Speed Change

[dontendupzero]

I am changing my tire size from 235/75/15 to 33x10.5x15. I was wondering how much my speedometer will change?

 

[twoj05]

Just a rough estimate, but at 65 MPH on the speedo, you will be going almost 75 MPH. At 35 it would be about 40.

 

[ranger_mclaren]

I'm no professional but I really don't think i'll change at all, I went from 235x75-15s to 31x10.50-15s to 32x11.50-15s never noticed a difference on a '86 ranger. But when I bought it, it had 31s on it and maybe the previous owner took care of the speedo. but thats just my .02 cents.

 

[Mark_88]

There was a speedo change calculator on the site years ago...check the tech library...

EDIT: Just checked...here's the link...


Speed Calculator

 

[Hahnsb2]

It will read 15% slower. So get a speedo gear with 15% less teeth than the stock one.

 

[dontendupzero]

any idea on where to get one?

 

[Earl43P]

From Ford, a junkyard; I have a red one (21 teeth) sitting right here on my desk.

The only markings on it are D4 and 21T.

 

[Hahnsb2]

I got mine from a speedo shop..

21 tooth, 4.56 gears, 34" tires and 1354 t-case puts my speedo dead on according to my GPS. You probably need something like a 15 tooth.

 

[dontendupzero]

Will changing the gears change the speed to. I plan on going to 4.56 gears front and rear. I am going to change my tires to 35's when I get the body lift but for right know I have the 33's

 

[Dweano]

I did the exact same change (cept with 12.50 wide tires) and the 15% is dead right. Gps verified lol. I don't have speedo gears tho so i just use my gps as a speedmeter. And gears will change things too.

 

[93Ranger4x4]

When my truck was running the stock 3.73 gears and 33X12.50s it was off by 5mph(i ran 36's for a little while also and i know it was more than 5mph off then lol). I upgraded to 4.56 gears and went back to 33X12.50 tires, when doing 55mph on my speedo i was actually doing 45-50mph. What gears are in your xploder now? I'm going to assume 3.27s seeing as they didnt really put low gearing in the xploders stock, so your speedo might be off a little more than 15%. You might be able to stop a cop and ask if they could follow you and use the radar then pull over at a gas station or what not and ask him how fast you were going when you hit 55mph on your speedo.

 

[Hahnsb2]

When my truck was running the stock 3.73 gears and 33X12.50s it was off by 5mph(i ran 36's for a little while also and i know it was more than 5mph off then lol). I upgraded to 4.56 gears and went back to 33X12.50 tires, when doing 55mph on my speedo i was actually doing 45-50mph. What gears are in your xploder now? I'm going to assume 3.27s seeing as they didnt really put low gearing in the xploders stock, so your speedo might be off a little more than 15%. You might be able to stop a cop and ask if they could follow you and use the radar then pull over at a gas station or what not and ask him how fast you were going when you hit 55mph on your speedo.

Gears don't factor into how much the speedo is off. If the new tires are 15% bigger than the old ones, then the speedometer is 15% slow, regardless of gears.

 

[dontendupzero]

that's exactly whats in my rig is the 3.27s. How many teeth for the speedometer gear are factory for the explorers with an automatic tranny.