Will 225/50/15's work? Will the old 94 turbo wagon handel as good as the 195/65/15 b.f.goodrich tires that are on it now? Stock is 205/55/15. I'm thinking like a Dunlop ultra performance or a Kumho ultra performance. you can look up the tire calculation at this web site: http://www.miata.net/garage/tirecalc.html
Great site for tire calculation.
Thanks in advance, Notta...

 

I'm not sure what the tolerances are but using that site there doesn't seem to be much difference between the tyres you want to fit and the 205/50zr16s on my 850 T5.

I think the 850r may have wider rims, they are bigger anyway at 17".

 

If the stock tyre is 205/55/15 the only difference to the 225/50/15 is the footprint is 20 mm wider. There should be enough clearance for this.

You may find the speedo gives a different reading as the revolutions will increase from 807 to 845. However, as the stock tyre would give 845 revs as well the speedo is probably calibrated for that. The speedo reading, therefore, should be correct.

 

They work great and make the wheels look much more beefer. New tires and an alignment wow what a difference. Notta...

 

Quick note. When going over a bump (driveway or other) with full wheel lock to the right or left they will rub ever so slightly. I don't make it a habit but it heard it accidentally. Notta...

 

So do mine and they are Volvo Volan wheels with the exact right size tire. They just don't have much clearance in the wheel wells.

 

If this is relevant at all, the picture in my profile of my wheels is 205-60-15. stock was 195-60-15. Didn't want to mess with the height of the tire. Made it a little wider. Rides softer also.

 

But you did add slightly to the height if my understanding of tire size is correct. Correct me if I'm wrong, but my understanding is that the middle number is the percentage of the width that is the height. So the height of yours is 60% of 205 vs. 60% or 195.

 

Yeah - according to the tire calculator that the OP posted the sidewall is .2" higher on 205/60/r15 than 195/60/15.

The stock 205s (or certainly the 205s on my car which are stock) are 205/50/16 which have a radius of 12" as opposed to the radius of 12.3" on 205/60/15 (again according the the tire calc).

There's not all that much clearance on my car either.

 

Hmm. Interesting. The way I understand is that the first set of numbers is the width. The middle number is the sidewall height. And of course the last is the rim size. If my stock size is 195/60/15, then going to 205/60/15 was only going to add width. That's the way I saw it. I'm sure it's more technical than that but.....

I've parked next a S70 once with same stock wheels with stock size tires and I can tell mines was a little beefier. Don't know about the height though.

 

No, it's not more technical. 195, 205, 225 are the measurements across the tread from shoulder to shoulder and are millimetres. It is still possible to catch the tyre on the wheel arch by only adding to the width but not so likely as adding to the height (second set of figures). We always worked on 10mm either side of the width stamped on the wheel rim.

Any good tyre supplier will be able to tell you the width you can go to on any particular rim.

The main problem with playing about with the height is the speedometer reading. It will definitely go out as the number of revolutions the tyre makes per mile will be different to the spec laid down by the car manufacturer.

 

Yes, the place I purchased the tires from said that I have to get "V" rated if I want to go 205. My tires are BFGoodrich G-force Sport.

 

So is a 205-60-15 the same height as the 195-60-15?

 

No,iirc your previous post was correct.

The second number is the aspect ratio of the tire width (first number), so on the 205/60/15s the sidewall height is 60% of 205mm (123mm) and on the 195/60/15s the sidewall is 60% of 195mm (117mm).

The sidewall of the 205/60/15s is 6mm taller than the sidewall on the 195/60/15s, that will mean the 205/60/15s are 12mm taller than the 195/60/15s.

As for letter rating iirc it has nothing to do with tire size rather speed rating. IIRC they got up to K or some other letter half way through the alphabet and they used Z as "over 149mph" (My tires are rated ZR16 - ie Z speed rating), unfortunately to rate a tire at "Z" the manufacturers don't have to specify how far over 149mph the tire is good for, so ratings such as "V", "W", "X" and "Y" were created to be more specific.

I don't know about the 850R but the T5 is supposedly limited at 149mph so I don't suppose Z rated tires are much of a problem - I don't know about you but I'm certainly not brave enough to see if I can hit the 149 limit.

Iain