ORIGINAL: Grant

http://www.stoptech.com/tech_info/wp...rakedisk.shtml

This is an interesting read concerning brake rotors and warping, etc. It's written from more of a track car/high performance viewpoint, but I'd think most of it still applies...

ORIGINAL: f5fstop

Bulletin 07-02-35-006, and been replaced by #07-02-35-006B and does NOT include 06 Hummers. I am not implying that an intermediate steering shaft on any vehicle, including 06 Hummers can’t go bad, but this bulletin is only for 07 Hummers (and Colorado/Canyon) due to the new designed that was initiated on this platform in 07.

Subject: Clunk or Knock Noise Heard and/or Felt Through Steering Wheel or Brake and Accelerator Pedals (Replace Lower Steering (Intermediate) Shaft) #07-02-35-006B - (10/18/2007)
Models: 2007 Chevrolet Colorado, 2007 GMC Canyon, 2007 HUMMER H3 with 3.7L Inline 5 Cylinder Engine (VIN E -- RPO LLR)


This bulletin is being revised to provide important steps to follow when replacing the lower I-shaft. Refer to "Important" information found in the Correction Section of this bulletin. Please discard Corporate Bulletin Number 07-02-35-006A (Section 02 -- Steering).
Condition
Some customers may comment on a clunk or knock noise being heard or felt through the steering wheel and/or brake and accelerator pedals. This issue may be more prevalent in hotter temperatures.
Cause
This condition may be caused by a slip/stick condition in the lower steering (intermediate) shaft.


As for bulletin 00-05-22-002H it is now a J revision:
SUBJECT: Disc Brake Warranty Service and Procedures #00-05-22-002J - (05/15/2007)

It is primarily an informational bulletin to the technicians on how to check for rotor variations due to warping, or lateral runout, along with the correct way to turn a rotor and submit for a warranty claim.

The entire bulletin is about twelve pages long, so I won’t post here.

However, brake pulsation is covered under warranty and the dealers are given labor operations to use for brake warranty service. Another however, is that under most circumstances the brakes are not actually warped. To warp the type of ventilated rotor used on the H3 is pretty hard, but not impossible. What sometimes happens, that is cured by turning the rotor is pad build-up on the rotor, causing the pulsation feeling in the brake pedal.
However, if the pulsation is felt through the steering wheel at slow speeds, I would look at other areas too:
Easiest in my opinion is to pull off the front wheel/tires and check the balance of the assemblies. Unbalanced front wheels will give a pulsation during braking and during slow speed acceleration. After the wheel starts turning faster, they are less likely to pulsate. (If you have the Goodyear Wranglers, I personally would look at those first. My opinion (and this is mine from personal experience), they have a propensity to become unbalanced too easily.) If the tires are Bridgestone tires, it is less likely, but still could be a balance problem. (Balance problem could be due to many things, including a spun internal belt on the tire.)
You can rotate the tires from front to back and if the pulsation now is in your butt, it will be the tires.
Next to look at is the radial runout of the rotor to the hub. If this is out of spec, you will get a pulsation during acceleration and while braking.
Last would be a bearing/hub assembly, but that usually causes a pulsation during high speed braking and at low speeds is not felt, unless the bearing is shot to sh*t at which time you should be hearing a grinding noise in the front.