[topladyj]

I have a 2000 Mitsubishi Galant my car has been shaking for a while. I took it to the shop got new tires, had them rebalance them twice to make sure, they said it's my brakes. I got all new brakes, and when I got on the highway to go home I ran into traffic and had to slow down. I pressed the brakes and my whole car shook. It seems worse when doing over 50. When over 50 it shakes a little but when I hit the brakes it's worse. I was wondering could a worn out motor mount cause this? When I first got the car I took it to the shop and they said my Transmission motor mount was going bad. It's not missing pieces but it is a little skwishy. (however you spell that) God please help me.

[TxGreaseMonkey]

If the car only shakes, when you brake, it's probably a lateral runout (LRO) problem. This is where the axis of the disc and the axis of the spindle are not at right-angles to one another. Frequently, this comes about by having discs turned to the lathe's axis, not the spindle's axis. This situation can be avoided by using a ProCut machine, which is available at Firestone Tire Centers, among other places. The ProCut machine machines the disc, while it's on the car--this prevents LRO.

I do not automatically turn discs--many people do. Basic understanding, and attention to detail, makes all the difference in the world with brakes. Be sure to change brake fluid every 2 to 3 years and have the caliper pins lubricated with silicone grease. Only use OEM, Wagner, Bendix or other premium pads. If the car came with ceramic pads, don't switch to semi-metallic--stay with what came on the car.

[topladyj]

I really don't know what that is, but I'm going to print this out and take it to Firstone or something. I was also thinking about taking it to sears for a free inspection. Do you think Sears would help? I wonder if they even check that part.

[topladyj]

I searched more on this I really appriciate your help. God your so smart. I really feel this is how it feels when happening. But does it just happen on it's own or is there typically a cause?

[TxGreaseMonkey]

With a LRO situation, every time you apply the brakes and the high point of the disc comes around, the car shakes. The pad and the disc are no longer parallel to one another--they are at an angle. Rust on the disc and hub can also cause LRO. I think you get the idea.

I would not go to Sears. How about Mitsubishi? Some Toyota dealers use the ProCut machine. Ask Mitsubishi if they do.

[TxGreaseMonkey]

Having discs turned on a lathe often causes the problem. They mean well--but they are mechanics, not engineers. Acceptable tolerances here are very small; i.e. +/- .003 inch.

[topladyj]

Awsome very awsome thank you! And BLESS YOU!

[topladyj]

Hey I wanted to ask you. Like I plan on getting this fixed, but in the mean time can it cause me to have an accident or something to break? I don' neglect my car just worried about driving it. You know.

[TxGreaseMonkey]

Since I'm not there, it's hard to assess the situation. If it is LRO, the situation will get worse with time. I would try not to drive it much, especially in stressful situations, until you can have it fixed.

You will likely be happiest, if you believe my diagnosis is correct, to get the brakes done at Mitsubishi. Have them install new Mitsubishi brake pads, new discs (rotors), clean and lubricate the caliper pins with silicone grease, and completely change the brake fluid.

[topladyj]

Part of it was my motor mount. I just got it replaced. However it still shakes a little and I'm sure it's the rotors. So next time I do a brake job I plan on just replacing them with new ones. Thanks so much!

[TxGreaseMonkey]

Thanks for the update. There's no need to automatically replace rotors--they should be inspected first. In fact, I've never needed to replace, or even have turned, rotors on any of my cars.