Forum

[Tim NZ]

In which case one of two situations exist: The two holes in the brake plate that the cams pivot in are not on the same Pitch Circle Diameter? Check the PCD with a dummy axle secured into the brake plate...


OR


One or the other of the two cams are not machined identically?


Variation in brake-cam PCD of up to 0.5mm is not uncommon, and for other than racing service one can typically live with it. Over 0.5mm variation of PCD and either a new brake plate is in order' (check it; 'new' does not mean that it is true and correct...) otherwise BOTH cam pivot holes need rebushing so that they lie on the the same PCD. Raidialy AND Axially.


Why is 0.5mm 'wiggle room' acceptable for street use? There is always at least that amount of 'slop' (lost movement) at the trunions which is usually able to be successfully accommodated via the fine adjustment of the LH/RH link rod.





Tim NZ

[John R]

'86 Bullet. I started with an SLS drum, fitted a TLS, spent ages trying to get it right, got it right and it was fine but needed loads of readjustment, got sick of the whole business and fitted a disc. Works 100%, 100% of the time. Worth the money.

[jawa-enfield]

Well, after 2 'new and improved'brake plates9with quite a difference in quality i mist say) and a lot of measuring, you always have to adjust 1 cam steeper then the other, giving always different forces on the drum from the shoes, even if you have the levers paralel.

The position of the 2 holes for the brake-cam axles are a-symmetrical.
Even when you have linings made on the plate on the lathe-made to fit- it still does not work.

The only solution i can think of is measure the difference in lift and mount (screw?) a plate in this thickness to the foor of the shoe to compensate..

[Adrian]

I don't know if this is practical, but if you know which of the spindle holes is the incorrectly bored one, could you not have the hole bored/milled out oversize, but with the correct centre position, and then sleeved with a bronze bush for the cam spindle?



Failing that I have also seen a Grimeca 4 leading shoe front hub fitted in a set of RE forks, you would need the fork sliders off a 350 Thunderbird or an Electra-X/EFI with the central mudguard lugs to give you an anchor point for both brake straps.



I would be thinking very seriously about a disk brake front end by now, as others have recommended.



A.

[Jamesy]

Spent an absolute eternity time and money trying to get a decent front drum brake on 2003 B350 I had without any success.The rear brake worked perfectly though.

[Tim NZ]

If the shoes' heel pivot posts or the cam axle holes are off center and NOT axially and radially aligned. (Occasionally they are a mile off). You will be farting against thunder no matter what method of adjustment is used.
In the first instance rebush the axle hole so that it is concentric to the brake shoe heel pivot posts, and then confirm the cam holes, and bush as required,


Otherwise get a new brake plate, and ask H staff to confirm concentricity of the cams etc prior to dispatch.


Tales all of a couple of minutes to check with a dummy axle and a vernier.


All is fully described and explained in the doc file...




Tim N.Z.

[jawa-enfield]

Ofcourse the pressure against the shoes is bigger with smaller cams, but distortion of the shoes because of this force.. would it?
One thing is clear, it does not matter if you apply the front brake with 2 fingers or full-force.. This indicates that smaller cams indeed have no use?
(pic of mine)
I had a set of smaller cams from Jochen Sommer, but the material he uses is too soft, the cams wear out to the corners pushing the linings aside..

Re-boring the holes in a plate seems to be a problem (thought about installing needle bearings in them) and after 3 brake plates, including one with very big tolerances from our host, i won't buy a 4th one..

It's unbeleiveable it won't brake normally with these cams, also not with very soft linings, all on late made to diameter to fit etc..

[Wheaters]

I think you have posted this on the wrong thread, in reply to my post on your other thread elsewhere.

I misunderstood what you meant; I see now from the photo that you fitted cams with less "lift", rather than less width, which might present another problem. Using cams with less lift will give more leverage, but less movement of the shoe for the same movement at the handlebar lever.

If the shoes are making full contact with the drum, and everything else is in order, it must surely be that the shoe lining material still isn't "soft" enough.

You could try getting advice from these people: https://villiersservices.co.uk/index.ph ... cts_id=146

[jawa-enfield]

The leverage is far enough to get the brake working within half an inch pulling of the brake lever at the handlebar..
I tried 8 or 9 different linings as i said, no difefrent response in thje original, ferodo AM4, oldtimer, very soft lining you kan pusch a vingernail in, nothing.. That's why i think the drum material is also at stake..

[jawa-enfield]

Another thing, the original linings seem to work better then the 2 types of Englisch and other linings i have.
But when in damp/wet wheater the front brake tends to clutch/grasp at tiniest squeeze, causing the front wheel to block (But whehn dry, brake is very poor)
i reworked the leading edges of the linings, but no effect.
Can this be solved?