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Discussion Starter #1
Hey guys, I just put in new 4.56 gears and 35 inch tires and i used my flashcal to change the ratio and tire size but it definitely seems my speedo is off.. says im doing 60 kph at the top of 4th gear I'm scared to overheat.my new gears by going over 55mph.

Any hints? I looked around and cant find info
 

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You’ll need to verify your speed with a stand alone GPS, either an app on your phone or maybe a GPS unit. You cannot use your Jeeps built in Nav GPS if equipped.
 

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What did you enter for tire size? For 35s, use 33.75 to start, 33.5 for 315s. You'll be within .25.

Also, you're not going to hurt your new gears.

Mark

Sent from my SM-G935V using Tapatalk
 

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Discussion Starter #4
What did you enter for tire size? For 35s, use 33.75 to start, 33.5 for 315s. You'll be within .25.

Also, you're not going to hurt your new gears.

Mark

Sent from my SM-G935V using Tapatalk
I thought I was going low when I entered 34.5 or 34.75. I will actually measure the tire tomorrow and reset the size so its accurrate. Good call man
 

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No need to measure, as nearly all 35" radials will be 33.75 weighted rolling diameter, +/- .25. Set it, run it, try .25" different if you think your speedo is off, and drive the thing. :)

Mark

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I will actually measure the tire tomorrow and reset the size so its accurrate. Good call man
If you decide to measure, go to the center of the hub and double. Not to the top of the tire.
 

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If you decide to measure, go to the center of the hub and double. Not to the top of the tire.
On my Procal the directions said to put a flat edge on the top of the tire an measure from the flat edge to the ground and use that measurement. I did and my speedo is right on.

You need to get the diameter of the tire on the ground with weight on it. Only measuring from the ground to the center of the wheel will be a shorter measurement than the way I described as you would be measuring the flattest part of the tire twice (if you double the measurement)....
 

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Or you can just convert the revs/mile number for your tire to weighted rolling diameter, and be +/- .25 every time.

Mark

Sent from my SM-G935V using Tapatalk
 

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Discussion Starter #9
I am fairly confident some things wrong maybe with these cheap new wheel speed sensors or something, because I'm trying to get an idea on mpg and the number is all.over the place, varying 1-3 whole numbers just in startup. Seems to shift at the correct times in auto, but I know for sure my speed is increasing but my speedo stays at 60. Thoughts?
 

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OK so your speedo says 60 but you think your going faster? What did the stand alone GPS say when you verified your speed?
 

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Discussion Starter #11
Gonna have to check that. Phone is always dead by the time I turn on ignition.

If there was a variance, what would be the cause and or solution?
 
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