Wheel Sizing

We know that for a 12a RX-7, the standard wheel size is 13 x 5.5 with offset of +25.
That data provides a starting point, but it doesn't tell exactly one how wide and how deep you can go without "major tire rubbage".

Originally Posted by mortenf on rx7 club
Well, since a lot of people have been asking about what fits and how lately, i thought i could make a thread about it. I would like others to contribute, so that in the end, we could have a sort of "wheelguide" for the first gen!

To start of in general with some FAQ`s.

Q: What wheels will fit my 1st gen?

Answer: due to the uncommon bolt pattern and high offset of the 1.st gen from 79-83, there isn`t a lot of new rims out there. There are however ways to get by this!


Q: Wait, wait, bolt pattern? Offset? Please explain!

Answer: OK, here we go. The RX7 is available with two bolt patterns. The early ones are the most uncommon ones, the late 84-85`s had a more common one. The pattern is 4*110 for the old ones, and 4*114,3 for the latest. So what do you have? Well here is a little picture of how to measure your bolt pattern with a ruler, measuring tape etc.



Measure the length between two opposite holes. The easiest is to do it on the rear axle. Its also easier if the wheel is off the car! The result in mm is your bolt circle. You should be able to measure eiter 110 or 114,3. Then count the number of bolts. There should be 4!  If not, you are lacking a bolt or you have a transplant axle from another car! The first gen, as said, was only available with 4 bolts!

Right. You should now have measured your way to the mentioned numbers stated above. This is your bolt pattern.

Q: OK, i got the bolt pattern part, but im not sure of the offset?

Answer: You cant measure the offset without the desired rim. Normally this is inscripted in the rim itself, or any good wheel shop should know what offset the rim is. Here is a pic, hope you understand



See? Basically the offset is the distance from the mounting part of the rim to the imaginary center of the rim. The lower the offset, the longer out the wheel sticks. The early RX7`s require a low offset, especially with large wheels.

Q: Aha, i get it. But what size can i get?

Answer: The RX7 originally had 13`s, and at the end of production it went up to 14`s This said, there is no problem going bigger than this. 15`s are common and probably the easiest and the best comfort/performance option. On the oldest RX`s, 16`s will fit with minimal to no rubbing. The newer ones can with up to 17`s. Of course, this depends on what tire size you choose. A good rule of thumb is not to go more than 5% than the original rolling diameter. (the diameter of the rim/with tire)

Larger rims will also fit, there are people running 18`s on the old SA`s. This will require rolling of the fender lips, and/or modification of the inner/outer fender.

Generally, the bigger the tire, the lesser the comfort. Performance wice, for a road car, i would not recommend anybody going over 16`s. The profile of the tire also has a lot to say.

Q: Profile? 15`s? My tires have 205/60-13 on the side. What does this mean?

Answer: Easy one, but for those of you that dont know: 205 is the width of the tire in mm, hence 205 equals 20,5 centimeters (gotta love the metric system). 60 is the profile of the tire. This means that the height of the tire, measured from the rim out is 60 % of the width! 13 is the size of the rim itself (without tire) and 13 equals 13".

Q: Aha i get it. But now im having a hard time finding rims that fit!

Answer: well, as stated in the beginning, the selection is limited if you just search for 4*110. (The 4*114,3 is more common, no problem finding rims here) There are however some solutions. You can for example:

1. Do a suspension swap from a GLS-SE. Not only does this give you a more common pattern, but you also get rear disc brakes and LSD!
2. Redrill the rims. Some vendors offer this service, usually at a fair price.
3. Use 4*108 rims with "loose head" bolts. This requires the use of bolts that has loose heads that allows you to fit 4*108 (Ford etc.) on your 1.st gen. i myself has ran this option for 3 years now, no problems here. Just make sure the boltheads are steel and not copper. (Copper breaks)4. Import wheels from Japan or Australia. For example Simmons can deliver, but the price is hefty, plus shipping. not a cheap option, but you get what you pay for.
5. Ebay. Now and then there are wheels in the desired size on auction. Happy hunting!