Servicing brake callipers - random questions

[jimster]

Hi chat,

The brake callipers on my front disc have seized. After much swearing, I managed to pivot the callipers up after giving the pads a good squeeze with a pair of water pump pliers to shove the pistons back in. However, some questions:

- I only have wet & dry sandpaper handy. Can I use that to clean glazing off the pads or do I really need emery paper?

- the pads are really jammed in place (I can't shift them even with pliers). Any tips to get them out? I'm scared of snapping something but will go at it with a chisel and hammer next.

- I'm hoping to avoid having to bleed the brakes but if I do need to, is this something I as an enthusiastic but limited knowledge person with a Haynes manual and a decent tool set can realistically figure out by myself?

- I don't have a low range torque wrench. Should I get one for this? Or will my "tighten until it feels tight but not too tight" technique work here?

Sorry for the noob questions but I've never done this before so am a bit nervous as I think the front brakes are apparently quite important for not crashing at high speed into things.
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Current: Yamaha Diversion XJ900
Previous: Yamaha Diversion 600cc, Piaggio Zip 50cc, Honda CG125-W, Siamoto Caddy 50cc moped

[Bhud]

The calipers need to be completely overhauled and cleaned, and the seals renewed. At the same time, the pads sound like they are in need of replacement.

Don't ride the bike, as they will get worse and worse when the brakes are applied.

With every project bike I've ever got my hands on, the brakes were a job that needed doing. I learned to do it through trial and error, and I have messed up a couple of calipers in my time, so watching videos and reading Hayes isn't the best way to do it. There are also serious safety considerations if you get this wrong.

The way to do this, ideally, is to get a bike mechanic over to you, to show you how to do the whole process step by step. You could buy brake fluid, seals sets, pads and pistons right now if you like, and then just watch him and ask him questions. He will probably use the master cylinder on the bike to pump out the old pistons first.

You can approach this however you like, but if the front brakes are seizing then there's nothing you can do with a bit of sandpaper to the pads that will change that. They are overdue servicing.

[Robby]

Bhud is probably correct. If the brakes are that seized externally, they will be as bad internally. You will have to bleed the brakes (really do a full fluid change) because the piston(s) need to come out so you can scrape out the corrosion behind the seals. You may get away with re-using the seals, or you may need new pistons and seals. Depends on how bad the pistons look.

This is one of those bike jobs that remains a pain in the arse. Car calipers manage to last for decades with minimal maintenance, and replacements are cheap. Bike calipers need a complete overhaul about once a decade, and parts are expensive.

[jimster]

Thanks both! Will gird my loins (so to speak) and give it a crack.

I'm pretty sure I can figure it out having looked at the Haynes manual - I have some experience with bicycle brake discs which use the same principle, and the bike will be MOTd before it goes back on the road anyway so they'll double check the brakes then.

Bleeding the brakes looks easy as well so I'll definitely do that too - the fluid is overdue a change.
____________________
Current: Yamaha Diversion XJ900
Previous: Yamaha Diversion 600cc, Piaggio Zip 50cc, Honda CG125-W, Siamoto Caddy 50cc moped

[MCN]

I think certain makes or certain models suffer more or less from sticking pads.
My Yamaha Thundercat was very prone to binding brakes.
Triumph Sprint never any problems.
The 2 BMW GS bikes never had any issue.
BMW S1000RR never any problems (Other than munching it's way through front pads.).
BMW K1300 bastirt front brakes (breaks ) bind religiously if not used regularly. The Rona nonsense has me away at work for months so it's a strip-down job when I come home. (Need to show the Mrs. how to do that.)

'Normally' the steel backing rusts, combined with pad dust and road shite caking between the free-spaces around the backing and pad guides of the callipers. That free-space is there to let the pads 'float' and not bind.
Removing the callipers and digging out the pads, gouging out the cake, using a small file or an old flat screwdriver restores things.
Assemble, preferably with new pads.
I smear some brake paste on the 'contact' surfaces of the backing to help the pads slide. A few puddles later that shit gets displaced though.
Never had to open a callipers yet. Just cleaned out the hard kak.
A scoot of brake cleaner down their gullet when the bike is washed helps to wash out shite build up too.
Brake dust is corrosive and also tends to cake if not blown/washed out.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[bikenut]

Don't forget the master cylinder and the importance of that tiny tiny tiny hole ( the larger one also ) in the m/cylinder floor. It may be covered by a shiny tin shield or at the bottom of a countersunk hole.

Most brake fluid is good paint strimmer.

Red rubber grease comes with wemoto brake piston/seal kits but is available seperately
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nuts about bikes

[bikenut]

You do not say but what bike is it ?

You say calipers so twin front disc, disc for rear brakes as well ?

How many pistons per caliper ?

I assume you have protective bits of wood, g clamps etc..

Post some pictures of the caliper and master cylinder...

It's wise to get info as to parts availability before you touch anything

Also get some plastic clear or the blue aquarium air pipe, penetrant, a drill that will fit in the brake bleeder nipple fluid hole ( they may be double diameter, say 3 mm at the top and 2mm deeper down ) to make sure they are clear all the way down as far as is possible.

Place short length of pipe on nipple and fill with penetrant and leave for as long as possible, time for the penetrant to do its job. This method can only help.

Post some pictures.

DO NOT shear/break the bleed nipples !!!!!

Pictures.....I hope this job goes swimmingly but has the potential to go horribly wrong, give your self lots of time and go very easy....particularly since this is your first time !
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nuts about bikes

[jimster]

Thanks bikenut & all,

It's a 97 Yamaha Diversion 900 with about 65k miles (!) on the clock, twin front discs, each side having two pistons & single rear (which I think is OK, at least it's not binding).

Will post pictures later but am about to head off to wemoto to click-and-collect (it's handy that I'm in Brighton right now!)
____________________
Current: Yamaha Diversion XJ900
Previous: Yamaha Diversion 600cc, Piaggio Zip 50cc, Honda CG125-W, Siamoto Caddy 50cc moped

[jimster]

Photos & videos of the callipers below.

For the refurb, I have new brake pads, seals, red rubber grease, dot 4 fluid, a PVC pipe (£4 from a pet shop after some searching!) and all the tools (apart from a torque wrench which I might go pick up tomorrow).

Video: https://www.youtube.com/watch?v=xfdQFU8I0Bc

Photos

https://i.postimg.cc/Fd9vwRsC/IMG-20210817-154222351.jpg

https://i.postimg.cc/3kXfDZYV/IMG-20210817-202722177.jpg

https://i.postimg.cc/21RX6tRn/IMG-20210817-202726913.jpg[/img]
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Current: Yamaha Diversion XJ900
Previous: Yamaha Diversion 600cc, Piaggio Zip 50cc, Honda CG125-W, Siamoto Caddy 50cc moped

[MCN]

[jimster]

[jimster]

A few more pictures (including a couple of random ones under the bike) and yes I did notice the cob webs

https://i.postimg.cc/MMDrw8mK/IMG-20210818-170149109.jpg

https://i.postimg.cc/T5Kjs8ks/IMG-20210818-170157810-HDR.jpg

https://i.postimg.cc/9RFYGwyC/IMG-20210818-170159650-HDR.jpg

https://i.postimg.cc/8FbbJmJZ/IMG-20210818-170208084-HDR.jpg

https://i.postimg.cc/PNJMJZtM/IMG-20210818-170257727-HDR.jpg
____________________
Current: Yamaha Diversion XJ900
Previous: Yamaha Diversion 600cc, Piaggio Zip 50cc, Honda CG125-W, Siamoto Caddy 50cc moped

[Fizzer Thou]

I would be stripping those calipers to their basic components and thoroughly cleaning every nook and cranny of the associated parts.It is worth doing correctly and you will notice the difference if the master cylinder is also cleaned.It would also be an ideal time to replace the brake hoses with lines from the likes of HEL or Goodrich for example
https://www.helperformance.com/motorcycle
https://www.goodridge.co.uk/collections/motorcycle

https://i.postimg.cc/43QqrGGH/20200603-120409.jpg
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Just talk bikes.What else is there?

Always have a 'Plan B'

[Kris]

[jimster]

Thanks Kris & Fizzer Thou,

Thanks for the feedback and the links also very helpful. I have all the bits for the callipers (hopefully) but it will take a couple of weeks to get the hose lines ordered and I'd like to get the bike through it's MOT next week.

I assume I can fully rebuild the callipers, repace the pads & bleed the brakes for the MOT, and then do the cylinder & hose at a later stage?

Thanks - really appreciate all the helpful feedback and support - am really enjoying figuring all this stuff out, it's like Lego for adults
____________________
Current: Yamaha Diversion XJ900
Previous: Yamaha Diversion 600cc, Piaggio Zip 50cc, Honda CG125-W, Siamoto Caddy 50cc moped

[Fizzer Thou]

[jimster]

So the job is underway. Photos attached.

I ran into a really annoying problem; without an airline I planned to pump the pistons out with the brake lever once the calipers were loose. Unfortunately, the lever lost pressure after a single pump. So I used a grease gun to pump out the pistons - which worked well on one piston but unfortunately, not the second! So now I need to get a stronger g-clamp to jam the free piston in place and then give it some muscle to loosen the other one. I've also sprayed a lot of brake cleaner on it and gently tapped the piston with a hammer.

Getting the grease out of the caliper will I'm sure be a lot of fun...

PS The calipers, pads and master brake cylinder don't seem as bad as I thought (even the brake fluid looks OK) but I'll still replace the pads, fluid & seals. The pistons however are VERY rusty so I have a nasty feeling will need to be replaced, although I'll try to clean them up as best I can once they're out...

I haven't started on the second caliper as I don't want to release the grease gun until both pistons are out on the first caliper.

https://i.postimg.cc/jDzWVskd/1629488823568.jpg https://i.postimg.cc/gwmxmffy/1629488831681.jpg https://i.postimg.cc/d76L15Yb/1629488834675.jpg https://i.postimg.cc/CBKdfbMz/1629488838875.jpg https://i.postimg.cc/S2tRLjjV/1629488843641.jpg

Rusty calipers being freed by a grease gun, with the loose one being held in not tightly enough by a plastic g-clamp

https://i.postimg.cc/75VxMbW7/1629489333851.jpghttps://i.postimg.cc/CZxwvY32/1629489335711.jpg
____________________
Current: Yamaha Diversion XJ900
Previous: Yamaha Diversion 600cc, Piaggio Zip 50cc, Honda CG125-W, Siamoto Caddy 50cc moped

[Bhud]

The brake master cylinder will always work to pump out the pistons (just keep topping up the reservoir and pumping away, with the G-clamp over one piston then the other), but as you've found another way, it doesn't matter. You're on the right track and the G-clamp alternately placed over one and then the other is the right way to do it.

I'm less and less a fan of Wemoto these days, but they do stock cheap replacement pistons under their own brand "TRK". Just to let you know, in case you decide to replace those pistons. The originals on these old bikes are usually very badly pitted.

The sliding pins will need cleaning up, and the rubber boots that go over them are simply unobtainable, so be careful to not damage them. Anyway you're halfway there now.

[jimster]

Thanks Bhud! Do you have any recommendations for an alternative to Wemoto?

Since I still need to do the second caliper on the other side (and would prefer to avoid the horrific grease mess if possible) how would I solve the problem of the brake lever having zero pressure preventing me from driving the pistons out?

I did try bleeding the brake but because there was no pressure on the lever nothing happened when I cracked the bleed nipple, until I did it too lose and then it started dribbling.
____________________
Current: Yamaha Diversion XJ900
Previous: Yamaha Diversion 600cc, Piaggio Zip 50cc, Honda CG125-W, Siamoto Caddy 50cc moped

[jimster]

Success! At least partial. My g clamp wasn't strong enough so I just jammed some spanners between the piston that wasn't stuck and the edge of the caliper, and pumped the grease gun. This transferred all the force to the stuck caliper which immediately started moving. A small victory but a satisfying one.
____________________
Current: Yamaha Diversion XJ900
Previous: Yamaha Diversion 600cc, Piaggio Zip 50cc, Honda CG125-W, Siamoto Caddy 50cc moped

[Bhud]

[jimster]

Here are the pistons - do they look salvageable if I scrub with mild sandpaper and brake cleaner to get the rust off? Or are they totally fubarred?

https://i.postimg.cc/YGrTzT38/IMG-20210821-010645801.jpg https://i.postimg.cc/B8GrXjPr/IMG-20210821-010650218.jpg https://i.postimg.cc/n9cZMCgF/IMG-20210821-010918670.jpg
____________________
Current: Yamaha Diversion XJ900
Previous: Yamaha Diversion 600cc, Piaggio Zip 50cc, Honda CG125-W, Siamoto Caddy 50cc moped

[bikenut]

It's been wet all week here so the internet is more crap than usual.

How we say they are the best network is beyond me !

How they didn't manage to slit that guys throat in the advert, they must have had a direct link.

We at the moment and the internet is crap !

Spanners are for nuts and bolts, you have some old pads ?

Those pistons in the above pictures will be pitted and scrap.

Wemoto trk, expensive box ?

You have jumped the gun a but by not dealing with one caliper and one piston at a time.

Always "exercise" the piston by pumping it out as far as you dare, clean and lube then with g clamp and protective wood etc. Gently screw back in. Repeat until that piston Is free, then move onto the next, untill all pistons in that hydraulic system is free and will be easy to remove.

Do not open or disconnect hydraulics until all pistons are free in that system.

The pumping out, clean and lube ( brake fluid ) and screw back in via g clamp will help clear that tiny tiny tiny hole in the master cylinder floor, which you have now noticed ?

If that tiny hole is blocked, screwing the pistons back in general a g clamp will be very difficult.

Yes, brake jobs can be very messy !

Look at the caliper piston holes with seals out. Much "white crap" in the seal "slots" ?

The area between the hydraulic seal and dust seal, much white crap and pitting there ?

You can get small diameter rotory wire brushes for electric drills, and smaller ones for Dremel type drills, which are great for cleaning these areas.

When seal areas are de
crapped and the caliper outside clean including the bleed nipple hole and slide pin holes, the caliper can he finally cleaned with very soapy ( fairey liquid) water, well rinsed and dried, ready for painting and assembly.

Get everything clean and dried and painted etc. ready for reassembly, for one ( one ) caliper, then come back.

You where told at the begining to give yourself lots of time to do this job....

Ps m and p do brake stuff....

Do not wire brush the internal bore of the caliper below the hydraulic seal.
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nuts about bikes

[Fizzer Thou]

[moezop]

'm pretty sure I can figure it out having looked at the Haynes manual Roblox Guides get-mobdrovip.com