Hello List.

I wanted to replace the stock rims on my '91 2+2 with something a bit nicer and larger... perhaps an 18" rim.

However, in doing so, how does this affect performance? I imagine it would provide more power but require higher RPM's to attain a speed, say 60 miles per hour, than the same speed as the stock wheels. Is this correct?

Also, moving to a larger wheel, does it affect the speedo in anyway?

Thanks.

 

no, the wheel is not the problem. The tires are.

If your wheels are larger diameter then you must buy lower profile tires so that the new tire's outside diameter matches the diameter of the factory wheels. (mainly the rear wheels)
245/45/16 is stock

using this webpage, http://www.miata.net/garage/tirecalc.html
you can see that 245/35/18 is a close match
18x8.5 minimum width for the rear

A larger wheel is heavier. Even if the overall weight matches (for a really expensive light weight wheel) the weight is further out from the center so you have more centrifugal weight. Your braking and accelerating will be slightly worse.

 

Thanks Bleach. That site was helpful.

I was hoping there wasn't going to be a performance hit in acceleration, but hopefully it will be minimal and not noticeable.

I'm thinking of something similar to a 350z rim, but alloy, not chrome and something with straighter spokes, not curved like the 350z.

Anyways, after the holidays, I have no cash right now anyway so I will probably put a purchase off until later in the Spring.

Thanks for your help.

--Rick

 

This is also a good one for checking tires sizes.

http://www.1010tires.com/TireSizeCalculator.asp

 

just remember there are added expenses to factor into the budget when buying new wheels that many people don't think of, mainly the cost of an alignment which you have to get.

 

don't get discouraged about it, alignment isn't that expensive most places i checked out only quoted 10-15 a tire but you will have to have someone put the tire on for you there's no way you can get that low of a profile tire on a rim without a machine

 

Are you aware of the difference between "mounting and balancing" and an "alignment" ?

Usually alignment is one price for the whole car, even if only the front is adjustable.... they charge you as though they aligned front and rear. I suppose they can give you the specs on the rear, but most cars aren't adjustable back there.

Personally I never bother with an alignment if I change wheels and/or tires. I only do that when I have a steering issue or if I lower the car.

 

ya i do but will still have to get someone to mount the tires and ya i did get mixed up. but i've helped put tires on ones of my buddies car and we didn't have them balanced

 

Looking forward to more posts like this....they are very helpful. Welcome to Zdriver. I can tell you will be a valued '***'et to this form. Extra emphasis on the '***'.

 

and of course on a z32 pretty much nothing is adjustable. so they basically charge you to tell you your current specs and that they can't adjust. anything

 

Replace the rims and get more power? I KNEW IT!!! *runs off to autozone*

 

You're a good friend to help your buddy with his old car. That works fine for farm vehicles that never go over 35mph