How to: Overhaul Tokico six-pot callipers

[abn]

You could detect a taper on the o-rings Nice write up, and kudos for taking the time do describe and photo each step.

[OldTLSDoug]

Well and duly stuck, TLR Junkie

[cyclecamper]

Somebody said there's better Hayabusa front brake pistons made of titanium that drop right in. Is that true? Same seals etc?

[TLR Junkie]

Originally Posted by abn

You could detect a taper on the o-rings Nice write up, and kudos for taking the time do describe and photo each step.

Yep. Look along the angle shown in the pic; if it helps, put a piece of paper behind the seal to give you a better view.

Turn it this way and that, and you will see a taper. It's very slight, but I promise you it is there!!

It probably won't be the end of the world if they go in the wrong way round (it really is very slight and the seals are very supple when new), but there's a secondary recess for the taper machined into the fluid seal's recess.

I'd imagine that if you put them in back to front, you'd have the wider part of the seal up against the narrowest part of the recess. The extra pressure will probably be enough to make that piston bind slightly. Would you notice? Possibly not, but it won't do the pad life any favours. I reckon it would expose the fluid seal recess to further corrosion as well, as you'd have a gap in the recess behind the seal.

I also think that if the seal's the wrong way round, problems will become apparent when you apply the brakes. It looks to me like the seal's designed to squash (and provide a better seal) when hydraulic pressure is applied. If it's back to front it will distort and not squash, possibly resulting in fluid leaks under hard braking.

This how-to seems to be quite useful to people; if I write any more I'll post them up

I've got one more I've written so far - a complete beginner's guide to removing wheels. Would that be useful to anyone?

Originally Posted by cyclecamper

Somebody said there's better Hayabusa front brake pistons made of titanium that drop right in. Is that true? Same seals etc?

I've not heard of this. There may well be some, but the only advantages I can see are:

* A very small weight saving. Might be worthwhile on a race bike (it'll reduce unsprung weight), but pointless on a road bike IMHO

* Less corrosion issues. This could have a benefit on a bike that's not regularly maintained; corrosion on the sides of the pistons can damage the seals through abrasive action and it would stop the pistons sticking to the backs of the pads. Copper grease does that though, and it's a lot cheaper

* Bragging rights down the pub and a lighter wallet

[bentlr666]

Damn man... that is thorough

Nice job

[Octofinger]

Originally Posted by TLR Junkie

* Bragging rights down the pub and a lighter wallet

Those are all the reasons I need.

[TLR Junkie]

Originally Posted by evl tvn

Very well written and recorded!

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

I'm not a betting man, but if the soon-to-be-Mrs-TLR Junkie were to see the bathroom at the moment (fortunately, she's not here at the moment ho ho ho), I think I'd get slaughtered...



Squeaky clean inside (as you'd expect on an 11,000 mile bike), but ye gods there was a lot of filth in between the fins. Lots of dead flies as well. Horrible job.

I think I got to the bottom of a mis-fire as well today; the front plug had a damaged electrode and the rear one wasn't tightened down properly (not me, m'lud. T'was the previous owner. I've only started getting to grips with this bike fairly recently). I've also reset the front forks from:

Fork height: Left 14.0mm, Right 14.5mm (!)
Preload: Left 8th line, Right 8th line
Rebound: Left 5 clicks out, Right 5 clicks out
Compression: Left 4 clicks out, Right 4 clicks out


to:

Fork height: Left 6.5mm, Right 6.5mm
Preload: Left 6th line, Right 6th line
Rebound: Left 9 clicks out, Right 9 clicks out
Compression: Left 9 clicks out, Right 9 clicks out

(i.e. the Suzuki recommended settings for soft road use and solo riding)



First impressions are it feels like a bike, at least sitting on it and riding round the car park. Looking forward to the first proper road test.

[Loki-TLR]

That's one well written article, great job!

A few weeks back I've been looking for the problem of bleeding the 6-pots. On these photo's everyone can see how weird the rubber rings between the cast bits are sitting..

I'm fairly sure that's where the air gets stuck! Would try it myself but I'm short of banjo bolts

And I wonder if tying the lever over night won't reduce lever movement, that could make it feel like it's firmer. And/or rubber that is reshaped, possibly not retracting the pistons fully, draging?

[TLR Junkie]

Originally Posted by Loki-TLR

That's one well written article, great job!

A few weeks back I've been looking for the problem of bleeding the 6-pots. On these photo's everyone can see how weird the rubber rings between the cast bits are sitting..

I'm fairly sure that's where the air gets stuck! Would try it myself but I'm short of banjo bolts

And I wonder if tying the lever over night won't reduce lever movement, that could make it feel like it's firmer. And/or rubber that is reshaped, possibly not retracting the pistons fully, draging?

My feeling is that if you're filling the callipers from empty, the fluid sloshes around so much (because of the large internal volume of the six pots) that it's very difficult to avoid the fluid becoming aerated.

Here's my interpretation of why tying the lever back works.



1 - The fluid is aerated. The bubbles are so tiny that they just sit in suspension. There's so many it'd take forever and a day to bleed the fluid through to get them all out.

2 - Tying the lever back puts the fluid under pressure and somehow encourages the small bubbles in suspension to co-alesce overnight. They find the highest point (inside the lever mechanism), so in the morning you have one big airbubble in the system instead of thousands of the buggers sitting in suspension. I can't tell you a mechanism for why this works, but this seems to be what's happening.

3 - Release the lever and the air bubble is free to rise further into the reservoir and on to freedom The fluid level drops visibly. Top up and you're done





I think this is what's going on, because this method always works better when you have two hoses going direct to the m/c. It never seems to work as well when you have a crossover hose over the mudguard (which makes sense - air in the left calliper cannot rise higher than the highest point of the crossover cable. I've always had to still bleed the left calliper afterwards.

Also, I would hope (immediately after a rebuild with new seals) that the pistons aren't dragging!!

[Octofinger]

I think one reason that the tied up lever works is that the pressure in the system compresses the bubbles as well, making them smaller. The smaller bubbles can easier rise, because they have less surface that can stick to other parts, and the smaller bubbles can pass passages easier.
Leave it during the night and they will probably join into bigger bubbles higher in the system as you describe. But I don't think the pressure itself makes the joining to bigger bubbles easier though.