Inconsistent brakes

[motomadness]

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?

[Baltobuell]

 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.

[motomadness]

Thanks.  I check it out.

[mdr14]

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.

[Bernie]

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?

[mdr14]

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.

[Bernie]

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.

[motomadness]

Thanks again.

[tzracer]

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).

[Baltobuell]

 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.

[motomadness]

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.

[Eric Kelcher]

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(???).