Front brakes binding

[StuartWags]

bike had stood for ten years with a broken cct
I had the pistons out the calipers and clean out all the crap rebuilt and bled. did not remove seals .... binding.
Stripped removed seals, ultra sonic clean, clean crap out of seal groves, rebuilt ... binding .... did not replace seals

current status
stripped, ultrasonic clean again. including masters, replaced the seals...not refitted yet

not got much confidence in this working as I found nothing wrong.

So any ideas if they are still binding this time?

[KermitLeFrog]

Has to be the seals. They should be a little elastic and pull the pistons back a tad when the pressure is released.

Shouldn't bind with new seals....

[fabiostar]

ten year old rubber seals that havnt moved? they will be well past there best.

[Watty]

ten year old rubber seals that havnt moved? they will be well past there best.

They'll be like wood

[Wicky]

In the caliper's seal groove esp the dust seal one, corrosion like kettle scale / teeth tartar can build up which distorts the seal causing binding. Careful and thorough scraping is required like a visit the dental hygienist to remove this build-up and new rubbery seals are best fitted with a good smear of red rubber grease.

[popkat]

seals can wear to a tapered shape, if you remove them and put them back in the other way round from how they came out then it can cause binding or lots of travel on the lever, one way will push the pistons on, the other will pull them back.. It really isn't worth putting old seals back in. buy some new ones and not the cheapest you see, Powerhouse automotive is the best place to get good quality seals.

Other possible causes which I've seen before are master cylinder seals and/or corrosion of the master cylinder.. In rare cases the brake lines can break up inside and a flap forms, this can act like a one way valve and cause the brakes to bind.

To be sure of tip top brakes especially after such a long lay up I would replace all seals and brake lines.


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[popkat]

new rubbery seals are best fitted with a good smear of red rubber grease.

Yes smear red rubber grease on the new seals but before putting the pistons in wipe off the excess grease, you don't want it contaminating the brake fluid, think of the rubber grease as a corrosion barrier in the seal grooves.. dip the pistons in fresh brake fluid then put them squarely back in to the caliper.


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[StuartWags]

many thanks for the input. It would be nice to get them feeling crisp and sharp.

[StuartWags]

think it is sorted - MOT tomorrow .... will post some pic over the weekend