Brakes: Is she warped ??

[highbeem]

Hi Lads,

S60 t5 02.

Having a shudder through steering and brake pedal under braking.
Weird thing is only between 40-30mph.
Could this be warped discs??
I thought warped discs would shudder through all speeds.

Any help or explanation of the physics would be appreciated

HB

[RollingThunder]

This sounds more like wheel balancing to me - an out of balance wheel will usually cause vibration at narrow speed bands leaving everything reasonably smooth at other speeds. As you say, a warped disc would cause vibration under braking at all speeds.

Quick way to check (if this has only recently started to happen) is to look for a gluey residue on a wheel (assuming its an alloy) near any remaining weights - its highly possible that one has simply fallen off.

If you can't spot anything, the easy way to check for a warped disc is to chock the car, raise one wheel, use an axle stand for safety, remove the wheel and hold a sharpened pencil JUST off the disk - literally a paper thickness if you can. Rest/steady your hand on the caliper and have someone rotate the hub. You'll either feel the pencil touch the disc at the point of the warp, or else will see the gap get bigger in a hollow. Using someone else to rotate the hub eliminates any movement in your body caused by you rotating the hub.