Brakes need a pump

[Freebird]

This has long been a bit of an issue with the Vitesse - not so the Spitfire.

The initial pedal travel is longer than I would like and a very swift pump brings it right up.

I don't think there is any air in their having bled it until I'm blue in the face, also the 1st application isn't spongy. I think the caliper pistons are returning too far - in fact you can see them do it from the drivers side if you stand next to the door with ya left foot on and off the brake. Now that the pistons and seals are new and freer to move, the effect is more pronounced.

I know you can buy non return valves to prevent this effect, but why should you need them with a standard (ish - vented discs) system?

[Nick Jones]

What size M/C?  0.7" (11/16) is standard I think, mine works ok with 5/8".  Mine has Aeroquip hoses though which definitely shortens pedal travel.

I think quite alot of extra movement can come from the rear - does having the handbrake on make any difference?

Not too much slack in wheel-bearings?  Calipers mounted perpendicular to discs (could be an issue if spaced unequally as part of vented conversion).

Nick

[rubberhead]

hi mate,i had the very same problem a couple of weeks ago,long pedal. I adjusted up the rear shoes  and all sorted.

[Freebird]

7183 wrote:

hi mate,i had the very same problem a couple of weeks ago,long pedal. I adjusted up the rear shoes  and all sorted.

Tried that mate - no difference.

[ferny]

Sounds like pad knock-out or as Nick says, rear drum not being completely round and moving the rear shoes. Do you get feedback through the pedal if you go slowly around a tight corner with your foot on the brake? That's when I knew it was time to replace my front bearings.  :B

[Freebird]

ferny wrote:

Sounds like pad knock-out or as Nick says, rear drum not being completely round and moving the rear shoes. Do you get feedback through the pedal if you go slowly around a tight corner with your foot on the brake? That's when I knew it was time to replace my front bearings.  :B

Mmm - the nearside rear drum does seem suspect, it doesn't sit flat against the hub - rocking noticably. Also the steel backing of the front shoe that side had been digging into the drum a bit. I couldn't see why, so ground the shoe down until I can get a new pair of drums. Think I need s trip to Wins this morning.

Wheel bearings are fine. I've aslo got Aeroquip hoses and it's a standard M/C.

Caliper spacing - need to check that.

Cheers

Glen.

[Nick Jones]

Funny shaped drums can definitely cause this problem - I have that T-shirt!  I also have a large selection of funny shaped drums and no truly rounds ones  :(

Been reviewing the situation this very afternoon in an attempt to produce an MoT-able handbrake......  :-/

Nick

[Pete Lewis]

if the drum  doesnt fit flush and rock then suspect the hub flange has been distorted by past removal bending the faces, make sure if you have upped the stud size that the splined shoulder is not protruding thro' the hub flange and the drum holes need enlarging to clear them.


always disconnect the handbrake when locking up the rear adjuster, reconnect to suit after locking, then back off the adjuster. dont do it with the wheels 'hanging'.

if this does push back after leaving overnight but is reasonable after a padal press then hub float has to be the main culprit.

worth a check on the wavy washer on the Mcyl recupleration valve .

Pete

[Freebird]

Got it pretty good now, very slight improvement on pump, but not much.

I fitted another drum, but that was the same - they were rocking on the edge of the hub location diameter where it had been bruised by ham fisted re-fitting at some point in the past. I took the studs out and carefully filed the high spots off it.

Still had a low pedal though, so I did the old trick of jamming the brake pedal down overnight with a length of timber - hey presto, near perfect pedal. Must have has some air in it after all. :-/

All ready and packed for Spa now. :) :) :)

[Qman]

Have you worked on the front calipers?
I once had a low pedel caused by the seals in the calipers twisting and pulling the pistons back as they twisted back to normal.
If this is the case you would have to remove the pads (1 side at a time) and work the pistons until they settle to a stable state.