New Wheels And Speedo Is Off!

[WhiteRabbit]

Hey guys. Just wanted to confirm what I need to do.. I replaced my dinky 17in wheels with some 20's and now my speedo seems to be off by about 5mph. Do I have to take it into the dealership and have them techstream it? (aka program specify it for 20's)..

 

Thanks!

[Nytemare]

Hey guys. Just wanted to confirm what I need to do.. I replaced my dinky 17in wheels with some 20's and now my speedo seems to be off by about 5mph. Do I have to take it into the dealership and have them techstream it? (aka program specify it for 20's)..

 

Thanks!

You need to program it for the size of tires and wheels you have now....

 

You probably had something like 255/65/17 now you have 275/55/20...so there abouts...

 

you can get it done at the dealership...a good tire shop should have the programmer too...or you can buy one of these....they're 200 bucks but worth it if your going to be switching back and forth.

Or if your planning on a tune in the near future...get it done than.

You can also do this with just about any hand held tuner...Diablo for example.

[jro909]

you do realise you lose power going to bigger rims right? thats why HDs roll on 16s lol...congrats though i wish i had 20s

[Badass69]

you do realise you lose power going to bigger rims right? thats why HDs roll on 16s lol...congrats though i wish i had 20s

 

 

There is less than 1/2" in overall outer diameter from the stock 265/70R17 to the 275/55R20 tire. Your speedo should be out by so little it is not even noticeable if those are and were your tire sizes. I mean my 2500HD went from 245/75R16 to 265/75R16 (1" overall taller) and my speedo is less than 2 mph out as confirmed by my GPS. That being said the dealership can't even correct mine as the 265's come on the 1 ton version of these trucks. I tried 3 different dealers with my 06 and was told they were no longer able to do tire size corrections with the scan tool after the NBS trucks came out in 1999.

 

You don't lose any power when increasing rim size if the overall outer diameter and overall rim and tire combined weight doesn't change. I think the OEM's stick with smaller rims on the HD line simply for load rating with the tires.