How to: Overhaul Tokico six-pot callipers

[TLR Junkie]

Hello everyone!

I haven't posted for a while, but here's a guide I wrote for another forum which people on here may find useful. I hope this is the right section; getting your brakes working properly is a performance enhancement of sorts anyway...



First of all, a disclaimer. Brakes are a critical component of your bike and your safety depends on them working as they should. If you are in any doubt as to your ability to carry out the overhaul procedure, then get someone who knows what they're doing to help you, or pay someone to do it for you.

This guide is not intended to replace a proper workshop manual; it's meant to complement it and is aimed at demonstrating what is involved to someone who hasn't done it before.

There are various approaches you can take; mine involves removing the front wheel. Although you don't *have* to do this, there are reasons for it. This technique means you can take several steps that make life easier once the callipers are off the bike.









And so it begins....



Get your bike on an Abba stand or equivalent. A paddock stand is no good because the front wheel needs to come out.



Remove the front road wheel.


This is one of those jobs where preparation is key. You can make life much easier for yourself by doing a few jobs whilst the callipers are still on the bike. Crack these four nuts with a breaker arm and hex bit. DO NOT undo them; just loosen them enough so that they 'crack' so you know they will come undone when the calliper is off the bike.



This is the tool you want for the job



But make sure you support the calliper as you do it. You don't want to put undue strain on the fork calliper mounts.



Remove these two bolts so that you can remove the pad retaining spring. This will give you access to the pad retaining pin.



Remove the pad retaining pin, which is secured by a single R clip on the outside end of the pad pin. I will be replacing this one. It's easier than cleaning it up, and they are prone to corroding and seizing in place.



Remove the pads from the callipers. This will expose the pistons; the 'pots' in six-pot callipers. Just remove the pads from one side for the time being. Put a piece of wood or a spanner between the pads on the other side. You'll see why in a minute.



If you plan to re-use the pads, lay them out in a sensible fashion so you can put the pads back in the same place they came out. The pads will be matched to the disc if they've been in there a while, so you will avoid un-necessary wear by putting them back where they came out.



Which of these pistons is going to present a problem when trying to remove them? There's an easy way to find out, and this is why the callipers are still on the bike




Pump the brake lever, and odds are that one piston will move. This is the 'most free' piston.



Hang a spanner between the pistons. You should really use something soft to avoid damaging the pistons, but this is all I had to hand and to be honest I've not damaged one yet to my knowledge.



Continue to pump the lever. You'll see that the free pistons move first, and then you'll probably hear any stuck pistons 'pop' as they're freed up by the hydraulic action of the brake lever. This is why you didn't undo the calliper halves joining bolts earlier. It's also why you haven't removed the pads on the other side yet. Having the pistons move out this far means the fluid would have dropped considerably in the master cylinder reservoir:





Push the pistons you've freed up back into the calliper body, and pop the pads back in. This means you can repeat the freeing up procedure for the other side.




Pads out from the other side



All pistons now free to move Out of 12 pistons, three of mine didn't want to move. Had I not freed them up in this manner, they would be almost impossible to remove with the calliper off the bike later on. Well, you can get them out, but it's very hard to do it without damaging them. They're bloody expensive and I'd prefer to avoid replacing them!




Put the pad retaining pins, R clip, retaining spring and bolts back in. No real reason other than it stops you losing tiny pieces.



Place a drain tray under the callipers. We're going to take them off the bike now, and they're still full of hydraulic fluid.



Undo the banjo bolt




And put it back in the calliper after removing the hose, so you don't lose the bits.




Repeat for the other side, and remove both the callipers from the bike.




Stopper the ends of the brake hoses to avoid contamination and excessive leakage of brake fluid. I've used a latex glove and a zip tie.

[TLR Junkie]

Preparation is key. Gather the parts you need for the overhaul. I'm replacing the seals (£40 per calliper), Pad retaining pins (£3 each), Brake pads (£24 per calliper) and copper washers (40p each).




Gather the tools you need.




Work on one calliper at a time to keep all the bits together.



Remove the spring retainer



Remove the pad retaining pin. Either clean it up, or discard and replace (much easier IMO)




Split the halves by undoing the four bolts which join the halves. This is very difficult to do unless you've already loosened them.



Drain as much remaining brake fluid as possible.




Remove the two 'o' rings. Take a look at the recesses in the halves - one is deeper than the other. The deeper recess is where the new 'o' ring goes when you come to re-assemble the calliper.



Use a rag to protect parts from damage by plier teeth




And twist out each of the three pots from the two halves. Had you not already freed up the pistons, I can assure you you'd almost certainly turn the air blue trying to get the things out.




Spot which part of the piston is exposed to the elements....




The thicker rubber ring on the fluid side of the piston is the fluid seal. It is this that keeps the brake fluid in the calliper.



The thinner one is the dust seal. This one is supposed to keep the elements away from the fluid seal and protect it from damage. However, it is not kept supple by brake fluid so they have a habit of drying out and perishing, causing corrosion and seizure issues.



You can see the corrosion and gunge behind the dust seal - yuck!



If they've been doing their job though, you should see considerably less corrosion behind the fluid seal (although there probably will be some if the dust seal is on the way out). This is one of those jobs where prevention is far better than cure. I'd say my callipers were on the cusp of going from 'could do with an overhaul' to 'really needs an overhaul really rather quickly'.



Six pot callipers have two different sizes of piston as you can see here.

[TLR Junkie]

Yuck They're rather mucky. Bear in mind this is still a low mileage bike, that until the last year or so barely saw rain. It did get used a lot in the crappy weather this year though. This is the price you pay for year round riding.



Clean up the halves as best you can with a tooth brush and an ALCOHOL based cleaner such as methylated spirit (the purple stuff I'm using). You MUST NOT use anything petroleum based such as paraffin. The water content will contaminate the brake fluid and the petroleum base will attack the new seals you're putting in, causing premature failure. The rubber may also swell, which will cause your brakes to bind.

You can see that most of the grime has fallen away, but there is some still there which is stuck fast. Scrape this off with a wooden or plastic scraper ideally, but if you need a bit more purchase use a flat blade precision screwdriver (which is also useful to hook the seals out in the first place). Just don't apply much force as the calliper bodies are precision machined and made of a soft material - they're easily damaged. You've been warned.




Much better After scraping the hard deposits, scrub with a toothbrush again to make sure it's all dislodged. Then, blast all the remaining 'bits' out of the calliper body with an aerosol based brake cleaner. Get it as clean inside as you possibly can. Getting the outside clean is a matter of aesthetics, but getting the inside clean is mechanically important



Lay out the cleaned parts to aid re-assembly.



The fluid seals (but not the dust seals) actually have a very slight taper to them. If you look carefully in this direction, you will be able to see the taper if you move the seal about. It's very slight, but it is there....




Lay out the new seals that are going in. Make sure you know which way up the fluid seals are, so you can put them in the right way round. Note also the different sizes - two different size pots remember



Fluid seals go in this way round. The wider part faces the dust seal. If you look carefully in the calliper half, you will see the fluid seal recess actually has a machined recess within it for the taper to sit.



Prepare a dip bath of clean brake fluid. You will dunk the new seals and pistons in this prior to re-assembly. The fluid will keep the seals supple and provide lubrication to aid re-assembly.




Install the fluid seals, dust seals and pistons making sure you put the fluid seals in the right way round. Push the pistons home, taking care to make sure they go in square. They'll need a fair bit of pressure to get them in past the seals. Once they in though, they'll push home quite easily.




Repeat for the other side. Don't forget the 'o' rings as well! (It's easily done!)



Apply some copper grease to the joining bolts



Bolt the halves back together. Finger tight on the joining bolts is enough - they don't need to be fluid tight yet.



Put in the other bits like banjos and bleed nipples.



And the pad retaining springs. Mainly this is so you don't lose the bits. No need to put the pads back in yet.




Remove the reservoir cover on the bike. On the TL-R access is easier if you remove the screen.



Re-install the front wheel. No need to torque the axle; hand tight is enough.



Re-install the callipers, and torque up the bolts. 39Nm for the mount bolts on the TL-R. Do them both evenly and in stages. I go 10Nm, 25Nm then final tightening of 39Nm.



Torque up the calliper halves joining bolts (it's easier now the calliper is back on the bike you see). Do them evenly; Uppermost, Lowermost, top middle and lower middle. Do them in stages; I go 10Nm, 15Nm, 21Nm final torque. Not 100% necessary, but good practice.



Re-install the banjo with new washers. 23Nm for the bolt IIRC (but check with the manual - all the torque settings given here are from memory). My callipers have one hose per calliper, but you may have a cross-over hose running over the mudguard. Each hose end should have one washer each side of it. Use new washers. It's a false economy to re-use them. When you tighten the banjo, keep the hose snug against the stopper on the calliper. The offside requires more care because the action of tightening the banjo will try to pull the hose away from the stopper on the calliper body.

[TLR Junkie]

Prepare the new pads for fitting. Take care not to get brake fluid or copper grease on the pad surfaces. You can grease the back of the pads to stop the pistons sticking to them, but I don't feel it's necessary on these EBC pads because of the perforated metal shim. I also tend to clean up the pistons in situ whenever I take the wheels out so I tend not to get a problem in this area anyway.



Slide them home from the rear of the calliper.



Grease the pad retaining pin to stop it seizing. They can and do seize in the calliper body which gets expensive if you can't get it out. Prevention is better than cure.



Secure with the R clip.



Top up the master cylinder with fresh fluid



And bleed the brakes. I use a vacuum bleeder to pull fluid through until I get enough air out the calliper so that I can use the traditional technique of spanners, brake levers and hoses.


Once your brakes are bled enough to work, torque up the front axle to 100Nm. Pump the forks a couple of times and tighten the offside pinch bolts to 23Nm.

Finish bleeding the brakes and you're done. Six pots are a pain to bleed though. Chances are the fluid will get rather aerated as part of the bleeding process, so you might find it helps to tie the brake lever back to the bar and leave it overnight.

[lowes_man]

HEY I SAY WE NEED A STICKY ON THIS.

Thanks TLR Junkie. Great review and instructions. Thanks for all of the pics......

[Octofinger]

Excellent writeup!
Can we get this a sticky somewhere?

A tip, if you have it, is to use the aid of compressed air to get the pistons out. Whatch out for them coming flying out if you're not careful though.

[TLR Junkie]

Glad it's useful

Compressed air is a good way of getting stubborn pistons out, but because I use the brake's own hydraulics to push them out, it's not something I've ever had to resort to If they're so seized that the brake's own lever can't move them, in all honesty the pistons aren't going to be any good once they're out anyway. In that case you might as well just split the halves, clamp the piston in a vice and twist the calliper off it. Then spend £££ (or $$$ if you prefer) on new pistons

What you can do is, rather than push them back into the calliper body after you've got them all moving and up against the spanner (as I did in the above pics), just top up the reservoir again with fluid and leave them sticking out.

If you leave the spanner in place and use another spanner on the other calliper, there's no reason you can't take them off the bike sticking right out the calliper body. They'll be easy to remove then.

[fresh meat]

excellent post, thanks for recording everything for the rest of us.

[evl tvn]

Very well written and recorded!

It's time to clean out those radiators, and probably change the coolant

[TLR Junkie]

They're on the list It's service time, hence the overhaul in the first place

My current job is correcting the previous owner's fiddlings on the forks. The left fork was 14mm proud of the top yoke and the right fork 14.5mm proud, which probably explains its willingness to turn one way instead of the other. Both are now 6.5mm as per the manual and boy does it turn better at slow speeds. I was doing figure-of-eights in the car park with no bother; first time on this bike.