Steering shimmy/shudder

[flathead6]

I've tried searching for my problem on the forum but couldn't find it exactly and got lead off onto many other interesting tangents. But anyway, here's the situation:



When braking hard, or when loaded and braking kinda hard (4K-8Klb trailer), the steering wheel will shudder or shake. I don't feel it in the brake pedal at all. The tires were recently (couple thousand miles ago) rotated and front end aligned. The rubber brake hoses were replaced several years ago.

Jacked up I can't detect any looseness in the tie rods or wheel bearings. Its a '92 with a Borgeson and stock wheels and tires.



If it was the rotors I'd feel it in the pedal right?

Any ideas on where to look? I'm stuck



Thanks,

KRB

 

[AKimmel]

I would bet it's the rotors, that are warped. The hydraulics of the brake system will absorb some of the warpage, so you probably wouldn't feel it in the pedal. If you haven't found anything loose in the frontend, just have the rotors turned, its not very expensive.

 

[R C Cola]

Vibration

Agreed, and the next time you have to brake hard when loaded you most likely will have to do it again.

 

[Reb.B]

if its a side by side shimmy then its rotors, if its a up and down shimmy and you have 4wd, then change or shim up the springs on top of the king pin

 

[TWorline]

I agree with everybody else on the rotors, also check the web thickness in between the 2 braking surfaces on the rotor. If the web is getting thin it will allow the braking surfaces to squeeze together at a weak point then flex back out, the only cure for that is new rotors.

 

[flathead6]

if its a side by side shimmy then its rotors, if its a up and down shimmy and you have 4wd, then change or shim up the springs on top of the king pin

Its 4wd but yes it is side to side, not up & down.



Looks like the concensus is rotors. I'll check them out. I was thinking that maybe when braking and the front end went down it changed the geometry enough to where something was "loose". And with no pedal sensation I wasn't thinking rotors necessarily. Guess I was making it more complicated than need be.



While they're off I guess I should think about an upgraded disc huh? Last time I just went with NAPA Premiums. Any suggestions on a better set of discs?