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Discussion Starter #1
Hi,

so I'm just starting my 4 year service, and decided to follow the book on replacing the Calliper Piston seals.

I managed to get a replacement LH calliper off ebay for £30 to replace mine which has almost zero thread in the lower mounting hole after a ham-fisted tyre changer did it up this summer.

I've had it apart and no pitting on the pistons, but I can barely see the seals back in the hole.

Anyone got tips for replacing these seals without splitting the calliper (bad idea)?

Rexx
 

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I use dental picks for seal removal. I just blunt the ends and curve them. Most good hardware stores have seal removal hooks, but they can run a bit large.

I put rags between the pistons so that they don't bang into each other and to restrict their travel and then push them out with shop air.

Only apply enough air to move them out of the bores so that you can wiggle them out the rest of the way by hand. Increase the air pressure slowly and expect the pistons to pop loose. Make sure that you do it over some rags in case they do pop free.:D Cleanliness and no nicking/scratching are your objectives.

I do not use anything except brake fluid for lubrication. Some people use brake grease. If you do, make certain it is specifically brake system grease, nothing else. Lube the pistons and seals before installation

Installation can be tricky due to the close tolerances. If they are not going in in a positive manner, stop and start over. You want to avoid any misalignment. You will know by the feel if you have it correctly aligned to the bore. I said they can be tricky, but once you get the feel for it, it will go quickly.

Well, after typing that, I see you already have the pistons out. I decided to leave the removal tips in for anyone else that has never done it.
 

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I can testify from personal experience that it is very easy to launch a piston, complete with remaining brake fliud (which goes everywhere), like a cork out of a bottle with an enormous BANG if you are not very careful with the air line method :eek: Understatement of the month OnD ! And I'm still mentally scarred by the whole affair, even though it was many years ago. In fact, I think the ringing is still in my ears.
 

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I can understand that. I took a wobble plate hydraulic pump apart over 40 years ago and can still remember the sensation of springs flying past my head at high velocities. To this day, I am scared of disassembling anything with a spring in it, and will usually try to rig something up to restrain it as a precaution.

I heeded your advice and added some more words of caution. Usually I err on the side of being too cautious in my advice, but this time I was careless. Thanks for catching it.
 

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Discussion Starter #5
Not so much a bang, as a whimper

Thanks for the advice so far. I don't have 'shop air'. Nor do I have 'free air' - sorry OnD couldn't resist. I sealed a foot pump to the calliper, and they come out gently.

Okay, so a curved, blunted tooth pick will remove the old seals. Thanks. I'll do that.

How do I get the new ones in, or do they slide down the bore and ease in with some fluid?

Rexx
 

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Might be a difference in our definitions. ;) A dental pick on this side of the pond is one of those devilish pokey things about 160mm long the dentist prods with as he tortures you, not a tooth pick. A tooth pick to us is a wooden pick about 40mm long. I buy my picks at local flea markets.

http://defensedevices.com/dental-pick-set-steel.html

The new seal will slide in easily so long as it and the bores are lubed with brake fluid. If you have been living right, the seal will slide in uniformly around the circumference. If only one segment of it starts into the groove, be careful and use gentle persuasion with finger pressure to work the rest of it in. Do not force it because the bore edges are sharp and could nick a seal. It is rare for that to happen if you use a modicum of care.
 

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I think it should be "teeth" picks because you pick between two teeth implying more than one tooth.

Next time you at the dentist getting tortured ask for some old picks and burrs. I get handfuls of them for free. They can only use them for so long due to dullness or sterilizing concerns but work great in the shop and the burrs in the wee mini grinder.

Rexx, they look like a nut pick. As in Walnuts.

Don

Might be a difference in our definitions. ;) A dental pick on this side of the pond is one of those devilish pokey things about 160mm long the dentist prods with as he tortures you, not a tooth pick. A tooth pick to us is a wooden pick about 40mm long. I buy my picks at local flea markets.

http://defensedevices.com/dental-pick-set-steel.html

The new seal will slide in easily so long as it and the bores are lubed with brake fluid. If you have been living right, the seal will slide in uniformly around the circumference. If only one segment of it starts into the groove, be careful and use gentle persuasion with finger pressure to work the rest of it in. Do not force it because the bore edges are sharp and could nick a seal. It is rare for that to happen if you use a modicum of care.
 

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Never though to ask the Dentist for those. Good idea. I think they forgot to heat treat the ones I get from the flea market.

Nut pick! That sounds sick. Only a Mod could get away with saying that. :p
 

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Discussion Starter #10
Interesting difference

Okay,

before you I place a can of wormss....

Click..... ping.... and it's open.

I bought a brake calliper off ebay that the seller said was from an 04 ST. I have an 04 ST. So far so good.

I strip down the eBay item to check the pistons (Didn't replace the seals yet, but do have the dentists torture kit you mention, not the wooden tooth pick :eek:). Still okay.

Now I strip down the dodgy one from my bike.... hold on, my pistons are pale gold in colour.... back to the eBay item.... they are silver.


Well? Why are they different? I wonder if this is something to do with the dreaded soggy brake issue so many have experienced?
It's almost as bad as starting an oil thread!


Rexx
 

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Are they pale gold all over ?

I have pulled brakes apart that have significantly discoloured or could they be the Daytona 675 teflon coated ones?
 

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Discussion Starter #12
Piston Colour

they are a nice pale gold all over!

I did wonder if they were putting teflon ones in the calliper, but I can't see why. Mine was bought in July 04 and so shouldn't have been too near the end of the run (when the parts bin can sometimes be raided - Like to make an RS!!!:D)

Sorry, that was a cruel and underhand remark, and to compensate I shall relinquish my ownership of one of your offspring!

Rexx
 

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My girl friends appreciate silver, but they really love gold. In fact, they told me, you can never go wrong with gold.
So, based on their expert opinion, I'd go with the gold. :D
 

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Discussion Starter #15
sage advice

I went with the gold. Both stoppers are now refurbished, and back on the bike. Easy to bleed too!

So I moved on to the back one. Easier to work on with the wheel off, and gives me a chance to clean those awkward nooks and crannies.

Noticed that the rear brake carrier rotates slightly. It appears to be stopped by a cheese head bolt into the swingarm, in a slot in the carrier, but that has been flattened over the years and the brake can now move by about 1mm.

Should it do this?

Rexx
 

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The cheese head bolt is the caliper carrier positioning stud. It is Triumph's method of allowing fore and aft movement of the caliper for chain adjustments. Play of 1 millimeter is not excessive.

You should also have a small amount of lateral play in the caliper mount also.

Good onya for taking care of the bike and noticing things like that.
 

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Discussion Starter #17
1mm free play

OnD,

my plate rotates by 1mm in the same plane as the wheel. The top and bottom side of the cheesehead have been flattened.

Hope you mean that freeplay is acceptable!

Now they've started throwing salt molases on the roads over here, I thought I'd do my own 30,000 (chassis)/ 6,000 (engine) service as a sort of winter project!

Discovered that once a hugger is fitted to the pre 05 ST, you can't take the chain guard/hugger combo off with the wheel still on!

Rexx
 

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IMO, it is acceptable. But, if you want to, you could remove the bolt and place a washer under it so that the head would be repositioned about 180 degrees from the original position. This would position the un-flattened portions of the head to take up the play in the carrier plate. If you do this, you will need to verify that you have sufficient clearance between the bolt and the rotor. It is pretty close at best.
 
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