brake caliper piston inserts??

[Greenbraes]

Hi guys
I am rebiulding a set of front calipers from a Kawa ZX900 (4 piston) to go on the new wheel on my GS1000. The pistons had 'caps' on them that I have had to remove/drill out so I could get the piston removal tool in. My Zephyr 1100 has small inserts that look to be for the same purpose which I think is to keep the piston from making contact with the pads. Now I can't find these items for sale anywhere but if someone can tell me what they are made of or something similar I could easily turn some on the lathe. They look to be made of some kind of heat resistent plastic, even bakalite. Any ideas?

cheers for any help, and hope you all have a great festive break

RB

[Agemax]

Hi RB, i have fitted a ZX9R caliper to my GS as well. i fitted an aftermarket wavey disc at the front which is slightly thicker than the GS disc and therefore the caliper would not fit on the disc as there was not enough travel on the pistons to give clearance and stop the brake from binding.
my solution was to remove some of the material that is inserted in the pistons to give the extra clearance.
i used a file to remove the material and all i can describe it as is a very hard wood, that is what it looked/felt like when filing and it shaved off almost like sawdust.
i have no idea what material it is actually made of.
if you want to replace yours i would suggest using delrin or acetal rod machined to fit the pistons

[Greenbraes]

thanks for the info agemax, I have managed to find what I'm looking for but it only comes when you buy new pistons....my pistons are good...doh! I have looked about for plastic that is heat resistant but the cost is high..bakalite or it's substitute would be good I think but again hard to find....might have to wait until I get back offshore and speak to the electrical guys and see if there is anything I can use from the high voltage switchgear

RB

[tatu]

I'm not clear on what you actually need but maybe some Tuffnel insulator?

[Agemax]

acetal will work fine, it has a very high heat resistance......

http://en.wikipedia.org/wiki/Polyoxymethylene

it is also quite cheap!

http://www.ebay.co.uk/itm/Acetal-White-Round-bar-rod-25mm-dia-x-250mm-long-/150652608728?pt=LH_DefaultDomain_3&hash=item23139860d8

[Greenbraes]

I think the temperature of a brake pad must get up to 300 maybe 400 deg C, there is stuff called Duratec 750 and comes in 25mm rods that looks to be good but it costs about £60 a foot..granted that would do for a while..and it is machinable....I will have to call the supplier for more details. I have found out these inserts are to stop heat transfer into the caliper and it would be best to have them. I think I will also call one of the companies that rebuild calipers and get some friendly advice
anyway cheers for the info

RB

[Agemax]

i cant see a brake pad reaching that kind of temperature, unless maybe under extreme race conditions, but i may be wrong

[Greenbraes]

I have to be honest I can't find out how hot they can get but if the disk gets hot enough to make water hiss when it rains on it then that is at least 100 deg C and I was thinking (not good for me..lol) that the pad must be some what hotter.....all just guess work...if the temp is lower than i think then it makes thing very much simpler
anyway cheers again....and have a go one when it comes

RB

Just found a bit on pads, orgainic pads are good up to 800 deg C and sinter pads are good for higher temperatures...if they only get to half the max temp then I'm looking for some kind of material that is good for 400 deg C

STOP PRESS...just spoke with a specialist brake builder, unless the bike is going racing the inserts are not required as long as the piston has enough length to reach the pads all is fine for road riding

[Agemax]

race spec carbon fiber pads run at upto 400c so a road bike will not get anywhere near that kind of temperature....quote..........

But for motorcycle racing applications it is possible to push technology even further with carbon motorcycle brake pads, but these only work properly at extremely high temperature (close 400 degrees celsius) making them no good for everyday road use.

[Maddevill]

Huh?

I don't understand why you had to drill out anything on the pistons to remove them. I just use an airchuck and compressor and blow them out.

[Greenbraes]

Happy New Year Guys

4 pistons per caliper, all seized in place and I needed to get the removal tool into the cavity to take hold, hence I had to drill out the fitted inserts. Even if they were free once one is out the pressure to push the others is lost, well maybe if they were moving free all would be well

RB

[Agemax]

have you sourced any insert material yet?

[chuck hahn]

Greebbraes ...what you do is put the brake pads in and blow the pistons out as far as they will go till they lock on the pads..then just pry the pads apart far enouigh to get them out. At this point, all the piatons are just a few MM from just falling out and a simple pull and twist with some pliers finishes the job.

[chuck hahn]

Post note...on most calipers you just need 1 pad to trap the pistons as i noted above.