Why does Tirerack specify different size 17" tires for SE and SVT?

[96RedSE5Sp]

According to Tirrack, I would need 205/50-17 tires for a '98 SE and 215/45-17 for a '98 SVT. Why the difference? What size should I use for 17" ST200 rims on a '98 SE Sport?

[Pudmunkie]

you should use a 235/40/17 :-D

[Steeda...]

you should use a 215/40zr I have a set in the classifieds for sale

[fordsvt98]

SE's came with 17's?

[Ray]

If you aren't using the OEM ri and OEM size tire, then thier "recommendations" are irrelevant.

The recommendations they are making for a set size (17" in this case) is their attempt to keep the overall size/ratio correct for the original rim and tire equipped on the car. Since the SE and the SVT came with DIFFERENT size rims and tires, the recommendations would be of different sizes, even though you are using 17" rims in the end, either way.

the size they are showing for SVTs would keep the speedo, and overall diameter the same, based on OEM SVT sizing.

You can't use the same exact size on an SE, since it came with 15" rims and different sized tires, you'd end up throwing off your speedo, and overall sizing.

If you are going with St200's, and are placing them on your SE, look at what sizes you WANT, then find a tire/speedometer calculator online to see where that would place your sizing, and accuracy. If you aren't okay with that, drop back and pick another size. It will come down to one of two things: your budget for (perhaps) a more expensive size in order to keep things accurate, or your personal preferences on whether or not you care.

[96RedSE5Sp]

SE's came with 17's?

No - SE's came stock with 15's. TireRack, however, tells you the proper tire size to use on your car when you are upsizing. I was just surprised to discover that an SE with 17s would require a different size tire from an SVT with 17s.

All along, I have been using the 215/45-17, which according to TireRack is the wrong size for my car.

[Ray]

That's just because the SE and the SVT had different original tire sizes, so to maintain that aspect ratio on your SE, you need a different size than an SVT would (to maintain THEIR respective ratio)

[Big Jim]

This may help you in determining the correct size:

http://www.miata.net/garage/tirecalc.html

I have another theory about why they may show a difference. Actually two theories. One is that the steering stops are different on the SVT. The steering stips are built into the steering rack. The wider tire may contact something it shouldn't with too wide of a tire. There are a lot of non SVTs running around with SVT tires and wheels with no problems. The second is that they may simply have some sort of formula based on what the car started with.

[fordsvt98]

get some width outta it i think for a wider footprint so i think 235-245's are good, and I like a good low pro tire so a 35 series or maybe a 45 tire is what im gonna get next time. Ya i didnt think se's came with 17's lol. Neither did svt's either right duh. I have FSVT17's, and konig imagine 17's and i think 17's are a good size theyre a good compromise. between what I dont know but they do the job nicely.

[beyondloadedSE]

This may help you in determining the correct size:

http://www.miata.net/garage/tirecalc.html

Theoretically, thats correct, but even tires with the same size do vary depending on the manufacturer. For example, Im running some Goodyear Eagle F1s that are 235/35/19. However, before that I bought some BFG Scorchers in the same size and the BFG were at least a half inch taller than the Goodyears. I returned them because I thought I would have fitment issues and got the Goodyears instead. Your best thing to do is read Tireracks specs on the tires and find something that matches the stock diameter.