So during the offseason I put stainless brake lines on the front of my 05 636. I emptied both calipers, master, and the reservoir. I used air to purge all of the remaining fluid (dot 4) out of the components and reassembled, filled with Bel-Ray 5.0 and bled. After bleeding I got a very firm lever, so I checked for leaks and thought I was good to go. Fast forward a few weeks and I am at Summit dusting off cobwebs, and during my second session I turn it up a notch, after about 8 laps the lever is going to the bar, WTF. I had zero problems last year on this machine with the old dot 4 and rubber hoses. I changed because I was changing the lines and thought it would be one less thing to have to deal with as I get faster. Is this strictly a fluid problem or would the steel lines be playing a part. I have bled the system again to be sure, and once the bike cools the lever feels great again. I read that the dot 4 and the 5.0 can not be mixed so I took alot of time making sure the components were clean, however I was nervous about putting any solvent or cleaners into the calipers and m/c so there may have been a very slight amount of residual dot 4 in the system. Sorry for the lengthy post but trying to cover everything. tanx y'all Joe
You have put a silicone based brake fluid into a system that previously ran glycol based fluid. You can use 3, 4 or 5.1. I would clean the system well and go back to DOT 4. Just my 2 cents.
Get rid of the silicon, which does not absorb water but DOES not work well in race situations either. Get RBF600, or one of the other RACE only fluids.
Interesting information found here, might help explain the sponge feeling. Also checkout the statement on racing appication, glycol based only. http://www.afcoracing.com/tech_pages/fluid.shtml
Well then...Thanks for all the input. Henrytwin thanks for the link, lots of good info in there. I wish I would have found that a few weeks ago.
Tilton makes a new fluid that is less compressible than other brake fluids with a 622 degree dry boiling point that is reasonably priced. We've been using it this year with excellent results.
Dot 4 or 5.1 is the way to go. I have seen more than once you can never get good feel back because once all your seals in your master and calipers are exposed to one fluid you cant switch to the other and going back to what you had in the first place wont work either. I never read up on why this is but you may be looking at changing all your inner seals to get that firm feel back. IMO Scrap the dot 5 too
No, its listed as 617 degrees on the bottle. The Tilton fluid is less compressible than the motul from what we have seen. We get a firmer lever with it, especially when the brakes are up to temp. The Castrol SRF fluid is listed as 590 Degrees dry but has a really high 518 degree wet number, making it a very good choice for someone who only changes thier fluid yearly, we change ours before each weekend of racing normally so for us the other fluids are better. Brakes are a very important part of the bike that too many people take for granted and do not service often enough.
Once I started changing brake fluid regularly, my fade problems became much less of a headache. I use the RBF. I am sure the more expensive products are better.
You should replace your seals and rebuild your MC. Dot 3/4/5.1 (glycol)is not compatable with 5.0 (silicone). I have seen numrous HD riders (5.0) add Dot 3/4 and turn their shit to jelly. The fluids have characterisitcs vs. rubber, one swells ,one shrinks (I dont recall which) Additives are used to combat this behaviour and the additives wreck havoc on rubber when combined. Don't risk it. Start fresh. Turn 1 sucks with no brakes.
Make sure your rotors arn't warped. One of mine was warped, and i could feel it when braking hard. But it didn't bother me too much. But then i realized after prolonged hard braking i would get that fade. I replaced the rotor. And hasn't done it since. I think it may have been generating too much heat. Fixed my problem tho. Good luck.
I put the 5.0 in my bike before I knew it was not compatible. The purple stuff at cycle gear, freaking guy working there recommended it for my R1. Luckily I flushed out all the original so there was only 5.0 in it. I ran it that way for about a year before I came accross some information stating the facts. I flushed my lines very thoughly about 2 months ago with 3 bottles of cheap 4.0 and then put in the RBF and bleed them. I did 4 track days and they seem fine. I don't get near the amount of brake fade I use too. I've "heard" that when 5.0 first came out it would ruin seals etc... but the later stuff people have used without ill effect. Again this is just what I've heard no facts. Only think I know is I had it in my system for a year and it didn't seem to wreck anything.
