Brakes

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Falcopops · #16 Post by **Falcopops** » Sat Mar 26, 2011 3:25 am

Dalemac wrote:I never really got round to fixing this issue - knida bad as i have done quite a few miles since then!

If i use the rear brake - it binds the wheel, makes it very difficult to turn and manouver.

brake fluid level is fine, everything seems to be working mechanically.

another poss cause of the problem is no free play in the actuating rod
so when the piston is back it will not clear the recuperation hole so fluid cannot get back to the reservoir ... normally only happens when peeps adjust the pedal position
Could someone explain this a little more?

Dale

There is a little plunger pin attached to a ball joint at the rear of the brake pedal, it dissapears into the rubber dust seal on the rear brake master.

This pin is threaded at the ball joint end. You should be able depress the brake pedal a little before the rod starts to actuate the brakes. if there is no slack, undo the lock nut in front of the ball joint and screw the rod in a little (normal threads and 10mm nut) until you get a little play nip the lock nut and try.

Olig7475 · #17 Post by **Olig7475** » Mon Mar 28, 2011 10:44 am

Andy, did you replace the seals on your rear calliper?

I need to look at mine, it got an advisory at the mot last week so was going to strip it down (along with the front callipers) and was wondering if anybody had bought a set of the seals for sale on ebay.

Cheers

D-Rider · #18 Post by **D-Rider** » Mon Mar 28, 2011 5:36 pm

Olig7475 wrote:Andy, did you replace the seals on your rear calliper?

I need to look at mine, it got an advisory at the mot last week so was going to strip it down (along with the front callipers) and was wondering if anybody had bought a set of the seals for sale on ebay.

Cheers

No - I've never needed to do this

Dalemac · #19 Post by **Dalemac** » Thu Apr 14, 2011 8:57 pm

Any mor suggestions as to why my rear brake lock on a little bit while being used? getting very iritation now!

Dale

D-Rider · #20 Post by **D-Rider** » Thu Apr 14, 2011 9:01 pm

Dalemac wrote:Any mor suggestions as to why my rear brake lock on a little bit while being used? getting very iritation now!

Dale

please let us know what you've done of the suggestions we've made so far and what difference (if any) they made.
Might give us some clues as to what to suggest next ........

#21 Post by **Kwackerz** » Thu Apr 14, 2011 9:17 pm

Well youve got in theory 4 places where problems can occur.

1. The pedal. If it sticks it could hold the brake on
2. The rear master cylinder incl. actuating rod from the pedal. This is common as a sticking point (pun intended) on RSV and SL (overfilled reservoir/lack of freeplay)
3 The brake line itself. If it's excessively kinked or twisted or crimped somewhere along it's length, the fluid will be squeezed through however will resist flowing back the other way as quickly, thus keeping the brake on
4. The rear caliper. Shitted up pistons, poorly assembled caliper assemblies.

Bit of steady fault finding should find the cure easy enough

Dalemac · #22 Post by **Dalemac** » Tue Apr 19, 2011 4:47 pm

so far i have:

1. removed the lines and cleaned, removed the caliper and piston, cleaned and put back together. reassembled and the problem is no different.

2. checked the fluid is at the correct level. even removed some to make sure.

3. adjusted the pedal/ actuator rod - this is now screwed in as far as possible (away from the mastercylinder) and still no difference.

To sum up the problem again, if i use the rear brake, it stays on until it has sat for a few minutes to cool down. This only happens while riding, if i have it on a paddock stand, rotate the wheel and use the brake, it is fine. Until it gets some major friction it works perfectly!

gonna take the system apart again, nothing like a tripple check....

Aladinsaneuk · #23 Post by **Aladinsaneuk** » Tue Apr 19, 2011 4:59 pm

am guessing that the inside of the caliper is where the fault lies - iirc there are a couple of returns that can get occluded easily and would do this kind of thing

I am really digging into the depths of my memory and i think some one on af1 had a similar set of symptoms...

D-Rider · #24 Post by **D-Rider** » Tue Apr 19, 2011 4:59 pm

Dalemac wrote: 3. adjusted the pedal/ actuator rod - this is now screwed in as far as possible (away from the mastercylinder) and still no difference.

Won't that tend to load the master cylinder if you wind it too far that way?

.... assuming I've understood correctly what you've done.

Dalemac · #25 Post by **Dalemac** » Tue Apr 19, 2011 5:30 pm

Aladinsaneuk wrote:am guessing that the inside of the caliper is where the fault lies - iirc there are a couple of returns that can get occluded easily and would do this kind of thing

I am really digging into the depths of my memory and i think some one on af1 had a similar set of symptoms...

i dont have a clue what you just said....

D-Rider wrote: Won't that tend to load the master cylinder if you wind it too far that way?

.... assuming I've understood correctly what you've done.

As i understand it, this removes the loading from the master cylinder. unscrewing it essentially makes the rod longer, which pushed into the mastercylinder more.

anzacinexile · #26 Post by **anzacinexile** » Tue Apr 19, 2011 7:30 pm

OK, try the following.

Get the brake to seize on and IMMEDIATELY undo the bleed nipple. If still seized its the caliper at fault, if it frees then there's a problem in the hydraulic circuit somewhere

Also, reading your post you have screwed the push rod the wrong way. you should shorten it to make absolutely sure there's free play between the pedal and the piston

D-Rider · #27 Post by **D-Rider** » Tue Apr 19, 2011 8:01 pm

anzacinexile wrote:OK, try the following.

Get the brake to seize on and IMMEDIATELY undo the bleed nipple. If still seized its the caliper at fault, if it frees then there's a problem in the hydraulic circuit somewhere

Excellent plan

That should clarify things a fair bit

anzacinexile wrote:
Also, reading your post you have screwed the push rod the wrong way. you should shorten it to make absolutely sure there's free play between the pedal and the piston

Yeah that was what I was trying to get across - I think you've explained it better

Dalemac · #28 Post by **Dalemac** » Tue Apr 19, 2011 8:38 pm

anzacinexile wrote:OK, try the following.

Get the brake to seize on and IMMEDIATELY undo the bleed nipple. If still seized its the caliper at fault, if it frees then there's a problem in the hydraulic circuit somewhere

Also, reading your post you have screwed the push rod the wrong way. you should shorten it to make absolutely sure there's free play between the pedal and the piston

I shall try this tomorrow before taking it all apart.

maybe i didnt explain it too well, but shortening the push rod is what i did.

i will post back tomorrow with my findings...

Dale

Dalemac · #29 Post by **Dalemac** » Wed Apr 20, 2011 1:54 pm

Ok, i believe the problem is now sorted.

i took the bike for a spin, using only the rear brake, so it wqas nice and siezed on. bled the system and after a little bit of fluid, a rather large line of air came whizzing out. the wheel freed up instantly.

took it for another spin, and although the disks were red hot, they were no longer locking on.

i can only conclude that the air was being held in the caliper, but was moving when warm, but at thge same time moving back when cooling down, relieving the system. weird how it never came out when bleeding with a cold system, and yes i did remove the caliper when bleeding.

the rear disk is now well and truely shagged. a wavey one will be here soon, chuck it on, replace the pads and be done with it for the rest of the year.

So, basically, there was an air pocket which was moving around based on temperature, but when cold wasnt being forced out through bleeding.

Thanks for all the input everyone.

Dale

Samray · #30 Post by **Samray** » Wed Apr 20, 2011 3:13 pm

You sure it was air and not steam? If you have water in the fluid it would boil in the caliper and expand when that hot.