MV Agusta Forum banner
1 - 11 of 11 Posts

·
Registered
Joined
·
115 Posts
Discussion Starter · #1 ·
Yesterday to celebrate my 51st Bday, I went for a short ride up the coast. It was a beautiful day and life was good! After about 30 miles of easy cruising my rear brake suddenly locked up! The car behind me, hit my rear tire....not too hard but enough to almost make me crash. It happened it a split second! HOLY Crap!:thewife:

You all know the story, let the bike cool down for a few minutes and caliper releases and all is well. We all know the rear brake cylinder is millimeters away from the exhaust pipes etc...This happened to me about 8 years ago on my 95 Ducati 900SP, mid corner and lowsided because of it. I know the causes and how to repair this problem so I'm not looking for that. I just wanted to vent and warn others who have not had this happen to them.

It really has scared me to even get back on my bike ever again. I can't fathom why engineers have not found a way to prevent this from happening. I don't think I have ever had a car's brakes lock up on me before. I know some guys have had this happen to their front brakes! Yikes. My machines are always properly maintained and the braking system on Brutale was in tip top shape until yesterday. :popcorn: I stopped (pardon the pun) to take a picture of the beauty of the day after my almost death. :violin:

 

·
Registered
2005 F4 AGO 2017 TVL RC
Joined
·
6,647 Posts
never even thought about that and glad you are okay. I can see a new cooling fan mod for the rear brake master cylinder in the future :0
 

·
Registered
Joined
·
1,558 Posts
For the use it gets, maybe I should save the weight and remove the system and rotor. If custom Harley's can get away with only back brakes, I feel pretty good about only having fronts :)

Glad you came out of it okay, must have been quite the pucker moment. Happy belated birthday :)
 

·
Super Moderator
Joined
·
22,073 Posts
Happy Birthday man.
The heat does not lock up the rear brake, it degrades the brake fluid. Wrong adjustment of the rear brake push rod or lever will lock up the rear brake. Think of it, if the heat expands the fluid, the master cylinder port has to be open to allow the fluid to apply pressure onto the caliper pistons.
You have something else wrong here.
Glad you're okay.
 

·
Registered
Joined
·
17,191 Posts
Happy Birthday man.
The heat does not lock up the rear brake, it degrades the brake fluid. Wrong adjustment of the rear brake push rod or lever will lock up the rear brake. Think of it, if the heat expands the fluid, the master cylinder port has to be open to allow the fluid to apply pressure onto the caliper pistons.
You have something else wrong here.
Glad you're okay.
My analysis wasn't as sophisticated as Donsy's, but I was thinking similar thoughts. I've been on this forum for a long time, and I've never heard anyone else with a similar complaint. If the rear brake problem was a design problem, we'd have heard about it before, right?
 

·
Registered
Joined
·
14,741 Posts
Happy Birthday man.
The heat does not lock up the rear brake, it degrades the brake fluid. Wrong adjustment of the rear brake push rod or lever will lock up the rear brake. Think of it, if the heat expands the fluid, the master cylinder port has to be open to allow the fluid to apply pressure onto the caliper pistons.
You have something else wrong here.
Glad you're okay.

you got the rest right but you might want to rethink this bit :stickpoke
 

·
Super Moderator
Joined
·
24,102 Posts
:popcorn::popcorn::popcorn:
 

·
Old Wing Nut
Joined
·
22,164 Posts
The master cylinder return port is blocked by the piston cups because there is insufficient clearance in the pedal linkage. Improper brake pedal adjustment. Expanding heated brake fluid cannot escape into the reservoir applying increasing pressure to the caliper pistons. Dragging brakes create more heat which compounds the pressure on the caliper pistons until they finally lock up.

Why was this car tailgating you??

I had a similar incident on CAG's SPR at the last Bubba track day. Rear wheel locked up in the middle of the track!! Fortunately not in the middle of the corner.......cracked the bleed nipple and steam came out! Brake pedal was mis-adjusted.

Love that orange Brutale!!
 

·
Vendor
Joined
·
5,638 Posts
Yesterday to celebrate my 51st Bday, I went for a short ride up the coast. It was a beautiful day and life was good! After about 30 miles of easy cruising my rear brake suddenly locked up! The car behind me, hit my rear tire....not too hard but enough to almost make me crash. It happened it a split second! HOLY Crap!:thewife:

You all know the story, let the bike cool down for a few minutes and caliper releases and all is well. We all know the rear brake cylinder is millimeters away from the exhaust pipes etc...This happened to me about 8 years ago on my 95 Ducati 900SP, mid corner and lowsided because of it. I know the causes and how to repair this problem so I'm not looking for that. I just wanted to vent and warn others who have not had this happen to them.

It really has scared me to even get back on my bike ever again. I can't fathom why engineers have not found a way to prevent this from happening. I don't think I have ever had a car's brakes lock up on me before. I know some guys have had this happen to their front brakes! Yikes. My machines are always properly maintained and the braking system on Brutale was in tip top shape until yesterday. :popcorn: I stopped (pardon the pun) to take a picture of the beauty of the day after my almost death. :violin:

Glad you are OK mate and escaped serious injury but has any work or adjustment been done recently to the rear brake,just curious.:jsm:
 

·
Super Moderator
Joined
·
22,073 Posts
you got the rest right but you might want to rethink this bit :stickpoke
Please explain in English then your royal highness, just kidding, but really, what is wrong with that statement of mine Noel ? The way I see it, there's not enough fluid in that part of the pipe which goes to the caliper, to move all four pistons enough to lock up the rear brake.
If the OP seems to think that heating up the caliper, will cause the rear brake to lock up, how does this happen ?
I'm always willing to learn.
 
1 - 11 of 11 Posts
Top