18" Wheels on Sierra 1500 Denali

[MrLeadFoot]

I have 22" stock wheels now, and tried a friend's stock 20" wheels, which improved the ride noticeably. And, contrary to what I would have thought, even around hard corners the 20" were infinitely better, even though the 18" had stock AT Duehlers with 29,0000 miles on them! I now wonder if 18" wheels would be even better, and am curious as to whether or not any of you run 18"wheels on on your Denali, or have tried them. Feedback, experience, opinions welcome. 

[Gangly]

I went from the factory 20's down to 18's and definitely preferred the ride of the 18" wheel and tire combo.  The additional sidewall helped smooth things out, especially on dirt roads and improperly maintained city streets.

[MrLeadFoot]

4 hours ago, Gangly said:

I went from the factory 20's down to 18's and definitely preferred the ride of the 18" wheel and tire combo.  The additional sidewall helped smooth things out, especially on dirt roads and improperly maintained city streets.

Thanks for chiming in. Looks like you have an Silverado LT whereas I have a Denali, so I wonder how 18" would affect my adaptive ride control shocks.

 

BTW, are those wheels in your profile pic GMC wheels or Chevy?

[Gangly]

The adaptive ride shocks are basically accounting for axle movement(shock compression) and taller sidewalls will absorb more irregularities, minimizing axle movement.

 

Basically, you have more sidewall so your ride would be smoother/softer, regardless of your adaptive ride shocks. 

Edited March 10, 2023 by Gangly

[MrLeadFoot]

Thanks for that. Do you think 18s will affect my gas mileage?

 

In case you missed it, are the wheels in your profile pic GMC or Chevy wheels? I'm wondering how they would look on my Silver Sierra.

[Gangly]

The wheels in my profile pic are GMC factory 18" wheels that came off a GMC AT4.  I used my bowtie caps from my fatory 20" wheels instead of the GMC caps, that might be where some confusion comes from.  Google "Silver AT4" and you will probably find a bunch AT4's with those wheels. 

 

The factory wheel offerings are close enough in weight that the gas mileage wont be affected as long as the overall tire diameter is close to the same and you stick with C rated tires.  Stepping up to E rated tires will increase your rotational mass and you will see a small drop, a little less than 1mpg usually. 

[MrLeadFoot]

If I went to 18s, I think I might have to step up to 70 sidewall because I think the stock 65 on 18s is significantly smaller than my stock 32.9" diameter on 22" 50 series tires. 20" rims are 60 series at 33", and 70 series on 18s is 33.2".

 

I thought those wheels of your looked more like GMC wheels than Chevy. Now I know why. 

[Gangly]

21 hours ago, MrLeadFoot said:

If I went to 18s, I think I might have to step up to 70 sidewall because I think the stock 65 on 18s is significantly smaller than my stock 32.9" diameter on 22" 50 series tires. 20" rims are 60 series at 33", and 70 series on 18s is 33.2".

 

I thought those wheels of your looked more like GMC wheels than Chevy. Now I know why. 

The stock size on the 18's is a hair over 32", so yes, you would need to have a wider tire in the 65 series, or go to a 70 or even 75 series with stock width.

 

275/65/18 will put you right about 32.1" diameter 

285/65/18 will put you right about 32.6" diameter

275/70/18 will put you right about 33.2" diameter

 

[MrLeadFoot]

I'm after more comfort, and don't go offroad, except when I sometimes have to drive on the dirt shoreline of a lake to get to a launch ramp to launch my bass boat, which is not often, so I'm trying to stay with all-season tires like the Michelin LTX Defender. The problem I'm finding is that when I try to go bigger to get closer to my stock 32.9" diameter, I get into an E-rated tire. I don't have that problem if I move to a 20" wheel instead. Thoughts?

[Gangly]

E rated tires are not comfortable unless you air down, or have a significant load.  The Nitto Terra Grappler G2 is an SL rated tire in 295/70/18, but you are correct regarding most tires in this size range being E rated.

[MrLeadFoot]

That size tire won't work for me because I am not lifted.

 

Since you had 20's you faced the same issue I am facing, because your stock tire was a 33" diameter, wasn't it?. What tires are you running on your 18s? And, how did you recalibrate for the diameter difference?

[Gangly]

I just took my 18's off and put my 20's back on because the duratracs got too loud.  I'll be putting 34"-35" tires on the 18's shortly, but I'll wait until summertime to do so.  The Silverado's can run all of the sizes mentioned above without rubbing and without a lift.  The wheel well on GMC's is smaller so y'all run into more problems with tire fitment, but you should still be fine with anything around 34" diameter.

[Gangly]

I never recalibrated for the difference.  My speedometer was off by 3 mph at 70 mph, I just corrected my driving accordingly.

[MrLeadFoot]

2 hours ago, Gangly said:

I just took my 18's off and put my 20's back on because the duratracs got too loud.  I'll be putting 34"-35" tires on the 18's shortly, but I'll wait until summertime to do so.  The Silverado's can run all of the sizes mentioned above without rubbing and without a lift.  The wheel well on GMC's is smaller so y'all run into more problems with tire fitment, but you should still be fine with anything around 34" diameter.

Nice that you are able to switch back and forth between sizes when you need to.

 

I didn't know the thing about Silverado wheel wells vs. Sierra wheel wells. And, at first glance it doesn't look like there's much room for a bigger tire, so the add'l info about the tires you previously mentioned is helpful.

 

2 hours ago, Gangly said:

I never recalibrated for the difference.  My speedometer was off by 3 mph at 70 mph, I just corrected my driving accordingly.

So going to the 18s made your speedo read faster by 3mph, correct?

Edited March 14, 2023 by MrLeadFoot

[Gangly]

Yes, the TB and AT4 with 18" wheels actually have ~32" Duratracs.  GM's off road package has smaller tires than the non off road package, ironic huh?