Skip to content

Ask an Expert Sticking brakes... Technical

You are in... Forums > Ask an Expert > Technical > Sticking brakes...

Got something to say?

Got something to say?

Go to most recent reply

swen

Joined:

Aug 08

Posts: 21

swen says:

Sticking brakes...

Hi all. I need your help: when I move my bike in a morning - front brakes(Nissin 4 pots) pops(Suzuki TL1000S).There are pad marks on a disks(abe-aftermarket).First I serviced brakes(new seals,cleaned,pads are Goldfren-plenty of meat left)-same.Next master cylinder repair kit-same.Bled the brakes,fluid level- fine. Now run out of ideas. Could the aftermarket disk are cheap metal or maybe pads are crap somehow?... Cheers

Reply to this Topic  
  • Posted 2 years ago (21 March 2013 19:44)

Post a message in Technical

Fields marked with an asterisk * are required

   

Please note. You cannot submit more than 4000 characters as a message.

Upload image(s) from your computer (up to 3 images)

  1.  
  2.  
  3.  

Terms of use

Use of our community areas and forums is subject to important terms of use. By joining our community and using the features you agree to be bound by these terms. See terms of use below. 

Cancel
davidstowe358

Joined:

Jun 08

Posts: 185

sticking

sounds like your caliper pistons are not being pulled back in enough that could be because there is no vaccum in the master cylinder.

try this.....
1. Remove brake fluid reservoir cap and rubber diaphragm
2. Remove the first front caliper and push the pistons in so that they are flush with the caliper (make sure the reservoir dosen't overflow) also do not pump the lever yet.
3. Do the other caliper and follow step 2.
4. Refit both calipers fitted with pads back to there rightful places
5. Refit the rubber diaphragm and the cap to the reservoir 
6. Now you can pump the lever which will cause a vaccum in the system and suck those pistons back a little bit further.
7. Have a cuppa

Reply to this Topic
Arthurshandy

Joined:

Mar 13

Posts: 26

Arthurshandy says:

Vacuum in reservoir

Hi


Just getting my head around the idea of a vacuum in the reservoir pulling the pads back as I've never heard that before.

I can see how the vacuum is created but will it be sufficient to pull the caliper pistons? 

If that were the case, surely the oil level in the reservoir would always rise to the top and the pads would get pulled further away from the disc as they wore.

Very interesting statement though and definitely got me stroking my chin.

I'd be very careful attempting to, in effect, try and keep the fluid level at its lowest possible level. Could be risky!

Reply to this Topic
kcmc

Joined:

Jan 08

Posts: 7191

kcmc says:

Suzuki TL 1000S Year?

Hi Swen

I would go with the aftermarket disc's being the problem(not necessarily cheap?)the after market disc's could well be of a higher iron content than the standard equipment.The higher iron would have the disc's a lot more susceptible to the weather i.e. rain and salt corrosion,this combined with the sintered brake pads your probably getting an electrolysis problem happening.Probably need to wash your brake disc's and calipers in clean fresh water and dry them before putting it to bed for the night?,that's just my take on this anyway,not so sure of the other fix?never tried it:wacko: Good Luck

KCMC:tongue:

Reply to this Topic
davidstowe358

Joined:

Jun 08

Posts: 185

sticking

hi arthur this is the correct way to set up the braking system, as the brakes will work fine without the rubber diaphragm but the pistons will not retract enough without it. diaphragm is there doing a job for a reason.


so if you bleed brakes with the cap and diaphragm removed (which is the only way because you need to keep adding fluid) and you get a good lever you should follow the steps above. otherwise the diaphragm is not doing it's job at all. 

Reply to this Topic
Arthurshandy

Joined:

Mar 13

Posts: 26

Arthurshandy says:

Brakes

Hi again.


Just my two penneth, but I tend to agree with kcmc with regard to your "problem". 

If it is just a "click" first push of the bike in the morning it is probably not much to worry about as long as the discs rotate freely after the first push. I've had the same symptoms on most bikes over recent years, although not usually just overnight. But it has always coincided with water being involved the last time I used the bike.

There was a time when cast iron discs on European bikes greatly out performed those of the stainless discs found on jap bikes. So iron is not necessarily a totally bad thing. Cast iron is actually a reasonably good material for brakes. But it rusts! And is heavy!

Things have moved on.

Reply to this Topic
Arthurshandy

Joined:

Mar 13

Posts: 26

Arthurshandy says:

Sucking brakes

Hi davidstowe358


Sorry, but I was typing just as you submitted your post. I didn't mean to necessarily disagree with you. Only that I agree with kcmc as to the likely cause. 

In fact I'm very interested in what you have said.

But surely we could have a vacuum above the oil without needing a diaphragm? Just a good seal against the top cap (sealing against atmosphere) would allow a vacuum to occur?

No?

[This Reply has been modified by the Author]

Reply to this Topic
Arthurshandy

Joined:

Mar 13

Posts: 26

Arthurshandy says:

Vacuum?

Ok. 


I thought about this and reckoned the diaphragm must be vented. Then it would all make sense.

Been out to the garage and checked three brake reservoirs. They're all vented.

The way they achieve this is that under the screw on cap there is a large plastic washer. This looks innocuous enough, but a careful look reveals three little radial slots..

These will vent the top side of the diaphragm to atmosphere. 

Sorry, but it looks like no vacuum.

As long as these little slots remain clean, the top side of the diaphragm, and therefore the fluid in the reservoir, is at atmospheric pressure. It looks like the fluid in the reservoir can never be anything else.




Reply to this Topic
davidstowe358

Joined:

Jun 08

Posts: 185

sticking

hello arthur

                 I'm not saying i'm right and your wrong.
But what i am saying is i had this problem a couple years ago where my pads were sticking to my discs so bad it was causing rust spots/pitting on two pairs of discs. as you can imagine i was very upset to see this.
so after a lot (and i mean a lot) of chatting to motorcycle techs about it i was told to try this method and it worked for me at least. Now this is how i do it all the time and the wheel spins more freely.
But yes i do see the vent holes youre on about.
just one more thing if there is no vuccum how does the diaphragm get pulled inside out. also i do see your point but as i say this does work on my bike...

Reply to this Topic
Arthurshandy

Joined:

Mar 13

Posts: 26

Arthurshandy says:

Balanced diaphragm

Quote: "just one more thing if there is no vuccum how does the diaphragm get pulled inside out"

Hi davidstowe358

I can explain that. 

First of all imagine there is no top on the reservoir, so it is more like an open tank, as you might have in your loft. Then as the pads wear over several thousand miles the fluid in the tank would go gradually down.

The diaphragm is put there precisely to let this happen, but at the same time exclude any contact with the (humid) air above it. Brake fluid is extremely hygroscopic, meaning it readily absorbs water contained in the atmosphere. This has at least two very undesirable effects on brake systems so has to be kept out. Water boils a lot easier than pure brake fluid and obviously water also corrodes aluminium and steel, two materials used in critical instances in both master and slave cylinders.

The diaphragm (or bellows might another good name for it) allows atmospheric pressure to keep acting on top of the oil in the reservoir, whilst excluding any contact with the atmosphere. 

Actually, the cap on top of the reservoir needn't be a cap at all. A ring would work fine, but it wouldn't be very practical at keeping debris out or damage occurring to the diaphragm.

Make any sense?

[This Reply has been modified by the Author]

Reply to this Topic
eatcs01

Joined:

Aug 02

Posts: 3260

eatcs01 says:

sticking brakes

Do the brakes bind on, or stick at any other time? Or are they merely sticking onto the discs due to residual water/salt left over from the previous ride??

If they free off as soon as you move, and stay free, then it's normal.

And FWIW, goldfren pads are shite.

Reply to this Topic

Page

Compare Insurance

Save money by comparing quotes. It's quick and easy

Motorcycles for sale

 

It's only £13.99 to advertise your motorcycle on MCN

Sell your Motorcycle

Motorcycle pricing tool

New! Find used bike prices