Vitesse disc brake drag

[steveray]

Hi, I have a mk1 vitesse the front disc brakes appear to be dragging, the front wheels dont rotate freely, anyone have ideas on how to diagnise this and what the common faults, or adjustments could be. Also we have a long run tomorrow - whats the risks if we run with slightly dragging brakes??? Cheers Steve

[ferny]

Are you sure it's the brakes? It could be the wheel bearings - people often over tighten them. Take the wheel off, the cover cup and then turn the castle nut back onto the next slot. Put it back together and see if it's still dragging.

If they are actually dragging then it could be that the caliper piston isn't returning properly Possibly due to hard seals or pitting on the piston. Check those if the bearing thing makes no difference. It could also be that the flexible hoses are breaking down inside.


If they are dragging then it won't be long before you boil your brake fluid. It doesn't take much. 10 miles spirited driving boiled mine when I had a rear flexible hose at as a one-way valve which made one rear wheel drag slightly.

[Clive]

I would start by levering the pistons back into the calipers, see it it stops the drag. If so you may get away withe pushing the pistons in and out a few times to loosen it all up. A temp fix that often lasts longer than intended. In fact pumping the pistins out a long way (but not until they come out) can reveal crud behind the dust cover, careful cleaning would be a good idea.
If the pistons do not go back easily then the front brake hose may be the problem as Ferny mentioned, they can break down into "one way" valves.
Of course WB is also a possibility...

[Pete Lewis]

one other long shot  make sure there is some free play on the brake master cyl push rod,, lift the baulkhead boot and see that the rod just wiggles a bit or press pedal lightly with fingers  1/4" and feel the the play before it just touches the m/cyl piston  but the stiff pad/caliper/bearing adjustment is as said  the the most likley Peter

on another though does she have a servo fitted ??

[toomanyprojects]

Agree with Clive,

First thing to do is to take your pads out, and see how easily your pistons go back in.

It should not take a major effort to squeeze them all the way back in (but watch the fluid level in your Master cylinder when you do this). If it does you should probably rebuild your callipers with new seals and pistons.

[Hasbeen]

Why not do your testing the easy way?

Take a bleed nipple spanner with you, & go for a drive. When you feel the brakes  draging, stop, & crack the bleed nipples.

If you get a spurt of fluid, & the dragging has stopped, you know something, hose, master cylinder or distribution valve, is holding line pressure, preventing fluid return, & causing the problem.

If no spurt, & still draging, its your calipers. You can then start repairs from what you learn.  

If your hoses are much over 5 years old, I'd suspect them.

[steveray]

Thanks for all the advice, we had to wing it in the end and completed 300 miles to the Brighton Classic run and back event free - really pleased. Only at one point did the brakes smell hot when we got our foot down to 70 mph. I wonder if I worried too much, they are in contact with the discs the whole time and I cant remove the pads (guess I will have to bleed the system to remove) easily is this too tight and therefore should prompt the testing and cleaning as suggested, or is it a normal amount friction?

[Nick Moore]

Steve, the brake pads should be touching the disc, but not causing any drag until the pedal's pushed. If they're being pushed on you'll use more fuel, glaze the pads and risk cracking the disc.

A bit of motoring history - the first disc-braked Corvettes had 1mpg worse fuel economy than the previous, drum-braked model, as GM fitted small springs to hold the pads against the disc. Triumph were never so daft!