Hot rotor on rear brake

[HeckticHaze]

I got the EBC replament rotor installed. Went through the caliper again. I only installed the main seals in the caliper. I left the dust seals out. Performed my regular Mightyvac bleed and then tried a reverse bleed. A real mess with brake fluid leaking at the bleed valve while performing the reverse bleed process. Good firm pedal was obtained. Installed the OEM brake pads and removed the PO EBC pads. Took the bike out for a ride. Still getting a warm rotor but not piping hot like before. Trying to figure out why I am getting a squeal when I engage the rear brake each time. Not sure if it's just initial seating of the new brake pads.

 

[gentsvmax]

Ooooohh, deja vu..If you didnt get ALL the air out of that caliper you could get a high frequency "chatter"
that'll sound like a squeal.
Thing is during my ordeal with the heated rotor/caliper I never had a problem bleeding that stock caliper,
it was the Harrison that was super sensitive to , 1. the elevation of the m/c in relation to caliper(during bleed),
m/c needed to be above the caliper.
2. The super long 34" brake line having any rise above either m/c or caliper.
3. I had to completely compress all pistons before beginning the reverse bleed.
Hopefully one or all of these three points can help out. I am right with you in getting off the bike and having
the front rotor/calipers barely even warm and the back caliper so hot I was sure it was cooking the rubber
seals etc.
Another thing! I just remembered this, I have a size 14 hoof. My brother said he would sometime notice my
brake light coming on during acceleration or just cruising.....made me wonder how often I had been doing
this, riding the brake, maybe building up pressure in the line causing the drag, just enough to heat things up.
Maybe that would be something else to pay attention to.

 

[HeckticHaze]

So I thought I had this rear brake issue pretty well fixed. I went out to winterize the bike today. It was about 45degF today. I was going to take the bike for a spin to warm it up and I could barely spin the rear wheel. So could this be an indication of moisture in the lines that has expanded do to the cold? I used brand new DOT4 brake fluid when I bled the brake system. Looks like it's back to the drawing board next spring.

 

[gentsvmax]

So I thought I had this rear brake issue pretty well fixed. I went out to winterize the bike today. It was about 45degF today. I was going to take the bike for a spin to warm it up and I could barely spin the rear wheel. So could this be an indication of moisture in the lines that has expanded do to the cold? I used brand new DOT4 brake fluid when I bled the brake system. Looks like it's back to the drawing board next spring.

Could it be that your M/S is adjusted for a short pedal travel, too short, causing this issue?

 

[Fire-medic]

I got the EBC replament rotor installed. Went through the caliper again. I only installed the main seals in the caliper. I left the dust seals out. Performed my regular Mightyvac bleed and then tried a reverse bleed. A real mess with brake fluid leaking at the bleed valve while performing the reverse bleed process. Good firm pedal was obtained. Installed the OEM brake pads and removed the PO EBC pads. Took the bike out for a ride. Still getting a warm rotor but not piping hot like before. Trying to figure out why I am getting a squeal when I engage the rear brake each time. Not sure if it's just initial seating of the new brake pads.

I think you're referring to the fluid leaking from the hose over the bleeder nipple? I use a piece of transparent/clear plastic hose, and a small hose clamp on the hose/nipple, that usually does a good job of allowing the brake fluid to enter the nipple and caliper, instead of peeing all-over the place. Sometimes I've had-to use teflon tape on the bleeder nipple, but I've found that to be more of the case when trying to use my MityVac to suck-down brake fluid from the master cyl through the bleeder nipple.

I tighten the hose clamp on the transparent hose enough to make a decent seal so when I press the plunger, the fluid doesn't leak around the hose. I can easily remove the hose/syringe, and also replace it once I draw-up more brake fluid, without having to tighten/loosen the hose clamp each time.

 

[MaxMidnight]

I think what he means is that the m/c piston is not fully returning so is keeping pressure in the line.
Have you tried disconnecting the pedal and linkage?

 

[Fire-medic]

You might want someone to check your foot position, you may need an adjustment to its pedal to allow your big foot to not keep pressure on the pedal, creating a dragging brake.

 

[HeckticHaze]

Guys, thanks for your replys. I made sure I set the linkage so the end of the adjusting bolt is visible through the lower linkage view port. I did adjust the pedal position a little lower so my foot would not press down on the pedal while riding. If I remember there is a dot on the side of the pedal assembly you line up with the spline it slides onto. If I was out of alignment between the pedal assembly and the spline would that effect the amount the brake pads retract from the rotor when the pedal is in its normal position?

 

[MaxMidnight]

If I remember there is a dot on the side of the pedal assembly you line up with the spline it slides onto. If I was out of alignment between the pedal assembly and the spline would that effect the amount the brake pads retract from the rotor when the pedal is in its normal position?

Doesn't the dot relate to the gear change?
Don't think so, brake pedal height is adjusted via the rod that connects the pedal to the m/c and NOT by rotating the lever on the spline..

I am suggestion you remove this rod to see if that allows the m/c piston to fully return to its rest position.

 

[Fire-medic]

Doesn't the dot relate to the gear change?
Don't think so, brake pedal height is adjusted via the rod that connects the pedal to the m/c and NOT by rotating the lever on the spline..

I am suggestion you remove this rod to see if that allows the m/c piston to fully return to its rest position.

Measure the exposed thread length and draw a diagram to recall where you started if you choose to try MaxMidnight's advice.

I think Sean might agree, the dust seal as it 'rolls' helps to retract the piston as pressure in the system is released. Also, the rotors aren't perfectly-smooth, they have high-spots which will push-back the pistons along with the dust seals. It's not a huge amount, if it was, you would feel the pulsating under your foot as you braked. A warped rotor would be very noticeable, and it would cause foot pulsating to a marked degree.

If you can smoothly move the piston in and out of the caliper bore with just finger-pressure, there has to be something in the hose or the linkage causing a failure to retract:

a] in the hose, it would be action like a 1-way valve, in an extreme case. I do not believe that's what you are facing here. A narrowing of the hose diameter due to deterioration, delamination, or accumulated crud could delay the smooth, rapid movement of brake fluid. That could cause a dragging brake, and the resulting heat would worsen things. The 'totally-collapsed internally-hose' would not allow the brake fluid to move back and forth. The wheel would lock-up, and you'd have to open the bleeder valve to release the caliper pressure, to allow the wheel to turn again.

b] in the linkage, I'm thinking the pedal isn't properly set-up for your foot, and you are partially activating your brake when riding. If it's a used bike, take the time to ensure that the pedal is set properly for your size.

You could adjust the brake light switch so that a small movement would illuminate your tail light. Someone behind you would easily-see that you're 'riding the brake.'

 

[Screwloose]

I got rear disk rotor overheating and pads seizing a few times over a couple of years. When I serviced the clutch master and slave cylinders I also done the brakes, now there are no problems with the back brakes at all. I‘m convinced the above is correct in saying there will be a certain amount of hydraulic suction that pulls the pads away from the rotor when you let go the brakes. 6 months and its never happened again.

 

[02GF74]

This is a strange one as you have addressed the obvious by replacing parts.

When the rear wheel is turning, there is a tiny amount of disc runout that pushes the pads out of the way so the pads do not drag.

Also when the brake lever is released, the small spring inside the master pushes the piston back drawing brake fluid and together with the square cross section piston seals, the pistons are pulled back.

Also, and FM will have a cow, I read that reverse bleed can reverse the piston seal. TBH I can't see how that could happen but I have never come across a service manual that suggests that, I've never had problems bleeding brakes nor clutch the normal way (except on a land rover which I fitted larger drum brakes and the bleed nipples not being at the highest point... but let's not get off track).

I still think the problem is with the calliper. Can you buy a replacement, ebay for example, clean and fit it? Do you know if the pistons fitted are original or aftermarket, possibly not in tolerance?

Also the push rod should have some slack, the brake lever needs to move a fraction before it starts to push brake fluid. Also check your foot is not resting on the pedal when riding, easily done (don't ask how I know but clue is a blued rear brake drum on a honda CG 125)

Lastly the rear wheel locked after no use is a bit strange, my theory, and bear in mind this could be BS, is that brake fluid is getting past the piston seal in the master so the slack is taken up. I have this problem on a mountain bike hydraulic brakes, holding the lever and cracking open the nipple to let out some fluid fixes it but it is not the solution.

Good luck, 'tis frustrating I'm sure.

 

[Fire-medic]

This is a strange one as you have addressed the obvious by replacing parts.

When the rear wheel is turning, there is a tiny amount of disc runout that pushes the pads out of the way so the pads do not drag.

Also when the brake lever is released, the small spring inside the master pushes the piston back drawing brake fluid and together with the square cross section piston seals, the pistons are pulled back.

Also, and FM will have a cow, I read that reverse bleed can reverse the piston seal. TBH I can't see how that could happen but I have never come across a service manual that suggests that, I've never had problems bleeding brakes nor clutch the normal way (except on a land rover which I fitted larger drum brakes and the bleed nipples not being at the highest point... but let's not get off track).

I still think the problem is with the calliper. Can you buy a replacement, ebay for example, clean and fit it? Do you know if the pistons fitted are original or aftermarket, possibly not in tolerance?

Also the push rod should have some slack, the brake lever needs to move a fraction before it starts to push brake fluid. Also check your foot is not resting on the pedal when riding, easily done (don't ask how I know but clue is a blued rear brake drum on a honda CG 125)

Lastly the rear wheel locked after no use is a bit strange, my theory, and bear in mind this could be BS, is that brake fluid is getting past the piston seal in the master so the slack is taken up. I have this problem on a mountain bike hydraulic brakes, holding the lever and cracking open the nipple to let out some fluid fixes it but it is not the solution.

Good luck, 'tis frustrating I'm sure.

When the master cylinder and the system is properly-bled, there is no "slack to-be taken-up." The slack is at the lever, where it contacts the piston end, outside the entire hydraulic system. Remaining air not thoroughly-bled from the hydraulic system just makes for a 'spongy' pedal/lever, and excessive travel before any hydraulic action.

As-to reverse bleed can reverse the piston seal, uh, no! The possibility of that happening is about on a par with a certain politician announcing he's lost re-election. The brake fluid enters the master cylinder chamber through the smaller of the two holes in the floor of the chamber, which is before the rubber piston seal on the piston's end. The only thing that a reverse-bleed could do, if you pushed enough fluid into the master cylinder to completely-fill it, is to cause fluid to pee-out-of the pressure equalization hole, when you squeezed the lever. Have you ever looked-at a handlebar master cylinder? There's a tiny kerf cut into the edge at the top of the reservoir, in the end of the cap, which you need to have the piston retract properly. A minute amount of air is allowed to vent the chamber so the piston can retract.

If the 'end of the piston' seal has a defect so it no-longer seals, rendering the brake ineffective, you have a condition known as an internally-bleeding master cylinder. Fluid bypasses the seal, no pressure from piston movement is generated, and it's time for a re-build kit, for new seals, or master cylinder replacement. If the rear of the piston seal fails, you have an externally-bleeding master cylinder, and you end-up with brake fluid dripping-off the ball-end of your brake or clutch lever.

 

[02GF74]

Re reverse bleed; I posted what I read on Internet, but can't see it happening. I don't do it that way but again reading on Internet there are those who swear by it. Nuf said on that.

Re. other point. This happens on a pair of formula r1 brakes. After a lengthy period of non use, there is a almost no lever travel I. e. all slack has gone, which is what I was referring to, and brake pads are locked onto the wheel.

The brakes were not touched so my explanation is that bake fluid has gotten into the system from the master and has pushed the master cylinder piston back. Don't understand yet how that can happen.

 

[Screwloose]

I should have mentioned when I strip and clean braking systems I clean out the callipers also. Taking the entire system apart and pulling out any crap caused by over-aged brake fluid done the trick for me. As for flatness tolerance control of the rotor between inner locating face and pad faces, all disks would have some anomaly as nothing can be perfectly flat, so I assume braking systems would use that error to their own advantage by pushing the pads slightly apart when rotating and also letting some air through for cooling. But i’m certain some of the people on here that work on brakes could give a better explanation. My brakes are now working as a new bike would. For an entire summer I had no confidence in the back brake not seizing and kept my speed down just incase, after doing all the work I thrash Trigger regularly with confidence and the brake rotor never heats up.

 

[Screwloose]

For reverse bleeding; i’ve been doing that all my life on different bikes, I just never knew what it was called until I came on this site. Even if I bleed by gravity I always finish by levering the pads apart to ensure the air is out through the master cylinder (reverse bleeding). As for the clutch I left the slave cylinder screws loose, then for last few bleeds tightened them to reverse the flow, without doing that there would be no clutch, because I tried it the gravity way first. I’m too tight to buy the kit, so devise my own ways to reverse bleed, getting every bubble I can out the system.

 

[Fire-medic]

For reverse bleeding; i’ve been doing that all my life on different bikes, I just never knew what it was called until I came on this site. Even if I bleed by gravity I always finish by levering the pads apart to ensure the air is out through the master cylinder (reverse bleeding). As for the clutch I left the slave cylinder screws loose, then for last few bleeds tightened them to reverse the flow, without doing that there would be no clutch, because I tried it the gravity way first. I’m too tight to buy the kit, so devise my own ways to reverse bleed, getting every bubble I can out the system.

If you read my post about changing-out the clutch slave cylinder, I describe making your own reverse-bleeder from a supermarket-purchase 'flavor-injector' syringe they sell in the kitchen goods, or by the meat dept. Buy at the auto parts store, a threaded wheel valve stem. Cut-off the hub of the flavor-injector syringe, drill-out the end to tightly-fit the threaded valve stem, placed into the barrel and protruding-through the hole you just-drilled in the syringe barrel end. This is where a trip to Ace Hardware may help. You could use a wide rubber fender washer, and a steel fender washer, placed on the outside the syringe barrel threads of the valve stem, to get a fluid-tight seal. Use the valve stem nut to snug-up the valve stem and the rubber and steel washers. Place a short 3" to 4" piece of clear-plastic hose onto the valve stem, use a small hose clamp to secure it. Use another hose clamp on the end of the plastic hose. Place the free end of the hose onto the bleeder nipple (don't forget to open the nipple!). Tighten this down before you push fluid into the bleeder valve. That will lessen the possibility of leakage of any brake fluid. The entire expenditure for that is probably the same for a six-pack of craft beer.

Draw fluid up so that the hose and the syringe are filled with fluid before trying to attach the hose to the bleeder nipple.

There is no need to not secure the slave cylinder to the engine case before reverse-bleeding the system. Torque those two screws down and get to reverse-bleeding. I know of no-way to more-quickly bleed the clutch completely with a minimum outlay of cash. Pay-attention to the master cylinder, when you see that solid geyser of brake fluid, and no tiny bubbles through the tiny master cylinder hole, it's bled. Install the reservoir cap, fan the clutch lever a few times, and you should have a great-feeling clutch lever, encountering resistance with little movement of the lever before it contacts the piston.

 

[Screwloose]

This is great stuff thanks, I’ve read it intensely and good for you putting the time into the cause.
To add; I always read your input as your command of the English language is better than mine and your technical input is excellent. Unfortunately (and this is maybe your flaw) any talk of syringe or money gets me arrested in Scotland LoL. Reverse bleeding for G1’s is the only way forward and is just what your getting across for this particular subject.
I can also see that you are good at inventing various ways of getting the job done, pushing forward on innovation and creativeness. For me though every penny is a prisoner.
For the clutch above, I could not have explained it better, better to reverse bleed than have in the back of your mind there may be some old fluid in your system.

 

[HeckticHaze]

Folks, thank you for your input. Next spring I am going to disassemble the brake pedal assembly and see if I have an adjustment issue at the master cylinder. Someone asked if the OEM pistons are in place in the caliper. I do not know. Not sure if they are stamped with the Yamaha part number. I will probably be disassembling the calipers again and I can check. I have replaced everything except the caliper casing, pistons, and the master cylinder casing. The rotor was replaced with an EBC. Yamaha does not sell the OEM rotor. I did use the Yamaha OEM brake pads. Looks like I have a few more things I can check.