How To Correct Speedometer

R Gage · October 10, 2009

If I was to install 285/75/16 on 04 sierra 2500hd with 2" lift can I use stock rims safely and how can the difference in speed be adjusted,by dealer etc. or would 265's be safer bet. I carry camper and tow small quad trailer don't want any tires breaking the beed etc.

shocktrp · October 10, 2009

If I was to install 285/75/16 on 04 sierra 2500hd with 2" lift can I use stock rims safely and how can the difference in speed be adjusted,by dealer etc. or would 265's be safer bet. I carry camper and tow small quad trailer don't want any tires breaking the beed etc.

Get a Bullydog or Diablosport programmer and you can do it yourself.

builderpaul · October 10, 2009

If I was to install 285/75/16 on 04 sierra 2500hd with 2" lift can I use stock rims safely and how can the difference in speed be adjusted,by dealer etc. or would 265's be safer bet. I carry camper and tow small quad trailer don't want any tires breaking the beed etc.

By the book, no 285s are to wide for the stock rim. Some tire shops will not mount them. Is there a godzillion people that have mounted 285s on stock rims with no problems, yes.

Dealer will not be able to reprogram for that tire size. They can only program for sizes that were available on that truck.

You will need to get it tuned or buy a hand held tunner as mentioned in the previous post. Or use your gps.

CTM · October 12, 2009

If I was to install 285/75/16 on 04 sierra 2500hd with 2" lift can I use stock rims safely and how can the difference in speed be adjusted,by dealer etc. or would 265's be safer bet. I carry camper and tow small quad trailer don't want any tires breaking the beed etc.

Robo,

I have the Chevy 04 version of your truck, and also carry a truck camper.

I have 265/75/16 on the stock alloy rims, with the factory 2" inch lift (RPO # HVY-IDEN 2 INCH BODY RAISE, HD MODEL). Is this what your lift is? Or did you raise the truck an additional 2"?

With the larger tires, the speedo is only off 1.5> 2 mph slower than actual moving speed.

I wouldn't bother spending the money to correct this.

BTW, The truck has been perfectly safe with this wheel and tire combination, carrying a fully loaded 3,000 lb truck camper. Other then the oversize tires, the truck is fully stock!

R Gage · October 13, 2009

Yes sounds like the same except GMC. I found out mine was raised with after market tortion bar keys and 2" lift spacers in the rear with new shocks all the way around.I want to add 265/75/16. I wanted to add mine is also off about 2-3 mph slow if I add larger tires maybe it will correct it?

CTM · October 13, 2009

Yes sounds like the same except GMC. I found out mine was raised with after market tortion bar keys and 2" lift spacers in the rear with new shocks all the way around.I want to add 265/75/16. I wanted to add mine is also off about 2-3 mph slow if I add larger tires maybe it will correct it?

You didn't say what tire size you have now?

It sounds like you have the room to use the 285/75 tires, but you will have to get widder rims.

I think the larger the tire, the slower the speedo will be.

If it where my truck, I would return it to stock ( adjust the torsion bars to factory specs, and remove the 2" back spacers), because this will cause a much shorter life on front end parts, like ball joints, etc, if you don't.

This seems to be a common problem with various lift configurations I have read about on various truck forums.

R Gage · October 14, 2009

Yes sounds like the same except GMC. I found out mine was raised with after market tortion bar keys and 2" lift spacers in the rear with new shocks all the way around.I want to add 265/75/16. I wanted to add mine is also off about 2-3 mph slow if I add larger tires maybe it will correct it?

You didn't say what tire size you have now?

It sounds like you have the room to use the 285/75 tires, but you will have to get widder rims.

I think the larger the tire, the slower the speedo will be.

If it where my truck, I would return it to stock ( adjust the torsion bars to factory specs, and remove the 2" back spacers), because this will cause a much shorter life on front end parts, like ball joints, etc, if you don't.

This seems to be a common problem with various lift configurations I have read about on various truck forums.

I am running stock 245/75/16 I was going to have the torsion bars adjusted down after I get larger size tires. looks like I will lower 1" if I get 265/75/16.I will need to go to dealer a have speed-o adjusted after. I found the 265's were available on my truck and they can adjust it there.hope it all works out

CTM · October 14, 2009

Yes sounds like the same except GMC. I found out mine was raised with after market tortion bar keys and 2" lift spacers in the rear with new shocks all the way around.I want to add 265/75/16. I wanted to add mine is also off about 2-3 mph slow if I add larger tires maybe it will correct it?

You didn't say what tire size you have now?

It sounds like you have the room to use the 285/75 tires, but you will have to get widder rims.

I think the larger the tire, the slower the speedo will be.

If it where my truck, I would return it to stock ( adjust the torsion bars to factory specs, and remove the 2" back spacers), because this will cause a much shorter life on front end parts, like ball joints, etc, if you don't.

This seems to be a common problem with various lift configurations I have read about on various truck forums.

I am running stock 245/75/16 I was going to have the torsion bars adjusted down after I get larger size tires. looks like I will lower 1" if I get 265/75/16.I will need to go to dealer a have speed-o adjusted after. I found the 265's were available on my truck and they can adjust it there.hope it all works out

Roy, I't sounds like you are going in the right, and the lowest cost direction!

Just make sure that your 265/75 tire's are "E" load range, and you should be good to go.