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Discussion Starter #1
Hey guys,

I'm in the market for new tires since the Coopers on the car right now were production halted in 2001. Yikes......

Anyway - they are 235-60-14 fronts and 245-60-14 rear.

So, who ever decided on these sizes I'm not sure they calculated the tire size changed in height with keeping the same profile but in a slightly wider tire.

How much difference would this make in the speedo? My Speedo is pretty far out but I'm not sure how much as a result of the profile difference. Thanks.

What were the stock sizes BTW?
 

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Discussion Starter #2
PS - Not that it matters for the question I asked ..... but they are standard sizes rims and spacers on the back.
 

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I had 235/60/14 tires and 3.50 gears on the rear of my car and the speedo was way off. Tried to correct it at one point and got the wrong speedo gear and it was even worse. It's very helpful to look at tire specs on TireRack.com tirerack.com/tires/TireSearchResults.Make=Ford Model=Mustang+5-Lug 70&diameter=14 and look for the diameter and revs per mile. The basic equation to calculate speedo gears is here: performanceparts.ford.com/SpeedometerGearUsageChart.pdf. All that matters with speedo gears is revs per mile or diameter. Spacers have no effect.
 

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