998 Front Brake Lock Up with Ducabike Levers - Ducati.ms - The Ultimate Ducati Forum
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post #1 of 17 (permalink) Old Sep 11th, 2019, 8:38 am Thread Starter
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998 Front Brake Lock Up with Ducabike Levers

Hi all, I think I might know the answer behind this issue but just wanted to reach out and see if anyone else has experienced this.

I bought some Ducabike levers, LEA02 which are designed for the 998 series master cylinders. I replaced the stock levers with these last night and did a short little spin around the block and everything felt good. This morning I rode into work and everything felt fine until I reached the front gate of where I work and I noticed that the front brake felt like it had lost some travel, not a lot but definitely felt a little different. I made it about another 700 feet before the bike just comes a complete stop. Luckily I was moving along at about 5 mph so it wasn't violent or anything, just a slow down and then no more forward movement.

All I could do was a burnout if I kept giving it throttle and letting the clutch out; the front brakes were totally locked up. After blocking traffic there for about 15 minutes while a friend brought me a 10mm socket and flat head to remove the brake lever the brakes loosened up some and I was able to idle out of the way into a parking lot.

I'm wondering if the lever was possibly dragging some the entire ride in (about 10-11 miles around 50mph or so) or something of that nature and causing the front to lock up slowly? I'm for sure going back to the old levers but I'd like to solve this in my mind just for curiosity sake.
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post #2 of 17 (permalink) Old Sep 11th, 2019, 8:55 am
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the pin that pushes on the piston needs to be adjusted until you have a little free play in the lever AND LOCKED with loctite so it can never loosen. brembo do this from the factory, aftermarket dont.
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post #3 of 17 (permalink) Old Sep 11th, 2019, 9:03 am
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Originally Posted by theapp View Post
Hi all, I think I might know the answer behind this issue but just wanted to reach out and see if anyone else has experienced this.

I bought some Ducabike levers, LEA02 which are designed for the 998 series master cylinders. I replaced the stock levers with these last night and did a short little spin around the block and everything felt good. This morning I rode into work and everything felt fine until I reached the front gate of where I work and I noticed that the front brake felt like it had lost some travel, not a lot but definitely felt a little different. I made it about another 700 feet before the bike just comes a complete stop. Luckily I was moving along at about 5 mph so it wasn't violent or anything, just a slow down and then no more forward movement.

All I could do was a burnout if I kept giving it throttle and letting the clutch out; the front brakes were totally locked up. After blocking traffic there for about 15 minutes while a friend brought me a 10mm socket and flat head to remove the brake lever the brakes loosened up some and I was able to idle out of the way into a parking lot.

I'm wondering if the lever was possibly dragging some the entire ride in (about 10-11 miles around 50mph or so) or something of that nature and causing the front to lock up slowly? I'm for sure going back to the old levers but I'd like to solve this in my mind just for curiosity sake.
Probably unlikely, but if the brake pads were dragging on the rotor there may have been enough drag to create enough heat to "boil" (aka heat up) the brake fluid causing it to expand to the point where there was enough pressure to make the brake pads clamp down on the rotor(s).

Especially so when you began riding slower (near work) and there wasn't a lot of air moving over the calipers which allowed them to heat up enough to the point where they clamped down on the rotor(s).

Like I said, probably unlikely. Just throwing a guess at this. That used to happen on bikes that were road raced ... the rotors/calipers would become very hot ... then when the riders went putt-putt into the pits and there wasn't much air flowing over the calipers/rotors the brake fluid would heat up and expand to the point the brakes would clamp and the bike wouldn't move at all.

Meh ...
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post #4 of 17 (permalink) Old Sep 11th, 2019, 9:22 am
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Probably unlikely, but if the brake pads were dragging on the rotor there may have been enough drag to create enough heat to "boil" (aka heat up) the brake fluid causing it to expand to the point where there was enough pressure to make the brake pads clamp down on the rotor(s).

Especially so when you began riding slower (near work) and there wasn't a lot of air moving over the calipers which allowed them to heat up enough to the point where they clamped down on the rotor(s).

Like I said, probably unlikely. Just throwing a guess at this. That used to happen on bikes that were road raced ... the rotors/calipers would become very hot ... then when the riders went putt-putt into the pits and there wasn't much air flowing over the calipers/rotors the brake fluid would heat up and expand to the point the brakes would clamp and the bike wouldn't move at all.

Meh ...
a for effort. f for diagnosis.
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post #5 of 17 (permalink) Old Sep 11th, 2019, 9:26 am
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Freeplay in the lever needs to be checked when installing any aftermarket lever. Properly adjusted, there should be a small (5% – 10%) dead-band of the full lever movement before there is pull resistance felt at the lever.

What's happened is that the mispositioned master cylinder piston is obstructing the vent port preventing fluid return to the reservoir.

When you apply the brakes the calipers get hot and the fluid heats up and expands. If it can't return to the reservoir to prevent a fluid pressure increase caused by the expansion, it expands the other way and pushes on the caliper pistons and applies the brakes. After the fluid cools the brakes release.

Similarly, if the vent port in the clutch master cylinder is plugged or covered, as the clutch fluid heats-up from engine heat the fluid expands and instead of returning to the reservoir, it pushes on the slave to separate the plates and cause slippage. After it cools the clutch will function normally until it heats up again.
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Last edited by Strega; Sep 11th, 2019 at 9:41 am.
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post #6 of 17 (permalink) Old Sep 11th, 2019, 9:46 am
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a for effort. f for diagnosis.
Hey hey hey now ... take it easy man! .... I never said I knew what the hell I was talkin' about.



I think I deserve an A for effort, and another A for ~All Fuddup~, and one more A for admitting I was probably wrong.


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post #7 of 17 (permalink) Old Sep 11th, 2019, 9:47 am Thread Starter
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Thanks all, I'll put the lever back on and check the freeplay; I could of sworn there was a little last night when I installed it but I might just be mis-remembering things
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post #8 of 17 (permalink) Old Sep 11th, 2019, 9:50 am
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a for effort. f for diagnosis.
And besides ... if my diagnosis is wrong ... THEN SO IS HIS!!! (below) ... that the same thing I said!!!

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Originally Posted by Strega View Post
..... When you apply the brakes the calipers get hot and the fluid heats up and expands. If it can't return to the reservoir to prevent a fluid pressure increase caused by the expansion, it expands the other way and pushes on the caliper pistons and applies the brakes. After the fluid cools the brakes release
So there!


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post #9 of 17 (permalink) Old Sep 11th, 2019, 1:16 pm Thread Starter
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Hmm, after looking at the master cylinder I don't think there is an adjustment for the front brake MC. I can do the clutch because it does have the threaded push rod with the flat and set screw that goes into the barrel in the lever but the brake side is just the barrel with a hole that interfaces with the push rod in the master cylinder.

Looking at the disassembly of these style MCs from https://www.ducati.ms/forums/80-hall...ing-force.html seems to indicate the lack of the adjustment for these. I measured the Ducabike lever versus the old one that worked and there were some geometry differences (definitely not a machinist though so my caliper skills are quite rusty) which might be enough to move the master cylinder piston and obstruct the vent port.
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post #10 of 17 (permalink) Old Sep 11th, 2019, 4:23 pm
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Put the old lever on and ride to confirm. Only takes a few minutes.
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