I hate my brakes!

[a13x]

What the shit is wrong with my brakes! I can't get them to work propery. There is a mushy feel at the lever and it WILL NOT go away. It is inconsistant and I can force the lever all the way back to the grip. Not good and I'm not stoked.

I have 99 GSXR 6-piston Tokico's with brand new SS lines and HH pads. I've bled them about 1000 times and even done Liononaleash's handy tip found elsewhere in this Forum (did last night) No dice.

I thought perhaps the rotors / wheel / whoknows could be causing some issue, so last night I removed them from the equation. I put a solid piece of metal between each set of pads and did Liononaleash's trick (again) and still I get mega-mush.

I pulled the calipers off (again) and pumped up the lever to see what happened. Well 3 of the 6 pistons (per caliper) moved, and they weren't even. Am I getting major piston stickage? When I got these calipers I cleaned them and sprayed them out with cleaner a bit. Didn't do a full caliper disassemble however.

The brakes working like this make it basically impossible for me to race the bike effectively. Everytime I enter a corner the feel at the lever is different. Some laps it's not bad, others it's horrendous. Needless to say... I can't brake with any real confidence and as a result ride rather slowly.

Help.

[bigred875]

bad valve in teh master cylinder?

[OreoGaborio]

Sounds like the Man of 1000 Connections needs to make some friends at Brembo

I'm w/ Red... maybe switch out the master cylinder w/ one from another bike? or is it the same m/c you used before?

[a13x]

It's a M/C I got off a WERA BBS racer.... a possible lead.

any other thoughts?

[13]

I can't see why a master cylinder would cause the pistons to come out with differing pressures/distance. I'd like to look at them, but I think it would be in the calipers themselves. Do the same pistons come out every time you do your test?

[sandman]

wire tie the brake lever to the grip.

put a good amount of pressure on it and leave it for several days.

one of my bikes had a spongy feel after it sat for a winter. i dont remember who told me to tr a wiretie, but it worked for me.

[bigred875]

Originally posted by Stupidhawk007
I can't see why a master cylinder would cause the pistons to come out with differing pressures/distance. I'd like to look at them, but I think it would be in the calipers themselves. Do the same pistons come out every time you do your test?

it did for me last year..same problem. I would bleed them and they would be "ok" then you'd be able to pull it to the bar...there was a diaphram(sp?) or valve in there that was letting air in

[bigred875]

Originally posted by sandman
wire tie the brake lever to the grip.

put a good amount of pressure on it and leave it for several days.

one of my bikes had a spongy feel after it sat for a winter. i dont remember who told me to tr a wiretie, but it worked for me.

ya i was doing that a lot too...and it would be fine for a little while then same thing

[GMAN226]

I hear that those calipers suck. Do you have any of the 4 piston ones and will they fit? Also does that MC move enough fluid for a 6 piston caliper?

G-man

[a13x]

Originally posted by GMAN226
Do you have any of the 4 piston ones and will they fit?

Also does that MC move enough fluid for a 6 piston caliper?

No and I don't know.

[R7]

Originally posted by sandman
wire tie the brake lever to the grip.

put a good amount of pressure on it and leave it for several days.

I used to do that on my Motard overnight at the races, worked pissah. It was also the only way I could ever get any feel out of a stock KTM brake, I could always pull the lever to the grip without much effort, after the zip tie trick, I can only pull it half way

[a13x]

That sounds like a neat trick, I'll go put a ziptie on now and test in the morning, but I'd rather my F#CKING brakes work properly and I don't have to worry about Micky Mouse biting me in the ass as I barrel into Turn 3.

%$#%#$^%$

[sandman]

Originally posted by R7
I used to do that on my Motard overnight at the races, worked pissah. It was also the only way I could ever get any feel out of a stock KTM brake, I could always pull the lever to the grip without much effort, after the zip tie trick, I can only pull it half way

the o2 52o exc is the only bike i have that needs the yearly brake tune up.

i've never had a problem with the duke.

[Tabby]

a13x, don't be afraid of a complete teardown of the calipers. There isn't much to them. Pistons, seals, dust seals, that's about it. It wouldn't take too much brake fluid to break down and cause a piston or two to stick and be the main cause of what you are experiencing. If you have a factory service manual, follow it. To help clean the caliper bores on my old gixxer, I used a small brass wire wheel on my Dremel tool to clean out the hardened brake fluid. In my case, the bike had many miles, so it was a bit crusty. One small trick I used on assembly was to use some KRYTOX grease, made by Dupont, on the seals. It is a special synthetic grease designed for very high temperatures {jet engines!}. It is very inert, so it doesn't attack rubber, or break down with other fluids. It helps keep the seals pliable. I have about 40,000 miles since the rebuild, and the bike even sat for 7 years and the pistons work as good as new. Oh yeah, I'm one of those DOT 5 converts also, hence the complete rebuild. If you choose to use that, the system HAS to be completetly clean of the alchohol based fluid. Dot 5 has its' pros and cons, and has been debated to death. So far I personally haven't had ANY issues with it. At any rate, if you do a rebuild by the book, you will KNOW what is in your system.

[Awesome]

I don't know what the tricks you tried were but maybe a bubble somewhere in the calipers that needs to get out of there.

Don't you think 6 piston calipers are a little overkill?

[Degsy]

The master cylinder is not big enough for those calipers. You need a brembo radial master cylinder size 19X20.

buy one here


derek

[a13x]

Originally posted by hessogood

Don't you think 6 piston calipers are a little overkill?

They came with the front end.

[a13x]

Originally posted by Degsy
The master cylinder is not big enough for those calipers. You need a brembo radial master cylinder size 19X20.derek

Weird the stock MC isn't big enough for the stock calipers isn't it?

[Degsy]

Originally posted by GMAN226
I hear that those calipers suck. Do you have any of the 4 piston ones and will they fit? Also does that MC move enough fluid for a 6 piston caliper?

G-man

There's your answer. those calipers sucked on the gixxa, they're gonna suck on your race bike....without a better/bigger master cylinder.

My choice for my race bike is galfer wave rotors floating on brembo buttons, stock calipers with PF pads, a brembo master cylinder (18mm) and goodrich type-2 lines with a double banjo bleeder by the master cylinder for easier bleeding. AP racing brake fluid completes the setup (changed every second race weekend).

I had to zip tie the brake lever to the throttle every night and bleed the brakes every morning for about 4 days to get the system empty of all the tiny bubbles, but the leverfelt like it was hitting a brick wall after that, and the feel/power was unbelievable.

On another note, I think that if you get those calipers working well with a bigger master cylinder, you might just find out that the whole setup is too much for your bike. You may get no feel from the system because it is just overwhelming stopping power for the size of the bike and the speeds that it is doing. Just a possibility, I'm not an expert in matching braking systems to bikes, but I do know that you can overdo it with caliper size.


derek

[LiononaLeash]

so when you pull the lever to the grip and assentially pressurize the system, you are disolving the bubbles into the fluid correct?

Let me see if I can think this through....

feeding new fluid into the system immediately after doing the above gets rid of the fluid that contains the airbubble gas before it can re-release it into the system in gas form. Therefore you fill your system with pure brake fluid that had no disolved gases to slowly release later which would make the brakes spongy again?

Is the that general idea behind the brake lever thing?

[Degsy]

No, I think it just keeps high pressure in the system and assists in getting the small bubbles to the top of the system (the bleeder by the reservoir) faster.

derek

[LiononaLeash]

Originally posted by Degsy
No, I think it just keeps high pressure in the system and assists in getting the small bubbles to the top of the system (the bleeder by the reservoir) faster.

derek

I think I got it... the bubble gets dissolved and when the brake lever is released, the gas is released near the top of the system.

[Degsy]

Originally posted by LiononaLeash
I think I got it... the bubble gets dissolved and when the brake lever is released, the gas is released near the top of the system.

Well, actually, the bubbles slowly rise to the top of the system and before you release the zip tie, you attatch a hose to the bleeder valve and open/shut it quickly, releasing a little brake fluid with bubbles in it (looks like spit). After you shut the valve, you release the brake lever, pump it a few times and zip tie it again to start the next round of bleeding. Repeat four or five times for best results.

derek

[Paul_E_D]

Put your old front end back on?

I had inconsistent lever performance when the caliper mounting flange on the fork leg was bent... misaligning the caliper. I did my best to shim it straight, but never resolved the problem til I got a new fork leg...

[Degsy]

Originally posted by Paul_E_D
Put your old front end back on?

I had inconsistent lever performance when the caliper mounting flange on the fork leg was bent... misaligning the caliper. I did my best to shim it straight, but never resolved the problem til I got a new fork leg...

Ooh, that's a good one to remember. I have known a few people who have had this type of issue after a crash, checked out everything BUT the caliper mounting flange. Never thought of that.

derek