Caliper overhaul on 91 Trident

[screene]

I've removed one of the front calipers from my Trident - the pads are stuck on both calipers. I've driven one of the pistons out by pumping it with the brake lever (I don't have a compressor), but I could do with some advice please...

How do I get the second piston out? I tried but failed to drive them out simultaneously.

Also, the caliper is badly scored (see pic). Does this mean I need a new caliper, or can I just replace the seals?

I've cleaned the piston with 1200 grade wet-and-dry with WD40. It's pretty clean, but there's a bit of pitting. Is this OK to reassemble?

[MotT3]

I had the same problem with the rear on my Speed triple..in fact that caliper looks exactly the same as the rear caliper just that the hose is connected to the lug protruding in the foreground of your pic.

I ended up mashing the piston and replacing both...Truimph do a service kit, both pistons and seals..cost about £40.00 but what used to be Sprint Manufacturing could probably do it a bit cheaper.

You could reinstall the clean piston and zip tie it in the reconnect the caliper and bleed the system thus allowing you to pump out the stuck piston..From what I can see the piston you have cleaned up looks ok but it is difficult to get a feel for the finish in a pic. You will need to pull out the rubber seals you see in the bores and clean the grooves out of any corrosion ( a hooked metal tooth pic does a grand job available in Boots) being carefull not to score them. Lube with brake fluid or Renolit Red Rubber grease before putting the piston back in.

The metal bracket the the brake caliper bolts to the forks with is connected to the caliper via a couple of slinding pins, the whole bracket will need to be pulled away from the caliper to allow you to clean off any corrosion and copper grease them back up because no only do thei piston push the pads onto the disk they also pull the caliper along those pins to pull the pads on to the disk from the opposing side.

If the pad retaining pins are a little worn on the inside of the allen head replace them as if they do stick they round out quite easily meaning a drill out job.

I've just removed my 4 pot calipers to upgrade to 6 pots.. the old set are in top condition if you need upgrade/replacements..I've also got speed triple disks to match..

Any way good luck

[screene]

Thanks for your advice.

The kit Sprint do is cheaper but consists only of seals (no piston). £17, seems a lot for 4 little pieces of rubber though!

Do you think I need to try to reduce the scoring eg with 1200 grade and wd40? I find it hard to imagine how it got like that in the first place, there are no corresponding marks on the piston. In fact the piston has little more than pinholes that show up as black dots, hard to see on the photograph.

I think I'll get the kit and give it a try.

[MotT3]

A mild rub down just to make sure the scoring dosen't catch on the piston would be wise..but it shouldn't affect the perfomance of the piston too much if when you've finished they move freely in the bores..after all it's the seals that actually contact with the pistons not the bores themselves. You are right £17.00 for a few bits of rubber seems a lot as we all know they are pence to produce...but that's bikes for ya !!??

Mole grips and a peice of leather was the advice given to me to help man handle the piston out..if you are carefull it might be worth a go before bleeding pumping etc but you will probably need a vice to put the caliper in to get the leverage you need but to honest I wouldn't hold your breath if you took this route.

I do agree it's mr & mrs ham fist to be able to score the bores like that ?????

[KitNYC]

I used pliers & some cut up pieces of old inner tube to pull my pistons out. It was quite a pin, but maybe slightly easier than hooking it back up to the MC & using brake fluid to push it out. The second time around, I had an extra set of brakes lying around & I just hooked up a line to a master cylinder & filled it with water to push the cylinders out. That was also a bit of a pain, but totally worth it with the 6-pots I was working on.

Anyway... I never actually got around to rebuilding my spare rear caliper, but I'm about 95% sure that the seals from a Honda CBR 600 F2 or F3 should work. That should be less than £10 for all 4 seals.

Cheers, HTH,
-Kit

[screene]

Guys thank you very much for your advice, I have a week off work so I'll have a go with the pliers tomorrow.

Mot please could you check your mail.

[trypcil]

Or ebay some six pot Tokico's, reconditioning the Oem ones at your leisure!

[ozzyfzr]

To extract pistons after removal of caliper from bike, I insert a piece of wood into the caliper (minus pads) sufficient width to enable piston to come part way out using an air compressor, once most of the way out I use an expanding bolt fixing (for use in concrete) that expands to grip the inner bore of the piston, a bit like an internal lathe chuck, then just pull lightly - hey presto!
never fails to remove them.
If I am doing 4 piston opposed type caliper I seperate the 2 halves and clamp down onto a 3mm sheet of rubber and do the same, one side using the banjo bolt fixing to blow air into and the other side using the bleed nipple hole.

Hope it helps
Regards
Ozzyfzr

[tubby885]

When my piston seized I discovered by chance that a bicycle handlebar stem can be used to free it.
What you need is a quill stem,it's like an "L" shape.
The stem diameter(that fits into the bicycles steerer tube) is 22.2mm,insert this into the the piston bore and tighten the stem's pinch bolt.It should grip enough for you to be able to rotate the piston.
The stems can be bought for about £10.Make sure you get the 22.2mm because there are different sizes.
When I released my pistons I threw them away and made a pair out of stainless steel.Hope this helps.

[Roden]

Hey Tubby, nice tip. I'm guessing you have access to a lathe and the necessary skill to use it?

I would definitely look at that if the need arises.

Cheers,

Roden