GMT T1XX brake upgrade

[mars2878]

My truck, 2000 GMC Sierra SLT 1500 2wd ext cab.
The 20in rims are from a 2025 GMC Yukon at4 Ultimate. RPO code R4L.

Now that I've swapped to the 20in wheel setup, I'm looking to do the brakes.
I'm looking to start with the fronts 1st.

I didn't notice the info on this site. I did see info on this in several other places, but see conflicting info.

From what I've read, you can put the front T1xx brakes onto the GMT800 platform. Supposedly only requires larger rims to clear & several washer to center the caliper correctly.

Some places say all 20in or larger.
Some say certain 20in & all larger.
To fit the 4-piston caliper.

Then there is a factory 6-piston Brembo upgrade.
I get conflicting info on which rims clear these calipers.

I grabbed a Vin # from a 2025 GMC Yukon at4 Ultimate, but it has the 4-piston, which is what my rims are from. I went on GM's website, entered that Vin # & it says that the Brembo is not compatible.

I have seen pics online of this rig with my rims & Brembo on them. But no Vin # is listed. They are just random pictures.

So I don't know what makes them compatible or not?

Also, I don't see anyone mentioning about the dustshields. These are bigger rotors. So are the dust shields modified or replaced?
I have asked these questions to several people who state that they did this mod, but no one has responded yet.

Either way I'll be doing the front brakes, so I might as well upgrade to larger.

No one local to me has these parts in-stock, it all has to be shipped from across the country & the parts are heavy, so I'm not looking to pay for multiple shipping.

If anyone could shed some light on this, it would be greatly appreciated.

Thanks in advance.

 

[Marky Dissod]

You likely do not need the Brembo 6piston caliper, though I get why anyone would want them.
Since I think EVERYONE should own the 4 piston calipers, let me focus on that here.

4piston calipers require a wheel of a certain shape. Think I found a (the?) GM OE 17" wheel that works with the 4piston caliper:

STLGN096U45 Chevrolet Colorado, Silverado, GMC Sierra 1500, Yukon Wheel/Rim Steel Black #84440192

There are quite a few 18" wheels that don't work with 4piston calipers, without clearancing the caliper.
If you look carefully at the GM OE '84440192' wheels, you'll understand why some 18" wheels also don't work without clearancing the caliper (by which I mean):

4 piston calipers fitment with which wheels, list. - PerformanceTrucks.net Forums

GMT K2xx Trucks General Discussion - 4 piston calipers fitment with which wheels, list. - The 2020+ optional 4 piston fixed calipers have already started replacing the NNBS brake upgrade, and fits on NBS, NNBS, and K2XX. Its been reported that some 17s are fitting and some aren't. (There may...

www.performancetrucks.net

4 piston calipers fitment with which wheels, list. - PerformanceTrucks.net Forums

GMT K2xx Trucks General Discussion - 4 piston calipers fitment with which wheels, list. - The 2020+ optional 4 piston fixed calipers have already started replacing the NNBS brake upgrade, and fits on NBS, NNBS, and K2XX. Its been reported that some 17s are fitting and some aren't. (There may...

www.performancetrucks.net

If you're unwilling to alter the part of the calipers that might interfere with the wheel, then you are limited to a specific wheel shape.
If you prefer oversimplification, wheels older than 2019 are likely to interfere with the 4 piston calipers.

 

[mars2878]

You likely do not need the Brembo 6piston caliper, though I get why anyone would want them.
Since I think EVERYONE should own the 4 piston calipers, let me focus on that here.

4piston calipers require a wheel of a certain shape. Think I found a (the?) GM OE 17" wheel that works with the 4piston caliper:

STLGN096U45 Chevrolet Colorado, Silverado, GMC Sierra 1500, Yukon Wheel/Rim Steel Black #84440192

There are quite a few 18" wheels that don't work with 4piston calipers, without clearancing the caliper.
If you look carefully at the GM OE '84440192' wheels, you'll understand why some 18" wheels also don't work without clearancing the caliper (by which I mean):

4 piston calipers fitment with which wheels, list. - PerformanceTrucks.net Forums

GMT K2xx Trucks General Discussion - 4 piston calipers fitment with which wheels, list. - The 2020+ optional 4 piston fixed calipers have already started replacing the NNBS brake upgrade, and fits on NBS, NNBS, and K2XX. Its been reported that some 17s are fitting and some aren't. (There may...

www.performancetrucks.net

4 piston calipers fitment with which wheels, list. - PerformanceTrucks.net Forums

GMT K2xx Trucks General Discussion - 4 piston calipers fitment with which wheels, list. - The 2020+ optional 4 piston fixed calipers have already started replacing the NNBS brake upgrade, and fits on NBS, NNBS, and K2XX. Its been reported that some 17s are fitting and some aren't. (There may...

www.performancetrucks.net

If you're unwilling to alter the part of the calipers that might interfere with the wheel, then you are limited to a specific wheel shape.
If you prefer oversimplification, wheels older than 2019 are likely to interfere with the 4 piston calipers.

I have read that before. Unfortunately nothing useful.
It's mostly trying to fit 17, 18 or aftermarket rims on a gmt800 with 4-piston calipers.

The T1xx came from the factory with 4-piston brakes, optional 6-piston.

I'm trying to find the determining factor why some can have the 6-piston & others can't?

If I I'm using the T1xx rims, then I can use the 4-piston front brakes.
But the 6-piston are not much more money.

I can find random pictures online of a 2025 Yukon at4 Ultimate with Brembo 6-piston calipers with the R4L rims. But I can't find any for sale for which I could borrow the Vin #.

I took the Vin of 2025 Yukon at4 Ultimate which has a 6.2L & went to the GM website. It says that the 6-piston is not compatible. I don't understand the reasoning?

 

[AuroraGirl]

j61


j55


j49

j61, j55, j49

two of those are fixed type, one appears to be floating type.

 

[stutaeng]

I did the 4 pistom caliper brake upgrade on my 1999 Silverado. I'm running some 18" wheels from like 2014-ish Tahoe.

I just had to do a bit of grinding on tbe calipers. I've put about 6-8k miles on it. Works great! I think it was around $550 for calipers, rotors and pads from Rockauto.com

 

[mars2878]

I did the 4 pistom caliper brake upgrade on my 1999 Silverado. I'm running some 18" wheels from like 2014-ish Tahoe.

I just had to do a bit of grinding on tbe calipers. I've put about 6-8k miles on it. Works great! I think it was around $550 for calipers, rotors and pads from Rockauto.com

Some factory 18s do not clear the 4-piston setup without grinding or spacers.

I'm using the T1xx 20in rims that would've been paired with the 4-piston, so there won't be any clearance issues on that front.
The 6-piston on the other hand, I conflicting info.

As of right now, I can get a practically brand new oem 4-piston take-off set with about 2k miles on them for $450.

 

[mars2878]

j61
View attachment 5939

j55
View attachment 5940View attachment 5942

j49
View attachment 5941
j61, j55, j49

two of those are fixed type, one appears to be floating type.


View attachment 5943

When I look it up, there are only 2 options.


Without High Performance (4-piston).
With High Performance (6-piston).

 

[Marky Dissod]

Some factory 18" wheels do not clear the 4-piston setup without grinding or spacers.

Most of the 18" wheels that do not clear 4pistons caliper are 2018 or older. 2019 & younger 18" wheels should clear 4piston calipers just fine.

I'm using T1xx 20" rims that would've been paired with the 4-piston, so there won't be any clearance issues on that front.
The 6-piston on the other hand, I find conflicting info.

This may only mean that GM never bothered to pair 6piston calipers with those / your wheels, so GM have nothing useful to say about that pairing.

 

[mars2878]

Most of the 18" wheels that do not clear 4pistons caliper are 2018 or older. 2019 & younger 18" wheels should clear 4piston calipers just fine.

This thread is about using the T1xx 20in rims with the brake upgrade. Yet people insist on talking about about is needed to be possibly done to fit smaller rims or regurgitating what I or someone else has already stated?
Of course those older or smaller rims may potentially have issues, those rims were not designed with the 4-piston in mind.

 

[AuroraGirl]

This thread is about using the T1xx 20in rims with the brake upgrade. Yet people insist on talking about about is needed to be possibly done to fit smaller rims or regurgitating what I or someone else has already stated?
Of course those older or smaller rims may potentially have issues, those rims were not designed with the 4-piston in mind.

They also have different backspacing and track and suspension travel and steering articulation.
You should not use washers to space the brakes on the rotor. Like, don’t even try unless it’s one single one on each bolt. And it’s 10.9 hardness or more.
Still relevant to talk about other wheels that work.

And you

Frankly I don’t know how much one SHOULD use those brakes without also using something like SBA or the 25 booster and master setup lol

 

[mars2878]

This may only mean that GM never bothered to pair 6piston calipers with those / your wheels, so GM have nothing useful to say about that pairing.

My original post states I've seen pictures of a 2025 Yukon At4 Ultimate with the same Rim as what I have but with the 6-piston installed. As of this past Thursday night, I could not find any for sale with that setup.
GM offers the Brembo 6piston as a upgrade for the 2025 Yukon at4 Ultimate.
When I put in the Vin # of a 2025 Yukon at4 Ultimate with 6.2L with the same rims as me, it says that it doesn't fit.

What I'm trying to find out is what on a 2025 Yukon at4 Ultimate with my rims, is needed for the 6-piston to be a GM approved upgrade?

Talking to the people at my local dealership is useless. They will only tell you what is on the screen & if you don't have a Vin #, they won't help you at all.

 

[AuroraGirl]

My original post states I've seen pictures of a 2025 Yukon At4 Ultimate with the same Rim as what I have but with the 6-piston installed. As of this past Thursday night, I could not find any for sale with that setup.
GM offers the Brembo 6piston as a upgrade for the 2025 Yukon at4 Ultimate.
When I put in the Vin # of a 2025 Yukon at4 Ultimate with 6.2L with the same rims as me, it says that it doesn't fit.

What I'm trying to find out is what on a 2025 Yukon at4 Ultimate with my rims, is needed for the 6-piston to be a GM approved upgrade?

Talking to the people at my local dealership is useless. They will only tell you what is on the screen & if you don't have a Vin #, they won't help you at all.

Are you saying you want a calibration approved from Gm? But I’ll check a Yukon too see if I see anything

 

[mars2878]

They also have different backspacing and track and suspension travel and steering articulation.
You should not use washers to space the brakes on the rotor. Like, don’t even try unless it’s one single one on each bolt. And it’s 10.9 hardness or more.
Still relevant to talk about other wheels that work.

And you

Frankly I don’t know how much one SHOULD use those brakes without also using something like SBA or the 25 booster and master setup lol

While I understand that there are other differences involved for the older/smaller rims & the involvement about the quality/quantity of washers, that subject is beat to death on so many places & is not relevant to me as I'm using the larger rims that were designed to fit these brakes.

I only found a couple of people who have done the 6-piston swap while using other T1xx 20in rims. But they haven't responded to any inquiries.

Now, this is the first time in months of threads/post readings that anyone physically mentioned about potentially needing a booster/master swap.
That is useful info for someone to look into further.

Thank you.

 

[mars2878]

Are you saying you want a calibration approved from Gm? But I’ll check a Yukon too see if I see anything

Yes, what vehicle setup will make them say yes.
Because theoretically you may need to swap those parts too?

I know that the PPV comes with the 6-piston, but that is a different animal to compare against. Same as checking an Escalade.

That is why I kept my comparisons strictly on the 2025 Yukon at4 Ultimate with the rim that I have so that it is an apple-to-apple comparison.

Since I left the field in 2024, I don't have access to any of the necessary software to do my own research as I did on my lunch breaks.

 

[mars2878]

Also, I don't see anyone mentioning about the dustshields. These are bigger rotors. So are the dust shields modified or replaced?
I have asked these questions to several people who state that they did this mod, but no one has responded yet.

 

[AuroraGirl]

					Size Description
Drive Type	Body Style	Vehicle Option	GVWR (lbs)	Front/Rear/Both	Standard	Optional	Inflation (psi) Front-Rear	Torque (ft-lbs)	Wheel Base (in) Min - Max	Rim Size	Bolt (# - mm)
4WD	4D Utility		7400-7700	B	275/60R20 115S		35 - 35	140		9J	6-139.7mm

couldnt find moire details sorry

Yes, what vehicle setup will make them say yes.
Because theoretically you may need to swap those parts too?

I know that the PPV comes with the 6-piston, but that is a different animal to compare against. Same as checking an Escalade.

That is why I kept my comparisons strictly on the 2025 Yukon at4 Ultimate with the rim that I have so that it is an apple-to-apple comparison.

Since I left the field in 2024, I don't have access to any of the necessary software to do my own research as I did on my lunch breaks.

gm will not endorse this setup at all because of the fact the brakes are not in the design specs of stock. however, you CAN get gm to approve it for 20 inch wheels in one tire size only.

But if you want to know about a factory calibration to get it close, heres what you need:

Subject: 20" Wheels Available Through GM Accessories Models: 1999-2007 Chevrolet Silverado 1500 Series Only (Classic) 1999-2007 GMC Sierra 1500 Series Only (Classic) Excludes 1999-2000 Vehicles with 4.3L Engine (VIN W -- RPO L35) Excludes Vehicles with Quadrasteer (RPO NYS) Excludes Parallel Hybrid Truck (RPO HP2) Excludes 2001-2004 Vehicles with Traction Control (RPO NW7) combined with 3.42 Axle Ratio (RPO GU6) Refer to the Model Application Chart in the beginning of this bulletin to verify usage. This bulletin is being revised to include 2007 model year and calibration information. Please discard Corporate Bulletin Number 03-03-10-006E (Section 03 -- Suspension). [H3]Model Application Chart:[/H3] Cab​ Box​ 2WD*​ 4WD​ Regular​ Standard 1.8 m (6 ft)​ Y​ N/A​ Regular​ Long 2.4 m (8 ft)​ Y​ N/A​ Extended​ Standard 1.8 m (6 ft)​ Y​ Y​ Extended​ Long 2.4 m (8 ft)​ Y​ Y​ Crew​ Fleetside​ Y **​ Y **​ Excludes 1999-2000 vehicles with 4.3L (VIN W -- RPO L35) engine. *Excludes vehicles with Traction Control combined with 3.42 Axle Ratio (RPO NW7). [H4]** Excludes 2WD Crew Cab built prior to:[/H4] • Sierra built prior to VIN breakpoint 51334993 • Silverado built prior to VIN breakpoint 51334946 [H4]** Excludes 4WD Crew Cab built prior to:[/H4] • Sierra built prior to VIN breakpoint 51334978 • Silverado built prior to VIN breakpoint 51335001 [H4]** Excludes AWD Crew Cab built prior to:[/H4] -- Sierra Denali built prior to VIN breakpoint 51334762 The purpose of this bulletin is to provide a reference guide for the technician to upgrade a vehicle from factory wheels and tires to 20" wheels and tires, which are available through GM Accessories (dealers must confirm availability of parts prior to utilizing this bulletin). This guide will cover Tire Specifications, the Spare Tire, Balancing, Center Cap Installation, Wheel Nuts, Re-Programming and Label requirements. [H3]Tires[/H3] GM has designed 20" wheels based on the Goodyear Eagle LS and LS2 P275/55R20 tire. The Goodyear Eagle LS tire has a Tire Performance Criteria spec #1235 and the LS2 has a Tire Performance Criteria spec #1245. These tires have been designed to GM's specific Tire Performance Criteria. GM's Tire Performance Criteria specifications meet or exceed all Federal safety guidelines. When mounting the tires, rubber lubricant, P/N 12345884 (in Canada, P/N 5728223), MUST be used. The vehicle should not be driven aggressively (hard acceleration or braking) for at least 6-8 hours after tire mounting to allow the lube to dry. Failure to do so may cause the tire to slip on the rim. This condition will affect wheel balance which could result in a vibration. [H3]Spare Tire[/H3] A P265/75R16 or P265/70R17 tire should be used as a spare. Re-use the vehicle's original spare wheel to mount the spare tire. The spare tire should be used to drive the vehicle to a tire repair/replacement facility and is not intended for extended driving conditions. [H3]Tire Changers[/H3] Dealers must have the correct level of tire changing equipment to perform tire changing services. GM requirements and recommendations for servicing glamour wheels are as follows: • Rim Clamp design • Runflat capable (preferred) • Side mounted bead breaking to reduce stress on the wheel and tire • No metal contact to the wheel at the clamping jaws • Protective devices to prevent damage during mounting and dismounting operations • Regulated air pressure to protect user and wheel assembly • Approved lubricant (P/N 12345884 [in Canada, P/N 5728223]) to avoid wheel slip and damage to the wheel For further information regarding equipment meeting the requirements for this program, call 1-800-GM-TOOLS. [H3]Balancing[/H3] MC style coated weights are recommended and will provide the best balancing of the tire-wheel assembly. If stick-on weights are used, be sure to follow the manufacturers' recommended installation procedure (SI Document ID #664222) making sure the surface is clean and dry. Using the incorrect type of weights will result in improper fit, and such weights may fall off the wheel. Balancing of the tire and wheel assembly must be performed on a computerized balancer, capable of static and dynamic wheel balance modes. Assemblies should be balanced to within 1/4 ounce on either rim flange. Proper cones and adapters should be used, free of nicks and burrs to ensure proper balancing. [H3]Center Cap[/H3] Install the center cap onto the wheel after the tire has been mounted and balanced, but BEFORE the assembly is installed onto the vehicle. The preferred method for center cap installation is to push in by hand. As an alternate, use a nonmetallic object to push the center cap into place. Attempting to "hammer-on" the caps may result in damage to the cap. [H3]Wheel (Lug) Nuts[/H3] ALUMINUM WHEELS REQUIRE SPECIAL WHEEL NUTS. Each wheel nut should be torqued in the appropriate torque sequence (refer to graphic) and to 190 N·m (140 lb ft). The torque should be re-checked after the first 160 km (100 mi). To help protect the wheels from theft, a wheel lock kit is also available.

 

[AuroraGirl]

Caution: Incorrect wheel nuts or improperly tightened wheel nuts can cause the wheel to become loose and even come off. This could lead to an accident. Be sure to use the correct wheel nuts. [H3]Wheel Nut Caps[/H3] Install the wheel nut caps after tightening the wheel nuts. Install the wheel nut caps finger tight, plus 1/2 turn. [H3]Jounce Bumper[/H3] Important: This modification is required on all 2WD vehicles EXCEPT the following: Excludes: • 2006-2007 2WD Extended Cab -- Short Box (model C15553) • 2006-2007 2WD Crew Cab -- Short Box with Enhanced Trailering (RPO NHT) (model C15543) • 2006-2007 2WD Extended Cab -- Standard Box with Enhanced Trailering (RPO NHT) (model C15753) It will be required to replace the existing front suspension spring/jounce bumper with Jounce Bumper kit, P/N 12499481. The following procedure should be followed: Raise and support the vehicle. Remove the nut from the spring bumper stud. Remove the spring bumper. Install a new spring bumper assembly for 2WD 1500 Series Only with 20" wheels. Reuse the nut from the original bumper. Install the nut to the spring bumper stud. Tighten Tighten the nut to 30 N·m (22 lb ft). Remove the safety stands. Lower the vehicle. [H3]Knee Bolster Deflector[/H3] Important: This modification is required for the following vehicles and ONLY applies to Extended Cab Long Box (K15953) Pickup models: 1999-2005 Chevrolet Silverado and GMC Sierra (1500 Series Only): • 2005 Vehicles Built in Pontiac (VIN Code E) prior to VIN Breakpoint 5E100134 • 2005 Vehicles Built in Oshawa (VIN Code 1) prior to VIN Breakpoint 51113131 • 2005 Vehicles Built in Ft. Wayne (VIN Code Z) prior to VIN Breakpoint 5Z126605 The following procedure should be followed: Apply the parking brake to prevent the vehicle from moving. Remove the fuse panel cover. Remove the I/P cluster trim plate bezel. Remove the knee bolster. Remove the 2 mm (0.078 in) thick knee bolster deflector. Install the 1.5 mm (0.059 in) thick knee bolster deflector, P/N 12499966. A detailed instruction sheet will be provided with the service part. [H3]Re-Programming[/H3] It will be necessary to reprogram the PCM for speedometer accuracy. Contact Techline (1-800-828-6860 English or 1-800-503-3222 French) to obtain a VCI number. Then refer to the table below for the appropriate calibration part number based on the model year and axle ratio. [H4]Calibration Information Documentation[/H4] Make a copy of the "Accessory Wheel and Tire Information Form" included in this bulletin. Provide all information required on the form. Make a copy of the completed form for the customer to keep in the vehicle along with their Owner's Manual. File the original completed form in the Dealership's Vehicle Service History folder. Important: Because this is not a warranty repair, dealers will incur a charge to obtain a VCI number. Important: A VCI number will only be available for the following models: • 1999-2007 Chevrolet Silverado and GMC Sierra (1500 Series Only) • EXCLUDES 1999-2000 vehicles equipped with 4.3L engine (RPO L35) • EXCLUDES vehicles equipped with Quadrasteer (RPO NYS) • EXCLUDES Parallel Hybrid Truck (RPO HP2) • EXCLUDES 2001-2004 vehicles equipped with Traction Control (RPO NW7) combined with 3.42 Axle Ratio (RPO GU6) Refer to the Model Application Chart to in the beginning of this bulletin to verify usage. Important: • Calibrations are not available for 1999 and 2000 model year vehicles with 3.08 axle. • Calibrations are not available for 1999 and 2000 model year vehicles equipped with 4.3L engine (RPO L35). MY 1999 Pickups Only​ MY 2000 Pickups Only​ MY 2001-2002 Pickups Only​ MY 2003 Pickups Only​ MY 2004 Pickups Only​ MY 2005 Pickups Only​ MY 2006 Pickups Only​ MY 2007 Pickups Only​ ​ ​ 12589876 -- GU4 (3.08)​ 12589880 -- GU4 (3.08)​ 12589884 -- GU4 (3.08)​ 12593917 -- GU5 (3.23)​ 12601282 -- GU5 (3.23)​ 12601286 -- GU5 (3.23)​ 12589869 -- GU6 (3.42)​ 12589873 -- GU6 (3.42)​ 12589877 -- GU6 (3.42)​ 12589881 -- GU6 (3.42)​ 12589885 -- GU6 (3.42)​ 12593918 -- GU6 (3.42)​ 12601283 -- GU6 (3.42)​ 12601287 -- GU6 (3.42)​ 12589870 -- GT4 (3.73)​ 12589874 -- GT4 (3.73)​ 12589878 -- GT4 (3.73)​ 12589882 -- GT4 (3.73)​ 12589886 -- GT4 (3.73)​ 12593919 -- GT4 (3.73)​ 12601284 -- GT4 (3.73)​ 12601288 -- GT4 (3.73)​ 12589871 -- GT5 (4.10)​ 12589875 -- GT5 (4.10)​ 12589879 -- GT5 (4.10)​ 12589883 -- GT5 (4.10)​ 12589887 -- GT5 (4.10)​ 12593920 -- GT5 (4.10)​ 12601285 -- GT5 (4.10)​ 12601289 -- GT5 (4.10)​ There is a tire size value in the ABS module that must also be updated using the Tech 2. Use the following path to update the ABS module: Diagnostics>Model Year>Vehicle Type>Chassis>Product Line>GVW>ABS>Special Functions>Tire Size Calibration>Verify VIN>Select New Tire Size. Important: If original equipment tires/wheels are reinstalled, it will be necessary to reset the programming of the PCM and the ABS module to the original specifications. [H3]Labels[/H3] After installing the recommended P275/55R20 tires, place the provided label on the vehicle. The label should be located on the door jamb, near the original tire label, and should not cover up the original tire label. Be sure that the surface is clean and dry. The surface temperature should not be less than 21°C (70°F). The label is provided as a guide for tire inflation pressures and information relevant to occupant/cargo capacities.

 

[AuroraGirl]

[H3]Labels[/H3] After installing the recommended P275/55R20 tires, place the provided label on the vehicle. The label should be located on the door jamb, near the original tire label, and should not cover up the original tire label. Be sure that the surface is clean and dry. The surface temperature should not be less than 21°C (70°F). The label is provided as a guide for tire inflation pressures and information relevant to occupant/cargo capacities. [H3]Parts Information[/H3] [H4]20" Wheels[/H4] Style #​ Single Sets​ Multi-Packs​ Wheel Name​ Part No.​ Pcs/Pack​ Part No.​ Pcs/Pack​ CK793​ 88962793​ 1​ 12499371​ 4​ CK795​ 88962795​ 1​ 12499372​ 4​ CK797​ 88962797​ 1​ 12499373​ 4​ CK799​ 88962799​ 1​ 12499374​ 4​ CK801​ 88962801​ 1​ 12499375​ 4​ CK803​ 88962803​ 1​ 12499376​ 4​ CK805​ 88962805​ 1​ 12499377​ 4​ CK807​ 88962807​ 1​ 12499378​ 4​ CK809​ 88962809​ 1​ 12499379​ 4​ CK040​ 17801040​ 1​ 17801041​ 4​ CK360​ 17800360​ 1​ 17800361​ 4​ CK363​ 17800363​ 1​ 17800364​ 4​ CK628​ 17800628​ 1​ 17800629​ 4​ CK631​ 17800631​ 1​ 17800632​ 4​ Part Description​ ​ Part Number​ Qty​ Valve Stem Cap​ ​ 09591607​ 4​ Center Cap​ Brushed -- Chevrolet​ 12499304​ 4​ Brushed -- GMC​ 12499305​ 4​ Polished -- Chevrolet​ 12499421​ 4​ Polished -- GMC​ 12499422​ 4​ Chrome -- Chevrolet​ 12499424​ 4​ Chrome -- GMC​ 12499425​ 4​ Lug Nuts Pkg​ ​ 12499500​ 1​ Wheel Lock Kit​ ​ 12497479​ 1​ Lug Nut Cap​ Black​ 15646250​ 24​ Chrome​ 15045768​ 24​ Stainless​ 88963146​ 24​ Jounce Bumper Kit​ ​ 12499481​ 1​ Knee Bolster Bracket​ ​ 12499966​ 1​ Door Jam Label​ ​ 12499559​ 20​

 

[mars2878]

GM has designed 20" wheels based on the Goodyear Eagle LS and LS2 P275/55R20 tire. Dealers must have the correct level of tire changing equipment to perform tire changing services. GM requirements and recommendations for servicing glamour wheels are as follows:

Interesting read.

I've never seen the rims referred to as "Glamour Wheels" before.

 

[mars2878]

Caution: Incorrect wheel nuts or improperly tightened wheel nuts can cause the wheel to become loose and even come off. This could lead to an accident. Be sure to use the correct wheel nuts. [H3]Wheel Nut Caps[/H3] Install the wheel nut caps after tightening the wheel nuts. Install the wheel nut caps finger tight, plus 1/2 turn. [H3]Jounce Bumper[/H3] Important: This modification is required on all 2WD vehicles EXCEPT the following: Excludes: ​ • 2006-2007 2WD Extended Cab -- Short Box (model C15553) • 2006-2007 2WD Crew Cab -- Short Box with Enhanced Trailering (RPO NHT) (model C15543) • 2006-2007 2WD Extended Cab -- Standard Box with Enhanced Trailering (RPO NHT) (model C15753) It will be required to replace the existing front suspension spring/jounce bumper with Jounce Bumper kit, P/N 12499481. The following procedure should be followed: Raise and support the vehicle. Remove the nut from the spring bumper stud. Remove the spring bumper. Install a new spring bumper assembly for 2WD 1500 Series Only with 20" wheels. Reuse the nut from the original bumper. Install the nut to the spring bumper stud. Tighten Tighten the nut to 30 N·m (22 lb ft). Remove the safety stands. Lower the vehicle. [H3]Knee Bolster Deflector[/H3] Important: This modification is required for the following vehicles and ONLY applies to Extended Cab Long Box (K15953) Pickup models: 1999-2005 Chevrolet Silverado and GMC Sierra (1500 Series Only): ​ • 2005 Vehicles Built in Pontiac (VIN Code E) prior to VIN Breakpoint 5E100134 • 2005 Vehicles Built in Oshawa (VIN Code 1) prior to VIN Breakpoint 51113131 • 2005 Vehicles Built in Ft. Wayne (VIN Code Z) prior to VIN Breakpoint 5Z126605 The following procedure should be followed: Apply the parking brake to prevent the vehicle from moving. Remove the fuse panel cover. Remove the I/P cluster trim plate bezel. Remove the knee bolster. Remove the 2 mm (0.078 in) thick knee bolster deflector. Install the 1.5 mm (0.059 in) thick knee bolster deflector, P/N 12499966. A detailed instruction sheet will be provided with the service part. [H3]Re-Programming[/H3] It will be necessary to reprogram the PCM for speedometer accuracy. Contact Techline (1-800-828-6860 English or 1-800-503-3222 French) to obtain a VCI number. Then refer to the table below for the appropriate calibration part number based on the model year and axle ratio. [H4]Calibration Information Documentation[/H4] Make a copy of the "Accessory Wheel and Tire Information Form" included in this bulletin. Provide all information required on the form. Make a copy of the completed form for the customer to keep in the vehicle along with their Owner's Manual. File the original completed form in the Dealership's Vehicle Service History folder. Important: Because this is not a warranty repair, dealers will incur a charge to obtain a VCI number. Important: A VCI number will only be available for the following models: ​ • 1999-2007 Chevrolet Silverado and GMC Sierra (1500 Series Only) • EXCLUDES 1999-2000 vehicles equipped with 4.3L engine (RPO L35) • EXCLUDES vehicles equipped with Quadrasteer (RPO NYS) • EXCLUDES Parallel Hybrid Truck (RPO HP2) • EXCLUDES 2001-2004 vehicles equipped with Traction Control (RPO NW7) combined with 3.42 Axle Ratio (RPO GU6) Refer to the Model Application Chart to in the beginning of this bulletin to verify usage. Important: ​ • Calibrations are not available for 1999 and 2000 model year vehicles with 3.08 axle. • Calibrations are not available for 1999 and 2000 model year vehicles equipped with 4.3L engine (RPO L35). MY 1999 Pickups Only​ MY 2000 Pickups Only​ MY 2001-2002 Pickups Only​ MY 2003 Pickups Only​ MY 2004 Pickups Only​ MY 2005 Pickups Only​ MY 2006 Pickups Only​ MY 2007 Pickups Only​ ​ ​ 12589876 -- GU4 (3.08)​ 12589880 -- GU4 (3.08)​ 12589884 -- GU4 (3.08)​ 12593917 -- GU5 (3.23)​ 12601282 -- GU5 (3.23)​ 12601286 -- GU5 (3.23)​ 12589869 -- GU6 (3.42)​ 12589873 -- GU6 (3.42)​ 12589877 -- GU6 (3.42)​ 12589881 -- GU6 (3.42)​ 12589885 -- GU6 (3.42)​ 12593918 -- GU6 (3.42)​ 12601283 -- GU6 (3.42)​ 12601287 -- GU6 (3.42)​ 12589870 -- GT4 (3.73)​ 12589874 -- GT4 (3.73)​ 12589878 -- GT4 (3.73)​ 12589882 -- GT4 (3.73)​ 12589886 -- GT4 (3.73)​ 12593919 -- GT4 (3.73)​ 12601284 -- GT4 (3.73)​ 12601288 -- GT4 (3.73)​ 12589871 -- GT5 (4.10)​ 12589875 -- GT5 (4.10)​ 12589879 -- GT5 (4.10)​ 12589883 -- GT5 (4.10)​ 12589887 -- GT5 (4.10)​ 12593920 -- GT5 (4.10)​ 12601285 -- GT5 (4.10)​ 12601289 -- GT5 (4.10)​ There is a tire size value in the ABS module that must also be updated using the Tech 2. Use the following path to update the ABS module: Diagnostics>Model Year>Vehicle Type>Chassis>Product Line>GVW>ABS>Special Functions>Tire Size Calibration>Verify VIN>Select New Tire Size. Important: If original equipment tires/wheels are reinstalled, it will be necessary to reset the programming of the PCM and the ABS module to the original specifications. [H3]Labels[/H3] After installing the recommended P275/55R20 tires, place the provided label on the vehicle. The label should be located on the door jamb, near the original tire label, and should not cover up the original tire label. Be sure that the surface is clean and dry. The surface temperature should not be less than 21°C (70°F). The label is provided as a guide for tire inflation pressures and information relevant to occupant/cargo capacities.

Lots of interesting info.

Never knew about the ABS module having tire specs in them. When selling them, we always matched the part number on them. Our system only gave a year, model, engine interchange on those.
Didn't know about reprogramming them either.

We usually just gutted the ABS system when it was faulty.