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Inconsistent brakes

Started by motomadness, May 06, 2003, 08:37:10 AM

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motomadness

I am looking into getting them bead-blasted as we "write".  I am also a fan of the Valvoline brake fluid.  I rebuilt the master cylinder last night, and plan on doing some work on the calipers tonight.

Wish me luck.

MightyDuc Racing

Just go to Jennings...only use the brakes in T1 and T13...lol. ;)
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motomadness

Thanks.  I'll remember that.

The rotors are now bead blasted.

xlr8tn

I have been fussing with my brakes all season as well...I ended up rebuilding the calipers over the winter and still mushy feeling following last round at VIR.  I actually rebuilt the master cylinder SAT evening and got a better feel, but it seemed to fade away, and like you said, pulling the bike into the pits, could easily pull the lever WAY back.  I also have been using Motul RBF 600 and EBC HH pads on my 98 gsxr600.  What are some of the other brake fluids you guys are using out there.  I just purchased a new master cylinder contraption including the resevior and lever...Any thing I should do prior to switching fluids.  If I move from RBF600 to a 5.1 or something, do I need to drain and flush the entire system.  How do I do this without contaminating the system by mixing fluid types?

-brent

motomadness

#16
My brakes work now.  This is what I did:
- new ss braided line - dash 2.5
- disconnected the calipers from the old lines and pressed as much fluid out of the caliper as I could.
- disassembled the master cylinder, cleaned with a quick shot of brake cleaner, then soaked the part in fresh brake fluid prior to reassembly

I reassembled the entire system, flushed it with about 1/2 bottle of fresh fluid, then bled the system twice (second time was the following morning.)

I first tried using the expensive racing fluids, but for the second time going with the expensive stuff, I've found myself to be quite disappointed.  I have found myself to be very pleased with the little silver bottle of Valvoline brand (Dot 3/Dot 4 and <$3).  Every time I have used the stuff, I have been more than satisfied.  

I ride a two-stroke, so I don't have a huge load to slow down, but one of my teammates from last year rides an F4 and I believe he is more than satisfied.

I think the real key is to keep fresh fluid in the system at all times.

Bernie

Sounds like a good plan.  I'll give it a go myself. :)

MELK-MAN

HEY.. ANYONE WITH WHEEL THAT WONT SPIN..
i had a problem recently where on the front stand, front would spin maybe 1 revolution if spun hard. This is a bad thing, and im sure was heading the rotor. traced it to a sticking piston in the CALIPER! i put new pads on and the thickness of new required me to push the pistons in. this got gook in there and 1 piston would stick while i was able to push the others in & out. Now the front FREEWHEELS many many times..
2012 FL region & 2014 South East overall champion
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Bernie

I also cured a front wheel not spinning freely this weekend.  Kevin Weir saw me crying inconsolably  :'( while staring at my front wheel that still wasn't spinning freely.

He told me to loosen the pinch bolts on both sides and wack the bottom of the fork tubes a few times with a rubber mallet.  Something about my front axle's sweet spot.  Guess what? I torqued the pinch bolts back down, and my front wheel spins like crazy. 8)

I'm sure lots of people have done that (or something like it) and wonder why I never thought of it, but without Kevin's suggestion, I'd still be pissing a fussing with that damn wheel.

Thanks Kevin!! :)

Tezboogie

Your brake fluid is supposed to be changed every race weekend.
The fluid gets weaker and weaker everytime it gets hot. Even with the best pads and the best lines, you will still get fade. Gotta change the fluid Sean.....
 
 Tez #3 EX MW/GP/GL
 

acruhl

Hi guys, I'm new here so sorry if I'm coming in on something and repeating what's already been said.

I'm riding a new ZX-6RR and I'm having serious brake problems. After about 4 laps they just don't work at all anymore, no matter where I am on the track.

So I emailed Sean Alexander from motorcycle.com who recently rode this bike in an AMA pro superstock race. Here was his advice:

o Stock pads will fade with a fast rider. Change them. (but nobody seems to have them yet, so he had www.lyndallracingbrakes.com sell him some pads that were close and they ground them down for him to fit. They would cost $200 if you bought the set)

o Use the motul DOT4 RBF600C (if there is such a thing). My bottle says RBF600. I have heard good things about the Castrol mentioned earlier as well.

o Use Goodridge lines.

After calling www.lyndallracingbrakes.com to buy pads from them (and then they told me they don't have them and would have to modify other ones and it would be pricey), they guy was nice enough to give me some tips. He sounded very knowledgeable, and being in the brake pad business exclusively, you'd think he would know something. He said that Sean Alexander was using the Goodridge -2 lines which are smaller, so they displace less fluid. This means less lever travel and less force to get the same braking power. The force part I don't care about because these things are scary brutal when they are working anyway, but if I could get more lever travel I might make it through a race. As it is now, they fade back all the way to the bar and when they get that far they keep on going to where I basically have no lever at all. I just have to pull them in and hope they come in at an opportune time.

I also have the problem that my front wheel seems to be a little tight. And I think I may have a partial reason for this. 2 of my caliper mounting bolts are slightly bent (!). These are the new Tokico radial mount brakes, so this may be a real problem.  I have a race this weekend at Arroyo Seco so I don't have time to straighten all this out, but I think I've got some serious work to do.

Racing for points sucks. If my bike was working right I'd be consistently getting trophies.

tzracer

The inner diameter of the brake lines should have no affect on lever travel. The volume that needs to move is determined by how far the pistons in the calipers have to move. The master cyclinder must provide this volume. The line connecting the two has no influence on this (no line expansion).

If the brake line is soft, it can expand with pressure, this will cause more lever travel. Perhaps the smaller ID line has less expansion. Getting rid of softer rubber lines also aids in better feed back through the lever, what most people call feel.

I would figure out why the mount bolts bent before I rode the bike again. It would not be a good thing to have a front brake caliper fall off.
Brian McLaughlin
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2 strokes smoke, 4 strokes choke

motomadness

Brian,

The inner diameter will affect lever travel.  The smaller the line, the fast the fluid moves through the line.  Expansion would hopefully be less with a SS braided line, but I think the smaller the id, the more "feel" you will get because the ratio of the volume of the master cylinder to the brake line is closer to 1.

Tez,

Thanks for the advice.  I have definitely been pay more attention to the state of my brakes.  I think major part of my problem was the excessive engine vibration and the fact that I was running rubber lines, not to mention that my pads and rotors needed serious attention.

Jeff at Ferodo suggest prepping your rotors every 3 or 4 race weekend.  Brake fluids changes are crucial to good feel, but hey if there weren't any 4-strokes in my way, I probably would need to use my brakes  ;D.

Note: CLEAN THE BRAKE DUST OFF OF YOUR CALIPERS
I was at the AMA race at Road America this past weekend.  The racer I crewed for had sticking pistons that would not allow the wheel to spin very freely.  I pressed out the pistons as much as I could without popping them out.  Then I clean the piston friction surfaces.  Changed and rebled the brakes and most of the problem was gone.  Now the pistons drop out of the way, but I think the drag that had been occurring may have slightly warped the rotors.