Guys, someone have some kind of wisdom for me here:

My brakes have been binding, so what I have done is the following:

1. Fitted new seals/dust seal to all caliper pistons.
2. Polished up the pistons, no scoring or blemishes, smooth
3. Bought new sliding pin recesses for the caliper mouting bracket
4. Cleaned out the recesses for the dust seal area
5. Cleaned out the sliding pin rubber mushrrom thing recess, as this was coroded and restricting the sliding of the caliper.
6. New pad fitted, an coppaslipped.
7. Brakes bled
8. discs not warped
9. New wheel bearings, wheel free with calipers removed.

OK. Fitted all back together after having wheel powder coated, and guess what, brake is bound again. I dont know what I can do here, cos it will fail an MOT like this. I did have difficulties actually fitting the piston in past the dust seal, but an airline can move the pistons in and out of their bores seemingly fine. The caliper bores were fine. Where do i go from here???

AAARRRGGGH!!


Ara

 

You say the brakes are binding. By how much?

Disc brakes do have quite a bit of drag. Best thing to do is find another bike with triple pistons and compare the drag.

 

Hi,
By drag, I mean unable to spin wheel by hand. I have dual pistons in mine the later ones had the three. Many thanks for the reply though.


Ara

 

If your bike is a later model, the linked brakes can cause the front to affect the back and visversa

 

It doesnt have the linked brakingsystem, it is the earlier L model. Twin piston caliper. Pretty simple system, but this seizing is really strange. As a last resort tonight, I will clean the hole that the cailper pin slips into on the mount bracket, and see if that cures it. Driving me mad, this.


Ara

 

You did fit the right pad, you weren’t given the wrong pad by mistake?

 

I'm having the same problem with the rear wheel on my Thunderace so I ordered a rear caliper rebuild kit for it.

While I was at the bike shop, I talked with my buddy who is the service manager and he told me to rebuild the rear brake master cylinder too. He said they have had several different brands and sizes of bikes with the same problem and it turned out to be the brake master cylinder was full of crud not allowing the fluid to return properly acting like a one way check valve. My parts are in I just need to pick them up and install them on Saturday so, I don't know for sure that it will cure the problem but I'm pretty confident that it will.

You didn't list that you rebuilt the brake master cylinder so I thought this info might help.

 

93kf... good call. not much left to consider. I would encourage Ara, to make shure there is no residual crud in his lines. Old tz 250 story... typical top end barf... but no one checkend the expansion chambers for frags... new parts, residual old problem!!!
new barf!!!!!!! I've got a 84 100f,w/ a"sticky" rear caliper... after rebuilding the rear, im going to check the rear master and line. Good stuff everbody!!!!!!! Thanks, I love learning. Clean and free, only smoke'n harleys!!!!!!!!! Ripp'n

 

Did you replace the guide pins? They get a wear groove, and the pads get hung up in the groove.

 

All of the above things mentioned are real brake issues but to be as severe as you're talking, it almost has to be something not allowing the return of the pistons. Severely stuck caliper pistons or something not allowing the master cylinder to return all of the way and capturing the fluid in the system. It's the latter that I would be most suspicious of. If the pedal is seized or not returning all of the way for any reason or a debris build-up in the master, on the backside of the piston, not allowing it a full return and opening the port to the reservoir to relieve all pressure, are the areas I'd be focusing on. Even without a kit, you can dismantle those parts and inspect them.

The rubber boot that's on the operating plunger rod can deteriorate and crack, allowing debris and corrosion to build up on the piston backside. I inspect those regularly and have replaced several fronts on the clutch master and front brake master. They are the same for either side so I keep a spare in my tool box and replace them as soon as I see a crack. Cheap from the dealer. A little cleanout with a silicone spray and silicone grease in the hole and on the inside of the boot is what I do. Silicone, not anything petroleum based. Petroleum based products will swell the rubber seals in a brake system. Hope that helps.