Brake caliper bolts

[Guest]

Hi, 1979 GS850GN.

When I picked up this bike, the brake calipers and brake pads were filled with grease and heavy dirt. The grease I think is from the bad fork seals which were pumping fork oil all over everything (I'm pretty sure). I've got new fork seals in and new brake pads on the way, but here's the question: Can you take those two bolts out that are on the caliper assembly itself? They are right next to each other on the caliper. Also, is it a problem that the rubber "things" that surround the bolts on the inside are falling apart? I'm just trying to get the inside of the calipers cleaned up. My first inclination is always to tear into something and then ask questions, but this time I'm going to ask first. There's nothing about it in the book I've got and I don't want to screw something up.

Thanks.

[earlfor]

Re: Brake caliper bolts

I assume you are referring to the two holts that hold the calipers to the hanger/mount. Yes, those can be removed without a problem.

Earl

Hi, 1979 GS850GN.

When I picked up this bike, the brake calipers and brake pads were filled with grease and heavy dirt. The grease I think is from the bad fork seals which were pumping fork oil all over everything (I'm pretty sure). I've got new fork seals in and new brake pads on the way, but here's the question: Can you take those two bolts out that are on the caliper assembly itself? They are right next to each other on the caliper. Also, is it a problem that the rubber "things" that surround the bolts on the inside are falling apart? I'm just trying to get the inside of the calipers cleaned up. My first inclination is always to tear into something and then ask questions, but this time I'm going to ask first. There's nothing about it in the book I've got and I don't want to screw something up.

Thanks.

[ptm]

Re: Brake caliper bolts

There are two sets of 'two bolts'. In addition to the two earl mentioned that hold the caliper to the fork, there are two that go right into the caliper. These allow the caliper to move.

Rather than have two pistons that each have a pad on them and squeeze the rotor, there is only one piston in the caliper. When you put on the brake the piston moves out and pushes its pad against the rotor. That pulls the rest of the caliper toward the piston (it slides on those bolts) which pushes the other pad against the rotor. That other pad is bolted directly to the caliper. I believe it's called a 'floating caliper'.

The bolts that the caliper slide on have a synthetic grease on them. The small rubber boots you see on the inside covering the bolts keeps the grease in and dirt out. If they deteriorate then the caliper doesn't slide properly and you get much less braking power, uneven pad wear, only one side of the rotor gets hot, and it's generally 'not a good thing'.

I would get a rebuild kit and replacement boots for the bolts (they're amazingly expensive for their size) and go through the whole thing. You don't want to skimp on your brakes.

[earlfor]

Re: Brake caliper bolts

Ahhh, I didnt realize a 79 850 would have the slider type calipers. I've only seen those on later models.

Earl

[quote="ptm"]There are two sets of 'two bolts'. In addition to the two earl mentioned that hold the caliper to the fork, there are two that go right into the caliper. These allow the caliper to move.

[mark]

Thanks

Thanks for the good info. Looking forward to spending more money than I wanted to also.

[first timer]

don't forget to take your discs off a and clean and soak them good in some MEK (methel-ethel-keytone) it is nasty stuff, so do it outside. this wil strip off any oil on the disk so you don't ruin your new pads.

-ryan

[KEITH KRAUSE]

Loosen the caliper bolts before removing the calipers. The bolts can be tight. I believe the correct torque for them is about 25 ft/lb. You'll find two o-rings on each caliper bolt too. Hopefully, the chromed caliper bolts will still have decent chrome.

[Wingnut]

Also, if your caliper slides and retaining bolts are like mine, the slide has a flanged head, and that flange has a flat spot on it to keep it from rotating while loosening or tightening the bolt. While reassembling make sure the flat spot on the flange lines up with the shoulder on the caliper, otherwise the slide pin ends up crooked and the brakes won't release.

[tfb]

Another thing to consider: the bolts that the calipers slide on are very hard, and don't wear much at all. However, the same cannot be said for the cast aluminium brackets which 'house' the sliding bolts: they wear significantly, and over the years your calipers start to skew to one side as things wear.

So, you may well need to get the caliper brackets re-bushed at a machine shop, or something like that. I had this done to the calipers on my Kat1100, and brake function was sooooooo much better after that.

Mike.

[mark]

Update

Thanks again for the help. I'm waiting for a couple of new dust boots now (geez those things are expensive) and some more time to play around.