20" wheels on a crew

jimi · March 10, 2005

Does anyone have information on putting 20" wheels on an '04 K1500 Sierra crew cab? I was told by a GM dealer that GM recommends AGAINST it. Something about the the frame not being strong enough due to the extended length. They couldn't give me details only that he "thinks he saw a service bulletin". I tried calling GMC customer service but they were clueless. Also I haven't seen any discussion on recaliberating the ABS or speedo when changing wheel size. I know you should but do you have to??

mudbug660 · March 10, 2005

The wheels shouldn't have anything to frame's strength. I would even go as far as to call . The spedo doesn't need to be recalibrated but to get accurate readings you need to but it is not at all required. The tire size might be different but the tire height might stay the same so no recalibration would be need. I say go for it and don't worry about it.

lrymal · March 10, 2005

Does anyone have information on putting 20" wheels on an '04 K1500 Sierra crew cab? I was told by a GM dealer that GM recommends AGAINST it. Something about the the frame not being strong enough due to the extended length. ...
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The 5'8" bed on the newer crews is the particular crew cab with a frame not rated for the 20" wheels. The forward shackle is mounted on an ascending curved area of the frame which is not the case for other pickups. Apparently, long-term testing demonstrated a concern when using the 20" wheels. Better than risking law suits, GM decided to pull the option. At least, that is the way I understand it.

I'm sure someone here will paste in the actual bulletin.

MS3DALE · March 10, 2005

I would NOT put 20's on your 1500 crew-cab.

We had a couple 1/2 ton crew-cabs here at the dealership that we put 20's on and when GM came out with that bulletin we pulled them back off and put the factory wheels back on.

Sorry but I cannot post the actual bulletin but it really didn't say much,only that the frames was showing a "weak" spot in them after testing the trucks with 20's on them,It didn't mention what lrymal said about the shackles but that makes perfect sense.

ProSport Tim · March 10, 2005

So this is only regarding a "crew cab" and not my ext. cab w/ the 20's?

asilverblazer · March 10, 2005

Does anyone have information on putting 20" wheels on an '04 K1500 Sierra crew cab? I was told by a GM dealer that GM recommends AGAINST it. Something about the the frame not being strong enough due to the extended length. ...
<{POST_SNAPBACK}>

The 5'8" bed on the newer crews is the particular crew cab with a frame not rated for the 20" wheels. The forward shackle is mounted on an ascending curved area of the frame which is not the case for other pickups. Apparently, long-term testing demonstrated a concern when using the 20" wheels. Better than risking law suits, GM decided to pull the option. At least, that is the way I understand it.

I'm sure someone here will paste in the actual bulletin.

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MS3DALE · March 10, 2005

So this is only regarding a "crew cab" and not my ext. cab w/ the 20's?

Yes,Your OK

GM-Tech · March 10, 2005

This is the gist of the message we got concerning the 20" wheels on crew cabs...

Effective immediately, we have been advised by GM Vehicle Engineering to stop selling dealer installed 20-Inch Plus-Size Wheels offered as Chevrolet or GMC Accessories on the 1500 Crew Cab version of Chevrolet Silverado and GMC Sierra Light Duty Pickups (Models C and K 15543, CC15543, CK15543, TC15543, TK15543). The stop sell is only for the crew cab - no other body styles are impacted. Continued durability and validation testing has identified a long-term durability issue that could potentially damage a suspension bracket and the vehicle’s frame. Changes to the crew cab have been identified and will be implemented next year. Until further notification, 20 Inch Plus Size Wheels are no longer valid for this body style. Since the crew cab has a unique suspension bracket interface to the frame, this condition does not apply to other body styles.

jimi · March 10, 2005

This is the gist of the message we got concerning the 20" wheels on crew cabs...

Effective immediately, we have been advised by GM Vehicle Engineering to stop selling dealer installed 20-Inch Plus-Size Wheels offered as Chevrolet or GMC Accessories on the 1500 Crew Cab version of Chevrolet Silverado and GMC Sierra Light Duty Pickups (Models C and K 15543, CC15543, CK15543, TC15543, TK15543). The stop sell is only for the crew cab - no other body styles are impacted. Continued durability and validation testing has identified a long-term durability issue that could potentially damage a suspension bracket and the vehicle’s frame. Changes to the crew cab have been identified and will be implemented next year. Until further notification, 20 Inch Plus Size Wheels are no longer valid for this body style. Since the crew cab has a unique suspension bracket interface to the frame, this condition does not apply to other body styles.

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Thanks for all the info. I learned more from this post than from 5 different conversations with my dealer. Kind of a bummer though that my so called "professional grade" GMC frame is not storng enough to accomodate 20s. Kind of scary actually. Too bad they didn't tell me that when I bought the truck. Thanks again.

GM-Tech · March 10, 2005

Kind of a bummer though that my so called "professional grade" GMC frame is not storng enough to accomodate 20s. Kind of scary actually. Too bad they didn't tell me that when I bought the truck. Thanks again.

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Doesn't say the frame isn't strong enough. Just that some sort of damage could occur. It doesn't really say what and even we don't really know at the dealer.

As for the dealer not telling you, unless you bought the truck in the last two months, they wouldn't have known. Besides, even if they did know at the time, did you ASK if you could have GM 20" wheels put on it? Kinda hard for a dealer to disclaim every single thing you should NOT do with your truck. You'd have a 100 page document you'd have to read and sign.

jimi · March 10, 2005

Kind of a bummer though that my so called "professional grade" GMC frame is not storng enough to accomodate 20s. Kind of scary actually. Too bad they didn't tell me that when I bought the truck. Thanks again.

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Doesn't say the frame isn't strong enough. Just that some sort of damage could occur. It doesn't really say what and even we don't really know at the dealer.

As for the dealer not telling you, unless you bought the truck in the last two months, they wouldn't have known. Besides, even if they did know at the time, did you ASK if you could have GM 20" wheels put on it? Kinda hard for a dealer to disclaim every single thing you should NOT do with your truck. You'd have a 100 page document you'd have to read and sign.

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I bought the truck in July. I did tell the dealer I was planning on 20" wheels when I bought it. My frustration with the dealer was when I tried to get specific info (in January of this year). When I first called a local dealer for pricing he said something like "I think I saw some kind of bulletin saying not to put them on the crew". When I asked for specifics he couldn't give them to me. Only that there was a frame problem. So I called the dealer where I bought the truck and he said " oh yeah, go ahead and put them on". When I told him what the other dealer said he referred me to GMC customer service. After several weeks waiting for GMC they came back and advised me that I shouldn't because they didn't have the ability to recalibrate the ABS on the crew. When I pushed them harder on the frame thing they said I would have to work through the service manager at the dealership where I bought the truck, you know, the one that said go ahead and put them on. After several more frustrating conversations with him telling me it wa an ABS issue I finally asked for a meeting with the GMC rep that comes to the dealership. They set up the meeting but cancelled the day before it was suppossed to happen because the guy had changed his schedule. I gave up and finally saw this forum. All of this aside the bottom line is I can't put the wheels on my truck. Sucks big time since that was the plan from the beginning.

ProSport Tim · March 10, 2005

That does suck Jim. That's why when I saw the pro sport I had to have it. All factory GMC parts. All stuff a normal truck guy would mount up already there. Covered under and by the warrantee. It's also a plus when you go through a carwash and they say "Hey we don't honor those ventvisors or toneau cover, yada yada if they're not factory, sorry"..Then I point out the nice GM emblem.. I had them throw on the stock wheels for the winter. However, they never mentioned recalibrating anything or even an allignment. Should it of been done?

jimi · March 10, 2005

That does suck Jim. That's why when I saw the pro sport I had to have it. All factory GMC parts. All stuff a normal truck guy would mount up already there. Covered under and by the warrantee. It's also a plus when you go through a carwash and they say "Hey we don't honor those ventvisors or toneau cover, yada yada if they're not factory, sorry"..Then I point out the nice GM emblem.. I had them throw on the stock wheels for the winter. However, they never mentioned recalibrating anything or even an allignment. Should it of been done?

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Not sure. I was told that if you go to a larger wheel that both the speedo and ABS had to be recalibrated. Maybe if the overall diameter doesn't change it's not required. Maybe someone who knows more about it will post.

GM-Tech · March 10, 2005

Not sure. I was told that if you go to a larger wheel that both the speedo and ABS had to be recalibrated. Maybe if the overall diameter doesn't change it's not required. Maybe someone who knows more about it will post.

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20" wheels are definitely going to change the speedo calibration. ABS is easy to recalibrate. It's done with the Tech 2 without any real programming. Just a selection in the Tech 2 menus.

But calibrating the speedo is a whole 'nuther story. That requires a special calibration that we can only get by calling GM's Techline and giving them the VIN. When they see from the VIN it's a crew cab, they'll just tell is it's not an authorized upgrade on that vehicle and they will not give us the calibration we'd need.

There are probably aftermarket solutions to this dilemma, but there's nothing we can do about it in the dealership. The dealer in question here wouldn't have known anything about this back in July of 2004.