Rear Brake...again!

Message

Dalemac · #16 Post by **Dalemac** » Thu Jun 23, 2011 8:13 pm

rear brake piston seals - where the hell can i get them? none of my "usual" suppliers carry them :S

I have read that KTM do them - does anyone have a part number?

Dale

D-Rider · #17 Post by **D-Rider** » Thu Jun 23, 2011 8:16 pm

I don't think anyone has investigated the rear brake yet - you could be the first.

Aladinsaneuk · #18 Post by **Aladinsaneuk** » Thu Jun 23, 2011 8:25 pm

A ktm dealer would be my starting point....

Dalemac · #19 Post by **Dalemac** » Thu Jun 30, 2011 11:28 am

Ok,

So i have replaced the rear disk (new), and the rear caliper (ebay) because i could not find anywhere to get piston seals.

The problem is still exactly the same. brake pads sticking on when braking/ binding on through heat.

I can only conclude that the mastercylinder is screwed. It seems to be letting fluid down into the caliper, but not enough back up into the reservoir.

Or could it be the fact that im using dot 5.1 brake fluid instead of dot 4?

Thanks for the advice.

Dale

Falco9 · #20 Post by **Falco9** » Thu Jun 30, 2011 11:50 am

Just a thought so don't flame me but............does the rod that pushes the piston into the master cyclinder have some free play on it?

I found I couldn't bleed the rear brake and the brake lever was tight with no free play (almost rock solid) until I figured out the rod had wound itself in. Once I backed it off and established some free play normal service was resumed

If memory serves its just a simple lock nut adjustment, might be worth checking as its easily overlooked

F9

dyzio · #21 Post by **dyzio** » Thu Jun 30, 2011 12:02 pm

Falco9 wrote:Just a thought so don't flame me but............does the rod that pushes the piston into the master cyclinder have some free play on it?

That.

I've tightened the rod too much and almost boiled the fluid which resulted in the brake being applied constantly. Glad I wasn't too far away and got back home ok.
Recently I've also helped a friend with her bikey, the rear was brake was dragging, main seal was ok but the dust seal was blocked with crap, that may have prevented the piston from returning freely.

As for falco rear brake seals: http://cgi.ebay.co.uk/BREMBO-CALIPER-SE ... 1e5f2bab32

But I think I'd look at the brake rod first (cheaper

)

HowardQ · #22 Post by **HowardQ** » Thu Jun 30, 2011 12:21 pm

I've had the same issue as F9, so certainly check for free play on the push rod.

To change the subject slightly.
Once I had freed mine up etc. which certainly helped performance, I never really got any decent improvement until I fitted some Gold Fren carbon ceramic pads. At least I now have a rear brake that does try to work.

Dalemac · #23 Post by **Dalemac** » Thu Jun 30, 2011 12:43 pm

The push rod thing. a while ago, i adjusted it. what i did was undo the lock nut and wind the bar all the way into the housing, away from the mastercylinder itself. Is this correct?

I can put the bike on the paddock stands, spin the wheen and apply the brake, and everything works as it should. it stops the wheel and releases as appropriate without dragging. When i ride it, if i press the brake, it brakes and releases, but not completely. Without appliying the rear brake again, just simply rotating the wheel causes it to bind on, the only thing i can do to get rid of this is to stop and let the disk cool down. the further i ride, the harder it binds on.

Dot 5.1 is fine im sure, and i always use gold fren sintered pads, infact im in love with them.

D-Rider · #24 Post by **D-Rider** » Thu Jun 30, 2011 12:46 pm

dyzio wrote:
As for falco rear brake seals: http://cgi.ebay.co.uk/BREMBO-CALIPER-SE ... 1e5f2bab32

Nice find .... and here is the company's website in case the ebay listing goes obsolete:

Roadrunner Motorcycles

.... and now saved with all the other calliper service part info in the technical area

Falco9 · #25 Post by **Falco9** » Thu Jun 30, 2011 1:47 pm

Dalemac wrote:The push rod thing. a while ago, i adjusted it. what i did was undo the lock nut and wind the bar all the way into the housing, away from the mastercylinder itself. Is this correct?

I can put the bike on the paddock stands, spin the wheen and apply the brake, and everything works as it should. it stops the wheel and releases as appropriate without dragging. When i ride it, if i press the brake, it brakes and releases, but not completely. Without appliying the rear brake again, just simply rotating the wheel causes it to bind on, the only thing i can do to get rid of this is to stop and let the disk cool down. the further i ride, the harder it binds on.

Dot 5.1 is fine im sure, and i always use gold fren sintered pads, infact im in love with them.

If you have free play at the lever i.e free movement on the lever before the brake is applied, the rod sounds likes like its adjusted properly. Have you removed the rod and made sure its clean and has a smear of grease on it?
Its sounds like something is binding and not releasing the pressure. Have you tried reverse bleeding the caliper to make sure there are no blockages in the Hydraulic system? Also how much clearance is there between the pads and the disc, you should be able to see daylight (just) between them. Do the pistons move freely? pushing one in should make the other push out, I use this cleaning system on both front & rear claipers to make sure all the pistons are free and not stuck when I check the calipers. You should be able to do this by hand / finger pressure on the pistons and get a nice smooth movement.
One last thought does the actual brake lever move freeley? is the return spring fitted properly?
Sorry for waffling on I'm just doing a mental re-call on the things I'd check if it was happening to me

F9

Dalemac · #26 Post by **Dalemac** » Thu Jun 30, 2011 2:22 pm

Thanks for the info f9.

I just took it to duo in lincoln, where the owner confirmed my fears. The brake is pushing fluid into caliper, but is not releasing. He told me i need a new mastercylinder.

he said that when you release the brake, the master cylinder should pull the fluid back into the reservoir. In my mastercylinder, it is pushing in, but then not releasing properly and hence keeping the brake on.

So i need a new rear mastercylinder if anyone has one lying around? new he can get one for £86 but i would prefer to get one second hand because he cant get it in for 7-10 working days. There are none on ebay, unless i can use a mille or tuono one?

Thanks,

Dale

Falco9 · #27 Post by **Falco9** » Thu Jun 30, 2011 2:50 pm

You can use the Tuono and Mille master cylinder as the disc size & caliper are identical, there wil be many other Brembo ones you can use as well from most Italian bikes but check the bore size is the same as the Falco as some are different on the Ducatis and MotoMorini etc..

I found these pretty quickly though. I've bought a few bits from Time Machine bikes on fleabay and his parts have always been very good. Make him an offer first though, I've always manged to get a few quid off as long as you dont take the pi*s of course

http://cgi.ebay.co.uk/Aprilia-RSV-1000r ... 53e806909e

http://cgi.ebay.co.uk/RSVR-RSV-Mille-Tu ... 5644e967d1

F9

Dalemac · #28 Post by **Dalemac** » Thu Jun 30, 2011 2:59 pm

Yes, i did look at the tuono/ mille ones, only problem is that the brake line attaches to the master cylinder on the top for the falco master cylinder, wheras it fits on the front for mille/ tuono.

falco: https://www.apriliayorkshire.co.uk/cata ... 20cylinder

mille: https://www.apriliayorkshire.co.uk/cata ... 20cylinder

may as well strip mine down and see if i can find the problem. got nothing to loose as its broken, no-one has spares and its nearly £90 new...

Dalemac · #29 Post by **Dalemac** » Thu Jun 30, 2011 5:14 pm

Im confused. Mastercylinder apart - everything looks fine. put back together and test and the pump works perfectly.

there MUST be air in the system still...

Dalemac · #30 Post by **Dalemac** » Thu Jun 30, 2011 8:12 pm

i fixed it. asolutely positively 100% fixed it.

I dnt know how or why, but somewhere between taking off the mastercylinder, rebuilding it and putting it back on, it is fixed.

i also figured out a brilliant way to get the fluid into the braking system without letting in any air, at all. and best of all, it took less than half an hour to do. If anyone is interested in how i did it, let me know.

Dale