brakes / vibiration....

[BHerring]

Morning all,

I recently did a complete front brake overhaul. I replaced the master cylinder, both calibrators, disc pads, had the rotors turned, replaced the seals. It’s been about 7K miles, and now when I brake the front end shakes and lots of vibrations. What would cause this? and what should I look at? I am thinking the rotors might me warped or the bearings are shot.



All comments and suggestions will be greatly appreciated.



Cheers

Brad

 

[Greenleaf]

When you buy/install new rotors, they are warped. Period. Just the way it is. They MUST be turned prior to install. I didn't believe it untill I had done it. They are warped right out of the box.



Another thing, if your rear brakes don't grab like they should, the recently turned rotors will warp rapidly. If the front end noses down when you make a normal stop, the rears are not working or your shocks are trash. The back end should "feel" like someone applied the brakes on a trailer you are pulling. The rear of the truck will actually pull you. You can feel it in the s eat of your pants.



Are the shocks any good? I have to keep good shocks on the trucks or the front end will feel sloppy when the load (torque) is applied by braking.



About all I can come up with at this time... ... .....

 

[JLEONARD]

Rotors can warp... especially aftermarket ones because most of thos re cheap Chinese made junk (I need to learn to express my feelings).

But hot braking then going thru cold puddles with warp them in one shot, even if they are good ones.



If the bearings are gone you will most likely hear that when you go around a bend on a expressway or back road if you have some speed up.



One thing SURE... warped rotors and shaking WILL damamge the bearings if you leave the brakes as is for a long time. You don't have to ask how I know that.

 

[Tippin Spotted Cow]

Try retorquing the lug nuts. My buddy replaced the front rotors on his truck, and just torqued his lug nuts by feel, and ended up with a strange noise and vibration. I've replaced rotors numerous times and never had that problem. The problem is, when you first replace the rotors, the studs need to be seated the first time you crank down the lug nuts, which in turn pulls the whole hub/rotor assembly together. No, hammering them in the first time doesn't always seat them properly. The first time you put the wheel back on after the rotor change, getting the torque and tightening pattern right is very important.



What you end up with is the rotor will sit just slightly cock-eyed on the hub casing. Then when you hit the brakes you get this weird "wub... wub... wub... wub... " noise and a shake to go along with it. Crack all your lug nuts loose, and retorque them all in the proper sequence. Then go around one more time when your done to make sure they're all still tight. Sometimes you torque one down to the right ft-lb, and then when you make your way around it pulls the rotor tighter agains the hub, and you loose your torque. You end up going around a few times as your lug nuts pull the rotor in.

 

[RedRamAndy]

I went through exactly the same thing with my wife's 90 Chry NY'er. I put on all new front brakes, including the cheap rotors. The car ended up with a big shudder in the front in a short time. She said it was terrible. I drove it and recognized the symptoms of warped rotors. Sheesh. I went back to the store and asked the parts guy about buying the way-expensive rotors. He told me that those expensive ones are already 'healed-in'. They are heat relieved, the cheap ones are not. He told me I could get by with the cheap ones though. He said that if I simply put on the cheapos and drove, they would warp since these aren't heat relieved. He told me to break them in as follows: Drive around the block lightly using the brakes for only a couple of stops, then back in the driveway to cool. After cool, venture out a little further, maybe five gentle stops, and then cool then for a half hour. Next, go around town for a dozen or more, then cool off. He warned me to save the hard stops, or exiting the freeway stops until the brakes were set in with a few trips like this. You get the idea. I took the car on short hops to gradually wear in these new rotors. That was the trick. It's been smooth stopping ever since.