I posted in Crash analysis about a spill I had today. But the more I replay the event, the more I think the rear wheel locked up which was what caused me to go down. 3/4 finished with a slow left hand turn and since it happened so fast, I had no idea what happened. At first I thought I must've been hit, but I wasn't. Then I blamed my overloaded backpack...or thought I'd popped off the clutch too fast..or my balding tire..or maybe there was an oil slick. But I really feel like I remember the tire dragging, a violent drag on my rear end, then boom down.
I just replaced the rear caliper because of something similar 2 weeks ago. On the freeway I felt the bike bogging down hard. Immediately pulled over in case it was dying. No pressure in the brake pedal. Got home, took apart the caliper and found 2 cooked pistons. I figured I must've stepped on the brake accidentally even though that seemed really unlikely. When I replaced the caliper that was the hardest time I have ever had bleeding a brake line. I pumped, pumped, pumped, and even had to suck fluid through with my mouth at one point. And the pedal still seems mushy.
So, sorry for the long winded post, I guess I'm just wondering if my rear brake could be locking up by itself somehow. Twice, 2 different calipers.
It's pretty easy to adjust all the freeplay out of the brake pedal and block off the fluid return port in the master. That will lock up the rear brake
Do you have aftermarket rear sets?
I'll bet, if the rear is in fact locking, you have inadequate free play in the pedal.
Dan beat me to it...
seems to be plenty of freeplay. Hrrm. What else? The caliper is new..could something be causing the fluid to overheat? The bike has 35,000 on the original master cylinder..kinda want to replace that now. Or just scrap the rear brake altogether. I'm afraid to ride it now :/
How are you measuring?
measuring the freeplay? I'm not exactly...just judging the feel of it...
You need to be sure.
There should be 1.5 mm before the actuator rod hits the piston. Pull the rubber boot and look.
If there is that amount of free play and the caliper still locks up the piston in the master might not be returning all the way which would cause the same thing.
Thanks DP I will check. 1.5 mm that is it? that's less than a fingernail...
Quote from: Rudemouthsky on September 24, 2012, 04:38:05 PM
Thanks DP I will check. 1.5 mm that is it? that's less than a fingernail...
It's .060, or 1/16"
ime any issue with the rear brakes dragging or locking it is always the freeplay being not, as it were.
i say remove the pushrod and make it very short. then you'll know what freeplay feels like. it means pushrod not touching piston.
you probably need to rebleed it all too.
While you're working on stuff - ensure the guide pin on the caliper is clean. I had a pad hang on overly cruddy pin and cook my rear rotor.
Quote from: Slide Panda on September 25, 2012, 05:05:51 AM
While you're working on stuff - ensure the guide pin on the caliper is clean. I had a pad hang on overly cruddy pin and cook my rear rotor.
Good point, but he's already replaced the caliper.
But was it a brandy new caliper? Didn't say ;)
Quote from: Slide Panda on September 25, 2012, 05:33:16 AM
But was it a brandy new caliper? Didn't say ;)
(http://1.bp.blogspot.com/_pf67NibUSJM/S8iZF90XsyI/AAAAAAAACkQ/mVF9rFcuyzs/s1600/splitting+hairs2.jpg) ;D
I'd imagine even if it was a used caliper the pads would need to be installed and a cruddy pin would be dealt with.
Quote from: ducpainter on September 25, 2012, 05:47:02 AM
[ I'd imagine even if it was a used caliper the pads would need to be installed and a cruddy pin would be dealt with.
assumption can be the the mother of all f**kups....sometimes...LOL
Quote from: zooom on September 25, 2012, 06:03:35 AM
assumption can be the the mother of all f**kups....sometimes...LOL
Yup...
but I know he has a free play issue...
(http://upload.wikimedia.org/wikipedia/en/thumb/2/21/Carnac.jpg/220px-Carnac.jpg)
;D
Quote from: brad black on September 25, 2012, 02:57:30 AM
ime any issue with the rear brakes dragging or locking it is always the freeplay being not, as it were.
I had it happen to me when the rod got all rusty inside the rubber boot. There was an ugly mixture of rust and water which turned into a paste in there.
So yeah, it was the piston being held in past the bypass port that locked the brake up, but it wasn't the freeplay in the rod assembly…
big
Caliper is new and came with new pads. On a sidenote, it is ridiculous that sellers on eBay are trying to get more for a crusty used caliper than a brand new one can be had for. Still have not had time to inspect the pushrod and take an exact measurement of freeplay. My redneck shadetree analysis is obviously not going to cut it here amongst you Ducati geeks, and rightfully so. Brakes are not to be f*cked around with, they're pretty important. I'm still suspecting an issue with the master though considering what a difficult time I had bleeding the line. Thanks for all these fast, quality replies.
Quote from: Rudemouthsky on September 25, 2012, 09:08:18 AM
On a sidenote, it is ridiculous that sellers on eBay are trying to get more for a crusty used caliper than a brand new one can be had for.
Nah, what's ridiculous is that they actually will find buyers now and then. I see used part prices range from a reasonable amount thru 1000% over. The sellers on eBay Germany are the worst price-wise which may be due to local prices...
Rear brakes can be difficult to bleed on a Monster particularly if the caliper is mounted on the bottom with the bleeder at the lowest point.
They bleed easily if you remove the caliper, put a block or wedge in between the pads and hold the bleeder above the master.
I'm betting you have a freeplay or piston return issue.
can the break slave be opened up and cleaned with the same seals ? if they dont leak from the get go ? or would they need to be changed and cleaned while its open ?
What do you mean 'slave'?
There's a master cylinder and a caliper.
His caliper is brand new. I doubt it needs cleaning.
It isn't advised to disassemble brake units and not replace parts. You can't buy those parts.
i mean the rear master slave cylinder
Quote from: H-2 CHARLIE on September 25, 2012, 01:24:31 PM
i mean the rear master slave
It can't be the master and the slave at the same time.
There are no parts available for the master. It wouldn't be advisable to disassemble it.
Replacement parts are not available for the later "small bolt" masters or for the later coffin masters, but you CAN disassemble them and examine the parts, clean and regrease, and rebuilt.
The later units actually use a PLASTIC piston so be careful when removing everything.
Allied Metric can source the correct seals in EPDM. I have refinished (not rebuilt) these using new seals from Allied. Zero problems.
Could a master slave be a self employed braking system? :P
If there is proper free play and the caliper overheated badly enough the new caliper would be cooked. Check that the pistons move freely. After that, see if fluid returns to the reservoir after you release the brake lever. If not, either there is still not enough free play or the compensating (return) port is blocked. People have also overheated rear brakes enough to cook the master too.
If I was Ducatiz, with a small fleet to support and always had something to ride I would mess with finding seals for the master and overhauling it. Otherwise, for a little over 50 bucks you can get a brand new one from Yoyodyne. Call Fred for proper fitment if you need one.
Quote from: howie on September 25, 2012, 09:29:26 PM
Could a master slave be a self employed braking system? :P
If there is proper free play and the
If I was Ducatiz, with a small fleet to support and always had something to ride I would mess with finding seals for the master....
Lol... if i have the order somewhere ill post the seal info for the adventurous
Quote from: ducpainter on September 25, 2012, 06:10:05 AM
Yup...
but I know he has a free play issue...
~~~SNIP~~~
;D
Yes, most likely.
Essentially impossible to bleed when the bleed port is blocked.
It was lack of freeplay. Negative freeplay, rather. The rod was actually slightly pushed in. *facepalm*
Quote from: Rudemouthsky on September 26, 2012, 04:48:48 PM
It was lack of freeplay. Negative freeplay, rather. The rod was actually slightly pushed in. *facepalm*
Inexpensive fix... [thumbsup]