Discs dragging?

[Alex'n'Ane]

(Before you read, just to say this is a car with front discs and a servo) Whilst on quite a long drive (about an hour or so) i found that after the brake pedal not being depressed for a while, it would have a very long travel, if I then lifted off and re-applied the brake then the travel would be as normal. Again whilst driving around town (braking more often) the brake had a normal amount of travel. I didn't have to pump the pedal to get the travel to reduce, just one push down.
On a different note (or possibly the same one) when I got back I whipped off the wheel to have a look at the discs and pads, and found the wheel was warm to the touch. The hubs weren't that hot, as in I could still comfortably hold them to turn them, but again warm. The discs turned without too much resistance, but the pads were constantly in contact with the disc (I hear that due to disc not having a return spring this should be the case?)
Any advice on either case or if either is normal would be appreciated

[chrisryder]

i've only got drums and servo on mine, but i had a similar problem as your first one. the pedal going soft after prolonged lack of use. was fixed by replacing the master cylinder.

[Alex'n'Ane]

was fixed by replacing the master cylinder.

I dont like the sound of that :\ I fitted a brand new master cylinder just over a month ago..

[polo2k]

if you have a dial indicator, it could be worth checking the discs for runout, check your wheel bearings too. if there is any lateral movement then it can "knock" the pads back into the calipers.

I would be worried about the first long stroke.

[dp]

I know it's obvious but i'll say it anyway, is the fluid level creeping down?

[simmitc]

When the new master cylinder was fitted, was the "top-hat" seal removed. If not, then this would cause disc drag. The long stroke suggests either an air lock or, as said above, a faulty master cylinder - if it was stripped for the top-hat, was it reassembled correctly? A misplaced seal or washer could cause problems, as would dirt if the operation was not perfectly clean.

[Alex'n'Ane]

Points to polo2K on this one, the left hub was indeed loose, the outer race and rest of the bearing had seperated slightly, so even though the hub nut was nipped up there was still lateral movement. The issue appears to be fixed now and apparently the wheel getting slightly warm after a longish drive is usual? And since there is no brake burning smell i'd guess there not rubbing?

[beero]

Glad you sorted the first problem. Well done Polo2k.
Pads do touch the disc all the time and will be warm, so long as the wheels turn without any drag they are normal.

[polo2k]

My pleasure to help

[bmcecosse]

Long pedal is classic symptom of loose wheel bearings where discs involved. My wonder is - how has the problem been 'fixed'?

[Alex'n'Ane]

It was only the outerbearing, so by reseating and re greasing it, and tightening up the hub nut again.

[IslipMinor]

Alex'n'Ane,

When you fitted the new master cylinder, did you remove the 'residual pressure' valve at the bottom of the cylinder bore? It is required for the Minor drum brake set-up, but not for discs, so if it is still there, it will cause the pads to rub on the disc, and will create heat build-up.

The pads will be 'knocked back' if there is any significant free play in the hub bearings, which there should not be - they are angular contact and designed to run with pre-load, so no free play at all.

In summary, eliminate all bearing free play and make sure that there there is no residual pressure in the hydraulic system.

[simmitc]

Check what type of bearings have been fitted. For example, standard Minor bearings with drums should be done up tight against the spacer, but Marina bearings used on many disc kits most specifically should NOT be pre-loaded. To quote the manual:
Slacken the nut slightly, then whilst turning the wheel in the direction of forward rotation, tighten the nut to 5 lb ft.
Without moving the hub, slacken the nut and then do it up "finger tight" and NO MORE.
Without moving the hub or nut, fit the nut retainer in a position whereby one of the fingers half covers the hole in the axle for the split pin.
Slacken off the nut until the split pin can be fitted.
Check that the hub spins freely.
It is essential that the hub has free-play or serious failure may occur
At least the problem has already been solved.

[Alex'n'Ane]

I have removed the top hat seal and as i said earlier i dont think the discs are actually dragging, just the usual pads resting slightly on the discs. I did retighten the hub nut almost exactly as you described, except i tightened it up firmly initially in order to make sure the bearing was properly seated.

[IslipMinor]

Alex'n'Ane,

Good point about the type of bearings, I was describing the standard Minor type, which are the angular contact, and were retained for, among others, the Midget and Metro based disc brake conversions (as I have), but if you have a taper rollers, they usually run with a very small amount of free play, typically set up as Simmitc described.

What type of bearings do you have?

[Alex'n'Ane]

The marina roller ones, and they have been set up with 1/6th of a turns worth of free play.

[daveyl]

Good point about the type of bearings, I was describing the standard Minor type, which are the angular contact, and were retained for, among others, the Midget and Metro based disc brake conversions (as I have),

Wooah there!!! Are you saying that you have Midget disc brakes on your Minor? If so, how is that done?

[bmcecosse]

Spridget discs pretty much bolt straight on - using the Spridget hubs of course. Problem is - they are too small to be much good - doubtful if they are any better than 8" drums - and certainly not up to 9" drum standard!

[IslipMinor]

Spridget discs pretty much bolt straight on

Roy,

Really, how is that?

they are too small to be much good - doubtful if they are any better than 8" drums - and certainly not up to 9" drum standard!

Evidence please - bearing in mind I DO have a direct comparison between 8" drums and Midget based discs??? There is no comparison whatsoever - drums fade and discs, with the right pads, do not.

[bmcecosse]

As far as I know - the Spridget hubs fit straight on the Minor stub axles ? The standard Spridget discs however are barely adequate for a Spridget - been there, done that! Never mind a heavier Minor..... I believe however you have fitted Metro discs and larger calipers - obviously that's going to help considerably. I've never yet managed to get my 9" drums to fade, and I have tried.....but only on the highway, sadly not on the track.