95 K2500 Front brake Vibration

"Joe Cawley" wrote in message news: snipped-for-privacy@taconic.net...

You say leaks, but no sign of loss, sounds more like pads worn, remember as the pads wear more of the caliper piston is extended, more fluid is in the caliper housing. Pulsation is caused by warped rotors which are caused by few things. Number one is excessive heat. Can be caused by caliper mounts hanging up, but mostly from improper rear brake adjustment. Hoses can cause same and sticking piston, but these cause pull problems 90% of the time. Improper adjustment leads to premature pad wear out as well. Right behind in 2nd place is improperly torqued lug nuts

3rd on the list, cheap rotors. I've seen rotors with 30% less cooling fins than OEM, I've seen rotors that mic out ok, ie overall thickness, but if you look close or have the right mic, you find the thickness of the individual brake surfaces are thinner than stock. And it is normal for one side of the rotor to be slightly thicker than the other, this is done to combat the harmonics that cause brake squeal. Usually the outer is thicker than the inner, and the difference is about .020 of an inch. If the rotor and hub are separate parts held together by the lug studs, improper installation can lead to brake pulsation. While you can remove the studs with ye olde BFH if the studs aren't staked, they really need to be installed with a press, and they need to be replaced with new ones. If they are staked there is a special cutter to cut the stakes, and then the BFH removes them. While some BFH them anyways, it can result in oversized bore and studs that spin in the hub. Hubs are very expensive new. The mating surface of the hub needs to be free of rust and dirt before assembly, I like a very very light coat of moly grease smeared on the mating surface. If this is the style that uses a slip on rotor such as the front wheel drive cars use today, again no rust on the rotor to hub mating surface and proper wheel torque. If it uses composite rotors this is even more important. Composite rotors are those with a cast brake surface and stamped steel "hub" area. On rear wheel anti lock systems there can be problems with the RWABS valve bypassing, but as I have stated in previous posts this was much more a Ford problem than GM or Dodge (which uses, unless they have changed in the last 5 years, Delco Moraine Brakes, Dodge becomes more like AMC every year). And of course ones driving habits and loads also play a role. I had one used to come in every 4-6 months, took a year and a half to find out they pulled a 20 foot trailer loaded with lawn and landscape gear and no trailer brakes, Gee I'm sorry no more warranty. And of course there is also the possibility that you have something in the front end badly worn that when stressed by the brakes results in a bad shake. Tie rod ends, severely worn idler arm or pitman arm, very bad upper ball joint, or upper control arm bushings. All of these would also cause weird wear patterns on the tires.

Whitelightning

Warped rotors and or hot spots on the rotors. Myself I never use hard pads because the rotors last a lot longer and it minimizes the chances of warpage and hot spots with softer pads and I can deaal with changing them a bit more often in exchange for long rotor life. My 89 burb and 79 J20 still have original rotors and they are in great shape too. When I get a new vehicle, I take off the factory pads and get rid of them after a few thousand miles.

Thanks for the reply

You need to pull the rotors and inspect them because the problem is there. Rotors can warp when they hot spot due to uneven temps in rotor and they will warp worse as the rotor heats up more. If you really want to fix this, you need new rotors (you can try and resurface them but sometimes it does not work out) and new pads and when you get new pads, do not get the best pad you can that last forever because they put extra heat on rotor surfaces. This will fix it, or you can keep looking for and fixing other problems that are not the cause of your shake/shimmy trouble

While I agree that the cause of the vibration is most likely warped rotors, after reading the OP's post I have to ask what is causing the warpage to reoccur so soon. The simple answer is that the rears are out of adjustment putting more load (heat) on the front brake parts. Unless you want to repeat this process yet again in the next six months, I would have the rear brakes checked.

Not likely because the front brakes should not be that fragile if properly setup. When I got my 89 4x4 burb new, I had a lot of problems with the front brakes pulling and chattering and calipers sticking on occasion. Everytime I drove it cross country, they would screw up. Final I got tired or dealer warranty repairs and switched to softer after market pads and never had another problem with them and I still have vehicle today and it has 175k miles on it with original rotors and brakes are smooth.