viking396

Ok, the rims I want are on back order so I'm now looking at American Muscle ChromeMach1 rims that are 17x9 all the way around. The fronts will have Sumitomo255/40/17 (25" height) and the rears will have Nitto (yes, I know BFG DR's are better) 275/40/17 (25.7"height).

So, Brenspeed tells me that even though the back are .7 taller I will not get tossed an ABS code while driving, AMerican Muscle insists I will and also says that 275/40/17 is 2.3 inches shorter than Ford recommends as they want the height at 28 inches. This is driving me insane, I need to know if people are running a slightly taller tire in the back and is ANYBODY running a 275/40/17 tire on their S197.

I plan on ordering SOMETHING tomorrow and the above is what I would LIKE to order but not if I have to worry about codes. Please don't respond with guesses, I need people with experience to chime in.

I spoke with 2 Ford dealers, both "guessed" I should be ok, so if they don't know how can I expect others to know? Easy, the people here rock!

Pantera72

Nitto555 295/45/18 @ 28.31 inches overall diameter, no problems whatsoever. As for who is telling you the truth, try looking up the specs on your stock rear tire and seeing who's information matches the closest the the stock tire size.

Haze28

I run 295/45/18 in the rear and I have no problems at all. Call Americanmuscle up and tell them they're crazy! I love the look and ride with this size tire. Since your going staggered why don't you go with a 10 inch wheel in the rear and run the 305/35/18 DR that Nitto offers? It will fit and will give you alot better traction off the line, which judging by the power your putting down you will need.

Oh by the way, are you from Illinois? I saw your tuned by Kurgan, I'm hoping to have him hook my car up soon too.

daoh

This should help with the sizing calculations: (stock is 235/55/17)http://www.discounttire.com/dtcs/infoTireMath.dos

It looks like you could get a lot closer to the stock size by going with: 255/50/17 and 275/45/17, unless of course you are going for smaller tires to "change" you effective rear gear ratio...

As far as the bigger/smaller than stock throwing ABS error codes, I have no idea.

viking396

I know the stock diameter, every place I called today warned me about this ABS code crap, just about drove me nuts.

viking396

I saw your car at Busse Woods a few weeks back, it looks fantastic! I could go 30518's but if I do I can't use my current rims and buying new 18" rims that I like puts me way over budget and will require a new gear as well. I'm not looking to fill the wheel wells, I'm looking for good looking rims and less rolling mass than I currently have. The weight savings, less wheel mass and shorter tire height will help get me into the lower 12's without spending more money on the mechanicals right now. Using the Nitto's means that it won't grip so hard that something might break. If I can crack a 12.6 on the skinny tires that Ford put on the car then 275 DR's that are 2.3 inches shorter will get me a bit deeper into 4th gear and net better 60ft times. If I run a 1.85 60ft I should be at or near 12.3 at about 114 to 115mph.

Next year I'll hook it up with 3.90 gears and a better clutch and then I'll install the BFG's and maybe lower the car a little bit.

viking396

Stock for me is the 18" fanblades but they are the same 28" diameter as the 17 inch rolling stock. You're correct however in that I'm looking to effectively lower my gear a little by using 2.3 inch overall shorter tires.

Anybody have a calc that helps figure out what 25.7 inch tires reduce our 3.55 gears too when compared to the 28" stock tires? My brain hurts.

Haze28

Try this, http://www.miata.net/garage/tirecalc.html
I don't know what your stock tires are but if you go down to a 17" wheel you could run a 275/45/17 to kind of make it work like a 3.90 or 4.10 gear, not really sure about the calculations though. I think I saw your car at Busse too, I wish I could have got a look at the blower. Nice set up you got.
Did you see this?

viking396

Stock tires are 235/50/18 and are supposed to be 28" in diameter. I saw you drive through at Busse that day, your car looks unbelievable! I watched that burnout I believe, there was a lot of them.

Anytime you want to se the set up let me know, I'll meet up and show you. I just eye balled the car, I don't know if my plan will look right, I think I'm going to be seeing a lot of the wheel wells but the new set will be wider. []

viking396

Hey that worked out great! With the 25.7" tires I'll be going56.5 when my speedo will be showing at 60 if I don't change it using the SCT, a difference of 5.8%. So unless my math is off, and anybody who knows me knowsthat math is not my strong suit, my overall gearing with 25.7 inch tires will be 3.76 and if I go 3.90 gears next year with 25.7 inch tires then my overll gearing would be 4.13.

Am I wrong?