Transient steering wheel shimmy. Brake related but what?

[ktm525]

OK I have a weird problem going on with the LR4. About 6 months ago I got the front rotors replaced (through Rock Auto) as I had this same exact problem. I immediately thought the cause were cheap rotors and swapped them. Well the problem has returned and through careful analysis I am not so sure it is a rotor problem.

Here is what I am experiencing: When travelling at a high rate of speed (100 km/h) and I lightly apply the brakes I SOMETIMES get a very pronounce shaking through the steering wheel. Like back and forth and inch type of vibration, very noticeable. Here is the rub. If I apply the brakes even harder the vibration disappears. Also the vibration or more accurately the oscillation doesn't occur every time. It is not a heat issue as it seems to happen most times when the brakes are cool and the brakes are lightly being applied after a long time has elapsed since they were applied (like highway driving). The more the brakes are used and worked the symptoms tend to mostly disappear.

I am thinking the calipers are getting hung up on the pins? This would be strange as I was quite meticulous in cleaning and lubing the pins when I swapped the first set of rotors. Any other ideas I should be considering?

Thanks,
KTM

 

[AxelR]

Hi and welcome

Please make sure to use the search function as this has been talked about many times.
In my experience the problem comes from the hubs. There could be other reasons obviously but this happened to me on my former LR4 a few times until I went to a dealership employing knowledgeable mechanics.

 

[mbw]

Wheel Balance, Hubs, Suspension/Steering linkages

 

[AxelR]

Shaking due to improper wheel balance would occur at 100kmh but not when applying the brakes.

 

[ktm525]

Well the missing part is the hydro busings on my LCAs puked their guts not too long ago which means a replacement is due soon. Pehaps the worn bushing is screwing with front end geometry under braking?

I'll check the pads/pins and grease. If it doesn't solve it then off to LCAS and hubs.