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Very weak rear brakes.


ETZ

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I noticed that my 2000 rt rear brakes have very little stopping power(i.e. won't activate the abs in gravel) I bled the master cylinder with no improvement. Checked the pads and they seem to be adequate. Has anyone had any experience with this?

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You may need to rebuild the calipers, however, first thing I'd try would be to get a can of brake cleaner and spray down the rotor, then lightly sand it with 400 grit emery cloth. Lightly sand the pads as well, then give it another shot of brake cleaner, you may have glazed the pads or rotor. wave.gif

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russell_bynum

If you've still got the stock rubber brake lines, you might consider upgrading to braided stainless. It's possible that the old rubber lines are just bulging when you apply the brakes, so your pressure is wasted in the line rather than put to use in the caliper.

 

I'd check the other stuff first...make sure you don't have any leaks, make sure the rotor and pads are clean, don't have oil on them, etc. When you bleed the brakes, push the caliper pistons all the way in to make sure you get all the old fluid and possible air out from behind the pistons.

 

If all of that doesn't help, I'd replace the lines with braided stainless.

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You should be able to trigger the ABS easily on dry pavement, much less on gravel. I would guess that you may still have some air in there somewhere but as Russell noted, failing that I'd check out the rubber section of the brake line. Have someone really stand on the sucker as you check for expansion, bulging, or leaks. Rubber brake lines do have a finite life.

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I noticed that my 2000 rt rear brakes have very little stopping power(i.e. won't activate the abs in gravel) I bled the master cylinder with no improvement. Checked the pads and they seem to be adequate. Has anyone had any experience with this?

 

ETZ, are you getting a full stroke on the rear pedal & not much braking or are you getting a hard pedal part way through the travel & not being able to lock the rear brake?

 

If you are getting full stroke but not much braking I would suspect you have air in the system (probably up at the ABS controller) .. You will probably have to bleed the high part of the system right at the ABS controller.. If you do have air up high it is VERY difficult to get out by just bleeding at the rear caliper or master cylinder as the fluid just runs under the air pocket on a slow bleed) .. One thing that has worked for me in the past is to move the rear caliper (pry on it with cushioned pry bar) to push as much fluid as possible back into the master cylinder.. Then kick the rear brake pedal as fast as you can a couple of times.. In some cases that can move enough fluid volume to move the high air out with the fluid flow.. I seriously doubt your brake hoses are soft enough to not be able to lock a rear wheel on gravel..

 

If you are getting a hard brake pedal but not much rear braking then suspect oil soaked brake pads (at one time anyhow),, or frozen rear caliper piston in the bore,, or a line restriction,, or a restriction in the ABS controller..

 

 

Twisty

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I seriously doubt your brake hoses are soft enough to not be able to lock a rear wheel on gravel..
Unless, of course, they're like the front hose that I just lost that had almost the exact effect he described. In my case it was a leak though, not a soft hose. But I agree that I'd put my money on air in the system.
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russell_bynum
I seriously doubt your brake hoses are soft enough to not be able to lock a rear wheel on gravel..
Unless, of course, they're like the front hose that I just lost that had almost the exact effect he described. In my case it was a leak though, not a soft hose.

 

Same thing happened on Lisa's RS. We were in the parking lot practicing braking, and I was getting on her because she wasn't braking hard enough to engage the front ABS.

 

Then I tried it and sure enough...spongy lever and no matter how hard I pulled, it wouldn't kick on the ABS. Turns out there was a pinhole in one of the rubber lines. Because of where the leak was, it wasn't really obvious (i.e. no stream of brake fluid shooting out of the line) but I eventually figured it out.

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Yeah, kinda scary actually in that I had the same non-obvious symptoms... brakes seemed kind of spongy/weak, but not dramatically so. It took a close inspection to see the leak and I shudder to think about what could have happened if I had been more complacent about it, as in a sudden complete front brake failure. The experience pretty much convinced me that replacement SS braided brake lines is a pretty good investment on any bike with 5 to 10 years of service...

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I will give the lines a close inspection. Then bleed the unit again. I am getting full travel of the pedal and it never seems to give me a "solid pedal" no matter how fast or hard I push. Thanks for the input.

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The experience pretty much convinced me that replacement SS braided brake lines is a pretty good investment on any bike with 5 to 10 years of service...

One of the problems with this site is that it could lead one to spend all of their time replacing parts that might fail someday. Now I have to worry about my 8 year old brake lines.

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russell_bynum
The experience pretty much convinced me that replacement SS braided brake lines is a pretty good investment on any bike with 5 to 10 years of service...

One of the problems with this site is that it could lead one to spend all of their time replacing parts that might fail someday. Now I have to worry about my 8 year old brake lines.

 

The good news is it's a performance upgrade...so if you do it before the original lines fail, there's still a benefit.

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  • 1 month later...

Noticed a similar symptom on my 99 recently. I can still activate the abs, but not if I'm loaded heavy. So, I removed the caliper and started looking around today. While the rear piston moves pretty freely in its bore, the front one is sticking. Seen this before on my old honda, and it is not uncommon if the bike sits a lot. Crud can collect in the bore inhibiting movement of one or more pistons. On the old honda I disassembled the caliper and cleaned everything up, reassembled and all was well. No parts required. Manual says to replace the dust covers on the rt, but you might get lucky.

I used pliers to inhibit movement of the rear piston, sprayed both of them with wd 40 and then pushed them in and out several times to try to free things up. It helped, but it would be best to disassemble and clean them up. I'll do that when I replace pads, which is coming up soon.

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