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Changing To 20" Factory Wheels

jbstrick9

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jbstrick9 Enthusiast

jbstrick9

Posted
Posted

Hello,

I just purchased a set of factory pull off LTZ type 20" wheels and tires off of Ebay for my 2008 Silverado WT and was wondering if the lug nuts from the 17" gray steel wheels that came on the truck are the same as the ones used on the 20" wheels.

Also wanted to know what your opinions were on reprogrammming the truck for the new tire size. Will be going from a 245/70/R17 to a 275/55/R20. I don't think there is a huge difference, but will this throw the speedometer and DIC MPG indicator off much?

 

Thanks.

silverbullet2005 Enthusiast

silverbullet2005

Posted
Posted

tire size should equal out to be the same, the 20's are going to be wider but have a smaller side wall. I don't think you'll need to reprogram the computer but check with your local dealer or discount tire to verify for sure.

Zembonez Senior Enthusiast

Zembonez

Posted
Posted

I did this exact tire size swap on my Sierra. The difference at 60 is 2.8 mph (when the speedo says 60 you'll be doing 62.8) There wasn't much of a performance difference other than the truck had vastly improved handling with the 20s over the stock tires.

 

Mine have been on for a year and no problems. I did not reprogram for the new tires and everything (including ABS) works fine. This has been the case with every truck I ever owned and upgraded to larger tires. Several hundred thousand miles and no problems.

 

There are those who claim that you will screw up something but it simply is not fact.

VMax2007 Senior Enthusiast

VMax2007

Posted
Posted
There are those who claim that you will screw up something but it simply is not fact.

 

I beg to differ. You definitely WILL screw something up......

The LOOKS of the truck. :lol:

MrFritz99 Enthusiast

MrFritz99

Posted
Posted

Ok, speaking of rims and the looks... I purchased a used '07 NBS GMC Crew with the 17" wheels. I personally like the look of the GMC over the Chevy in the NBS, but I LOVE the Chevy 18" Stock wheels! Needless to say though, the center caps for those wheels come with BowTie logo's. Anyone know if they happen to make a replacement GMC cap for these?

tobias Senior Enthusiast

tobias

Posted
Posted
There are those who claim that you will screw up something but it simply is not fact.

 

I beg to differ. You definitely WILL screw something up......

The LOOKS of the truck. :dunno:

 

 

I do recall you saying something about jokes losing their punch... Hmm, hmm? :banghead::fume:

VMax2007 Senior Enthusiast

VMax2007

Posted
Posted
There are those who claim that you will screw up something but it simply is not fact.

 

I beg to differ. You definitely WILL screw something up......

The LOOKS of the truck. :fume:

 

 

I do recall you saying something about jokes losing their punch... Hmm, hmm? :banghead::lol:

 

 

What makes you think I was joking? :dunno:

TedH Enthusiast

TedH

Posted
Posted

I made a similar change to my 2003 Silverado Z71 Sportside. I installed the 2003 Silverado SS's 20" wheels and tires. Same total height as my 16" wheels/tires. Same effective speed/mileage. But lots better looks. :banghead:

rt66er Enthusiast

rt66er

Posted
Posted

I just did this myself (20-inch GMC take-offs to replace 17-inch wheels and 245/70-17 tires) and I calculate the tire diameter difference at almost exactly 5%. This is too much for me; drives me nuts to constantly calculate speedo error while I'm driving down the road. I'm sure that this doesn't bother some folks at all. At 70 mph, my speedo would be reading between 66 and 67 mph. I purchased a Hypertech Max Energy to fix the error.

VMax2007 Senior Enthusiast

VMax2007

Posted
Posted
I just did this myself (20-inch GMC take-offs to replace 17-inch wheels and 245/70-17 tires) and I calculate the tire diameter difference at almost exactly 5%. This is too much for me; drives me nuts to constantly calculate speedo error while I'm driving down the road. I'm sure that this doesn't bother some folks at all. At 70 mph, my speedo would be reading between 66 and 67 mph. I purchased a Hypertech Max Energy to fix the error.

 

Are your new tires larger in dia than stock or smaller? If they are larger, then your speed will read slow, not fast.

TedGEXT Enthusiast

TedGEXT

Posted
Posted

Make sure you run a gps, my 2003 SS Silverado showed about 3mph fast between 30 and up. The 20's just may correct the built in optimism GM puts in.

rt66er Enthusiast

rt66er

Posted
Posted
I just did this myself (20-inch GMC take-offs to replace 17-inch wheels and 245/70-17 tires) and I calculate the tire diameter difference at almost exactly 5%. This is too much for me; drives me nuts to constantly calculate speedo error while I'm driving down the road. I'm sure that this doesn't bother some folks at all. At 70 mph, my speedo would be reading between 66 and 67 mph. I purchased a Hypertech Max Energy to fix the error.

 

Are your new tires larger in dia than stock or smaller? If they are larger, then your speed will read slow, not fast.

 

 

 

That's what I said. When my truck is actually traveling 70 mph, my speedo will read about 66. Or, to put it another way, when my speedo is reading 70 mph, I will actually be traveling about 74 mph.

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