brake rotots for 1980' GS 550

[Guest]

Hey guys, first post. So glad to have found this place. First bike, first real wrenching project. I've done some searching so hopefully these questions are not of the annoying variety.

I just picked up an '80 GS with a whole host of issues. but today I'm asking specifically about the breaks. The front brakes seem to work well, but the rear brakes didn't have much stopping power and were squealing pretty badly at low speeds.

Here she is:


I took apart the rear caliper this past weekend and took some pictures. There's all this weird red goo on the backside of the pads. Based on the parts fiche, it looks like it's missing the pad shim. Also it appears that there are only piston boots but no seals. It looks like the red goo has fused with the piston boot.


This is what it's supposed to look like


When I pumped the rear brake, only one of the calipers moved. I'm not sure how it's supposed to work... but once it pushed out, I couldn't get it to retract back in... it's just stuck like this now. you can see here where one piston is worn down and is not coming out of the caliper as far as the other one. And the other one is currently stuck like that.


Anyway, I've ordered new pistons, boots, shims, and seals. I'm hoping I can rebuild this thing... what would cause one piston to not come out like that? Do I need whole new calipers?

Also, it looks like this crappy rear brake has done some serious damage to the rear rotor. Where can I find a good replacement? Are there any aftermarket rotors that are a good replacement for expensive OEM parts?

Thank you sirs (and madams)

[eil]

Nice looking bike ya got there! I'm not an expert but I have spent a fair amount of time rebuilding the brakes on my bike, so I hope I can offer some advice:

Shims missing = not a good sign. That red goop is most likely brake quiet. Just wipe/scrape it off as best you can.

You can't get to the seals until the pistons are out. They're what hold the piston inside the caliper.

Use compressed air to get the pistons out. I took a bicycle tire pump, jammed one of the cone-shaped adaptors into the banjo bolt hole, and pumped away. The pistons will come out with some force, so be careful. Keep fingers away, don't point it at people and pets, etc.

What I did to get the pistons out of my rear caliper was this: Remove the two bolts holding the caliper halves together. Between the two, there's a passage with a rubber seal. Remove the seal and put a 1/8" thick piece of rubber in its place to block off the passage. Bolt the calipers back together (but not super tight, just enough to hold the seal in place) and then use compressed air to get each piston out at a time. On one side, you put the air in through the banjo bolt hole and on the other, you remove the bleeder valve and put air in that way.

Make sure you clean the calipers out real good, particularly the seal groove.

You may want to order another passage seal (#5 on the diagram) as well, if you get the chance. The existing one may work fine, though. Just be careful not to smoosh it putting the caliper halves back together.

How bad is the rotor? Grooves are okay, as long as they're not deep enough to catch a fingernail when run across. If they are bad, the rotors can probably be skimmed by a machine shop for relatively cheap. (You would need new pads in this case as well.)

[eil]

Once you get the pistons out, check out the condition of things inside the caliper. If there's any crusty or sludgy fluid buildup, you probably want to rebuild the master cylinder as well.

And I would be remiss if I didn't mention that you should dispose of those old OEM brake lines which are now likely 31 years overdue for replacement and see about upgrading to stainless steel lines. BassCliff will be along shortly to point you to a variety of vendors for these.

[BassCliff]

Greetings and Salutations!!

Hi Mr. egetron,

I've documented a lot of the brake work I've done to my bike. It'll apply to your bike. You should probably take those calipers apart, inspect them, clean them, and replace all of the rubber bits with new seals. If the brake pistons are too scored up those will need to be replaced too.

There is supposed to be a shim on the back of the brake pads between the piston. Use a little brake grease just to dampen the vibration and squeal. Use a little on the caliper axles too.

Here are some "guides" from my little website. Perhaps they'll help. The "mega-welcome" is below.

Bleeding the Brakes

Front Brake Pad Replacement

Rear Brake Pad Replacement

Brake Caliper Overhaul
(by Mr. Stefnwolf)

If you are here you probably have a 30 year old motorcycle that needs about 20 years worth of maintenance. You'll find all kinds of helpful tips, procedures, manuals, diagrams, "how-to" guides, etc, in the links below. Let's get started.

Let me dump a TON of information on you and share some GS lovin'.

I just stopped by to welcome you to the forum in my own, special way.

If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Cleanup Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. This is what NOT to do: Top 10 Newbie Mistakes. Now let me roll out the welcome mat for you...



Please Click Here For Your Mega-Welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

[egetron]

Thanks all, I appreciate the warm welcome.

I have a couple more questions:

What is a caliper axle? I've been searching through the parts fiche but I don't it...

I see some brake line vendors on your website, Basscliff, but is there an ebay alternative to paying full price for brand new stainless steal brake lines? I'm trying to keep this build as budget as possible.

And same question, but for rotors... what's my cheapest (but safe) bet for finding new or used rear rotors?

Thanks guys!
-Ege

[eil]

Thanks all, I appreciate the warm welcome.

I have a couple more questions:

What is a caliper axle? I've been searching through the parts fiche but I don't it...

The rear calipers don't have a caliper axle, but the front ones do. On the front calipers, the two halves slide back and forth on two axles. The rear calipers do, however, have pad pins (#7). Those can get a light coating of caliper grease upon reassembly. Don't overdo it because you don't want a glob to fall off and get on your pads.

I see some brake line vendors on your website, Basscliff, but is there an ebay alternative to paying full price for brand new stainless steal brake lines? I'm trying to keep this build as budget as possible.

Lots of people recommend this guy: http://stores.ebay.ca/Rennsport-Auto...h&_sid=5680214

Prices are supposed to be very reasonable and he'll make the lines custom for you if you provide him with measurements.

I tried going the DIY route and making my own brake lines using the guide on BassCliff's site and find it a little frustrating. Part of it my fault for trying to cheap out in a few areas and part of it is that it's just a real hassle working with the braided hose.

And same question, but for rotors... what's my cheapest (but safe) bet for finding new or used rear rotors?

Thanks guys!
-Ege

Post your request in the Parts Wanted forum. Someone here may have one they can sell you. Failing that, eBay.

[egetron]

Thanks Eil!

Where do I go about getting measurements for my brake lines?

[steveb922]

For length, you can just measure the lines you currently have. He'll also need to know whether you want straight or cranked banjos.

I believe the rear line on that model is a 3-part affair. Two hydraulic hoses at either end of a length of copper brake pipe. Most would probably measure the total length, and just install one single hose there.

It's good practise to replace all the copper crush washers when you install new lines. Personally I fit new stainless union bolts as well, but that's a question of taste/budget.