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View Full Version : Tire Formula



Ross
01-02-2004, 02:39 PM
OK, I've followed some tire threads, and I know that a lot of you have gone to different size/brand tires. Sarge suggested trying 255/45's on the front and 255/50's on the rear, but after searching, it looks like only Pirelli makes both of those sizes, and they are pretty pricey.
Here's what I want to do. I want to keep the same ratio, size differential, or whatever you call it between the front and back so that I can use the same wheels and not have any sensors go crazy (ABS, Auto leveler, etc.). I know that I can use different size tires from the OEM and keep the same ratio, but I'm not sure what formula you use to figure out that front/back ratio. There are a million tires out there, and I need to know which I can use without wheel widening, height sensor adjustment, etc.
Anybody got any rules I can follow? Thanks

darebren
01-02-2004, 02:46 PM
I think you could chalk it up to those of us who have searched adnauseam for a better solution. On stock wheels to go wider with the same name/make of tire and keeping relatively close to the same front/rear height ratio, the Pirelli's are the only option. Unless you go very low profile tires like corvette style, but I don't think those wil look good witht he lines of our car, so I did not search for anything less than 1" apart from the stock tires heights.

Others will tell you they use all the same size, and if it can be done with or without a chip or traction control/abs sensor or gear change I don't know... if it could, I'd be all over the Goodyear F1 255's front and rear, but I recall the Ford rep telling us it can't be done without a gear change in the traction control sensor or maybe it was the abs sensor.. something like that.

Therefore, I have decided to get my rear wwheels widened soon and go to either pirelli's or Nittos using 275/45/18 rear and 255/45/18 fronts. still keeping the same height differential.

Good luck in your search, let us know if you reach any other conclusions...

Pantherman
01-02-2004, 06:41 PM
See http://www.miata.net/garage/tirecalc.html for help with tire sizes.

rumble
01-02-2004, 07:46 PM
The other tire/gear ratio site is
http://www.averagegeek.com/Evil_Jim/GearCalc.asp

It's fun to play with.