Macgyver brake pad modification?

[rusty boltz]

I had my front wheel off to paint it and change the bearings. While it was apart I decided to pilfer the nice drilled rotors off of the parts bike. Man does it look sweet. Put it all together, installed it and gave it a spin to see how smooth new bearings sound. Klank klank klank ...... darn. It seems the webbing from the rotors hits the very bottom of the inboard pad on each side. The bike this is on is the 79 gs1000 with circle brake pads. The rotors came off my 78 that has nothing 78 on it.I'm assuming they are from an 80's bike like everything else on it. What I was thinking since it only rubs the very bottom maybe 1/4" of the pad I could just hack the lining off the pad with a cut off wheel (not through the plate though). There is no rotor to rub there anyway, right? Anybody dealt with this? I have the old calipers that match the rotors (uses square pads,floating caliper too), but absolutely seized only lightly describes them. I cant get the pistons out for the life of me! I would like to use what I already have (like Macgyver) instead of throwing more money at it. Please give me some options other than putting the old rotors back on.

[rusty boltz]

Ok I've come to my senses, I'm not going to cut the brake pad. I like the design of the floating caliper anyway. Does anyone have any pointers for getting really really stuck pistons out of a caliper. I've tried 120 psi of compressed air, grabbing the very edge with channel locks and pulling, cursing angrily at it while holding my fists up and nothing gets it to budge. I was able to compress one of them with a c clamp but now it won't come out. I've got them soaking in brake fluid right now. I really want to use the drilled rotor set up. Any ideas or secret remedies? Thanks

[hikermikem]

. Does anyone have any pointers for getting really really stuck pistons out of a caliper. I've tried 120 psi of compressed air, grabbing the very edge with channel locks and pulling, cursing angrily at it while holding my fists up and nothing gets it to budge. I was able to compress one of them with a c clamp but now it won't come out. I've got them soaking in brake fluid right now.

I would try soaking with PB blaster, then use th compressed air again. If that doesn't work perhaps putting them in the freezer overnight might "small 'em up" just enough to use the air again. I'v'e seen some folks on this forum talk about a "freeze spray" product (don't remember the name) that is available at auto parts stores. Maybe you could blast the piston woith that stuff to shrink it. No matter what you do, I hope your caplier bores are unscored.

Good luck.

[SPARKSS]

Ok I've come to my senses, I'm not going to cut the brake pad. I like the design of the floating caliper anyway. Does anyone have any pointers for getting really really stuck pistons out of a caliper. I've tried 120 psi of compressed air, grabbing the very edge with channel locks and pulling, cursing angrily at it while holding my fists up and nothing gets it to budge. I was able to compress one of them with a c clamp but now it won't come out. I've got them soaking in brake fluid right now. I really want to use the drilled rotor set up. Any ideas or secret remedies? Thanks

Good idea NOT to modify your brake components! Using compressed air can work but is something done with the full knowledge of the force with which that piston may come out (try the math on a 2" diameter just for a ballpark figure and you'll soon see that having a piston catch your fingers with 400lbs of force won't be the best part of your day).

Obviously air didn't budge it.......I'd try one of 2 hydraulic methods: One is to attach the caliper to a working brake line, caliper NOT installed OR not installed with brake pads (to allow movement to occur), bleed the air (as you would normally) and try to pump the piston out with brake fluid - done this many times. A second method, if the first doesn't work, is to remove the caliper from the brake line, fabricate a grease fitting to fit the line connection, caliper removed and/or with no pads (as before) and then pump the piston out using grease pressure - VERY effective. Both of the latter methods will move the piston in small increments predictabily (safely) as opposed to using expanding air pressure. Note that the hydraulic force (especially with the grease gun technique) will be many times that of the air pressure idea AND will insert lube alongside the piston as it tries to move it - of course a good degreasing and cleanup will be needed afterwards (as it will in any case).

NOTE: Use normal safety precautions.....safety glasses, gloves, etc and most important - your common sense.

REMEMBER: The caliper you're trying to take apart is no good as is, so you won't "ruin" it.....if it works you might have a salvaged item

For what it's worth.

[Nessism]

How about soaking in penetrating oil? It's not like you are going to reuse the rubber parts afterwards. Another trick is to use two large flat blade screwdrivers working at 180 degrees prying the piston up. If you can get the piston moving upward, the compressed air should get the piston out. Last trick is to use brake fluid pressure; hook up the master and pump fluid until the piston pops out.

Hope this helps.

[buttonhook]

I would try soaking with PB blaster, then use th compressed air again. If that doesn't work perhaps putting them in the freezer overnight might "small 'em up" just enough to use the air again. I'v'e seen some folks on this forum talk about a "freeze spray" product (don't remember the name) that is available at auto parts stores. Maybe you could blast the piston woith that stuff to shrink it. No matter what you do, I hope your caplier bores are unscored.

Good luck.

If your going to try cold then you can try dry ice (at least -100 degrees) you can get it a most food store(atleast around here).

[crnbndr]

Stuck caliper

I used a lever type grease gun attached to the bleeder screw.
I opened the bleeder about 2 turns and the grease gun end pushed over the bleeder just like a zerk fitting. Pump until the piston pops out. Then of couse you have the fun job of cleaning all the grease out of the caliper but it did work quite well!

[dardoonk]

Good idea NOT to modify your brake components! Using compressed air can work but is something done with the full knowledge of the force with which that piston may come out (try the math on a 2" diameter just for a ballpark figure and you'll soon see that having a piston catch your fingers with 400lbs of force won't be the best part of your day).
.

PB Blaster soak for a couple days & compressed air worked for me.......

BTW - Don't ask me how, but yes it felt like 400lbs when it hit my finger..

You can easily hang the whole caliper from one finger after the piston smashes between said finger and the caliper body then jams sideways between the bore & your finger...... My wife had to pry the piston free while the caliper hung from what I was sure nothing more than a bloody stump of a finger..

A lot of F-bombs got thrown around the garage that day

[rusty boltz]

Thanks for all the suggestions. I think I'll try hooking it up to a master cylinder after I get home from work. Does anyone know if the rear brake line uses the same fittings as the front? I guess I'll find out later. If that doesn't work I'll try the grease gun method, that sounds like it should work since grease doesn't compress somethings got to budge. Also I've been looking at rebuild kits online and they all look the same in the pictures. Are the pistons the same diameter for both styles? I don't know what year the calipers are from so how would I go about ordering the correct rebuild kit? How many different designs are there for the GS series? So far I've only seen 2 but I've only been into these bikes for less than a month. Thanks again.

[TheCafeKid]

Thanks for all the suggestions. I think I'll try hooking it up to a master cylinder after I get home from work. Does anyone know if the rear brake line uses the same fittings as the front? I guess I'll find out later. If that doesn't work I'll try the grease gun method, that sounds like it should work since grease doesn't compress somethings got to budge. Also I've been looking at rebuild kits online and they all look the same in the pictures. Are the pistons the same diameter for both styles? I don't know what year the calipers are from so how would I go about ordering the correct rebuild kit? How many different designs are there for the GS series? So far I've only seen 2 but I've only been into these bikes for less than a month. Thanks again.

Yes the fittings are all the same. actually i think it is a standard on most of the UJMs.

[psyguy]

the calipers model changed in 1980 for most models, so (theoretically) any post '80 rebuild set should be ok

[salty_monk]

Once I've switched over my 80 1000G to Kawasaki Twinpots I'll have a good set of calipers with pretty new pads in them up for sale.

Going to be a couple of weeks yet though...!

Dan

[rusty boltz]

Thanks again for all the suggestions and info! And thanks Salty_Monk but if this thing isn't on the road in a couple weeks I'm gonna go postal!! I never intended to do this much to the bike but you all know how it is. I have a tendency to quickly go from "just get it running" to "frame off restoration" with my projects. Luckily bikes are a heck of a lot cheaper than muscle cars and mud trucks! Good news is: I got the pistons out of the calipers. I decided to try Blaster and air one more time. This time I cranked the reg on my compressor well above safe limits and after soaking them all day hit them with the air. It took a few tries of blowing it out and compressing it in again before the first one popped. WOW did it pop! Good thing I had a wadded shop cloth between it or I think it could have blasted right through the other end of the caliper. The 2nd one wasn't any easier but it's out. NOW for the question: The pistons have a little pitting on the chrome plating, not much but some. What would be recommended to clean this up? Also I've never rebuilt aluminum calipers before, can I use fine emery cloth to clean it up in the bore? Can I hone aluminum? They are surprisingly not scored at all just mildly oxidized from sitting with the lines off. Don't know why they were so stuck.

[Nessism]

You don't need to do anything to the aluminum bore other than getting the ring groove clean. The bore never touches the piston so pitting doesn't matter.

Polish the piston with a fine scotchbrite pad. If there are any pitts in the metal, replace the piston or the caliper may leak.

Lastly, make sure you replace the brake line; it's sure to have scale on the inside. Stainless/teflon is the way to go.

[rusty boltz]

cleaned them up today. not too bad. used ultra fine emery cloth to polish the small rust spots. little pitting on the pistons but appears to be behind the travel of the piston through the square cut seal. I ordered the rebuild kit today. Any recommendations on paint for the calipers or has anyone had any success with polishing these? Thanks