Softer shoes

[AlanJ]

Hi All,
Now, I was going to add this to the Viral Interlude" post because it was part of the rebuild of the Saxon, then I thought maybe better on it's own so.
When I was ordering for the Saxon, there was a bit of controversy over the size dia of the rear shoe. Some said 160mm but mine is, on both Saxons, 150mm.
The size sorted, I then noticed that one company was offering 150mm with soft shoes. Now my TS 250/1 has a standard front hub brake which as we all know
can be and is a load of crap, great idea all being inside the hub etc, but we all know for various reasons it's not good. Now this business of soft shoes, and this is
the reason for this post. Ok the ones I have ordered are for the rear, and it's probably going to be difficult to tell on the rear weather a softer lining is better or
not. I am not really worried too much about the rear because after all it's the front that does most of the work As soon as I saw soft shoes it started me thinking
about my TS and it's non-existant front brake, Question is, would softer shoes make a difference? Trouble is there are shoes on the market at 10 quid and shoes
at 35 quid, sorry about that £10/£35. know there is a lot of difference in those prices and those people selling the higher priced ones can and probably will, say
Its your life, and they might well be right. The thought still remains, is a softer shoe a better stopper or not.
Be safe Guys. Alan.

[AlanJ]

Hi again Guys,
I have just realized that I have mentioned mostly about softer shoes at 150mm dia but the size on the TS 250/1 front is 160mm
which I can tell you is available with softer shoes, just thought I had better mention it.
Take care Alan.

[AlanJ]

Hi,
Just sitting here thinking about the TS 250/1 front brake, or rather the lack of one. I recently read an article about a guy using a 4mm inner cable so not to get too much stretch, ok seems a bit drastic but I see his point. Then I was thinking, The various forces involved when you squeeze the lever, you load the inner wire
against the outer and something I have not thought about before, if the outer, in the manufacture, is not wound absolutely tightly, ie coil to coil, then the efort one puts into braking won't happen till you have shunted the coils together and if that outer is not too wonderful you must be wasting quite a bit of effort.
Anyway guys I have never particularly looked at the outer cable unless I have had to shorten it, perhaps it's one of those things we should look at, I don't know, what do you think?
Take care Alan.

[nice2day]

Hi Alan...I can't give any buying guides for the Saxon rear brake shoes.
However regarding the improvement of the TS 250 SLS front brake however I could write quite a lot.
The design of this brake shares the same design problems as does several British SLS type brakes in that there are 2x fixed pivots for the shoe ends but does not have a floating cam spindle. I wrote extensively on this problem on the Norton Owners Club GB which has similar action but larger front brake. As you would know, most of the braking force in an SLS design comes from the "LEADING" shoe and very little from the "TRAILING" shoe. This causes the leading shoe to wear much more quickly than the trailing shoe. This wear difference (which occurs straight from new) creates the problem that the fixed leverage geometry of the brake design cannot self adjust for the wear and thus leaves the powerful leading shoe with no pressure because the now thicker, trailing shoe touches the drum first and stops further movement of the rotating cam to push the leading shoe with any real pressure against the drum. So in effect you have the trailing shoe dictating the pressure that is delivered to the leading shoe.
Car designers overcame this quite easily with hydraulic system that automatically equalises the pressure on both sides of the pressure ram that pushes the shoes. Before hydraulics they used a system where the levering cam could float, usually held down by a couple of pressure springs. This allowed automatic compensation so the faster wearing leading shoe was always getting full pressure as the cam pivot could float to a central position and apply equal pressure to both shoes which overcame the shortage of pressure on the leading shoe.
So how do we improve the TS 250 brake?

One easy way is to ream the spindle hole a little larger. The extra clearance will allow some equalising movement to occur on the spindle We also need to enlarge the main spindle hole a touch too, as then we can equalise the brakes regularly by loosening the spindle nut and applying the brakes then re- tightening. This adjustment can only work if the brake plate can actually move a touch off centre to equalise the contact of the shoes but, as explained above, the improvement gained, will be short lived unfortunately.

Another way is to fit a very soft easily wearing shoe on the trailing side compared to the leading side. This will keep the wear differences more even. Another way is to remove a section of the trailing shoe lining* nearest to the cam. This has 2x benefits in that the cam can now lever the the trailing shoe more harder against the drum as the lining starts further away from the lever (improved mechanical ratio) and in doing so should wear the trailing shoe more quickly for 2x reasons; there is more pressure and there is less friction material. The main improvement though will come from the fact that the leading shoe, the one that does nearly all the braking, is receiving full pressure without being bigger hampered by the slow wearing trailing shoe that, in a normal set up, stops the cam from rotating fully and supply the full leverage power to the side that matters.

These mods have proved very effective with my Norton brakes.

* The lining only needs to be filed down a couple of millimetres, it does not need to be removed completely. Once the linings surface is lower it will not touch the drum and the first contact patch will have shifted along to a point further away from the cam lever. I would try about 20% of the original length to start with and increase if the brakes power has increased ( I think I once read that someone used 50%? ) Ultimately, the natural wear on the lining might, depending on the depth of removal, cause the lining to be in contact again which will be felt in the reduction of the brakes performance.

Les

[Puffs]

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[AlanJ]

Hi guys,
Got to tell you Les That's one hell of a lot to think through, more than interesting. the problem has been solved of course with a CB 175 Honda TLS
Front hub, it's about the right size. I've actually got hold of a Suzuki 350 TLS hub but for one thing I think it's a little on the large side. In any case I really want
to keep the TS looking original if pos, I have had that one for 35 yrs. With the softer shoes the guy that's selling these told me he has been selling these for 30
years without any adverse words about them. As I said earlier, I am not really worried about the back brake on the Saxon, after all with a disc on the front it's
no problem. When I have finished the Saxon, I will most certainly give your thoughts on the front of the TS a good sort out Les, it's a lot more than just
nteresting. Thank you both, wish you well Alan.

[nice2day]

Another concept of improving drum brake performance is the self energising type of system. This is where the natural grabbing power of the leading shoe is used to push the trailing shoe out at the pivot end (rather than have fixed pivots) via an adjustable link that transmits the movement (it does not need to be adjustable). If you study the action you are getting a quasi twin leading shoe action, so more braking force is created.
If one wanted to experiment, the MZ's fixed anchor pivots could be removed and the same holes used to fit pins that went through a pressure linking bar with slotted holes that allowed it to move and transmit force to the trailing shoe. This would result in no change of appearance on the outside face of the drum.

Les

[Puffs]

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[AlanJ]

Hi puffs,
An internal TLS now that would be something. How many spokes on the SP
Alan.

[Blurredman]

I thought it was quite a common 'mod' for people to buy rear shoe actuating assemblies and just put it on the front wheel- Brace the torque arm, and now you have a nice long external lever to pull against..
Indeed I have seen it on this forum - It's a cheap and easy if not ugly way to increase braking performance.

[nice2day]

That seems a good idea Blurredman, you are creating a longer leverage but the downside is a longer lever movement.

To create exactly the same effect is even easier though....All you have to do is reduce the the size of the internal cam lobe. I did this on my TS 150 which produced a very noticeable braking improvement. Making the cam lobe tips smaller by about 2mm is the same as turning it with a longer lever...it just increases the "mechanical advantage" ratio so the effect will be identical, assuming that the change in ratio is the same. In fact you can do this mod in stages to achieve the best brake power vs lever movement increase. Highly recommended.


Les

[Puffs]

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[nice2day]

Hi Puffs...Yes that's right.... With the smaller cam profile, the operating changes, as said, will be, or can be identical, depending on the amount of cam size reduction, including a longer lever movement. Fortunately the brake lever shape allows a very good range of movement so the extra movement without "sponginess" is not a problem I found.
As most riders would know, having the exact length of good quality cable run in the most efficient curve and well lubricated makes a massive difference to drum brake power. Making regular centralising adjustments help greatly too.

Les

[AlanJ]

Hi Puffs,
The internal TLS I was referring to would be on the TS. I have just fitted those new softer shoes on the Saxon rear, mind you using the side by side
and push down technique is a bit fiddly with the pivot pins. At the moment I am having a bit of fun with the rear stoplight, it's on all the time, it's all new
that's the switch, wire and spring, trouble is I think the spring is either too strong or too short or both. Have a good one.
Alan.