front brake operation

[MR.E]

Now then

Since i've owned the bike the front brake has always worked best after 'pumping the lever' once or twice.
Now i've fit a new lever & new top cable to the splitter bled the system BUT the brake still works better after a 'pump' but it does work, the lever just comes closer to the bar than i'd like!

Don't get me wrong, it grabs well without a 'pump' but feels loads better (to me) if i do (not putting pump here to avoid sniggers!!!).

Any advice please

thanks

[Bob_Roller]

Do you have the original OEM rubber brake lines ?

If so, you may want to consider getting braided stainless lines .

Any seepage from the master cylinder ?

You may have a leaky seal / corrosion / pitting in the master cylinder bore .

Do you have a twin disc front brake ?

If so, what size master cylinder do you have, it's cast into the bottom surface of the master cylinder, if you have a twin disc, it should be a 15 mm .

[MR.E]

Now then

new top line to splitter is braided goodridge line, but the 2 down pipes aren't, there the normal rubber lines.
There are no leaks on the brakes anywhere.

Yep it's a twin disc bike, have thought about making it a single side one though.

thanks

[nhmaf]

It is possible that you've still got a little air in the system - possibly exacerbated by either deteriorated lower rubber brake lines or a problem with some crud accumulating in the caliper itself.   Also, how much pad material is left on your pads?  

I found that replacing the lower dual brake lines from the old rubber ones to new stainless steel braided ones GREATLY improved my braking power.

[tvrla]

I've always wanted dual discs - so if a bike came with just one, I upgraded to two. Can't imagine going from dual discs to a single!

I've never had a problem with the brakes needing to be pumped even though most of my bikes have had the stock rubber lines. I'm with nhmaf on this - there's got to be something amiss - like air in the line, old brake fluid, master needing rebuild or calipers needing a clean.

New brake fluid would be my first try, bleeding the brakes or maybe leaving the brake lever strapped to the grip over night, and then rebuild the master if neither of those fixed it.

With the stock size master (15mm) the lever barely travels at all and feels hard as rock. The solution for that is a 13mm or maybe 14mm master.

So your problem is exactly opposite the norm. Something's wrong, and it's not due to wrong components. The system needs to be sorted out, problem located and repaired.

[nhmaf]

On occasion, the rubber lines, when old, have been known to deteriorate on the inside, flaking off small chunks of rubber that impede fluid flow between the master cylinder and caliper.  Just another thing to check, if none of the other things solve the issue.

[Mike V]

It is possible that you've still got a little air in the system

I would focus on getting any possible air out of the system. It took a lot of effort and time for me to successfully bleed the system after rebuilding both calipers and master cylinder. Your "spongy" operations leads me to believe you may want to give it another shot.

Just some suggestions; Turn the bars all the way to the left to get your master cylinder as high as possible (if you have a bar mounted m/c).  Try tying the lever down to the bar with a large rubber band or strap overnight (as wirespokes suggests).  Don't ask me why this actually helps - my assumption is it allows any bubbles to return through the spool and port opening in the chamber while the lever is depressed.  Make sure the very small return port in your master cylinder is free.  You may want to chase it with a small single strand of soft wire.  A gentle tap-tap-tap  on the calipers with a rubber mallet, carefully.  I left my lever tied to the bars overnight and the result was a rock-hard handle the next day after another bleed session.  Be slow with the lever movement while bleeding, especially on the return. And never depress the lever all the may to the bar if you can help it, 2/3 to 3/4 is plenty.  If you're using regular OEM bleed nipples, be careful to fully close them before release so not to pull any air into the system.  I love my Speed Bleeders. They make bleeding a one-man operation and very accommodating.

These are things you may already know and put into action.  But if you have no leaks and lines in good shape it seems to me air is the likely culprit.

Tiny Bubbles...

-Mike V.  

[bruce_launceston]

I would replace the old rubber hoses but the top line is the place where it is difficult to get the air out after the line is is replaced. It loops up and over and the small capacity master cylinder can't get the bubbles over the high spot.
Try using a vacuum bleed pump.

[steve hawkins]

Here are another couple of ideas:

1.  Lose the splitter and just look to buy two new braided hoses.  Also go to the Banjo type fittings.  Lead one long line directly from the master cylinder to the right hand caliper - Banjo fitting at either end.  The second shorter line links the two calipers together and goes over the top of the wheel.  Do not worry both calipers will operate the same - it is just hydraulics.  I have seen the same setup on a Suzuki GSXR.

You will need:

2 braided lines, one longer, and and one shorter - you will have to measure the required length.
4 nice stainless steel Banjo fittings, 1 straight and the three on the caliper will have to be the type with a bend on them.
3 Banjo bolts, 2 single and one double.

I use Goodrich pre made sets from my local bike shop.  I enclose a picture.

[steve hawkins]

Okay,

That was the first incarnation of my bike, however I was using an original round topped(1979) master cylinder meant for 2 ATE calipers, but was using Brembo's as I was able to aquire a second hand set far cheaper than I could rebuild the ATE's.  What I got was a very powerful but 'wooden' front brake setup.  Wooden, as far as I am concerned, means that it lacked progression and gave little feed back.

Then I had an issue with the new Grimeca discs, both of them warped after only 10 thousand miles or so.  And I got an MOT failure for my troubles.

So after some investigation, I decided I would try the single disc set-up (after all half the R65s produced come ith a single disc.), but go for a higher quality floating disc and a change of master cylinder for a single disc Brembo set-up and I already had the necessary braided hose.  It was cheaper to buy one new floating disc and a second hand master cylinder (+rebuild kit) from Motorworks, than it was to replace both discs (irrespective of type) and still not have the ideal Master cylinder (which had developed a very slight weep anway).

So what have I gained?  

1.  I have a much more progressive front brake.  
2.  I have lost the unsprung weight of a caliper, a disc and line with associated fixing bolts from my front forks.

What have I lost?

1. Outright power, obviously.  This is not an issue in normal even spirited riding.  It will still pull the bike up.  It is just that in occasional emergency situations you know that a twin disk set-up is more powerful.  I then looked to my rear brake to ensure that was working at peak efficiency and started using it more often (I had almost forgotten it was there).  But I like the progression.....

Improvements?

More power from your master cylinder? A different Master Cylinder (perhaps one from a single disk ATE bike) could produce more power at the expense of progression.  The piston sizes in the calipers are different (I invite Barry to chime in with the details).

Or perhaps I could have fitted a bigger disc?  But I would also have to make an adapted mount for the caliper and it is unlikely that I would have got the disc 'of the shelf'.

A 4 piston caliper from a later BMW?  Master cyclinder to match and an adapter plate or other modifications to fit it.

This is why whenever someone wants to improve their brakes, and are considering the expense of a dual disk set-up, I always recommend improvents to thier current single disc set-up first.  You have nothing to lose, except perhaps a rebuild kit for a now defunt single disk master cylinder - which you could sell.

But whatever you do, 30 year old brakes will be no match for modern brakes you might be used to.  Get used to it.

Rev. Light

[Barry]

I'll 2nd Steve on this too.

I've had twin disc bikes that were worse than single discs in fact the best brakes I ever had was a cast iron single disc. Where weight is concerned especially unsprung weight  "less is more".

[steve hawkins]

Just to add - this is my single disc setup.

As you can see I have still got the twin pull throttle arrangement of the 78-80 R65, which is better than the post 81.  The master cylinder is a single disc post 81 - a little but of ajustment require to mate the two together.