Brake Problem

D

dave48

Junior member
Location
Missouri USA
I have a 1978 Jarama with right side rear brake. The rear brake is basically nonexistent. The brake pedal is firm but it just barely slows down the bike.

It feels like what I would imagine oil on the brakes would feel like. The pedal is very firm but nothing is happening.

I’ve rebuilt the master cylinder. the caliper with new pistons and pads and also replaced the brake line, with no change.

Anybody else have or had this problem?
 
Has the rear brake ever worked OK or did you just purchase this bike? If you have had the bike for a while, did problems start after the rebuild or the brake has never worked OK? What type of brake pads are you using? The factory Brembo pads are not very good and pretty much any aftermarket brand will work better. I am using EBC sintered metal pads and they made a difference.

Not easy to answer your questions with out knowing a little history of the bike.

I can say moving the master cylinder to the left side as on early models will help some as you get rid of a lot of extra parts. I converted both my 180 triples to left side brake.
 
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You mean "Wooden" brakes for the Brembo's, known issue at times....front and back **** 1200ts beat me to it.....

Last i recall was to use Brembo green organic pads, others will no doubt have modern information. Copper based sintered pads were not always a best choice in the day. Perhaps a photo of the installed pads may help here. j.
 
Just been through this. Green pads not available any more. The new blue ones no good either.

Buggered if I can find the thread. I will get down the shed shortly and find the packet with the good pads
 
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I found my vastly reduced rear drum with simple spray lube to linkage joints that had seized, it's more than that with discs but lubing any joints will help.
 
Although the rear brake linkage system on an RGS is different I had the same problem, fixed by cleaning and lubricating the linkage spindle.
 
Legs said:
Although the rear brake linkage system on an RGS is different I had the same problem, fixed by cleaning and lubricating the linkage spindle.
Click to expand...
Spindle as in the pivot for the lever? That would be my first port of call before going for pads etc.
Hasn't there been discussion about altering the ratio from the pedal by drilling a new hole?
 
I tried this on the rear sets of my 3c with drum rear, I extended the 90deg lever length off the rear set with surprisingly no improvement in power. At the time I think Cam said I had gone the wrong way, I lengthened it and it should be shorter, Still doesn't make sense to get more leverage from a shorter rod. The same happens with rear set gear levers, the shorter the 90deg connection the less throw with your foot. Does my brain in, I need to see it happen. But it was mindblowing the effect of 2 seconds of spray lube on the joints. Still blows me away how much that helped. It's surprising how sketchy the lack of an effective rear brake can be especially in slow-speed maneuvers. One crucial thing is all links must be at 90deg to get the best effect, it doesn't take much to get an overrotation if it's more than 90deg BTW I did my annual check of how much front pad I still have, it takes me well more than 5 years to wear out pads and I am typically more on the brakes than most going into bends till I can see what's coming up.
 
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it is a very well known fact that the rear disc on all triples is just plain crap, end of argument. No further comment needed, if anyone says their rear disc on a atriple (as stock) is good then they are deluded and wearing rose tinted specs, or never exceed 8MPH.

On the 180's I have been trying various things for decades and not realy got there, I will in the end but havent achieved it yet, on the 120's a very easy conversion to a jap master cylinder works an absolute treat, I rode Paul Mullholland's Corsa which was fitted with this mod by a local classic dealer on the advice from Keith Nairn Laverda Scozia), and I was literally blown away the result was superb, ask keith for advice, I think he will freely give it, especially at this time, because the last thing he needs is another bike in his workshop as he prepares to switch buildings.
CLEM
 
The point is the "ratio" between the master, the slave and the lever. IIRC, the rear master is a 14mm one. Now keep in mind, that the front master is a 16mm one and serves 2 of the same calipers (and feels "wooden" even, too...).

Most japs rear master (as CLEM suggests correctly) have 1/2 => 12mm roughly. This results in a need for more travel of the lever but also more "feel" on the rear brake.

On the Jota, I have the rear caliper of a GSX-R together with the corresponding 1/2" master. This 150mm rear tire blocks if I force it ;-)
So - if you install a 1/2" master, I assume it will improve braking a lot compared to the original one. You might need a different arrangement though as I haven't found one that fits straight on onto the Laverda frame. But maybe there is one?!?
 
Quote: "the pedal is very firm but nothing is happening".
"it feels like oil on the brakes would feel like".

Are we answering the problem, seized linkage apart?

Paul
 
this only applies to 120's
quote Lothar "haven't found one that fits straight on onto the Laverda frame. But maybe there is one?!?"

there is one, I was told it but forgot it, Keith Nairn may well help, but remember he is a business and is trying to make a living, if I recall correctly there was a modification to do, that even a ten year old with a hand twist drill would cope with.
CLEM
 
Just use an Alpino rear master cylinder and you get a really nice rear brake on a standard setup. Ran one for years and was very happy 😀👍. Downside is finding an Alpino master cylinder 🙁
Tom
 
CLEMTOG said:
On the 180's I have been trying various things for decades and not realy got there, I will in the end but havent achieved it yet, on the 120's a very easy conversion to a jap master cylinder works an absolute treat, I rode Paul Mullholland's Corsa which was fitted with this mod by a local classic dealer on the advice from Keith Nairn Laverda Scozia), and I was literally blown away the result was superb, ask keith for advice, I think he will freely give it, especially at this time, because the last thing he needs is another bike in his workshop as he prepares to switch buildings.
CLEM
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Did you leave the P9 caliper on TOG Clem? Have to say I was quite surprised it didn't deliver a result for you. On m' Jota it makes all the difference. With a good press I can lock the rear wheel, and in general use it is just about right. I use EBC HH pads by the way.
 
Paul Marx said:
Are we answering the problem, seized linkage apart?
Click to expand...

I think the answer to that question is no, we're not answering the problem. But let's credit Dave with enough smarts to have figured out that the linkage is not seized. :rolleyes:

Some good advice about lubricating the linkages and fitting decent pads has been offered, but it seems to me that nobody has got to the root of the problem because nobody has asked the right questions. There's little point talking about master cylinder sizes until we know what we're working with.

First question from me is do you have rearset footrests or the original forward mounted setup. The hydraulics are the same, but the linkages are quite different.

Second question: Are the hydraulic components original? I'm not 100% sure about the master cylinder, but I think it's a Brembo PS15 (someone will correct me if I'm wrong here). I'm more confident that the caliper is a Brembo P2 F08.

Third question (and perhaps the most revealing): What are the angles between lever arms and connecting links? And what are the lengths of the lever arms? This is probably best answered with photos. Can you post some photos of your brake system showing the full linkage between pedal and master cylinder? Take a photo with the pedal in the rest position, and another with the pedal in the position where it applies pressure to the hydraulics.

Bear in mind that the rear disk brake on Laverda triples was never anything to get excited about (the old 3C drum was a better stopper) but the original components can be made to work well enough with a bit of fine tuning. My Jota has a right-side pedal and linkage like yours. The brake was pretty useless when I bought the bike but after some tweaking it'll now lock the rear wheel with moderate pedal pressure.

Cam
 
The stock 3CL set up with the long alloy lever isn't too bad at all, it's when these stupid rear-sets and cross-overs come into play that things go down the drain. No points for the factory for not even trying to make it work decently...:(

piet
 
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