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Rear Brake MOT scrape through

dazthephot

dazthephot

Joined Apr 2012
207 Posts | 0+
Hi all, yet again have I scraped through the MOT with an advisory on the rear brake. I think the only reason I'm passing is cos the tester knows my bike now and is expecting the issue.
I'd like to rectify it once and for all so that I can use it.
I don't have the budget or want new rear sets but I like the look of the Ducati master cylinder MOD. Has anyone done it with new parts?
Mines a gen2 beauty!
View attachment 4787
Btw the monstrosity is my old mans!
 

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bleed it properly, it might take a bit of practice but once you got it right its good for a very long time
other things that help are making sure you got some kind of heat shield for the master cylinder and using DOT 5.1 "race" quality fluid as it has a better heat tolerance

all of which can be done for little money and a bit of TLC time

http://apriliarsv.com/guides/68-bleeding-rear-brake.html
 
Last edited:
Thanks Wolf, I appreciate your help. I didn't know about using 5.1 fluid. I've seen the heat shields so I will source one of those and post my progress.
Daz
 
Like Wolf said bleed it properly and it will last. Done mine over a year ago and i have not had any problems with it, not using a heat sheild just a lot of patients and about an hour spare thats all it takes to get a good rear brake.
 
Thanks Evsy, appreciated.
It is only a simple hydraulic circuit after all so I'm gunna start with the simplest fix first, bleed properly as per the Aprilia instructions.
 
dazthephot said:
Thanks Evsy, appreciated.
It is only a simple hydraulic circuit after all so I'm gunna start with the simplest fix first, bleed properly as per the Aprilia instructions.
Click to expand...

As the coversation went getting some other parts with the local Aprilia dealer.....
Me.
By the way you don't happen to have or know for a second hand RSV4 O/S foot rest with rear brake set up do you.
A.D.
What do you want one of them for.
Me.
To try and sort out the crap rear brakes on the RSV.
A.D.
You dont need one of them to sort out your rear brake the standart set up is more than ample for any use.
Me.
How do you say that and the brake don't last that long after bleeding.
A.D.
You just need to do the job right in the first place.
Me.
And how do you do that.
A.D.
Just drop it down to us for about an hour and a half and you will have a decent brake that will last.
Me.
What's the secret.
A.D
No secret just just use your standard stock part's.

So that got me thinking thats all you need is patientce and a new tin of brake fluid. So i got myself a tin of Halford's DOT 4 racing brake fluid and an hour of very very very slow pumping of the brake pedal to make sure i got all the air out. That was back last July and sill the same good brake now a year later being used and stored over the winter and even being used a lot one day to the extent i melted the speed sensor by the rear caliper.
 
Wow good effort. Right that's what I'm gunna do. Up to now I've been bleeding with the caliper in place and only 2 or 3 reservoir fills.


Sent from my iPhone using Tapatalk 2
 
There's about a gazillion threads on bleeding the rear brake.
Google kzmilles rear brake fix, it's on AF1.

fwiw....about 7 people tried to bleed mine, two of them were official Aprilia workshops....

Fantastic pedal for about 150-200 miles.....then nada....soft as fresh ****.

You'll always get the smartarse tell you 'you're bleeding it all wrong'
Interestingly, three of them gave up trying to bleed mine...having all failed to get a pedal that lasts.
You want a firm pedal?...
Simply hang a 10kg weight on it overnight.....job done, but like the bleeding..it won't last.
Heatshields make no difference either as the problem is not heat related.....
I've tried AP race fluid which can withstand stupid temperatures...way way higher than that engine casing.

Fitted rearsets, relocated the master....used 'normal' bleed proceedure...and job done....that was 3 years ago....and not touched it since.

Most that have spent serious time on the problem have come to the conclusuion it's cavitation
If you suffer properly with 'dead brake' no amount of bleeding will fix it...try a different m/c....or treat it to some rearsets.
 
I do the weight hang the night before MOT and it used to work. Still faded after a few miles though.
My normal bleed technique hasn't worked so the next step is to get the calliper high then try. Failing that the rear sets will have to be the way forward.
What have you got and how much mate?


Sent from my iPhone using Tapatalk 2
 
its been probably 3 years since i bled mine, all i remember was i used a combination of all the known methods just to be a perfectionist and it paid off :)

my MOT is thursday.. now im worried the new back disc & pads wont be bedded in enough, feels alright to me but its lacking the bite im used to
 
Gotta say I did mine last week with the caliper off and I have only been out twice and its not the best. So I'm going to bleed it with a pressure bleeder at work next week and see if that does the trick.
 
dazthephot said:
Failing that the rear sets will have to be the way forward.
What have you got and how much mate?
Click to expand...

Gilles....istr about about £350 ish
I did have a look at some of the cheapies...decided agianst, tbh they are not too well made, and if you do a search there are stories of them falling apart. (mind you, I suppose a good dollop of loctite could maybe fix that?)
I've come to the conclusion that good quality kit is always dead easy to shift on fleabay...so you tend to get most of your spend back, if that makes sense?
 
i was advised to hang the cylinder as high as poss away from heat and to use dot 5.2 as one of the earlier versions 5.1 or 5.0 is silicon based and will do the lines no good.
 
stormav said:
silicon based and will do the lines no good.
Click to expand...

fairly certain thats why labels on the brake fluid bottles say "compatible with DOT 4" etc (or dont mention it at all..) i have also heard that mixing the two types of fluid causes funny stuff to happen and is a bad idea ;)

bottom line is read the labels and if you arent sure, do your homework!
 
Surely we can rule out the fluid given the number of people with a good brake still on standard dot4.
Normally when this type of problem occurs its batch related, ie a bad batch of MCs or rear brake line etc


Sent from my iPhone using Tapatalk 2
 
oh i agree the fluid is unlikely to be the problem, just wanted to try and do away with any confusion about the different types ;)

almost certain a thorough bleeding will get a nice firm brake and will last, at least until you change the fluid and let a bunch of bubbles in :D
rearsets are a very expensive fix, if you really want them for other reasons then sure why not.. but just to move the MC? crazy..
 
That's very true. I'm only a casual rider and £350 is a fair chunk just to make the rear brake functional again. I have a vacuum pump, I'm going to draw through a good half litre of fluid through with an upside down calliper then finish off with the foot lever. See if that sorts it.

Incidentally why couldn't you swap the position of the bleeder with the brake line so it's above the line, is still not high enough?


Sent from my iPhone using Tapatalk 2
 
It's got nothing to do with the type of fluid or heat.
However....silicon fluid is OK to use in the clutch, but not in the brakes.
If you want to switch to silicon, you'll need to fully strip down the clutch system, and clean out the dot 4 first.

Dead brake is caused by CAVITATION

Not heat
Not incorrect fluid
Not incorrect bleeding (usually)
Not faulty m/c's (usually)

CAVITATION
 
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