Working with the '05 Z71 brakes

[lrymal]

Y'all, I could type until ad nausem on glowing away with how great the '05's brakes are, with a rather large front rotor and a happy back drum assembly.

 

Ok, I don't want to lose this really nice braking feel or effectiveness that this new truck has now, as the miles gather. And I know that in years past, when brakes were always drum in the back that we had auto-adjusting brakes. Typically, one either didn't have to worry about them, or had to periodically brake in a straight line while going backwards, so the adjuster would do its thing. That's ok, for the most part, it worked.

 

The manual states that the '05 Z71 has auto-adjustng brakes. But, on my '03's manual, the same paragraph exists. Same verbage, same words. And my manual has a few pages with pasted in white paper, that covers up portions of the page, hiding something---probably non-valid content. Check your manual, if you have an '05.

 

My point: I don't trust the '05 manual. Too much "sameness". I just don't think it is THAT uptodate. The cynic in me isn't really sure if there are any procedural things we gotta to do on those back drums to keep them properly adjusted. And this truck feels so simply great that I ain't touchin' anything!

 

If anyone knows, and can put this cynic back in the closet......

[WyRam]

I think the brakes on my 05 are easily as good as the 4 wheel disc on my 03 Ram which were very good.........and to think 3 months ago I was bashing GM for going back to drums!

[number9]

Drum brakes are fine - when they work and are designed right. If they are good enough to stop big rigs weighing 80,000+ pounds you gotta know that is true. One thing on the old GM drums is that alot of them were the JB5 design, which SUCKS major. From they way I understand it, even when working great and new condition they still only have 1 shoe doing most of the work. The JB6 drums were much better as they put both shoes into play.

 

With the 05 GM had BOCH redesign the entire brake system from the ground up. I would be willing to bet that the drums are of the JB6 design and the hydraulic system compnents are designed/matched together to make the system work like it should (ie. MC bore to WC bore ratio / front to rear bias, etc...).

 

I'd love to drive an 05 truck just to see how good the brakes are but I know it would only make me feel even worse when I got back into my truck Maybe when GM puts a better looking face back on the trucks I will give one a whirl so if/when I am tempted a trade wouldn't be out of the question.

[asilverblazer]

Personally every GM I've driven has had spongy brakes. My truck included, but it has stopped very well including every amount of weight I tow. The brakes are easy to change, a thirty minute job, all other truck manufactures are getting good pedal feel out of their all disc systems. I'm very disappointed that GM went back to drums we should be progressing with new trucks not going backwards. With a little more developement the new trucks could have an excellent braking system. I know I won't be buying a new one till GM catches back up with everyone else and learns how to build disc brakes with "Proper pedal feel" and a real EMERGENCY brake, not some cheesy parking brake that doesn't even do what it was designed for.

[WyRam]

Personally every GM I've driven has had spongy brakes. My truck included, but it has stopped very well including every amount of weight I tow. The brakes are easy to change, a thirty minute job, all other truck manufactures are getting good pedal feel out of their all disc systems. I'm very disappointed that GM went back to drums we should be progressing with new trucks not going backwards. With a little more developement the new trucks could have an excellent braking system. I know I won't be buying a new one till GM catches back up with everyone else and learns how to build disc brakes with "Proper pedal feel" and a real EMERGENCY brake, not some cheesy  parking brake that doesn't even do what it was designed for.

 

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Go drive an 05 then report back!

[lrymal]

...I know I won't be buying a new one till GM catches back up with everyone else and learns how to build disc brakes with "Proper pedal feel" and a real EMERGENCY brake, not some cheesy  parking brake that doesn't even do what it was designed for.

 

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No problem. Don't buy one then.

In the meantime:

 

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http://wardsauto.com/ar/auto_gm_pickups_brake/index.htm

GM Pickups to Brake Better

 

Significant upgrades will improve performance and customer satisfaction of braking systems for GM’s ’05 fullsize pickups.

 

MILFORD, MI – General Motors Corp. says its ’05 fullsize pickups will be equipped with an all-new braking system that improves performance and is more pleasing to use.

 

The rub for GM engineers: Their one-step-back-two-steps-forward solution requires a bit of explanation. At first blush, the uninitiated might be convinced GM actually is cutting back on the pickups’ braking ability.

 

 

New front disc is larger, twin-piston caliper stiffer.

When the current Chevrolet Silverado and GMC Sierra pickups (internal designation: GMT800) were launched as ’99 models, GM bragged they were the industry’s first fullsize light-duty pickup trucks to come standard with 4-wheel disc brakes.

 

Until then, pickups – whose rear wheels typically don’t contribute much to the act of slowing the truck – traditionally used less-powerful, less-costly drum brakes for the rear wheels.

 

The new braking system for the ’05 Silverado and Sierra returns to drum brakes for the rear wheels, but it is not a retrograde move.

 

GM engineers, along with co-developer Robert Bosch GmbH, are leveraging their knowledge that pickups rarely use their rear brakes as hard as the fronts. They have taken the savings gleaned from using rear drum brakes and spent it on a serious upgrade of the trucks’ front brakes and other braking-system components.

 

Because the ’05 trucks’ harder-working front brakes now are considerably more powerful, GM and Bosch promise the new system delivers meaningful performance improvements, despite the return to drums at the rear.

 

Equally important, the new system, engineers say, will provide drivers with better feedback, require less pedal effort and deliver generally better overall response and “feel.”

 

Jully Burau, assistant chief engineer-fullsize trucks, says GM’s truck engineers pursued the new braking-system design because of continuous-improvement initiatives. “It’s an evolving product. We’re always driving for better quality, reliability and durability,” Burau says.

 

 

New master cylinder stiffer, enhances pedal “feel.”

She also says GM targeted the braking system because of J.D. Power and Associates initial-quality ratings and other consumer-clinic data that show customers believe there is plenty of room for improvement in the performance and feedback of pickup brakes – and because GM was not pleased with the Silverado/Sierra’s rating vs. rivals from Ford Motor Co., DaimlerChrysler Corp. and Toyota Motor Corp.

 

Issues most often cited include high brake-pedal effort, “mushy” feel from the pedal and the feeling the brakes don’t provide enough stopping power.

 

Fixing those problems, says Ken Hamann, director-brakes and chassis control systems, led GM and Bosch to a host of solutions that not only deliver quantifiable reductions in stopping distance and time but also generate more responsive feedback to the driver.

 

The primary hardware upgrade for the ’05 light-duty pickups is 1 in. (2.5 cm) larger-diameter front rotors and twin-piston calipers that are significantly larger and stiffer than the current twin-piston squeezers. Hamann says the larger rotor provides a 55 sq.-in. (355 sq.-cm )increase in rotor swept area, a tremendous aid in generating more stopping force.

 

The upgraded rotor/caliper components also deliver an important ancillary benefit, says Hamann. Their better stopping power means engineers could eliminate a booster previously necessary to comply with a federal safety standard that dictates the amount of allowable brake-pedal pressure in the event the braking system’s power-assist is inoperable.

 

The new brakes are powerful enough to eliminate the costly and space-consuming booster, which had to be added solely to provide extra pedal assist in the rare event of total power loss.

 

Hamann says the new brake system also includes a totally new master cylinder and booster that is stiffer and more efficient. That stiffness, combined with the extra beefiness found in the new calipers, helps to reduce the spongy feeling about which customers complain. By taking compliance out of these components, Hamann says customers will “experience more confidence with the pedal.”

 

GM engineers, in fact, developed in the early 1990s a matrix to help quantify the sometimes esoteric subjective facets of brake-system feedback. Their Brake Feel Index (BFI) assigns a vehicle a single BFI score based on a composite of weighted variables that contribute to a customer’s overall impression of the braking experience.

 

GM thought it could – and should – improve its fullsize pickups’ BFI scores, says Burau. “We’re focused on the customer interface,” she says.

 

The new system, says Hamann, registers a 41% BFI improvement vs. the ’04 brake system. GM’s numerous other GMT800-derived vehicles, including its fullsize SUVs, continue to use the current disc/disc system.

 

Hamann says the new trucks’ improved braking system will reduce stopping distance from 60 mph (97 km/h) by 85 ft. (26 m) and stopping time by 2 seconds. Meanwhile, the driver will not have to exert as much effort on the brake pedal, and the pedal will feel more responsive and deliver more of the confidence Hamann says is important to drivers, particularly when the pickup is heavily loaded.

 

As for those “new” old drum brakes at the rear, they are no slouches; Hamann says the 11.6-in. (29.5-cm) diameter drums are the largest in a light-duty vehicle.

 

But he knows the perception of returning to a less-sophisticated component is undeniable. That’s why GM and Bosch engineers point to the improved performance and feel of the new system that takes advantage of pickups’ unique braking behavior.

 

And why, Hamann says, he hopes pickup customers and auto critics try the new system before judging.

 

“They need to feel, touch and understand what we went through to make that call (to return to drum brakes),” he insists.

[Crazeecooter]

This thread amuses me. I'm glad everyone elses brakes work just fine. Mine are worse than any old car I've owned in the past. Including the 63 GMC truck I had a few years ago.

[lrymal]

This thread amuses me. I'm glad everyone elses brakes work just fine. Mine are worse than any old car I've owned in the past. Including the 63 GMC truck I had a few years ago.

 

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Well, this thread doesn't indicate "everyone else's brakes work just fine". It is the 2005 model that has improved braking.

[Crazeecooter]

Mine is a 2005!

[lrymal]

Mine is a 2005!

 

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Oh, didn't realize that. Didn't catch that in your .sig.

 

Why didn't you remind us or link to your other thread about the 2005 problems you are having? I didn't realize it was you until I did the scan of the messages. Hang in there....

[black&grayHD]

Hamann says the new trucks’ improved braking system will reduce stopping distance from 60 mph (97 km/h) by 85 ft. (26 m) and stopping time by 2 seconds.

 

 

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Wonder what the cost to replace the front brakes and booster on the '04 is?

[USA1Fan]

I was just thinking the same thing!

 

I love my 2004, and it stops well enough. It just doesn't feel like it. My wife likes to drive it too, but the brake feel makes her nervous. I've adjusted pretty well, but now the '04 Malibu brakes feel extra precise.

[asilverblazer]

Not arguing with anyone...

 

Yes, there are lots of improvements on the old system. But there is still much more potential for four wheel discs. My gripe is that I don't think GM wanted to invest in improving them. What were the reasons for switching to them in the first place? Hasn't it been decided that in light duty vehicles a disc brake can deliver more braking force than a drum? (Even though 18 Wheelers use drums because of the massive surface area that no disc brake can provide.) Not to mention how much easier there are to change. (I've replaced mine twice) Based on that, I know they are already doing more than previous generations, 88 3/4 ton still on original shoes with 200,000 thousand miles. And true a truck unloaded stops primarily on the front brakes due to lack of weight/traction on the rear. I like knowing that with my four wheel discs and anti-lock brakes ALL of my tires are stopping at there greatest potential limited by traction not braking force.

 

Just my .02$, on my experiences and opinions.

[lrymal]

I'll easily be the first to want four-disc systems on any and every vehicle. I know the theories and the arguments. But at least humor this: GM's four-disc system for 1/2 ton trucks, Z71s, is poor. It is not a good design and not taking advantage of the design. My '03 had the typical problems: rotor replacements, re-surfacing, high blood pressure, telephone calls, constant warranty attempts to get rid of the mush pedal, pedal to the floor panic stop.

 

Fed up with this, I replaced all 4 rotors and pads with aftermarket and, WOW! The truck stopped marvelously and even had good pedal feel. Rotors were Power Slots and the pads were Performance Friction. For whatever reason, The General just did an awful of disc brake design for the '03 and I guess, the '04.

 

Now, this '05..... sheesh. Different. STOPS. I mean, like whoaaaaaaaaa! Corneas against the windshield. Hardly any pedal pressure at all.

 

So, for what it is worth on these 1/2 tons, specifically the Z71 (since that is my only reference), The General did a simply amazing job.

 

Now, it has been years since I last did a brake job on a shoe / drum brake system, but my memories are that the rear brakes hardly need changing when the fronts do. And, since both shoes per drum are applied, rather than just the one, I speculate these shoes will never need replacement.

 

So in summary, I agree about the beauty of a four-disc system, but the '03 version is awful. You gotta accept that, unless yours is exceptional. The '05's disk/shoe-drum combo is incredibly well-designed. Indeed, I have never been in a

GM truck that stopped as effortlessly.

[kevenn]

Sorry Irymal, sent it to the wrong member should go to Silverblazer