I have a 2006 TL 5AT with 65K on it. Now, it vibrates during high speed/over 55mph braking. I can hear clunking and feel the vibration is from the rear. It happens on light and medium brake. I don't feel it when on hard brake. And also, when the rotors are cool, it won't vibrate; for example, the first and second brake on high way in the morning, I don't feel the vibration. But I do feel it when the brake system is warmed up.
I am sure, it's not the rims and tires. I have 2 set of tires/rims. It does vibrates on both set of tires/rims. I've already replaced all rotors/pads and brake fluid, and lubed everything, and plus wheel alignmented. There is no difference between before and after replacement. It's such a nice car, and I am not enjoying driving it cus the vibration.
I am lost.


Any idea/suggestion is appreciated.

 

Check the rotors for runout. They may be warped or not fully flat on the hubs.

 

also check for free caliper movement on the pins, if they are not moving freely on the pins, remove, clean, lube and reinstall

 

Here's a shot that might help.

There's really no such thing at a warped rotor. Rotors vibrate because the brake pads can leave an uneven deposit of brake material on the rotors--when the brake material is uneven it grabs unevenly, and there's vibration.

The way to remove this deposit (or more accurately, start over by applying an even deposit) is to "bed in" the brakes. Bedding in is accomplished though a series of hard decelerations.

Do this: Find an empty highway. From 70 mph, decelerate quickly down to 15mph or so--do not come to a stop. Back up to 70, and repeat this 4 or 5 more times. You'll smell hot brakes.

This should fix you up. Your braking will improve, and you should have no vibration. If some returns, re-bed the brakes a few times. Some brake materials and brands are more prone to uneven deposits than others. To avoid leaving deposits, you can also release your brakes (or roll a bit when you can) at stoplights to minimize leaving uneven deposits.

Good luck.

 

I don't have a dial indicator
It will be the last step -- take it to the shop

 

I am sure the pins are moving freely. I did lube them when i installed the rotors, and also I replaced one damaged rubber boot for the rear.

 

I did bed-in right after I installed the rotors.
The weird thing is that I don't feel the vibration during hard brake/ bed-in. I only feel it when I do light/medium brake.
I feel really lost, and I want to cry

 

just let it all out here....

 

Don't despair! You simply need to keep going all the way to bed them in properly. Depending on your pad material (what did you install?) this might take up to 10 hard brakings, plus another 10 moderate ones after a complete cooling hours later.

This sort of "cooks" the brake material, and evenly deposits the material on the rotors. Depending on your brake pad type--this can be less important, or critically important. The higher performance the pads, usually the more critical the bed-in is.

This is one reason why using track or race brakes on a passenger car is usually a bad idea--they're more finicky.

http://www.stoptech.com/technical-su...-system-bed-in

 

I installed Hawk HPS.
Did another set of bed-in tonight.
No luck, so frustrated.
I think I will have to either get a dial indicator or take it to the shop

 

Uhhh there is such thing as a warped rotor. I've cut plenty rotors on a brake lathe and seen the runout and warp issues of many a rotor. Here's some info....http://www.tirerack.com/FAQ/results.jsp?category=Brakes

 

did you inspect the caliper cylinder for any corrosion? it could be the caliper is freezing up. when your calipers get crudded up, the can do wierd stuff like not release properly or not fully engage when the brakes are applied.

other things to check for are bent rims and tires

 

Sorry, runout and warping are two completely different things. 99% of the time the brake problem causing pulsing or vibration is unevenly deposited brake material. It is nearly impossible to warp a rotor. Here's another good article:

http://www.mossmotors.com/SiteGraphi...ake_discs.html

 

update...
Finally, I got a dial indicator. Spent good 8 hours to index the hub/disk run out down to less than 0.002. Now, the vibration is intermittent but much less than before, and I can still hear the rubbing noise.
Did another set of bed-in, but no luck.

Any idea? Would it be something else?