timkil wrote:Thanks for that PITApan. I looked at the angle at the banjo bolt and thought that could be changed to accommodate the length. I had been wondering about those metal lines. That picture is my bike's twin. Guess I'll go with flexible lines off of the splitter even though I hate bleeding brake lines.
With flex lines off the splitter bleeding gets easier. You remove your ECU from the splitter, unstrap the splitter and you can angle it around and vibrate it. No pesky hard pipes there anymore. Takes care of any trapped air (like in the switch area) quickly.
Something you might try for bleeding: take two lengths of clear tube and connect to the bleed nipples and then run them up to the bar so they are a 8+ inches higher than the MC reservoir. Retain with electrical tape or something. They should be a very tight fit on the bleed nipples. Small band clamps won't hurt. You want to be able to open and close the nipples without disturbing them.
Then open the nipples and pour fluid in the reservoir. It will drain through the system and rise in the clear tubes to the height of the reservoir. Never let the reservoir run dry from now on---or you start again. Don't pump the brake lever, don't hurry it. If it takes an hour, fine. Clean your swing arm.
Close the bleed nipples (You do not want to knock the fluid filled clear tubes loose) and very gently pump the brake lever, you will likely see some air bubbles rise in the reservoir. You don't want to break large air bubbles into tiny ones, much less foam. So gently.
Try the brakes. if they feel good you are done.
If you are getting softness indicating some air, give a half dozen really hard squeezes to move the pistons a bit. Then open the bleed nipples and see if air bubbles rise in your tubes. You can apply some vibration. Use a 1/4 sheet palm sander minus the sandpaper. Shield the pad with a soft cloth on painted surfaces. Won't hurt to loosen the caliper bolts as you did with the splitter so they can vibrate a bit better. Don't go crazy, remember the hard lines. Vibrate everything, the MC, splitter, calipers and the lines. If you don't have a 1/4 sheet sander, get a really cheap one. They are good for scuffing in new road tires---nice not to have the shoulders real slick the first time you bank over onto them. Also gets the little nubs and stripes off the entire tire so you look more radical.
Then just wait a few hours with the nipples open. Brake fluid is a bit viscous and really small bubbles take their sweet time rising. Close the bleed nipples and repeat the gentle squeezing at the bar. You can also open the nipples and try a little squeeze to force some fluid out the caliper. if air comes out close the nipple quick so it can't go back in. Drain down your tubes into a can then set them up and flow fluid as at the beginning to refill them from below.
This is what might be called the static method. After filling the system under gravity, you just let air rise in either end. The "dynamic" method flushes a lot of fluid through the system quickly. The idea is the moving fluid sweeps air bubbles ahead of it. You really want good flow and internal turbulence in the system. An electric vacuum pump and receiver is ideal. Costly gear that's nice to not have to buy.
Some say filling the system under pressure from below works well. I tried it on a dual brembo setup and it didn't work at all. You are pushing fluid down through the caliper and it doesn't push all the air ahead of it in a neat bolus up to the MC. Maybe with some other setup...
It is good to have a pair of fresh metal seal washers on hand before disturbing a banjo fitting. I always try to reuse them and sometimes I get away with it, sometimes not. You can also use sealant with old washers but it's ticklish using exactly the right amount and you have to use the right stuff as well.
A worn hydraulic cylinder (MC or wheel) can have a ridge worn in the bore at the end of the customary travel of the internal seal. Push the seal past this ridge (like compressing the lever all the way to the bar or over extending wheel cylinders w/o pads in them) can cut the seal = no brakes. I don't worry about this. if I have that much wear in the bore I want to know about it. The cylinder should be rebuilt, my life depends on it, and I'd rather get on with it long before good riding weather returns.
My final item after any brake work is a double handed crunch on the lever for as long as I can hold it. Must be no leaks and the lever needs to hold position, no creeping towards the bar. I figure one hand, under panic conditions, will approach those forces. I want to make anything that wants to break, break. I test the front brake every ride before taking off, just a hard squeeze but I want that more severe test after any service.
Bleed nipples get removed and cleaned up before bleeding and then cleaned off with brake cleaner afterwards. No brake fluid outside the system to attract water and corrosion. Then pack w/ silicone grease and put the rubber caps on.
Good luck Mr. Phelps.
