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Rear brake blead |
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Aarong
Moto3 racer Joined: 26 Feb 2019 Location: Kent Status: Offline Points: 17 |
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Posted: 09 Mar 2019 at 16:33 |
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Has anyone one got any tips for bleeding a rear brake on a 07 rsv?
I've changed the fluid as the old fluid was pretty black and now I can't keep a solid pedal, I'm pretty sure it's air in the system and not a leak. I've tried hanging the caliper higher than the master cylinder and resivour with the bleed nipple at the top bit still no joy.
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redratbike
Moderator Group The Collector Messiah Joined: 07 May 2008 Status: Offline Points: 16146 |
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Reverse bleed it from caliper to m/c or use a power bleeder
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Tifa
Moto GP Alien I am Sparticus, only uglier Joined: 21 Apr 2009 Status: Offline Points: 1972 |
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Put a little ptfe tape on the thread part of the nipple.
Will help stop air getting drawn back in.
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IanG
Premium Member Joined: 04 Oct 2010 Location: N Wales Status: Offline Points: 10725 |
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Best tip for any bleed nipple on the bike Did you not bleed the old fluid out and replace it that way then? |
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Aarong
Moto3 racer Joined: 26 Feb 2019 Location: Kent Status: Offline Points: 17 |
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That's something I haven't tried but I will give it a go thank you
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Aarong
Moto3 racer Joined: 26 Feb 2019 Location: Kent Status: Offline Points: 17 |
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Sorry I meant the ptfe on the thread I haven't tried, yes I did bleed the old stuff out but I had the caliper in the normal position which is where I think I went wrong.
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IanG
Premium Member Joined: 04 Oct 2010 Location: N Wales Status: Offline Points: 10725 |
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In that case as long as the res didn't run dry the only way air could have got in is round the nipple threads. As with a lot of other makes the threads on bleed nipples seem to be very loose,possibly to hopefully stop dissimilar metals corroding together? What ever,I always wrap nipples with PTFE tape ( My Mrs sometimes wonders about it )
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426hemi
Premium Member owner of the big bore! Joined: 30 Mar 2012 Location: cannock Status: Offline Points: 5676 |
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I've been looking at getting some of these to help with the bleeding.
http://www.stahlbus.com/info/en/service/faq-s/bleeder-valves/64-stahlbus-compared-to-other-products |
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legend88
Premium Member Joined: 18 Aug 2013 Location: Newcastle Status: Offline Points: 6598 |
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I've heard this suggestion before but never actually used the idea. Of course the nipple is not supposed to rely on the threads for sealing. It's the taper that closes against the seat in the caliper that produces the seal. Sometimes it is suggested that air is drawn in p0ast the threads during the actual bleeding process. However whenever you have been able to achieve a solid brake lever then clearly that has not happened so I am not sure that this often happens?
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IanG
Premium Member Joined: 04 Oct 2010 Location: N Wales Status: Offline Points: 10725 |
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You wouldn't think so but it does help,I've needed to do it on several cars in the past and it's just second nature now. Another possible benefit is that it stops any brake fluid bypassing the nipple and finding it's way up the threads during bleeding which can get messy. It certainly helps with preventing the nipple ever corroding in place which I've had happen on some vehicles I've bought over the years so it's worth it just for that. Just make sure the tape doesn't go past the thread and foul the shank and mating taper and all should be good
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www.apworkshops.co.uk
www.apriliaforum.co.uk www.apriliaownersclub.co.uk Looking forward to the next track day |
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Aarong
Moto3 racer Joined: 26 Feb 2019 Location: Kent Status: Offline Points: 17 |
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Well I've now got a back brake, I took the caliper off and hung it from the rear passenger foot rest and re bled the system.
I still didn't have much of a pedal though so I placed the caliper on some rag on the floor at an angle so the bleed nipple was the lowest point, then pressed the brake pedal down and cable tied it down and left for a few days. Now I have a good pedal which seems to be holding.
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snowman
Premium Member Joined: 27 Oct 2010 Location: Romsey area Status: Offline Points: 1385 |
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Years ago on brothers Harley tried bleeding front brakes to no avail, so just cable tied front lever in at handles bars overnight and hey presto when cable tie was released the brake was nice and firm 😮
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Aarong
Moto3 racer Joined: 26 Feb 2019 Location: Kent Status: Offline Points: 17 |
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It's something I got told to do with my mountain bike disc brakes by a cycle shop, I thought I'd give it a go and bingo
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legend88
Premium Member Joined: 18 Aug 2013 Location: Newcastle Status: Offline Points: 6598 |
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I've never got how that can work. If you have air in the system, how can clamping the lever on resolve that? The only thing I can think is that it's not about air but more to do with sticking pistons and the constant pressure helps to free them off? |
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Aarong
Moto3 racer Joined: 26 Feb 2019 Location: Kent Status: Offline Points: 17 |
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On some bicycle disc brakes there are tiny holes in the master cylinder so I got told to put a cable tie around the handle bar and brake lever, stick it on the back wheel and leave it over night, apparently it leaves the system open and with the caliper at the lowest point and master cylinder at the highest point it gives it time for the air to get to the top. Don't ask me how it works but it seems to for me, I also used the method on my front brake and it firmed the lever up more as well.
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Tifa
Moto GP Alien I am Sparticus, only uglier Joined: 21 Apr 2009 Status: Offline Points: 1972 |
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It allows any air in the lines to rise and escape naturally.
Pulling in the lever allows the air to pass by the m/c piston.
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legend88
Premium Member Joined: 18 Aug 2013 Location: Newcastle Status: Offline Points: 6598 |
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I still don't see how. The pressure in the system increases the effectiveness of the seal in the master cylinder so the air may rise to the top but it can't escape past the seal or the fluid would too.
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Tifa
Moto GP Alien I am Sparticus, only uglier Joined: 21 Apr 2009 Status: Offline Points: 1972 |
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It's science dude. Not 100% sure myself...just my theory. Recon it's one of those crazy unexplainable hydraulic things, like hanging a weight on your rear brake pedal overnight will restore it and give a firm pedal.
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Tifa
Moto GP Alien I am Sparticus, only uglier Joined: 21 Apr 2009 Status: Offline Points: 1972 |
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snowman
Premium Member Joined: 27 Oct 2010 Location: Romsey area Status: Offline Points: 1385 |
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I don’t care how it just does ?
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MorathB
Moto3 racer Joined: 12 Feb 2019 Location: Germany Status: Offline Points: 13 |
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I think the pressure makes the small/micro air bubbles even smaller so they can rise up to the lever more easily and after releasung the lever they're going into the reservoir
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badapple
Premium Member Joined: 03 Nov 2014 Location: Norwich United Kingdom Status: Offline Points: 5608 |
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I've used this method before and it did work, I hung a tin of paint and a couple of weights on top of the tin off the rear brake pedal only trouble was for some reason it knackered the rear brake light switch I wouldn't do it again because of that never had a problem with regular bleeding on the clutch or front brake.
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I started out with nothing and I've still got most of it left
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IanG
Premium Member Joined: 04 Oct 2010 Location: N Wales Status: Offline Points: 10725 |
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I think the weight on the pedal or tie round the lever thing works in the same sort of way as cleaning the disc bobbins until they're free to spin. In as much as logic and reason fly in the face of proven results With the bobbins I think although it's not needed or probably even desirable for them to be freely rotating it's actually beneficial as if they are that clean then it means you've flushed out any foreign matter which could make the swept area run out of true. Like the can/tie practice which I'm guessing pressurizes any trapped air as small bubbles which will naturally try and flow upwards and find their way to the res in time. However these are very simple circuits and if in serviceable condition and bled properly they are quick and easy to get done with minimal fluid use. Now I've always had a serviceable rear brake with the standard cylinder arrangement, and I bleed the slave in situ every year ( or two ) to change the fluid and I usually manage to only use a couple of reservoirs worth of fluid. It just depends on how you go about it I suppose,a lifetime of working on old bikes and cars certainly helps
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www.apworkshops.co.uk
www.apriliaforum.co.uk www.apriliaownersclub.co.uk Looking forward to the next track day |
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