Posted By : Chris Taylor, 14-Aug-2006,
09:49pm
A couple of revolutions seems quite normal to me, but I would not describe them as needing a firm push. But what is "firm?" It's not pushing with a
finger, but with a hand, but it should not be anything of a struggle. If you are worried that the pads might be binding in use, check the temperature
of the wheels (carefully!) with your hand after a longish run. Unless you have just braked to a stand from 80mph, you should be able to place your hand
on the wheel at its centre (leave any hubcap off).
If you have fitted new pads, they will take a little while to bed in and shape to the exact profile of your discs, so they may drag a little more.
Unless you are very lucky, you will usually find that the pads catch the discs slightly more firmly at certain points of rotation. As long as there is
no "wobble" from the brake pedal under hard braking and no visible "run out" on the disc this is quite normal.
If you have any reason to think your hub bearings may be binding, take the pads out, or at least fully retract them. The wheels should then spin VERY
freely. If not the bearings may be knackered, short of grease or the hub nut done up too tight.
Posted By : Mark Palmer, 14-Aug-2006,
10:05pm
The duration of spin will also depend on the force you apply!
The idea behind MOT inspectors' wheelspin checks is to determine if there is any forced or damped deceleration from the brakes or overtightening of the
wheel bearings. It will be obvious if there is any - the wheel will obviously slow down quicker if the brakes or bearing are binding/rubbing. Hearing
your brakes rubbing against the disc/drum, immediately after braking, does not necessarily mean there's cause for concern, although you should check -
often after braking your pistons will take a moment or two to retract back into the calipers. Get a friend to apply the brakes as you apply a constant
forward rotational force on the tyre. Once they let go, the tyre should spin freely, with minimal or no rubbing. If the tyre decelerates quickly,
without hearing the brakes rub, you might need to check or overtightened, dry, or worn bearings!
-
Posted By : Graham Bostock, 15-Aug-2006,
01:24pm
Remember that there are no springs pulling the pads away from the discs so they will always be in light contact and this is probably what you can
hear. Two revolutions sound pretty good to me. When I had binding brakes on a modern car, the wheel became too hot to touch after a run and if you
tried to spin the wheel even a hefty push only resulted in a quarter of a turn at the most.
Graham