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marktheaxeman

Back brake binding and overheating

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Hi,

I wonder if anyone can help me??

I have had a problem a couple of times recently with the back brake binding on on my 2002 v11 sport and causing me to stop and let it cool down. The disc gets very very hot - so much so you can hear it ticking.

The brake pedal actually goes solid with no movement in it at all.

I had the caliper apart previously to clean it and check that the piston were moving. It looked pretty clean to be honest. I sprayed a load of wd 40 around the pistons. I couldnt get the pistons to go back in with some pipe grips - they should do shouldnt they? 

I wonder if it may be air in the line or if there is something wrong with the master cylinder.

Has any one else had this issue??

Thanks in advance,

Mark.

 

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For sure, remove the caliper and turn the bleeder to the top for bleeding. That alone may solve it. Also, pull back the rubber boot under the master cylinder, inspect, clean, and grease. But only use silicon based lubricants around brake parts. Petroleum based lubricants will damage the seals. It is possible the WD-40 destroyed (swelled) your seals . . .  :huh:

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Someone please correct me if I'm wrong, but I'm pretty sure that WD is bad for the rubber seals inside the caliper and could cause them to deteriorate... 

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WD-40 could be bad.

But another possible issue is the brake lever is not adjusted correctly. It sounds like the lever may be not allowing the piston in the master cylinder to fully retract. That can cause the brake to drag, and as it drags the fluid heats up. The fluid heats up and expands. Without a way to bleed the pressure from the expanding fluid the brake applies more pressure on the pads to the disk. Thus continuing the cycle.

If the seals swell, that is clearly bad, But for it to apply more brake pressure as it gets hot points to te master not being allowed to fully return so that fluid can freely pass back into the reservoir. Another way it can happen is if the reservoir is over-filled.

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Thanks for your feedback guys.

It looks like i may have done more harm than good with the wd40. What silicone based lubricant can i use? and do you think that i will have to replace the seals now?

Also docc i had the caliper off after the first time it happened and moved it around to the same side as the pedal to bleed it through with new fluid - so i had it with the bleed nipple at the top then. 

Should the pistons slide back into the caliper when applying pressure with the pipe grips as they seemed pretty solid - just wondering if there is a problem with the master cylinder which it not letting the fluid back into the reservoir - i did have the top off the reservoir btw.

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When I got my Rosso Corsa, the rear rotor was blue and cone shaped. (!) The bolts sounded like a gun going off there was so much pressure on them. The brake line was routed incorrectly. I'm thinking it was too close to the exhaust system, got hot, and held the brakes on. Dunno.

I bought a new rotor and caliper and made sure the line was routed correctly and totally bled. I've read of improper bleeding causing this issue too. Yes, you should be able to push the pucks back into the caliper.

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The pistons MUST slide freely. When you apply the brake the square section seals distort at first as the piston moves, allowing the  pads to firmly grip the disc. When you release the brake it is the distorted seal that pulls the piston back to release the pressure on the pads and disc. As the pads slowly wear the seal will distort and then allow the piston to slide through autimatically taking up the clearance. If the piston is not free to slide the distorted seal is unable to pull the piston back and the brake will bind. The Norton Racing team told me to never use silicon brake fluid as it is too slippery, allowing the piston to slide through freely rather than distorting the seal meaning there is no force pulling the piston back. I believe it was Dowty who discovered how the square section seal worked, earlier attempts with round seal led to binding brakes and rapid pad wear.

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7 hours ago, marktheaxeman said:

Hi,

I wonder if anyone can help me??

I have had a problem a couple of times recently with the back brake binding on on my 2002 v11 sport and causing me to stop and let it cool down. The disc gets very very hot - so much so you can hear it ticking.

The brake pedal actually goes solid with no movement in it at all.

I had the caliper apart previously to clean it and check that the piston were moving. It looked pretty clean to be honest. I sprayed a load of wd 40 around the pistons. I couldnt get the pistons to go back in with some pipe grips - they should do shouldnt they? 

I wonder if it may be air in the line or if there is something wrong with the master cylinder.

Has any one else had this issue??

Thanks in advance,

Mark.

 

All good answers here so far but to reiterate.

Make sure the brake pedal is adjusted so the master cylinder piston fully retracts and doesn't trap brake fluid in the system.As the dragging brake heats up it then starts applying the brake automatically. Simple to check. Take the reservoir cap off and check when you apply the brake quickly you get a tiny backflow of fluid into the reservoir as the master cylinder piston closes off the reservoir feed hole at initial travel.

Dont use silicon brake fluid. Spongy brakes result as well as lubrication properties are inferior to traditional fluid.

Dont use WD-40 or solvents on brake seals.

Made sure you arent unconsciously dragging the back brake. Racers were often bad for this, used to swear on a stack of bibles they didn't do it but they did. They just didn't realize it.

Buy a 12 dollar brake moisture content tester off ebay and use it. When it indicates water level of over 2% in the brakes and clutch system flush and refill the system.

When you have the wheels off pump the brakes until the pistons extend until the pads touch, clean any exposed piston surfaces and then lever the pads back to the point where the caliper can be just pushed over the disk. This helps un-stick the pistons from the seals and give a good lever esp on bikes that dont do many miles. 

A pressure bleeder is WAY better than a vacuum bleeder and hand bleeding. You can buy a good one for $60us that will do the bike and the cars.

Rear brake caliper need to be removed and inverted for effective bleeding.

Very often the front brake master cylinder needs to be loosened off and rotated 15 deg or so and the lever operated slightly so air trapped in the connection between the master cylinder and the brake hose can rise into the reservoir. You will see the bubbles appear in the reservoir with the cap off as you jiggle the lever. Esp critical for bikes with clip ons that position the brake master to hose connection slightly above the base of the reservoir.

 

Ciao  

 

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Thanks for all the great feedback. 

I think I’m going to start with checking the master cylinder and get a service kit for it and perhaps get one for the Caliper too. This bike was a Japanese import with very low mileage so I’m guessing it’s just been laying idle for many years - which doesn’t help. 

Lucky Phil - your point about accidentally dragging the rear brake pedal is valid as I thought I may have been doing this. I think I’ll adjust the position of the lever so that it’s well out of the way. Also it has rear sets on - not sure if this would make a difference? 

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4 hours ago, marktheaxeman said:

Thanks for all the great feedback. 

I think I’m going to start with checking the master cylinder and get a service kit for it and perhaps get one for the Caliper too. This bike was a Japanese import with very low mileage so I’m guessing it’s just been laying idle for many years - which doesn’t help. 

Lucky Phil - your point about accidentally dragging the rear brake pedal is valid as I thought I may have been doing this. I think I’ll adjust the position of the lever so that it’s well out of the way. Also it has rear sets on - not sure if this would make a difference? 

I would suggest starting with checking the master cylinder and possibly rebuilding the caliper, not the other way around. Given history (WD40 exposure+long idle time) and behavior.

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As mentioned a few times, simply having the brake lever mis-adjusted so that the lever does not allow the piston in the master cylinder to fully return can cause the brakes to drag and heat up which then causes them to drag even more and the whole thing just spirals down the toilet. Make sure the master cylinder piston is fully returning. You should be able to push the pistons in the caliper in and the fluid behind them should freely return to the reservoir at the master cylinder. If not, something is wrong.

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You can easily narrow down the problem. It is unlikely both pistons are seized at the same time. Do the simple stuff first. As GuzziMoto suggested, make sure the lever isn't constantly applying a slight amount of pressure to the master. Wiggle the lever up and down, the rod going into the master should have some free play. If that is OK, while trying to push the pistons back into the bore, open the bleeder. If the pistons still won't move (and the bleeder is clear) the issue is in your caliper. If fluid comes out and they suddenly move when you open the bleeder, it would indicate the problem is ahead of the caliper. The next step would be to close the bleeder pump the brake and get the piston back  out. While trying to collapse the piston loosen the line at the master. Again, if the piston retracts, you can rule out the hose.  At this point you can go after the master cylinder.

At the end of all of this, if you didn't swell the dust boots with WD40, get some brake cleaner and wash off all the lube you applied.The boots should be clean and dry. If they are swelled up or torn they should be replaced.

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23 hours ago, Dan M said:

You can easily narrow down the problem. It is unlikely both pistons are seized at the same time. Do the simple stuff first. As GuzziMoto suggested, make sure the lever isn't constantly applying a slight amount of pressure to the master. Wiggle the lever up and down, the rod going into the master should have some free play. If that is OK, while trying to push the pistons back into the bore, open the bleeder. If the pistons still won't move (and the bleeder is clear) the issue is in your caliper. If fluid comes out and they suddenly move when you open the bleeder, it would indicate the problem is ahead of the caliper. The next step would be to close the bleeder pump the brake and get the piston back  out. While trying to collapse the piston loosen the line at the master. Again, if the piston retracts, you can rule out the hose.  At this point you can go after the master cylinder.

At the end of all of this, if you didn't swell the dust boots with WD40, get some brake cleaner and wash off all the lube you applied.The boots should be clean and dry. If they are swelled up or torn they should be replaced.

Thanks Dan M. I stripped it all down today and fitted a service kit to the master cylinder. I had real trouble getting the white nylon sleeve out - I had to destroy it to get it moving. I found there was a small amount of corrosion on the bore behind the sleeve. I removed it  with some fine wet and dry. 

 I wonder if this may have caused the piston to stick intermittently- causing the problem?? 

Fingers crosssed ...

ive got the caliper service kit coming this week and some new pads. 

The disc looks fine thank god. 

 

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# 1 name everything you have done to this bike involving anything rear of the fuel tank filler . ANYTHING

 # 2 how long has this problem existed ?

 # 3 are you telling us everything / have you forgotten anything ?

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