I need help. I have very inconsistent brakes. Here's the situation:
- setup: new Ferodo CP911* + fresh Silkolene Pro brake fluid (bleed twice)
- approach to T5 at Road America mushy brakes
- approach to T6 at Road America hard brakes
- approach to T12 at Road America mushy brakes
- approach to T14 at Road America hard brakes
This doesn't seem like a air in the brake line type of thing. A fellow racer guessed that it was the rotors flopping around and pushing the caliper pistons back into the caliper body. If that is the case, how do I determine if it is due to a bent rotor or bad rotor buttons? Can I just replace the rotor buttons?
Even if the rotor is bent it would be bent all the time. I think I'd bleed em again or look at the master cylinder rubber for a minute inconsistency. Rotor button replacement is normal for EBC rotors but it is because they get tight, not loose. Keep slapping them on just sitting there and see if it ever feels different, if so it isn't in the rotors.
T5 pump T6 hard still would seem like air in the line somewhere.
Thanks. I check it out.
Well, The Ferodo CP 911 pads are good pads, but they are an organic material pad. That means to you that the pad has some compressability that you don't see in the new Ferodo XR sintered race pads.
What you will see with the 911 pads sometimes is that when they heat up after a long race, the lever feel may be mushy or the near the end of the race the lever may start to come to closer to the bar.
As to the brake fluid, In my own personal investigation, I have found that there is a new brake fluid formulation that is being used. It is European manufactured, I have found it packaged under : Ferodo Motul, Silkolene, possibly EBC so far. All of the fluids have the same bottle, but will be different colored bottles.
It appears that that fluid is not compatible with the Seals in the Nissin master cylinder.
After bleeding and racing, you will notice a drastic decrease in lever feel and firmness, where you almost have to bleed after every race.
You will have to rebuild or replace the master cylinder.
A safe racing spec brake fluid I have found is the Maxima Dot3/550 Racing brake fluid. While it is a dot 3, it is fine for dot 4. It is great for racing applications because of its higher minimum boiling points. As explained to me by Maxima, the difference between dot 3 and 4 is the ability to not absorb water. For racing you are perfectly fine. Us racers usually bleed brakes more often anyway.
If you have any specific questions, feel free to contact me.
Matt, that totally freaks me out. I'm on my third master cylinder this season and my brakes still feel like absolute doo-doo. I've been using Motul and my brakes always felt awesome until this year. WTF? How do we know if we are getting crap? Is there something on the container?
The old Motul Racing 600 in the the tall white bottle with red writing was really good. I have a a precious few bottles hoarded away.
The new Motul racing 600 in the silver bottle is part of that "new formulation". It is nothing like the old stuff. As far as I can tell it effects the seals in the Nissin master cylinder, Heck, for all I know it might be with the alloy the master cylinder is made from.
I do know I have seen a direct correlation with using the European manufactured brake fluid and poor brake system performance.
Ok, my Motul RBF600 DOT4 bottles say "Made in EU" on them. My three master cylinders were all Nissins. My brakes have been inconsistent and squishy like crazy while on track, but the front tire will barely spin when I pop it on the stand after I get off the track. I've got Braking Wave rotors and Vesrah RJL pads.
Looks like a master cylinder rebuild and fluid brand change will be in my near future.
Thanks again.
I had braking problems a few years ago. I traced it to brake fluid. The best brake fluid I have found is Castrol SRF (don't confuse with Castrol LMA). It is a DOT3,4 brake fluid with a dry boiling point of 590F and wet boiling point of 518F - http://www.racerpartswholesale.com/srf1.htm. It is widely used by car racers. It is not cheap, I paid $72 for a 1 liter can this spring (Pegasus auto racing supplies, New Berlin WI - http://www.pegasusautoracing.com/ - no they do not sponsor me, they do not sponsor anyone).
Woah! It looks like you guys have been dealing with this issue. Thanks for pipeing up, shareing that info could save alot of guys ruined weekends.
I guess I will have to take a credit on the ruined weekend thing because I have had two of them chasing this problem as well as others.
Clean rotors? Have you bead blasted the rotors since a sintered pad was run on them? sintered pads leave a metal residue (copper?) that must be removed for organic pads to work properly. I have never felt that problem with Ferodo pads and I have used them for years.
A cheap easy to find brake fluid I have found is the Valvoline sythentic fluid DOT 4
Be aware that DOT5 will destoy gaskets/seals in systems designed for DOT3/4 THe bottles no longer say that on them but upon checking with fluid manf. is is still incompatiable.
A side note DOT5.1 is compatiable and has many of the features of DOT5 without the seal issues but I think you cna get higher boiling points with DOT4(???).
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.
Just go to Jennings...only use the brakes in T1 and T13...lol. ;)
Thanks. I'll remember that.
The rotors are now bead blasted.
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
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.
Sounds like a good plan. I'll give it a go myself. :)
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..
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!! :)
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
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.
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,
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.
QuoteBrian,
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.
Think volume flow rate, not fluid speed. In a smaller ID line, the fluid moves faster than in a larger ID line, but the volume flow rate is the same. How quickly you pull the lever determines the volume flow rate. The pressure change in the system travels down the hose at a rate much greater than and independant of, the fluid speed.
If the fluid is incompressible and the line does not expand, if the master cylinder moves, say, 10cc/sec, then the piston(s) in the calipers will move at a rate of 10cc/sec. The diameter of the line, nor the actual speed of the fluid will have any affect. The volume that goes in one end of the line comes out the other end, there is no place to store fluid in the line, regardless of its size.
To me, feel comes from removing expansion in the brake lines and flex in the brake calipers. I don't see where the volume of the MC and the brake line being the same would matter. The pressure in the system is the "signal", the brake fluid is the carrier of the signal. The signal can move much faster than the carrier. I think it was Pascal who first noticed this for a closed fluid system (that a change in pressure is felt throughout the entire system almost immediately).
Example: DC electric circuit, turn on a flash light and the light goes on very quickly even though electrons in a DC circuit generally travel at less than a millimeter per second.
Another example: suppose I set up a signal system from my office to my a$$istants office at the other end of the hall. I set up a tube big enough for a bowling ball,and fill the tube with bowling balls. When I put in a ball, one will fall out the other end. The signal (the falling ball) travels much faster than the ball I put in. Also the ball I stick in does not have to reach the other end for the signal to reach the other end.
GREAT explanation, Brian! The bowling ball thing really helpedme understand it.
Here are my thoughts:
I only mentioned speed because you mentioned volume flow in an earlier example. True the fluid is incompressible, therefore the movement of fluid in the MC should match the movement of fluid in the caliper. The key is to determine the efficiency ("feel") of the operation. With rubber line, a lot of the force goes into expanding the line. For the street, where most braking is slow, ratio of the rate of expansion force to rate longitudinal force is less than in racing conditions where the braking operation is faster and considerably harder => greater losses to expansion. The effectiveness of the rubber line quickly falls outside of its peak performance design limit (not a rupture threshold), so one chooses the ss braided line.
Now, the thinner the line (the smaller the id), the lower the radial pressure exerted in the brake line (expansion force), and the higher the longitudinal pressure in the line. Therefore the smaller brake line should require less force and travel at the lever for the same amount of stopping force at the caliper. The more you can dial the expansion out, the better your assumed brake "feel" should be over the entire thickness of your brake pads, not just the first few 10ths of a millimeter. I would assume other limiting factors would be brake fluid boiling. The losses in the expansion, probably aid in keeping the fluid cooler due to less longitudinal motion (pressure waves), as well as the ability to generate enough pressure in the line during heavy braking at all temperatures.
QuoteHere are my thoughts:
Now, the thinner the line (the smaller the id), the lower the radial pressure exerted in the brake line (expansion force), and the higher the longitudinal pressure in the line. Therefore the smaller brake line should require less force and travel at the lever for the same amount of stopping force at the caliper.
Pressure is the same in all directions. By going to a smaller ID will not reduce the pressure on the walls. The pressure in the radial direction and the longitudinal direction will be the same regardless of ID. If the pressure were less in the radial direction, fluid would move in the radial direction, since fluids move from higher pressure to lower pressure until the pressures are the same.
QuotePressure is the same in all directions. By going to a smaller ID will not reduce the pressure on the walls. The pressure in the radial direction and the longitudinal direction will be the same regardless of ID. If the pressure were less in the radial direction, fluid would move in the radial direction, since fluids move from higher pressure to lower pressure until the pressures are the same.
I should have used the word force, not pressure.
I am thinking more that the radial distribution of force of the fluid pressing on the brake line wall. In theory, a larger line requires more lever motion to expand the line because there is more area for the expansion force to operate on. Since the thinner line has less area, less lever travel would be required to generate the same expansion force of the larger line. However, since more pressure is not generated in the thinner (as you said), more work effectively goes into moving the caliper pistons than into expanding the brake line.
Here is what I think is happening. Both IDs have the same OD. The smaller ID has more wall thickness which results in less expansion (how much ?) and (possibly) better feel. This is comparing the same type of hose with only the dimensions differing. Another thing to take into account is that when changing brake lines, the fluid is also changed.
Some of it may be placebo effect. Would really have to perform a double blind test to find if the better feel is real or not. The difference may be so small as to not be noticeable.
Guys,
With the smaller brake line I.D., more finger pressure is likely to be required to move the pistons.
A bigger pipe will flow the same amount of fluid as a smaller pipe with less line pressure. That's simple hydraulics. So pushing X amount of fluid through a -2 line in 1 second takes more finger pressure than pushing X amount of fluid through a -3 line in 1 second.
I like the Galfer -2.8 lines because they have the same line expansion rate as the Goodrich -2 lines and require slightly less finger pressure. This improves feel and reduces fatigue.
And tzracer is right about the line size not affecting lever travel, assuming line expansion is the same.
Scott
You guys have danced all around the answer. the expansion is a function of the elasitcy per square inch and with a smaller ID you have less surface area so less fluid is lost to filling the added volume of expansion and is directed to the expansion of the caliper stroke thus creating more piston movement.
Flip side with less volume of fluid in the lines the heat generated by braking has less fluid to heat and can cause brake fade/boil earlier. IE 100mph stop results in 10000 calories and brake fluid raises 100 degrees with 100cc of fluid decrease fluid to 75cc and brake fluid is going to get hotter 133 (not actual numbers for brake fluid or energy required to stop bik just an example)e
FYI the lever effort is constant to get the resultant pressure at caliper; direct ratio of lever pressure regardless of flex of brake lines. the movement will be more with more expansion.
Eric_Kelcher,
I didn't dance around anything!
You shouldn't make the assumption that a smaller I.D. line will expand less than a larger I.D. line. Galfer uses a line that expands less than the lines that Goodrich uses.
You wrote:
FYI the lever effort is constant to get the resultant pressure at caliper; direct ratio of lever pressure regardless of flex of brake lines.
That is true once the pistons have stopped moving. But, as long as fluid has to pass through the brake lines, more pressure will be required on the master cylinder side when using the smaller I.D. line.
Scott
That's it...
I'm converting to four leading shoe drum brakes. Cables are much more consistent... ;D
QuoteThat's it...
I'm converting to four leading shoe drum brakes. Cables are much more consistent... ;D
LOL!!!!
Dawn ;D
winders for same material a line with a smaller ID WILL expand less than a larger ID apples to apples. goodrich to galfer/apples to oranges if they use different construction