Brake update: Rear brake doesn't work at all now, front needs bleeding again... : LUSENET : MV Agusta F4 : One Thread

Just to let you all know, I had my dealer bleed my front brakes about a month ago and everything was working fine on the front end. Well, the same problem has cropped up again, feels like air in the line. I'm going to have him bleed them again.

The rear brake was never anything to write home about, but now it's not working at all. After my ride to Phoenix last weekend the brake just stopped working altogether. There's no pedal at all. I read about similar behavior in the article, but my pedal never came back.

So I'm taking it to the dealer tomorrow to get the brakes bled again. I hope this isn't something that is common. I went on a nice ride on the local mountain Saturday morning and I didn't have any confidence in the front brake at all so I had to take it easy. Maybe that's a good thing...

-- Andy Ruhl (, June 24, 2002


Sounds like my bike !!! Just re-bled the front....yet to ride it once re-bled....should be a lot better. Rear has totally gone as well...not that I use it much....... Absolute prick to get to the rear brake resevior too.... {bike is late 2000 with Evo 2 brake upgrade.}Pete

-- Pete Hughes (, June 25, 2002.

Yeah, I could bleed mine too, but when it comes to stuff like this I like to have the dealer do it so he is aware it's an ongoing problem.

Let me know if you pull a bunch of air out.

-- Andy Ruhl (, June 25, 2002.

I had the same problem with my back brake,I have since changed front & rear fluid for Castrol SRF,it does cost a fortune (40 half litre) it has cured my rear brake,i"ve now done 1000 miles without bleeding amd peddle still ok

-- mike tilston (, June 25, 2002.

As I said already in a previous mail, I had the same problem on my bike. First the reservoir was replaced (MV said they assumed an air in-leak between pump and reservoir) but of course without result. Then they replaced both calipers (because the cause was identified. Air comes in the circuit after a brake move between the pistons and the housing). At the same time, the disks have been replaced as they were severally bent. I have now the recent ones which are a lot thicker than the original ones. Braking is now a lot better (due to the new disks) However after a while, the pump becomes again spungy, but the intervals are indeed a lot longer. The best solution is this : when to soft : put the bike on its stand. Gently put 4 screw drivers between the disks and the pads and push the pistons inwards. Then, move somewhat the lines. Then slowly start braking again, so filling up the lines and the calipers. You will see that you will get the same result as the purging by a dealer and it takes only a few minutes and it is free of charge !.

good luck. Patrick

-- patrick maes (, June 26, 2002.

An even better way to perform the operation you are talking about (compressing the pistons back into the caliper) is to take a pair of spreading pliers, or just regular pliers, and spread the pads from the top side of the pad where they are hanging on that mounting pin. Once they are spread apart there, one can work the other side to get more compression of the pistons. Note that if your reservoir is near full, this practice can cause it to overflow or build up too much pressure, which is not the point of this exercise. The best way would be to loosen the top so it can breathe, but ensuring not to let it overflow or not to let anything in.

This whole procedure can force air back up the brake line and out the reservoir. Since air has a natural tenency to rise, it will already be somewhere near the top of the caliper, and if you're lucky, this process of compressing the pistons will cause flow upward which will take the air with it. Doesn't always work, but it's a good place to start. My dealer did this a few times, and then bled the caliper and there was still a bubble in there.

-- Andy Ruhl (, June 26, 2002.

Regarding rear brake, this is my second summer riding the 2000 f4 and after the first really hot day, the rear brake fluid evaporates completely from it's resevoir.

Took it back to dealer each time and found that refilling it returned power to the rear brake. However, this time it was pointed out to me that the resevoir sits just about 3 or 4 inches in front of the exhaust manifold pike (located just to the rear of the right side foot peg...and that excessive heat from the pipe at this juncture may be causing the brake fluid to evaporate...especially since there is no sign of leakage.) I thought this was a situation unique to my bike but now am beginning to think this is a design flaw after learning that all of you are having the same problem.

Any other opinions?


-- charles morgan (, June 29, 2002.

Design flaw, something overlooked, style before function... Call it what you want. Yes, the rear brake cylinder is too close to the pipes, and yes, the reservior probably is too. Can't really fix it except to do what another post said and put in high temp racing fluid. I'll probably try that.

Problem is, now that my rear brake allegedly works, it doesn't do much at all anyway. Why bother? Even if you lost the front brakes for some reason, I don't think you'd ever be able to get near sliding the back tire with that brake. Kinda pointless to even have it in there unless you can use it like Eric Bostrom to back it in...

-- Andy Ruhl (, June 29, 2002.

Wow Andy, sucks being you! I have the opposite problem with my 2001 MV's rear brake. It locks way too easily. Very little feedback, and it's not progressive enough. I just put 180 miles on it today (approx 90 degrees) with heavy brake use, and didn't get them to fade. In fact, I now have 4200 miles on it (I've had it a little over a year) and have never had to put any fluid in the rear brake.

-- Brad Cowell (, June 30, 2002.

Another one to the party. Completely lost the rear brake, and the front feel is going spongier by the hour. The bike has 1700 road miles, no track. Hasn't been ridden hard, but a lot of hot days, and some traffic. Heat could be a contributing factor here. There doesn't appear to be ANY fluid in the resevoir.

-- Larry Nipon (, August 04, 2002.

Larry, go back to your dealer and have them flush the rear and put in high temp fluid. I haven't done this yet, but it makes total sense as a fix. They did flush and bleed mine, but they just used standard fluid.

2 times now the front brakes have been bled, and the pads were worked back into the calipers. You can do this easily yourself by locating the top edge of the pad at the mounting pin (directly above about the middle set of pistons). Use some spreading pliers, or just regular needle nose and spread the pads apart. This tends to push the pistons backward into the caliper, which will accomplish 2 things: It will loosen it up if there was anything binding, and it will tend to push any air upward toward the master cylinder (a good thing). Work the lever a lot and this will help air travel upward if there is any. If you are brave, you can take the cover off of the brake cylinder (beware of splattering brake fluid, this stuff is basically acid for all practical purposes, it will ruin your paint and anything else it touches). Watch for bubbles coming out. I did this many times on my R1 when I put on the steel lines.

Back to the rear... It's practically useless. Next time I go on a good ride I'm going to try to unweight the back wheel enough with the front brakes to slide the tire just to see if it's possible (I'm sure I could but I don't make it a habit of sliding the back tire). If all I had on this bike was the rear brake, I'd probably choose to slow down Fred Flintstone style. It's that bad for me.

-- Andy Ruhl (, August 05, 2002.

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