Brake Squeal.

[Glyn.G]

Hi Folks,
So I finally got round to servicing the forks on my GT380, which included removing the rusted in fork plugs at the top. I stripped and cleaned all the old dirty grey oil and sludge out of the fork bottoms and any residue out of the stanchions then fitted new plastic piston rings and new oil seals then rebuilt the forks. I put 145cc of Silkolene Pro RSF 10 Racing Suspension Fluid in each leg then put the forks back in the bike. The difference in the feel of the suspension was instant as soon as I took the bike out for a ride with no more feeling like I was sat on a pogo-stick or space-hopper just nice and smooth.
Then the ear splitting squeal started as soon as I applied the front brake ( never did it before the rebuild ). I returned home stripped the calliper and put copper grease on the back of the pads but no difference, just pushing the bike and lightly applying the brake makes it sound like the proverbial pig. Has anyone else had this problem and somehow managed to solve it. I was thinking of trying a new set of pads as a shot in the dark.
Kind Regards,
Glyn.

[Alan H]

Make sure the pads are free and copper grease is between piston and pads, and pads and locating 'spring' which locates the pad.

Failing that, liberally squirt WD40 all over the disc.
That'll cure the squealing. The brakes may not work quite so well though............

Seriously, make sure the disc is clean - you can gently 'wipe' both sides with some fine emery/rubbing down paper to take any slight glaze off the disc faces. Just hold it against the disc and rotate the wheel a couple of turns, then t'other side.
If the new pads are shiny, they can benefit from the same treatment.

[Glyn.G]

Cheers Alan,
I will re-grease and run some fine emery over the disc. I've read somewhere on a previous thread something about re- bevelling the pads, my pads have no bevel on them they are completely flat. I'm presuming this is to reduce the area of pad in contact with the disc. Perhaps this may work?
Regards,
Glyn.

[Glyn.G]

Update; I found a set of new pads that I must of bought when starting the rebuild and these had been bevelled round the edges so I put them in and copper greased everything that Alan suggested and also ran some fine emery over the discs and to my dismay the brake squealed even worse.
I know the fixed pad is held in with a small screw in the back, but should the floating pad with the locating groove be a press fit in the caliper bracket or should it be free to move easily. I think the caliper bracket has been powder coated on mine so the pad is a very tight fit.
I was thinking of fitting some anti squeal shims behind the pads between the pad and the piston, has anyone tried this ?
Regards,
Glyn.

[Craig380]

The moving pad should be a smooth sliding fit in the hole in the caliper bracket, and definitely NOT tight, otherwise the pad will not retract properly when you release the brake. That's what's causing the squeal.

I would use fine wet & dry to remove some of the powder coat from all the way round the inner surface of the hole, and keep going until the pad will fit and slide easily through the hole. If you hold the bracket horizontal and level, the pad should drop through, the bracket should NOT grip the pad.

The little rubber-mounted metal tab that fits into the pad's cutout is there to 'tension' the pad and stop it rattling. Use a trace of copper grease around the inner face of the bracket hole to keep it free.

[Glyn.G]

Cheers Craig380,
I will strip the caliper again and make sure everything is moving freely.
Regards,
Glyn.

[Glyn.G]

Well I'm stumped, I have re-cleaned the caliper and copper greased everything that has been suggested, and everything is moving freely yet it still squeals like a proverbial pig. Surely upgrading the fork oil to a modern grade used on modern bikes can't be the problem can it.
The horrendous squeal seems to be resonating through the whole front end. If I put the bike on the stand and spin the wheel I can hear it squealing with the pads just touching the disc with no brake applied. It's getting to the point that I'm thinking of buying a replacement modern floating disc to see if that solves it. Perhaps the disc on the bike is too badly glazed, I've tried emery on it but no change.
Kind Regards,
Glyn.

[Zunspec4]

Have you tried applying brake really hard several times from a decent speed to get the new pads well and truly bedded in. Just a thought as you seem to have tried most other things.

Cheers Geoff

[Glyn.G]

Hi Geoff,
Yes I've tried that several times but no change, the brakes are actually working well it's just this annoying squeal. I have noticed that the new modern fork oil is a lot thinner in viscosity than the gunk I drained out so I was wondering if the oil I took out was actually acting as a sound dampener as well as stiffening up the suspension. I have had to put more of the thinner modern oil into each leg than stated in my manual (145cc ) to get the suspension working well.
Just as additional question does anyone know why it is only the 380M that has 145cc in each leg and how can you tell if you have the M type forks rather than the L,A, or B forks which according to my manual has 230cc per leg.
Regards,
Glyn.

[Craig380]

You may have already done this, Glyn, but try roughing up the friction face of the pads a little with a fine file (not emery or wet & dry, as that will leave bits of abrasive behind) then clean them thoroughly with brake cleaner

[Glyn.G]

Hi Craig380,
Already tried that, in fact tried everything that has been suggested. I've been looking at the e-bay ads for floating discs but they all state for L/H. Where are they looking from as the disc is on the right when sat on the bike.

[jabcb]

If you are willing to deal with the price of a new disc, the EBC VMD is worth considering. That’s what we used on the GT250 cafe project:
Cafe-GT250-0576 by jabcb, on Flickr

[Glyn.G]

Hi jabcb,
I like the look of your disc so I've looked on the EBC website but it seems they don't do the same one for the GT380. They do a different one though Part No MD3014RS at £175.00. Is the caliper on your photo standard for a GT250 or have you upgraded that too.
Regards,
Glyn.

[markush]

Hi!
It is also possible that the whole caliper will swing on the spindles if the bushings in the caliper holder are already a bit worn and dry.
I could get rid of the squeak by cleaning and re-greasing the spindles and bushings.

[Glyn.G]

Cheers Markush, I've already tried greasing the bushes I've even tried new O-rings on the spindles but no difference unfortunately but thanks for the input it's much appreciated.
Kind Regards,
Glyn.