[S] Ineffective rear brake... what to replace next?

[Rebeljah]

   Hey TT! So I have been having problems with the rear brake on my 2006 S; it will work immediately after bleeding the system but loses stopping power after a few pumps of the brake pedal. Just today I rebuilt the rear master cylinder (replaced all seals and cleaned the all parts with brake cleaner), but the problem persisted even after that, the brake worked for the first few applications and then lost almost all of its power. It seems that air is getting into the system somewhere and I can say without a reasonable doubt that it isn't the master cylinder since I've just rebuilt it.

   What is the next most likely place air is getting in? The lines are quite dirty and I'd guess they've never been replaced since the bike was made (06) Should I start there? It's a good excuse to with to steel braided lines haha! The reservoir is also looks a bit corroded and warped at the top where the reservoir cap goes on, so it's possible there isn't a good seal there.

Edited July 4, 2017 by Rebeljah

[38super]

There's corrosion inside the piston bore of the master cylinder which cuts the seal.  Either bead hone or replace.

[Rib Eye]

Yes, replace the old brake lines. And you could swap a crf master cylinder in on the rear.

[Rebeljah]

8 hours ago, Rib Eye said:

Yes, replace the old brake lines. And you could swap a crf master cylinder in on the rear.

As in a CRF 250? Like this? How would you fit that to the DRZ?

[jjktmrider]

I see a lot of recommendations for replacing the DRZ MC with a CRF . Even before I swapped the stock like with a braided one I had no trouble locking up the rear , and without having to stand on it real hard . For me replacing wouldn't gain anything . 

 

As too why yours is loosing it's power after a couple uses , does it do it if you don't ride it , as in can you sit there and hit the rear brake repeatedly sitting in your garage and it slowly quits or does it only do it when the motor is running and riding around ?  Back in '01-'02 Yamaha had certain model atvs and bikes that at certain rpms the vibrations would cause air bubbles to develop in the rear MC and you'd loose braking .On the Raptor I had it took high rpms and sustained for a period for this to happen so I never had an issue with mine but others did , possible the same reason here and why some have issues with low power braking thus the swap to crf's.   Maybe some rubber washer between the mount bolts would help.

 

 

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[Rebeljah]

38 minutes ago, jjktmrider said:

I see a lot of recommendations for replacing the DRZ MC with a CRF . Even before I swapped the stock like with a braided one I had no trouble locking up the rear , and without having to stand on it real hard . For me replacing wouldn't gain anything . 

 

As too why yours is loosing it's power after a couple uses , does it do it if you don't ride it , as in can you sit there and hit the rear brake repeatedly sitting in your garage and it slowly quits or does it only do it when the motor is running and riding around ?  Back in '01-'02 Yamaha had certain model atvs and bikes that at certain rpms the vibrations would cause air bubbles to develop in the rear MC and you'd loose braking .On the Raptor I had it took high rpms and sustained for a period for this to happen so I never had an issue with mine but others did , possible the same reason here and why some have issues with low power braking thus the swap to crf's.   Maybe some rubber washer between the mount bolts would help.

 

 

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This last time I tested out the firmness of the pedal a few times with the engine off and it seemed fine at first but once I started the bike, got going and tried to use it it didn't work. Is there a certain model of CRF master cylinder I need to find? It looks the the connections for hoses are slightly different on the CRF MC's.

[jjktmrider]

I think it is the CRF450 but it is used on many models IIRC . I found the RMZ(?)  master cyl. looked like it would fit better plus have an actual fluid res., which the CRF has very little. But I have not physically tried one to verify fitament , may be something to look into.

 

http://www.ebay.com/itm/12-SUZUKI-RMZ450-OEM-REAR-BACK-BRAKE-MASTER-CYLINDER-/272442189494?hash=item3f6ed1e6b6:g:0SIAAOSwcLxYIYCF&vxp=mtr

damn near new one , http://www.ebay.com/itm/2015-SUZUKI-RMZ-450-REAR-BRAKE-MASTER-CYLINDER-NISSIN-15-RMZ450-/162522237186?hash=item25d7148902:g:OIoAAOSww5hZH2ah&vxp=mtr

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Edited July 5, 2017 by jjktmrider

[HansLanda]

43500-MEN-305

2002-2007 CR125R
2002-2007 CR250R
2004-2015 CRF250R
2004-2015 CRF250X
2002-2015 CRF450R

[Noble]

I think we need more description of the problem.  Does the brake pedal develop excessive travel without engaging the brake? Or does the pedal hight stay constant and firm but the brakes are ineffective?  The description that the brake will work after bleeding but stops working after a few applications need more detail.

I would recommend rebuilding the rear caliper. (just from age even if it is working OK)

Brake cleaner is not for cleaning the hydraulic system.  It is for pads, rotors, backing plates etc, the external stuff.  Use ethanol alcohol, DOT brake fluid or soap and water for the internal hydraulic parts.  I do not know your skill at rebuilding brake systems so you will have to judge for yourself if you did a good job or not.

[jjktmrider]

I think he's moved on , made a new thread and is going with the crf mc because people say it's the way to fix bad DRZ brakes .

 

 

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[Rebeljah]

9 hours ago, Noble said:

I think we need more description of the problem.  Does the brake pedal develop excessive travel without engaging the brake? Or does the pedal hight stay constant and firm but the brakes are ineffective?  The description that the brake will work after bleeding but stops working after a few applications need more detail.

I would recommend rebuilding the rear caliper. (just from age even if it is working OK)

Brake cleaner is not for cleaning the hydraulic system.  It is for pads, rotors, backing plates etc, the external stuff.  Use ethanol alcohol, DOT brake fluid or soap and water for the internal hydraulic parts.  I do not know your skill at rebuilding brake systems so you will have to judge for yourself if you did a good job or not.

  The pedal can be pressed down with very little pressure and no braking, It feels like it's just the spring in the MC that's causing resistance. It's not until I am almost as far as I can push the pedal down that I feel some pressure and a little bit of braking occurs.

  About the bleeding, I will bleed until I stop seeing bubbles from the bleeder valve and the pedal feels firm at the top of it's range of motion and when the full range of motion can only be achieved by opening the bleeder valve. It almost seems like the firmness mostly goes away without even using the brakes. After bleeding I did a test ride and the brake had lower than normal stopping power for one maybe to applications and then went back to needing to be pressed down very far before I could even get any pressure feedback or braking power.

  I'm pretty confident that the rebuild was good, although, I didn't have the micrometers to measure the inside diameter of the bore. I just replaced the seals and cleaned out the grime inside. I should mention that there small black particles coming out of the MC when I cleaned it, I thought it was rubber from the seals, but wit the new seals in I still have the problem.

  Rebuilding the caliper is definitely something I'll have to save for next paycheck haha but I'm willing to give it a shot! Thanks for the tip on the brake cleaner.

Edited July 6, 2017 by Rebeljah

[Noble]

Based on what you are saying, I'm guessing your rebuild was ineffective. I advise you disassemble the master again including removal of the fitting that goes to fluid reservoir.  Under that fitting you will find 2 ports.  1 is very small.  Both of these ports need to be clean and open.  Re-clean everything and inspect the new seals for damage.  Also possible the rubber hose to the reservoir is failing and contributing rubber particles.  This hose is a special rubber and if it needs replacement, has to be an original part.

[Rebeljah]

7 hours ago, Noble said:

Based on what you are saying, I'm guessing your rebuild was ineffective. I advise you disassemble the master again including removal of the fitting that goes to fluid reservoir.  Under that fitting you will find 2 ports.  1 is very small.  Both of these ports need to be clean and open.  Re-clean everything and inspect the new seals for damage.  Also possible the rubber hose to the reservoir is failing and contributing rubber particles.  This hose is a special rubber and if it needs replacement, has to be an original part.

I made to sure to clean the holes when I did the rebuild. Yeah thinking it has to be one of the hoses either from the reservoir or to the caliper. But I'll probably end up replacing the hoses and rebuilding the caliper.

[Beta300REcat]

The reason to switch to the Honda master cylinder isn't so the brakes lock up easier. The cylinder is smaller diameter, improving brake feel and requiring MORE lever travel before it locks up. Plus, you can dump the janky looking reservoir guard that weighs four ounces. ?

[HansLanda]

5 minutes ago, Bermudacat said:

The reason to switch to the Honda master cylinder isn't so the brakes lock up easier. The cylinder is smaller diameter, improving brake feel and requiring MORE lever travel before it locks up. Plus, you can dump the janky looking reservoir guard that weighs four ounces.

Finally got mine rebuilt and I love it. DRZ is on/off. This one's nice!

[Beta300REcat]

......................and there ya have it, folks!

[jjktmrider]

Hmmm , I ride all winter up here in the north , that means ice , all winter . Yet I have zero issues with controlling the rear brake , doesn't lock-up when I don't want it too , have zero issues with it being  "On/Off" .

 

Strange , you'd think someone on ice would have all these troubles even worse ????  , hell I ride 4 different bikes on that ice without issues swapping from one to another (except that damn KLR I once owned). Guess I got a good one.

 

 

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[HansLanda]

3 hours ago, jjktmrider said:

Hmmm , I ride all winter up here in the north , that means ice , all winter . Yet I have zero issues with controlling the rear brake , doesn't lock-up when I don't want it too , have zero issues with it being  "On/Off" .

 

Strange , you'd think someone on ice would have all these troubles even worse ????  , hell I ride 4 different bikes on that ice without issues swapping from one to another (except that damn KLR I once owned). Guess I got a good one.

I swapped my stock MC out after 35k miles. Stock brake line, bulging reservoir. With the stocker, the pedal's had a short throw until the rear locked, so you had to be very precise if you wanted to brake but not totally stop the rear wheel. I ride a lot of dirt with my SM setup, and do a lot of wheelies, so I would use too much rear brake often. The CRF MC needs more travel, so since it's less sensitive, you have more opportunity to slow the rear without locking it. But you still can lock it if you want to.

If you don't feel the need to get rid of it, then awesome. Bleeding the CRF is really annoying! That reservoir is a thimble. 

[Beta300REcat]

On 7/7/2017 at 7:58 AM, HansLanda said:

I swapped my stock MC out after 35k miles. Stock brake line, bulging reservoir. With the stocker, the pedal's had a short throw until the rear locked, so you had to be very precise if you wanted to brake but not totally stop the rear wheel. I ride a lot of dirt with my SM setup, and do a lot of wheelies, so I would use too much rear brake often. The CRF MC needs more travel, so since it's less sensitive, you have more opportunity to slow the rear without locking it. But you still can lock it if you want to.

If you don't feel the need to get rid of it, then awesome. Bleeding the CRF is really annoying! That reservoir is a thimble. 

Indeed. There is a reason that competition machines like the CRF and the WR come with a braking system that is better matched to the skill level of their customers. The DRZ is a nice bike in its stock form, but once you start to venture outside its intended market, you will have to either modify it, sell it, or suffer with a bike designed for entry level to early-intermediate riders.

Organic pads, braided lines and modern rotors have transformed my brakes beyond what i thought was possible. Brakes are like suspension. To borrow a quote from Paul Thede, 'The best you know, is the best you've rode'   ?

[jjktmrider]

HAAAAAAA , that right there is funny  , keep thinking it, you'll start believing yourself . Seems someone that can ride on ICE , on "inferior" brakes, without ANY of the issues as some complain about while riding on pavement should point to more skill than those that need it tamed down for more control . Think about it !!!!!  Hell I've even had to use the front brakes, ON ICE(NOT recommended) to stop faster, once for a car that slid into the roadway from behind a building , but still able to not lock it up because I could control them good enough .

I can see why the CRF mc, or others, takes more pedal movement to build up the same force as the drz's at much less movement and why . Want slower reacting brakes try one of my 2 drum brake bikes , the pedal need to move 2 inches down to get full lock-up , but fairly good progressive stopping power up till then , within limits of the design.  But if a rider can use the drz's as good as others that need the CRF's style , where's the benefit ????  Remember I HAVE 2 bikes with the slower MC's , ------------- the Husky and WR , and have owned a pile of MX bikes through the years. No troubles going from one to the other , on all conditions . Again , Strange indeed !!!!!!

But with those involved , there's no way that'll sink in . Glad these types only hang out at TT , funny that all these "everyone must do mods or your wrong" things aren't an issue on other forums ,or with any other bike.

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Edited July 8, 2017 by jjktmrider