Rock hard brakes.....

J

Jota996

Junior member
Location
Northumberland
Finally Getting to try the bike now after the help of good guys here on the forum, runs clean, charges good, start great and runs very sweetly.
But the front brakes work,  but they have no feel at all and the lever is rock hard when applied, the bike has braided hoses and I don?t know what pads any suggestions for how this can be Improved without changing the master cylinder as I did on my last jota on the advice of Keith at Scotia.!?

Back brake is brill by the way

Stu

 
Just a question.. why you don't want to change the master cylinder? Have you tryed to remove it and clean it? mine was completely sized, but for removing the sized pistons, I put it out, clean it well, grease the o-ring and now is working super smoothly, I did it just to use the hydraulic pressure to de-seize the calyper cylinders, but now I am considering to leave it as it is without changing it until it starts to leak!  :LOL:

regards,
Miguel
 
Jota996 said:
Finally Getting to try the bike now after the help of good guys here on the forum, runs clean, charges good, start great and runs very sweetly.
But the front brakes work,  but they have no feel at all and the lever is rock hard when applied, the bike has braided hoses and I don?t know what pads any suggestions for how this can be Improved without changing the master cylinder as I did on my last jota on the advice of Keith at Scotia.!?

Back brake is brill by the way

Stu
Click to expand...

Have the calipers and M/C been treated to new seals?  Quite normal with 40-year-old rubber bits, especially when paired with non-expanding hoses.

piet
 
I had a set of pads, once, many years ago, which were about as feelsome and effective as a couple of nogs of tanalised timber.
Try a pair of Brembo Carbon Ceramics or Ferodo pads, that might be the solution.
 
Have a look where the brake lever contacts the m/c piston.  The lever should have a smooth radius, the piston end should be flat, and it should be clean and lightly greased.  Wear at that point is common and the resultant friction can produce an awful feel at the lever.  Also check the pivot screw and side faces, again should be free of wear/dirt and be lightly lubricated.
 
Thats exatly what mine was like, I had bought a replacement master before this was pointed out to me. 30 seconds with a file would have been a bit cheaper.
 
Is the master cylinder mounted as far in towards the centre of the bike for maximum possible leverage? I see plenty where they are as far out as they can go against the rh switch block, far less leverage.
 
helicopterjim said:
Dwang it ......... I have no idea what the blocking hell you are talking about.

Jim
Click to expand...

As easy as using a dictionary:

[ NOG ]
noun
a block of wood, as one inserted into brickwork to provide a hold for nails.
any wooden peg, pin, or block.

[TANALISED timber]  has been pressure impregnated with TANALITH wood preservative.
Tanalised timber has the ultimate long term protection against wood decay and insect attack, wherever the timber is to be used.
 
Hi Stu

You describe your problem as the lever as being rock hard. That can be a fault, but it could also indicate that everything is perfect. By 'perfect' I mean...
? Seals are sealing.
? Hoses aren't expanding (I see you have braided).
? There is absolutely zero air in the system.
? Disc run-out isn't causing excessive pad knock-back.
? Pads are well bedded onto discs.

If that is the case, then your standard system will have a lever that feels dead and hard - like it comes to a dead stop when the pads make contact with the disc. It is all about the master and salve piston relative areas (hydraulic ratio) which on the standard system is low. What I mean is that with a standard master cylinder you will never get 'feel' from your lever. That is just the way they are.

I would start with some good, high friction pads as they are a benefit whatever conclusion you come to and further changes you might make.
 
All true Paul.

It's why I switched from a 15mm m/c to a 12mm on my Ducrappi.  Less braking force, but much more feel ...

(Wouldn't do the same on my Corsa, tho' ...)
 
As Paul says, the feel of the front brake on my SF2 has always been rock hard. No movement in the lever so to speak. It's always been like that. Seals have been replaced a few times in the last 30 years.

I like it like that.

Paul
 
Hi Craig. Yep, 12.7mm for me. From a Suzuki something or other. Best thing I ever did to my Jota.

Original 15mm are a bit like my ex wife... more aesthetically pleasing than the one I currently have, but too much like hard work.  :) :)

With a 12mm master, your brakes should be super strong. Having messed around before I settled on 12.7mm, I recon 12mm is the bottom limit with P08 calipers. Nice.
 
When dramtically changing M/C piston diametre, the mechanical lever ratio must also be taken into account.  Not all 1/2"/13mm M/Cs will be suitable, if the lever ratio is close to the original, lever travel can be excessive.

A Brembo PS14 M/C is about the best match for the P08 calipers.  That equates to almost 2mm less piston diametre (PS15 is actually 15.8mm, or 5/8") with stock lever ratio.  Bit of a shame they are so rare...

piet
 
All good stuff....
I just wanted to keep that standard round m/c look.
I do think everything is working fine and in decent condition but I will try some different pads first.

But if I do change the m/c any thoughts on a good bet second hand? Or correct piston size in Brembo?

Does anyone make plates to allow fitment of say Ducati Brembo?s if so which ones....?

Stu
 
Ventodue said:
All true Paul.

It's why I switched from a 15mm m/c to a 12mm on my Ducrappi.  Less braking force, but much more feel ...

(Wouldn't do the same on my Corsa, tho' ...)
Click to expand...

Not doubting that you like the result, and yes, but your theory is incorrect -  smaller m/cyl piston dia will give MORE braking force with MORE travel in the lever (unless you alter the lever ratio as per Piet's post). Think of a smaller front sprocket as your m/cyl in the equation.

The increase in 'feel' is because the lever travels further for a given degree of braking force.
 
Piranha Brother 2 said:
Not doubting that you like the result, and yes, but your theory is incorrect ...
Click to expand...

I'm sure you're right.  Me, see .. I dumo nuttin' about theory, can only report the result ...  :o  :D
 
funnily enough, I'm looking at this exact thing on my 79 Jota. Everything is standard and rebuilt with new discs and pads. It's bedding in and getting better but there is very poor feel and 'bite'. I have a set of Brembo 34/30 gold lines that I believe are from a Duke (they are the twin pin, 65mm bracket version). I also have the conversion brackets that I bought from a company in the states (they look VERY nice).
I'm sure that these will make an improvement, but still not sure I will get the feel from the std master cylinder.

In addition, the sweep of the disc is much smaller than the pads from the P08, so once I go in that direction, I will need to stick with it due to uneven pad contact if I change back. I've done nothing yet, but am thinking that if I can change the MC and get bite and feel, there would be no point putting the 4 pots on. Decisions, decisions. They look bloody sexy though!!!
 
FWIW, I use the AP Racing CP3125 master cylinder on my 79 Jota with original disks and calipers. It retains the more or less classic look but works oh so much better than the original brembo, no friction problems and a nice progressive feel.  You can tweak the ratio, supposedly the equivalent of 16-19mm cylinder, but I find it feels more like a much smaller diameter than that.  Unfortunately they're not cheap (mine was retired from the racebike after the Phillip Island whoopsie-daisy) but are a good option.  They also do not have a mirror mount if that matters to you.
 
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