[urq] UrQ steering shaking at speed: me too.

[Martin Pajak]

>Brake pedal does not pulsate at all. New front Boge struts, “green” >front strut mounts and front wheel bearings. Tie-rods and ball joint >looks OK, as well the A-arm bushings (very stiff). Discs were cleaned >and the mounting surfaces + the hubs were sandblasted as well when I >did the bearings.  Pads are VW-Audi brand.

my front end is as tight as.... you know what.
Tires are fairly new and perfectly balanced (did it myself to be sure).

>Q1: could it be the main drive-shaft, with a bad CV or U-joint ?  When applying brake, front tires compress, rolling diameter is less than rear, torque is induced in the DS and vibration occurs ?

Thought of that, but no.

>Q2: If it’s the rotors, then why no vibrating brake pedal? Because our cars are hydraulically-assisted, and this device “absorbs” more than a vaccum assist ?

Nope, because of the nature of warp.  If the rotor is same thickness all around but just not true the caliper will take up the movement and translate it into the strut.
If the rotor has a thickness warp i.e. one side thicker than other this is when you will get a pedal pulsation as caliper piston moves in and out to follow the changing thickness.

I have a bent hub on mine, took me 10 tries of machining the rotors (once on a CNC machine) just to find a bent hub.
The vibration would be there very slightly at about 90-110km (felt like tires) but would be amplifies with application of brakes.
When rotors were machined there would be a hint, as time went by the problem would be worse and worse to a point of trying to rip the steering out of my hand when applying brakes over 80km/h.

Hope this helps someone.

Cheers
Martin Pajak
http://www.quattro.ca