory. Don't really need 2 degrees for negative camber for winter. ;-) Oh and the curent wheels are those odd ones that are Cup 1 replicas but with 23 mm offsets front and rear.

Yes, I would like the wheels to fill out the fender wells. So just trying to figure what the spacers need to be is critical. I've read the other threads that suggest 21 mm front and 28 mm rear but the math doesn't quite work out, hence I am asking questions.

Prospeed_Motorsport

FWIW, the tires are Blizzak LM-25 205/50/17 front and 255/40/17 rear if that helps at all

ALFAPU

This offset calculator may help:
http://www.1010tires.com/WheelOffsetCalculator.asp

According to this, you will need a 29mm spacer up front and a 24mm spacer at the rear in order for the outside lip of your new wheels to sit in the same position as your current wheels. However if I punch in the measurements for stock '86 951 phone dials (7/8 et23) then you need a 23mm spacer in the front and an 11mm spacer in the rear (this will tuck your new wheels in like the stock 951 wheels).

Prospeed_Motorsport

Thx