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Rear brake master cylinder swap

Printed From: rsvr.net Forums
Category: RSV / RSVR / FACTORY
Forum Name: General Chat
Forum Description: Everything and anything to do with the RSV. ... Aprilia's biggest seller!
URL: http://www.rsvr.net/forum_posts.asp?TID=30096
Printed Date: 27 Mar 2026 at 00:38
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Topic: Rear brake master cylinder swap
Posted By: tfcoulson
Subject: Rear brake master cylinder swap
Date Posted: 04 Mar 2024 at 08:13
Just rode to work and noticed the bike really slowing down quick when off the throttle, then noticed a lot of travel on the rear brake - turns out my master cylinder is leaking.
Has anyone replaced the Aprilia version with something different? I don't particularly want to go second hand gen1 and also don't really want to go with something Aprilia designed for the rear brake, seeing as it seems to have a habit of being rubbish.



Replies:
Posted By: tfcoulson
Date Posted: 04 Mar 2024 at 08:23
Ah maybe Ill just go for a rebuild!


Posted By: Spoonz
Date Posted: 04 Mar 2024 at 10:35
It’s a Brembo unit so not a bad design just poorly implemented. If you don’t want to relocate it via rearsets, I would repair it or fit a used item. If you relocate it, fit an rsv4 unit. 


Posted By: twinfan
Date Posted: 04 Mar 2024 at 13:15
I have an RSV4 unit on mine attached to AP rearsets and the system works great

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on my licence it says "tear down the dotted line" so I DO!


Posted By: legend88
Date Posted: 05 Mar 2024 at 07:48
Originally posted by twinfan twinfan wrote:

I have an RSV4 unit on mine attached to AP rearsets and the system works great


Me too, a definite improvement:



Posted By: snowman
Date Posted: 06 Mar 2024 at 13:36
I will do that on mine I think .


Posted By: tfcoulson
Date Posted: 06 Mar 2024 at 18:28
It actually just looks like it might have been the hjc? tube I have. Removed and re-tightned/bled it and will see how it goes. Might need to snip off the bottom bit thats a bit crushed from where its been clamped on if it keeps being an issue.
I've already got the AP rearsets so couldnt use the original resevoir. That rsv4 one looks good actually.
...It also looks alot less rusty in that area Approve


Posted By: IanG
Date Posted: 10 Mar 2024 at 14:37
Sorry,get the gist now,you didn't have an original res? 

As of course you can use the original res with the AP rearsets.

Easy and tidily in fact,I thought about one of those integral res units but decided against it on two counts.
a) I'm tight LOL   Why buy something new that's not needed and..
b)  They look to damn close to the s/arm for comfort to me and I'm using a brand new s/a.

I use the original master and res on both my Mille and Gen2 Tuono while using AP rearsets on both, although tbh I don't find any difference in rear braking before or after,I can still lock the rear wheel and never had any issues with bleeding or fade when things were standard.

One thing I did do which may have helped when first bleeding after splitting the system was when I replaced the brake line for a new HEL unit I specced it slightly longer and fitted it to the lower bleed nipple posn on the caliper with the bleed relocated to the upper posn.

No need for any of this stupid remove the caliper and hold it up by the seat nonsense.  You can bleed both the clutch and the rear brake easily with no issues and with only a couple of res fills by just doing the job correctly in the first place.

 I despair watching some modern 'technicians' they haven't got a clue if they don't have access to pressure or vac bleeding aids, let gravity do the hard work.

Old school rules  Wink 





These were 'dry build' pics  I'm now using a new Smoked Res to match the bar units and the caliper has had a complete overhaul with new fasteners throughout and and new seals etc.



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www.apworkshops.co.uk
www.apriliaforum.co.uk
www.apriliaownersclub.co.uk

Looking forward to the next track day


Posted By: tfcoulson
Date Posted: 11 Mar 2024 at 21:44
I didnt think the original fit, thought there would be a bit of a clearance issue. Have you got any washers or anything attaching it to the heel guard? The HJC unit clouds up as well from the brake fluid, not the best piece of kit. I have a spare HEL line I think (probably not longer but seeing as I didnt even realise I had ordered it and then ordered a goodridge who knows!).


Posted By: IanG
Date Posted: 11 Mar 2024 at 21:55
Regarding spacers or washers I'm sorry but I can't remember, it shouldn't need any as the rearsets were designed to be a straight swap as I understand it..

I do seem to recall slightly relieving either a clearance hole or or the side of a counterbore slightly to enable a straighter actuating rod run though.

I do remember making an alloy bobbin to mount the res on

I might have another pic of the install somewhere,I'll have a search


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www.apworkshops.co.uk
www.apriliaforum.co.uk
www.apriliaownersclub.co.uk

Looking forward to the next track day


Posted By: IanG
Date Posted: 11 Mar 2024 at 22:14

It does look as though I may have used a stainless washer between the cylinder and mount, it could be that the spotfacing on the cylinder fouled slightly and needed a standoff,it was a few years ago now and the fine details escape me.  I could have a look when the rains stop and I can get to my garage again.



-------------
www.apworkshops.co.uk
www.apriliaforum.co.uk
www.apriliaownersclub.co.uk

Looking forward to the next track day


Posted By: tfcoulson
Date Posted: 14 Mar 2024 at 20:49
Yep it definitely needs some sort of washer there otherwise the roundness of the pot sticks into the heel guard too much.


Posted By: V60
Date Posted: 28 Mar 2024 at 12:13
That green pipe is absolute dog sh!t.
It sweats like crazy and absorbs moisture from the atmosphere.  
I went through 2 separate ones in 2 weeks before I binned them and used the original reservoir.

No idea why they're still being sold.


Posted By: legend88
Date Posted: 28 Mar 2024 at 13:03
Originally posted by V60 V60 wrote:

That green pipe is absolute dog sh!t.
It sweats like crazy and absorbs moisture from the atmosphere.  
I went through 2 separate ones in 2 weeks before I binned them and used the original reservoir.

No idea why they're still being sold.

Weight saving on race bikes that only go an hour between bleeds. That's the only reason they exist.

And as you say, completely crap and potentially dangerous on road bikes but so many people are so blinded by 'Race bling' that they don't even think anything through.




Posted By: V60
Date Posted: 28 Mar 2024 at 16:02
The Honda forums are full of folk complaining about them there too. 

It makes zero sense that a receptacle for storing brake fluid reacts badly to said brake fluid and is porous to boot.. bonkers!


Posted By: 426hemi
Date Posted: 28 Mar 2024 at 18:25
If you’re going to use pipe for the reservoir use the tygon.
https://www.ebay.co.uk/itm/111215279138?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=cIQwD279Q8a&sssrc=2349624&ssuid=ildoydmaqc-&var=&widget_ver=artemis&media=COPY" rel="nofollow - https://www.ebay.co.uk/itm/111215279138?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=cIQwD279Q8a&sssrc=2349624&ssuid=ildoydmaqc-&var=&widget_ver=artemis&media=COPY


Posted By: redratbike
Date Posted: 28 Mar 2024 at 18:35
i run an rsv4 master cylinder with a built in reservoir … KTM items also work and probably cheaper 

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Posted By: Fitz
Date Posted: 26 May 2024 at 10:31
I got a KTM unit is the same Brembo unit as on the RSV4 but with out the tax !! and loads on eBay as it is used on lots of different bike models 




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