GMC rims - size question (*UPDATED*)

[GMTruckGuy74]

I like these 2005-2007 GMC Sierra 1500 rims, and I'm curious if I could install and use them on my 2006 GMC Envoy:

The size information I found is as follows: 6-bolt, 17x7.5, 31 offset, bolt pattern 6x139.7

This is the factory rim on the Envoy currently (size information I found is 6-bolt, 17x7, 50 offset, bolt pattern 6x127):

I know they are not matching sizes, but can the larger Sierra rim be used on my Envoy? I need someone that can educate me on rim sizing please. TIA!

Edited February 22, 2011 by GMTruckGuy74

[GMTruckGuy74]

*Bump*

I reworded the original post... if you are knowledgable on rim sizing, please help me out!

[Z-06]

Nope can't do. The offset and bolt patterns are not similar.

[balthazar]

Offset may possibly be OK, but the bolt pattern makes checking it impossible.

>>"6-bolt, 17x7.5, 31 offset, bolt pattern 6x139.7"<<

'17x7.5' is a 17" rim that's 7.5" wide.

-- -- -- -- --

Offset (31 vs. 50) is best illustrated by the below link:

http://www.infinitig37.com/images/tech-offset-image2.jpg

Offset gets tricky.

Hypothetically, if 2 rims were the same width but had different offsets, they would have the bolting surface located in different locations (in vs.out).

You can get an idea of this in general by noting how the Envoy rim is relatively flat faced, but the Sierra is 'dished' (and picturing the respective shift in where the bolting surface is located in each).

These measurements all start from the surface where the rim seats against the brake rotor.

Most modern rims are close to being 'flat faced' (not an industry term ), as opposed to this old school, heavily-dished Cragar:

http://www.v8americancarclub.com/images2/cragar%20ss.jpg

If you were dealing with rims potentially this deep, you would get into negative & positive offsets. Not a common factor with modern iron.

-- -- -- -- --

'6x139.7' is 6 bolts in a 139.7mm circle. You can visualize how this is not going to line up to a 127mm bolt circle.

-- -- -- -- --

I agree with your taste here- those Sierra rims are definitely a sweet design. I wish these were available for the 8-lug trucks- not enough choices there.

Edited February 23, 2011 by balthazar

[GMTruckGuy74]

Thanks Z-06 and Balthazar for responding. Numbers-wise, I can see that it was an apples-to-oranges comparison since they weren't exact. Balthazar, thanks for the link to the illustration. And you're point is spot on - I don't like the flat-faced rims used on all Envoys versus the deeper dish rims that came on the Sierra & Yukons.

So it seems that if I want a different design, I'd need to look at other Envoy rims. The only problem I have is that the designs I like are of the 18 inch variety:

Envoy Denali 18x8 (2006-2009)

Envoy SLT 18x8 (2007-2009)

I'll have to search a little more to find out the specs on these rims, but since they were used on Envoys I can't imagine that they wouldn't work on my 2006. My new question is what would other work would be needed going from a 17x7 to 18x8 rim? I'm assuming the speedometer would have to be compensated for the larger tire, right? Is that an easy to do fix on the Envoy?

Of course if I wanted to go aftermarket, I like these and according to TireRack.com, they'd fit the Envoy:

The problem is they're a little pricey!! http://www.tirerack.com/wheels/WheelCloseUpServlet?target=runWheelSearch&initialPartNumber=KM65077565245C&wheelMake=KMC&wheelModel=Slide&wheelFinish=Chrome+Plated&showRear=no&autoMake=GMC&autoModel=Envoy+4wd&autoYear=2006&autoModClar=Standard+Model&filterFinish=All&filterSize=All&filterBrand=All&filterSpecial=false&filterNew=All&filterWeight=All&sort=Brand

[Drew Dowdell]

did you buy the warranty yet?

[balthazar]

Going from a 17x7 to an 18x8 can be done easily enough: you need the same bolt circle and a relatively close offset (I would guess that a +/– 20mm difference should work fine). The concern is how close the tires are to anything behind them in the wheelwell, especially the front thru it's turning radius.

As to the speedo- what is usually done here is to get a correspondingly lower profile tire, so the overall tire diameter remains as close as possible to factory. I wouldn't sweat an inch diamter difference- but beyond that is worth considering getting the speedo corrected, IMO. Somewhere, no doubt there's a formula that can tell you 'going from Tire X to Tire Y will change speedo MPH by Z'.

As for that, on the vintage stuff- there was a speedo gear in the side of the trans case : it was merely a process of determining & obtaining the new gear, and installing it. Not sure if the modern stuff is more involved (of course it must be, they always are).

[Intrepidation]

Bolt pattern must be exact in order to fit, and offset should be close to avoid things like rubbing and stress on the wheel studs and suspension components.

You can do some research and see what other production vehicles have the same bolt pattern and similar offset. Offsets are considerably different for FWD, RWD, and IIRC AWD/4WD wheels.

If a tire is too wide it will cause rubbing along the wheel well over bumps and such.

When going to a larger tire size you want to get a lower profile tire so that the overall diameter remains the same, this ensures that there is no rubbing and that the speedometer will be correct.

[SAmadei]

Bolt pattern must be exact in order to fit,

I generally agree, but there are a number of different bolt patterns today that are very close. For example, I recently found that the '94 on Mustang bolt patterns (5x114.3) are close enough to the H-body pattern (5x115) that they fit, since most rims have 1~2mm of play around the lug nuts. And it turns out there are TorqueThrust-Ms (Mustang) which therefore would fit on my Bonneville for a somewhat old school look... but aren't as concave, and have similar offset.

And considering that there used to be rims with slotted lug holes, I wonder how much of a problem it would be to elongate the lug holes 2mm to fit, say, 5x120 on 5x115... but one has to have the proper lug nut and mating surface, as well, if doing that... preferably flat. Also assuming that the lugs or surface prep is hidden, so the lugs don't appear off-center...

[GMTruckGuy74]

did you buy the warranty yet?

No, I wasn't able to keep the mileage down long enough and subsequently ran out. I made contact with AAA at the Philly Auto Show and have to call the agent back for the price quote of their extended warranty. My neighbor uses the one repair shop listed on their website for most of his vehicle repairs with much satisfaction (called Highway Tire, a Goodyear retailer but not part of a system of dealers like Gemini or Vespia Goodyear dealers), and the local Chevy dealer (Lucas) is also listed as an authorized AAA repair facility. I just need to find the time during the workday to call the agent back for the price quote. Anyone have direct experience, or know anyone personally that has, an AAA extended warranty?

[GMTruckGuy74]

Thanks to all of the recent replies. Rims are not the top priority in a way, tires, an extended warranty, and some general maintenance are my main concerns. However, I don't want to buy new tires for my current rims, then find a set I can use on the Envoy that I like but not be the right size for the new tires. I don't need new rims, I just want something better.

Here's the 18x8 Denali rims on a white (Denali) Envoy:

Here's the '07-'09 18x8 SLT rims on a white Envoy:

Here's what my current 17x7 rims look like:

Though they're not deep dish style, I like the SLT rims the best on the Envoy.

[Drew Dowdell]

First things first I think

[GMTruckGuy74]

First things first I think

I know... but there are three "salvage yards" nearby that have mostly modern iron that I would be checking at for these rims if I were going to bite the bullet on this. Money for the tires is earmarked from our tax return, so that's checked off. But, I don't want to buy the tires yet until I decide on the rim situation. Decisions, decisions, decisions...

[GMTruckGuy74]

I think I'm going to pass on the rim replacement idea for now. I have the money to buy new tires but not new rims, even if I went the salvage yard route. There is nothing wrong with my factory 17" rims other than they're not my favorite design. I'll go forward with the new tires and maybe later look into the same size aftermarket rims. Thanks again for all the input and education on rim sizing.