Work truck tire sizes. Why?!

[BrizzoDaIzzo]

6 minutes ago, topgear1224 said:

Yep. You have to stay in an overall diameter offered by GM.

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I understand that now, just didn’t realize I couldn’t cross platform from the work truck to the custom, etc.   I wouldn’t figure it would be as big of an issue being that they are the exact same truck other than appearances. I know the trail boss would be out of the question because of the upgraded suspension, but I didn’t realize it would be this strict.  Bummer

[newdude]

2 hours ago, BrizzoDaIzzo said:

This statement alone has convinced me to probably never increase my tire size. I did not realize that the power steering and body control module also had to be reprogrammed. What a nightmare. oh well, time to look for some new “aggressive as I can get” tires on 17 inch wheels.  

 

 

 

You could do that.  You can also just go to a 265/70/17 tire which is 31.7" or you can do 265/65/18 tire on 18" wheels that is 31.5" inches or the 275/55/20 on a 20 inch wheel like I mentioned above which is 31.9", that way the speedo is off so little that it would really make no difference.  1 to 1.5mph.  If I got a WT or LT trim that came with the 255/70/17 I'd consider going to any of those 3 sizes and would just put them on and drive it.  

Edited September 2, 2020 by newdude

[BrizzoDaIzzo]

18 minutes ago, newdude said:

 

You could do that.  You can also just go to a 265/70/17 tire which is 31.7" or you can do 265/65/18 tire on 18" wheels that is 31.5" inches or the 275/55/20 on a 20 inch wheel like I mentioned above which is 31.9", that way the speedo is off so little that it would really make no difference.  1 to 1.5mph.  If I got a WT or LT trim that came with the 255/70/17 I'd consider going to any of those 3 sizes and would just put them on and drive it.  

Yeah, I might just throw it on and see.  It’s a $2,000 decision. I just don’t want to make any mistakes.  If I do that my only “big” concern would be the relative gear ratio change.  I’ll Definitely have to think about this a while

[Unknown_eyes]

I did the exact swap your talking about on my 2020 Sierra SLE. Replaced my stock 255/70r17 with a set of take off 275/60r20 with no ill effects other than the speedometer difference. My truck has the 3.23 gears, not sure if that would make any difference. 

 

My dealer did the tire size recalibration. I got lucky, the 275/60r20 was optional on my sle. They told me that GM would only authorize the recalibration if the new tire size was optional on your specific trim.

 

The speedometer difference bothered me, that's the only reason I did the recalibration. If you can live with that then I doubt you'll have any issues.

 

 

 

 

[topgear1224]

Yeah, I might just throw it on and see.  It’s a $2,000 decision. I just don’t want to make any mistakes.  If I do that my only “big” concern would be the relative gear ratio change.  I’ll Definitely have to think about this a while

You won't notice the gearing difference with the V6, it's torque curve is so flat.

Yes if you have GPS timing gear there will be a difference, but you won't notice it.

The speedo will be off without a calibration.

As long as you aren't talking about jumping to 35s or 37s you should be fine.

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[Quarkest]

On 9/2/2020 at 1:17 PM, newdude said:

 

2 options that I see here that would work.  Avoid the Hypertech inline calibrator at all costs.    

 

Option #1.  Change the tire size on the 20" wheel.  You can do a P275/55R20 which is a 31.9" tire.  This would only throw off your speedometer 1.5mph (2.5% faster) than stock.  So you'd go from a 31 to a 32 inch tire more or less.  This would be the least hassle route to get a touch larger tire in there on a 20" wheel.    

 

Option #2.  Have your dealer pull up GM Service Information Document ID: 5254629.  This is a calibrations chart for going from 17" or 18" wheels up to 22" wheels and shows what needs to be programmed.  I use the 22" one as the 20" and 22" have the same tire diameter, and GM has accessory 22" wheels but no 20" wheels.  Your dealer would have to try and get an authorization for programming the truck by calling GM Tech Line, which would grant, if they approve, the recalibration of the ECM (for the speedo), Power steering control module, EBCM and Body Control Module.  A big heads up however.  If your truck is a regular cab, or has VYU snow plow prep, GM DOES NOT have a calibration file for those.  

 

All of the 2019+up new body wheels will fit 2019+up new body trucks, no issues.  

 

@newdude Old post, but could you share the referred calibration chart? I couldn’t find that SID anywhere (of course, because GM doesn’t want us to find it). TIA