Another regearing question

Y

Yeahright

Member
I know this has been asked a million times but this Regearing thread is a little different.
So, I want to regear the JK, I have looked at the gearing chart that has been floating around, and on 35s it looking like 4.88 are the go, BUT!, I have used a ProCal to set up the recalibration of the speedo, taco, shift patterns and so forth. OK.
Stay with me please. So I measure my tyres the way the ProCal says to do it, measuring from the ground to the top of the tyre at normal driving pressures, I used on small level on the top of the tyre and a level with a tape measure to to get the height for the tyres so I can set the ProCal correctly.
I measure my 315x70x17 BFGoodrich ATs and they measure 33.25 inches, not 35.00 inches, 33.25inches.
So I get a friend to help me do it again, 33.25 inches is what we get.
And so we measure his 305x75x16 Bighorneys, 31.50 inches.
And finally here is what Im getting at when looking at the gearing chart, should I be looking at the chart for 33s or 35s?? Because I allways thaught 315s were 35s!!!!!

Thanks for your patients,

Yeahright
 
i understand your frustration with tire sizing. It seems every tire manufacture has a different idea what any given hight should be. I have a set of 315/70R17 and they measure in at 34.25. Because tire heights vary so much i would go on the theory that you have a set of 35's and go with the 4.88 ratio. just my thoughts on the matter hope you get some more input to help you decide.
 
no tire measures up to what is stated on the sidewalls and, for the purposes of lifts or even thinking about things like re-gearing, you should ONLY go off of what is stated and not what they actually measure up to. why? because manufacturers ONLY go off of what is stated and NOT what the true size of tires are. so, for your purposes, a 315 should be considered to be about the same size as a 35" tire and a 35" WILL NOT measure up to 35" - it'll be a lot closer to 33.5" or there abouts. having said that, 4.88 gears will give your 2007-11 JK a stock like feel and if you want a bit more power, 5.13's will give that to you but, at the cost of running a higher RPM at highway speeds.
 
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