Hot rotor on rear brake

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HeckticHaze

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Came back from a ride Monday and my rear brake rotor was very hot to the touch. I put the bike on the center stand and turned the rear wheel and it was dragging pretty bad.

So today I removed and disassembled the rear calipers. What a pain breaking them apart. I had to bolt the caliper assembly flipped back on the bike to be able to remove the two bolts holding the calipers together. Can't believe how tight the bolts were.

There is some corrosion where the seals go. I'll take a dremel and brass wire brush to them. One side has a small protrusion on the outer edge of the piston cylinder. Is there any way I can clean this up? There is some corrosion on both pistons I must clean up too. Had to use the air compressor to get the pistons out.

I am a bit worried trying to align the caliper halves together and tightening them down without them shifting.

I am probably going to pull the Master cylinder and go through it. Wondering if that return fluid hole is plugged.
 

HeckticHaze

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So I cleaned up the grooves where the piston seals go in. Used some brake cleaner to clean the passage ways. Cleaned up the bleed screws. I still need to figure out how the clean up the side of the cylinder the pistons go in. I'm wondering is there enough clearance from the piston seals that hold the piston centered in the caliper assembly cylinder that I may not have to do anything with the protrusion into the cylinder? I just hate to make it worse.
 

02GF74

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There is some corrosion where the seals go. I'll take a dremel and brass wire brush to them. One side has a small protrusion on the outer edge of the piston cylinder. Is there any way I can clean this up? There is some corrosion on both pistons I must clean up too..
What is this protrusion that you mention?

Note that when discs brakes drag, usually due to pistons not retracting, the whole system will get hot - heat causes parts to expand so they drag more causing more heat that causes parts to expand so they drag .... I think you get the picture.

Unless the pistons are stainless steel, they are usually chrome plated so once corrosion starts, you can clean them up with brass brush or fine wet and dry paper but real are facing a loosing battle as the rust will return.

Your best best is to replace the pistons.

I've not looked at the brakes section in the manual but am surprise that the callipers need to be split to get the pistons out usually there is sufficient gap to get one piston out at a time - and the bolts holding t he calliper together will be bloody tight.
 

02GF74

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just looked through the manual and it states: Never loosen the bridge bolts on either side of the caliper (bridge bolts being the ones that hold the two halves together).
 

HeckticHaze

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I was able to polish up the pistons. They look pretty good but I hear what your saying. There are some dings in the cylinder on the corners where the seals go in. I can run my finger over and feel and see that the metal has pushed outward ever so slightly. My dilemma is do I leave it alone or do I try and hone that high spot down. I just do not want to damage the cylinder interior doing it. Not sure if I get a small fine file, very fine grit emery paper, or one of the grinding tools for the dremel. I may just leave it alone and see if everything functions ok. That high spot may not come in contact with the piston when its reassembled.

When I used the compressor the pistons did not bind. I could not move them by hand. I was able to get both pistons out with the caliper assembly intact. I made a little rig with two pieces of thin wood and two machine screws on each side to hold the one piston in while I removed the other. I put a piece of cardboard and a rag over the cylinder hole while I used the compressor to push out the other piston. I was concerned I could damage the cylinder hole when that piston let loose.

I could not do a proper cleaning of those piston seal areas without removing the caliper halves. I could not get the right angle with the dremel brass wire tool to get that crap out of the corners. That has burned me before not getting the new seal to sit down flat in that slot because there is still material in there.
 

Fire-medic

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At this point, you've already split them, what's the big-deal to re-assembling them, and seeing how they work? You should be able to move easily by-hand the pistons in & out, once they're replaced. I would have no qualms about trying to dress those dings out. It's the seal which keeps the brake fluid in-place, the bore just needs to be the vessel in-which the brake fluid is held. You would have to do a real job on a caliper to warp it, though I can see where Stevie Wonder might not (!) do such a good job on dressing the caliper bore. I've split calipers before, yes, I saw the instructions in the shop manual about not-splitting the halves. All you really need to-do is ensure that the o-ring isn't pinched when you re-assemble them, in my experience. Some blue thread-locker, and look in the torque specs chart in the appendix of the shop manual to see how-tight those bolts need to-be.

If you had not been able to get the pistons out with shop air, I use a grease gun, it works every-time, if air pressure won't, of-course, you have to clean them thoroughly of grease, no real problem as you're splitting the calipers, anyway.

Don't forget to completely flush all the old brake fluid out of the brake master cyl & the line. I suggest a reverse-bleed, for me, it works better than even my venerable Mity-Vac does.
 

Zeus36

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Please post pictures! Brake fluid will absorb water -this will heat up during braking, expanding enough to force the piston out and cause your pads to hang up. Next time use fine witness marks first if you are going to split the caliper halves. I would clean up any high spots or dings as you have the thickness of the piston seals to take up any small inconsistencies. Recommend you use emery cloth wrapped around a rectangular piece of wood to ensure squareness. Wet the emery cloth with WD-40. If you are going to clean up the piston bores, use emery cloth wrapped around a dowel. The dowel should be as large as possible and still fit in the bore. Hold the caliper in a vise and keep the dowel perpendicular to the bore. Again do this wet with WD-40 or water. You can use finer grades of abrasive to get to the appropriate surface finish. Do all this by hand so you don't go overboard. Clean everything with isopropyl alcohol after sanding. Use silicone O-ring lubricant on the piston seals. (I also apply the O-ring lube inside the bores as a coating, then use a cloth to remove the excess.) Apply copper or Moly Never-seize lightly to any fasteners unless you're going to use a thread locker on them. Since they say not to loosen the bridge bolts, there is no torque spec in the manual for them. You will need to find the general torque specs in the manual for a comparable-sized, and same grade bolt. As Fire-medic states, flush the brake system. I use a syringe for reverse bleeding.
 

Fire-medic

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I often use deep sockets w/wet or dry sandpaper to sand-down something circular-bore, like a caliper. I use something a bit smaller than the bore on-which I'm working. I have ab S-K 3/4" socket set I can use for the big-stuff.

I use a slow drill for this: You can hone a master cyl in < 3 minutes by using a long extension 3/8" drive, w/fine grit sandpaper wrapped-around it. Take your time, clean out the crud/dust, check the bore, repeat as necessary. Rinse it thoroughly.
 
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Zeus36

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I often use deep sockets w/wet or dry sandpaper to sand-down something circular-bore, like a caliper. I use something a bit smaller than the bore on-which I'm working. I have ab S-K 3/4" socket set I can use for the big-stuff.

I use a slow drill for this: You can hone a master cyl in < 3 minutes by using a long extension 3/8" drive, w/fine grit sandpaper wrapped-around it. Take your time, clean out the crud/dust, check the bore, repeat as necessary. Rinse it thoroughly.
Interesting method!

I'd be afraid of using a steel socket on aluminum due to the possibility of scoring the softer base metal. I could turn out something similar on my lathe using wood with a reduced end as a shank to fit into a my variable speed cordless drill. Slot the side with a bandsaw to tuck in the sheet of abrasive....
 

MaxMidnight

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Please post pictures! Brake fluid will absorb water -this will heat up during braking, expanding enough to force the piston out and cause your pads to hang up.
Whilst brake fluid id hygroscopic (absorbs water) the water would only be relevant if its coefficient of expansion is significantly greater than the brake fluid as it heats up but is below its boiling point (BP).
Where it is an issue is the effect it will have on the BP of the fluid and the potential to corrode the metals in the system.
There are two BP's given for brake fluid; dry is for new fluid and wet for when the maximum permitted amount of water has been absorbed.
For example, Dot 4 has a dry BP of 230°C and wet is 155°C. Fluid should be replaced once is is below the wet BP.

The issue is not with the expansion of water but when it boils and becomes gaseous. This produces vapour locks which can be compressed and as a result a loss of pressure transfer from the master cylinder.
 

Fire-medic

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Interesting method!
I'd be afraid of using a steel socket on aluminum due to the possibility of scoring the softer base metal. I could turn out something similar on my lathe using wood with a reduced end as a shank to fit into a my variable speed cordless drill. Slot the side with a bandsaw to tuck in the sheet of abrasive....
The 'use a large socket' method is a manual-use only, no power equipment, method of finding a piece of equipment to aid in holding the shape of the socket to allow for the sandpaper to cut with a degree of control.

The 'piece of sandpaper wound-around a long 3/8" drive socket extension" and used with a cordless drill, is a way to quickly-hone a master cyl bore to return said-piece to service, before fitment of a rebuild kit. No lathe-turning, no bandsaw-slotting necessary. It's literally 'making-do with what's on-hand,' to repair a wounded ride. Yes, you could use the methods you've proposed, my lathe hasn't arrived in Santa Claus' sleigh yet. Fortunately, I did-receive a bandsaw recently, I had one, and sold it, and bought another. I also got a BORA PM-1000 swivel-caster dolly for it, because my workspace is constrained by a lack of workspace. The BORA dolly will allow me to easily retrieve from close-storage the bandsaw for work to-be done.

I agree with Max Midnight that a periodic changing of brake fluid will reduce the incidence of corrosion inside the sealed system of your brakes, hydraulic clutch, or whatever. Yes, brake fluid deteriorates with age. The brake fluid 5.0 is not hygroscopic (it doesn't absorb water) but it does not play-well with traditional mineral-based brake fluids, and they should never-be mixed. DOT 3, DOT 4, and DOT 5.1 all can be mixed, however, using DOT 3 to replenish DOT 5.1 results in a lowering of your boiling point, which could be an issue if you're coming to the end of the Mulsanne Straight and heading into the Virage de Mulsanne, where you need to go from near-top-speed to less-than 1/3 of that, to negotiate a right-hand corner. For those of us popping an occasional wheelie while testing our VBoost while riding with the Michigan Hooligans, something wet, suitable for the purpose, and not displaying dew-point water-holding characteristics will probably-suffice.

Craftsman bandsaw.03.jpg Craftsman bandsaw.04.jpg BORA PM-1000 done.jpg
 

HeckticHaze

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Folks, I want to thank all of you for your input. I did take Zeus36 suggestion with the wider diameter piece of wooden dowel and very fine grit paper and hone down those two high spots I had. I did have to use some of the gray it's like brillo pad to polish the cylinder after using the paper and water. Sorry no PICs. Camera is busted on the phone. So rear master cylinder was also rebuilt. That damn little hydraulic fluid hole was cruded up. Some brake cleaner, piano wire, and compressed air cleaned that out. Rear calipers are back together. Bled system with MightyVac. Took a while to get a firm pedal. First time I have had to go back and forth between two calipers and one oil feed. Getting ready to take a ride and check out my repair.

Fire-Medic, you had some information on the reverse bleed I think in another article you posted. What was the rig you built to perform a reverse bleed with? What is the screw size for a bleed screw on the 2007 Vmax calipers? What was the type of screw you purchsed and inserted instead of the using the bleed valve? I think you may have modified the screw too. Did you install teflon tape on this screw when you install it into the caliper to keep fluid from escaping or air entering? I have lab type syringes that I use to fill the master cylinders with. Could I use these with the proper tube I.D that will fit over the screw and the end of the syringe. At the master cylinder reserve, can you leave the rubber insert out and just loosely put the cover on? My concern is I push to hard down on the syringe and I will have hydraulic fluid on everything. One other question, you do not have to position the brake handle (tie it to the handle)or brake pedal (pushed down) when you force the fluid in from the caliper side? Sorry for all the questions. I want to get my ducks in a row when I try my 1st reverse bleed. From what all of you state, that this method sure beats the standard hydraulic bleeding procedure.
 

MaxMidnight

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...install teflon tape on this screw when you install it into the caliper to keep fluid from escaping or air entering?
I do

...lab type syringes that I use to fill the master cylinders with. Could I use these with the proper tube I.D that will fit over the screw and the end of the syringe.
Yes bet the larger ones are better as they can hold more fluid. I#ve found that silicon tube works best.

At the master cylinder reserve, can you leave the rubber insert out and just loosely put the cover on? My concern is I push to hard down on the syringe and I will have hydraulic fluid on everything. One other question, you do not have to position the brake handle (tie it to the handle)or brake pedal (pushed down) when you force the fluid in from the caliper side? Sorry for all the questions. I want to get my ducks in a row when I try my 1st reverse bleed. From what all of you state, that this method sure beats the standard hydraulic bleeding procedure.
Yes you can leave it out and also the cover; you are only pushing the syringe plunger slowly so shouldn't get any spillage. That said some rag around the m/c would be a prudent precaution.

One other question, you do not have to position the brake handle (tie it to the handle)or brake pedal (pushed down) when you force the fluid in from the caliper side?
Leave the pedal/ lever in the rest position.
 

Fire-medic

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MM (above) appears to have answered most of your questions, so thanks.

No-need to tie-down a hand or a foot lever when doing the reverse-bleed. Keep an eye on the fluid in the master cyl, when you stop viewing the air bubble 'fizzies' out of the hole in the floor of the master cyl, it should be bled. At that point, I would re-attach the cap, and a few pumps of whatever lever it is, you should quickly have a firm lever or pedal, w/minimal movement, assuming that you don't have an internally-leaking master cyl.

I made my reverse-bleed syringe out of a flavor-injector syringe you can buy at your local supermarket, probably in the meats dept. They're not-expensive. When you're done with it, I suggest rinsing it out with mineral spirits and let it dry thoroughly. Xylene would probably work too, though some solvents may remove the ink on the side of the barrel. I used a machine-screw thread tire valve, not the all-rubber one, with the valve core removed, and a piece of clear-plastic tubing to snugly-fit the tire valve body exterior, to attach to the bleeder nipple. You can use a spring-steel 1 piece hose clamp, or a small traditional screw-type hose clamp if you wish a tight purchase upon your bleeder nipple. I don't usually use one, I just contend-with a bit of seepage, having a roll of paper towels close at-hand.

As to the bolt I believe I used one of the caliper mount bolts to the brake stay.

Sounds like you've done bleeding in the past, just remember that the master cyl, if open, can throw a jet of corrosive fluid several feet, if you use a vigorous squeeze or foot-stomp. I have three various Mity-Vacs, and I rarely use 'em anymore, because a reverse-bleed is quicker and better.

When you are ready to begin, I add brake fluid to the caliper or the slave cyl before replacing the bleeder valve, fill it to the bottom of the tapped hole. Then insert the bleeder valve. If it appears that much fluid leaks-around the bleeder valve threads when pressing the syringe barrel plunger, I'll wrap a couple turns of teflon tape around the bleeder valve and replace it.

If you look at the pics I have in the thread for the slave cyl, I have pics of the bubbles, and the geyser of fluid, it's a small geyser, no 'Spindletop.'
 

Zeus36

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[QUOTE="Fire-medic, post: 488410, member: 6380" Fortunately, I did-receive a bandsaw recently, I had one, and sold it, and bought another. I also got a BORA PM-1000 swivel-caster dolly for it, because my workspace is constrained by a lack of workspace. The BORA dolly will allow me to easily retrieve from close-storage the bandsaw for work to-be done.

[/QUOTE]

A nice Craftsman bandsaw and Made in America too!
My bandsaw is a knockoff of a Walker-Turner I got for free. I picked up a slatwall display on wheels just for the slatwall, but the bottom section was a perfect fit under the bandsaw base, so it is now mobile. I just installed locking casters on my table saw (Roybi BT3000 -also free from my General Contractor when he finished out house). My Bosch mitersaw is now clamped to an Audio-Video cart/two-wheel dolly that was in the scrap metal bin at work. All three machines sit side by side against the shop wall. I just pull the one I need forward of the other two....
 

Fire-medic

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Yes, bringing the floor tools out when you need one is a good way to maximize limited space. My Powermatic table saw is on wheels, my 'pillar drill' as the U.K. guys call them, (what's that?) is not on-casters. I have two 12" 240V 1 Ph radial arm saws on casters or a collapsible table, in two different locations.
 

HeckticHaze

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So I'm not a happy camper. Took the bike out for a ride and the rear rotor got hot as hell again. Rebuilt the calipers and pistons went in smooth by hand. No issues. Rebuilt master cylinder. Cleaned everything out. New kit went in smooth. When I press the rear brake pad it engages the rear wheel and stops it. It just is not backing off enough to keep the brake pads off the rotor. The only thing I have not changed is the brake line. Looking at the printed info off the line. It is the original line. I would have thought if it had partially collapsed, I would have not been able to bleed the system. The other thing I noticed was the difference in distance between the brake pads and the rotor when reinstalled the caliper (not centered). I did not think anything of it because I thought as you bleed the system the pistons will extend outward until contacting the brake pad and rotor then retreat back when the brake pedal is released. I looked at the Yamaha manual and saw no missing washers on the caliper assembly mounted to the bracket.

I adjusted the brake pedal distance per the Yamaha manual. My understanding this does not affect the release distance of the brake pad just the distance to fully engage the brake.

What did I miss guys? Any words of wisdom would be appreciated.
 

Parminio

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Do this:

Hit the rear brake and get it to seize up. Once it does, brake the bleeder valve lose. If the pistons pop back in, you've got a clogged line or metering block.

Clean/replace as necessary.
 

HeckticHaze

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Parminio, do I have to hold the brake pedal down when I open the bleeder valve? The brake does stop the wheel, it just will not back off enough and I get the pads dragging on the rotor.

They are the original hoses and over the 10 year limit. I see posts from people that have used Galfer and Spiegler brake and clutch hoses. Does anyone have a preference quality wise to either of these manufacturers? Do these manufacturers install the rubber grommets on the outside of the hoses to attach them in certain areas of the bike like the OEM lines have? If they do not, what do you do, zip-tie them in place?
 

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