#99714
Royal Enfield Brakes
I've had quite a few people get in touch with me regarding a 6" brake that i converted to TLS asking could i do the same mod for them. The simple answer is no, i have far too many other things to do. I've thought long & hard over this, but was persuaded to write a "guide". Much of the stuff has been covered in another group i belong to but i've gathered it all up now & most of the info is here.
Front Brake conversion for RE twins & singles fitted with 6” SLS brakes
I’d had an idea floating around for quite a while regarding the 6” sls brakes fitted to various Redditch made bikes in the mid 50s to early 60s & how to improve them. The standard brake, the one fitted with the floating brake cam bush, isn’t too bad when correctly set up per the book but I kept thinking there was still room for improvement & I started thinking along the lines of TLS brakes. One thing I wanted to do was to only use RE parts that were available in the 50’s & 60’s. I did a series of drawings & finally ended up with a design using modified RE brake cams where one side of the cam would be filled in (creating a half moon shape) that would act as the new anchor for a brake shoe, the brake anchor itself being replaced with another modified brake cam.
I built the brake (double sided as its on my Constellation) last year & its been on the road now for a few months with excellent results. I shared my information with Allan Hitchcock who replied: “It is great to see projects that work well as so many do not get past the idea stage. Sounds like you have a winner here. May I suggest you write something about it for the Royal Enfield Owners Club maybe even a guide how to do it. There are many owners with the twin brake who need better stopping power.”
SAM_3927.JPG
SAM_3927.JPG (4.91 MiB) Viewed 405 times
Before starting the conversion:

On one group that I belong to a member commented on one of the photos of my finished brake: “so it’s a pretty straightforward (easy) thing to do?” to which I relied “yes & no”. There is one thing you need to know before getting started: if you measure your brake plate you’ll notice that the centre line of the brake shoe anchor is not the same as the one for the brake cam. To demonstrate this do a of the brake plate & mark the centre of the wheel spindle. Using a compass then draw a circle that intersects the centre of the brake cam & draw another circle which intersects the centre of the brake anchor. You’ll quickly see that the centre of the brake anchor is approx. 4mm further away from the centre of the plate than the brake cam. Keep that in mind.
The tools I used were: a hacksaw, some files, a pillar drill, 5mm tap & countersunk screws, emery & double sided sticky tape& finally some “devcon”. If you have access to a lathe, milling machine etc then so much the better.
I purchased a 2nd hand brake plate & some well worn 2nd hand brake shoes to practice on.
This “guide” is just a description of what I’ve done, nothing else, I wont take any responsibility for things going wrong in any shape size or form.
I’ve lost the latest correct drawing, the one here is an earlier one & some of the stuff on it is wrong as it was based on a brake cam with a ¾” radius.
Do a good drawing, check things on paper 1st. I made some templates of the parts using card & experimented with these before I cut any metal.
SAM_3916 (1).JPG
SAM_3916 (1).JPG (4.3 MiB) Viewed 405 times
The brake cams

The standard brake cams (part 27067), you’ll need an extra one if converting a brake on a single or 2 for a twin, need to be modified to a “half moon” shape. I used a piece of “dural” cut to fit on one side of the brake cam. The brake cam itself was drilled & countersunk, the piece of dural was then drilled & tapped (m5), loctite was applied to the mating surfaces & then the assembly screwed together using a countersunk screw. I used a file to create the 7/8” radius needed. If you’re doing the job by hand like I did then a set of radius gauges would be handy. If you have a lathe the job can be done in a minute or two.

The brake plate

You’ll have remembered the 4mm difference between the anchor & cam centres? In order for the brake to work properly both cams need to be the same distance away from the centre of the brake plate so Its not just a matter of discarding the brake anchor & whacking in another brake cam in its place.
If the centres of the cams are left where they are then one cam will be approx. 4mm closer to the centre of the brake plate & it will be doing most of the work, the other cam & shoe chiming in much later & at best you’ll have a brake that is only as good as the SLS being replaced.
What I did on my brake plate was move both of the cam centre points, 2mm on one & 2mm on the other, so that the centres of both cams now sit on the same circle & are exactly the same distance away from the centre of the brake plate.
The hole of the old brake cam housing (part no 26836 Hitchcocks have good 2nd hand ones) should be ok, I removed metal from one side of the part of the bush that goes into the brake plate, I also elongated the holes (for the mounting bolts) either side of the bush. With this mod done the floating cam bush can be moved the required 2mm .
The location for the new floating cam bush needs to be drilled in place of the old anchor location. The hole itself needs to be around 15/16” diam to accept the bush. Don’t forget the centre of the new hole needs to be 2mm away from that of the existing hole! Don’t worry too much about the amount of metal left of the area surrounding the hole for the new bush, if necessary this can be built up using devcon or similar (ally welding if you have it?). As long as the surface is nice & flat for the new bush to be bolted to & that the bush has something to sit on.
New holes need to be drilled both sides of the bush for the retaining bolts/nuts.
I used a pillar drill for all of the above. Having access to a milling machine would have been much easier! Always double check before cutting/drilling.

Brake shoes

The anchor point ends need to be modified. By far the easiest method is to saw the ends off & convert them to “floating” shoes. In case you don’t know what I mean then take a look at the at the 7” brake shoes as fitted to 1960s Triumph T90 & T100s & you’ll get the idea. I used this method as a quick expedient way to see if my brake worked on the bench. It did! However in the end I decided to make radiused ends (7/8”) for the brake shoes to match the radius (7/8”) on the back of the brake cams. This job was a bit of a pig, actually is was huge pig of a job. A friend built up the ends of the shoes with some ally weld, I wasn’t sure there would be enough metal left on there to act as a good “anchor” point. As it was turns out there was just enough metal but I noticed that not all brake shoes are equal! To cut a long story short the Redditch made ally brake shoes are far better than their Indian made counterparts.
A milling machine & fly cutter would have been handy for modifying the shoes, I didn’t have access to one so I modified the brake shoes by hand which was rather painful & took forever. Everything has to be “square”.
In my case I filed away a bit & then placed the shoe on my card template & checked & kept doing this till I was nearly there, finally finishing with some emery taped to a bit of suitable round bar & getting the end of the shoe to within a few thousands of an inch (& square). Someone with a milling machine could easily do the job within a few minutes, I think I spent around 3-4 hours on each shoe using nothing but a file & emery!

Brake linkage

An initial thought was to use Indian made components from their 7” TLS. That soon went out of the window as they do not fit any Redditch made brake cams. I settled by using the original brake arm which was welded to a modified rear brake arm of a 250 Crusader. The Crusader brake arm had a portion (half) removed where the splines are. The original brake arm was then welded to this using a brake cam as a jig so that the splines lined up on both.
Another 250 Crusader rear brake arm was used for the “slave” brake cam.
The rod connecting both cams is an engine cylinder stud (5/16”BSF part no 38428)

Setting the brake up

As a few things have changed it’s a good idea to radius or arc the shoes. If you have a lathe brilliant! If not, here’s what I did: cut a strip of emery/sandpaper to fit inside your hub & attach it to the inside of the hub using double sided tape, I used “tesa” tape & 80 grit paper. Provided your hub is good & all the mods you’ve done to the shoes, cams etc is good: Have a complete brake plate assy fully assembled, trial fit it into the hub. Spin around in a circular motion with the brake applied a little. You can use shims fitted between the shoes & cams if you want but I found I could lock the brake levers. Sand a little at a time & check. I found that one shoe can sand down quicker than the other which was probably down to the bottom (original) floating bush being a bit off in one direction. So make sure its all ok & do the nuts up tight on the bushes, from now on you don’t want any movement on the bushes.
I sanded away until both shoes were exactly the same, showing the same contact area, took my time etc etc.
When setting the brake up on the bike: its like doing any other TLS brake, only that if you have done a double sided conversion its twice as much work. I found that by doing the bottom brake cam 1st, i.e brake arm applied hard by hand & tons of slack on the slave cam, a helper is great, get rid of the slack in the cable. Then get your helper to push down hard on the slave cams arm, take the slack out off the connecting rod. Both cams (or all 4 cams) should be working in synch now. Some adjustment of the cable adjuster (adjusters) might be needed.

Performance

The double sided brakes on my Constellation since being modified to TLS condition (in effect a 4LS system) are well up to the job & as good as anything ever fitted to a Meriden made Triumph T140. I no longer have to anticipate having to brake. Its possible to come to a nice controlled stop using light hand pressure on the brake lever. Using the brake as before, i.e. gorilla type clenching of the brake lever will produce a squeal from the front tyre & chances are you have just locked or about to lockup the front wheel – be careful. It takes some getting used to, a few days.
Please remember that the drawing i uploaded is an early version & therefore wrong, but youll get an idea from it how the brake works.

A full list of the parts used to make one 6" TLS excluding the brake plate & existing brake arm all available from Hitchcocks:
27684 crusader brake arm x 2
7916 nut x 4
252 bolt x4
10314 nut x 2
27067 cam x 2
38428 stud, cylinder x1
140191 nut x1
140178 nut x1
26836used x1
SAM_3936.JPG
SAM_3936.JPG (4.79 MiB) Viewed 405 times

Shop for accessories at Hitchcocks Motorcycles