Vincent Brakes - an ongoing collection of VOC members experience and recomendations that should be valuable to review.
The invention of the wheel made it possible to move mass in a more efficient way, but then came the problem of stopping the mass. Hence the invention of brakes. Brakes have evolved from foot dragging to retro rockets, but unfortunately, the Vincent brake, it seems, is nearer the former than the latter. So with this in mind, if aiming for a proper restoration, brakes must be considered. At first glance it doesn't seem to be such a big deal to go through the brakes. Those who have, have probably learned the hard way that it ain't necessarily so.
It should be noted that the surface area of the braking mechanism on a Vincent, along with all of the mechanical leverages which determine surface area contact pressure, with the drum diameter to wheel diameter factor, when all are fitted properly, are adequate to lock up both front and rear tires in most cases on a dry surface when brakes are cold. With the four brake drum design, (excluding the D's, of course, with the three drum design) it's more difficult to achieve 100% efficiency, due to the extensive amount of brake parts that move each time the brakes are applied. Optimum equal pressures and optimum surface area contact aren't easy to achieve. The two front wheel brake drums, by utilizing a balance beam when the brake is applied, provide equal shoe pressure. Not the case with the rear brake. It's almost impossible to achieve equal shoe pressure to drums on the rear brake mechanism, and usually only an experienced wrench can achieve best results from the adjusting wing nuts.
When brake restoration is undertaken, one of the important factors is how true the drum rotates with the wheel axis. Most restorers who "over restore" the Vincent often get carried away with polishing hubs, chrome plating spoke rings, and painting brake drums. All of this can be done, if done properly, but sometimes it isn't. The brake drum is shouldered on the hub for alignment. The aligning shoulder on the hub, and the mating surface of the hub must not be disturbed during polishing. If there's any doubt that the hub flange mating surface doesn't run true, it's a good idea to take a light truing cut in the lathe. Next comes the plating of the spoke rings. Best to do your own preparation work prior to sending it off to the plater. When you do this, take a felt tip pen and mark the inner and outer mating surface, that's the surface where the 5 or 10 bolt hole pattern exists. Mark the surfaces. Do not plate. The plater has a way to mask the area not to be plated. Next, inspect the paint job on the brake drum, and remove any runs or paint on the outer mating surface to the spoke ring and any paint that may be on the aligning bore of the drum.
After going through the steps above you're pretty much certain that you've eliminated any wobble of the brake drum. This would be a port and starboard movement of the brake drum in relation to the wheel's hub. The next step is to see if the brake drum's friction surface is concentric with the hub's aligning shoulder. This can be accomplished by truing the wheel hub in the lathe, then bolting the brake drum to the wheel hub and dialing in, checking the concentric of the drum. In most cases it requires a very light cut to clean any rust deterioration, any surface scoring, and any out of roundness from a long time sitter. Usually 5 to 10 thousandths will do the job.
The next thing to make ready are the brake
shoes. The original brake shoes were riveted, various
linings of different compositions were also offered, and still
are. The green lining seems to be the preference of most
restorers, but most other linings work as well. If you
have the option to go with bonded lining or riveted lining, go
with the bonded lining. If for no other reason than that
you gain contact area lining to drum.
It's virtually impossible to achieve an adequate mating surface arc of the brake shoes without dressing the surface in a lathe. Dressing the surface isn't as straightforward as most would like to believe. Doing it properly requires a jig fixture to locate the shoes in the lathe for machining, and building the fixture isn't that difficult. With an 8" diameter 2" thick piece of aluminum, turn a 1 3/4"X 2" diameter stub. Then chuck and true stub in 4 jaw chuck. Take a truing cut on 1/2" thick 8" diameter flange. You're now ready to drill the fixture to accept the dowels that will become the two brake shoe pivot pins. One other precision hole will be required, and that's the bore in the plate that will accept the brake cam pin. This hole should be made a tight fit as well. Keep in mind that when setting up to drill the three holes, these are precision holes and must be done to a tolerance of plus or minus .001. So with your best Vincent backing plate, measure well, then take a cut to true the outside diameter of the 1/2" flange.
The next step is to mike the four brake cams. This would be the thickness of the cam flats. Select the thickest of the four and use this one for your jig fixture.
Now it's time to profile the brake shoes. Hopefully you marked the shoes in some way prior to having bonded lining applied. It's like anything else mechanical, where parts can be swapped, it's always best that they go back into their original location. If their location has been lost in the heat of things, with the four backing plates, shoes, and springs removed, you can usually fit the brake shoe by slipping the brake shoe over the pivot pin and turning the shoe towards the brake cam. The shoe shouldn't hang up on the brake cam outer guide plates. It takes a bit of fiddling, but by doing this you'll probably come up with pretty much where they were located originally.
The next step is to identify each of the brake backing plates as to their location on the bike. An easy one will be the right front, as it will have a hole in it to accept the speedo angle drive. On most bikes the left hand side is identifiable by the water excluder, or in the absence of the water excluder, the rivet holes identify it. The rear backing plates are normally the same, and are interchangeable. Sometimes you'll encounter a machine wherein someone has discarded the larger side car sprocket, and installed a water excluder. In this case if not previously identified, it will be anybody's guess as to the left side backing plate, and the right side rear backing plate locations. You might be able to detect a support wear pattern on the rear brake cam spindle brake backing plate boss. After you've made a decision on brake backing plate location, and have the brake shoes fitted to the backing plates, it's time to match by felt tip marking, the brake shoes to the brake drums in which they'll operate. One other mark to put on the brake shoes is the outboard location mark. This will prevent inadvertently reversing the brake shoe location after machining, which is easy to do, as everything is identical in appearance, but not in actuality.
Now for the turning of the brake shoe linings. Place your jig in the lathe, using a four jaw. On the outer edge of the flange, eyeball and mark a felt tip line directly outboard of the center of the two brake shoe pins. Dial the outer surface of the flange so it cams minus .005 at the felt tip mark. Place the first pair of linings in the jig fixture. With an inside mike, mike the drum in which they'll eventually find a home. Adjust the cutter on the compound to turn the exact diameter of the brake drum, then subtract .005. Using shims between the brake cam surface and the brake shoe flat, shim the lining's circumference on the trailing edge of the forward brake shoe, and do the same with the rear shoe, shimming the lining to the leading edge of the rear shoe. From now on I'll refer to shoes as front and rear, no matter whether they're left side or right side brakes.
If you have properly shimmed the shoes, it's time to fix the brake shoes to the jig. This can be accomplished by wrapping keying wire tightly around the spring shoe fingers. When a cut is made, it will take a cut on the full circumference of both the front and rear shoe linings, taking approximately .004 more from the leading edge of the front shoe, and .004 more from the trailing edge of the rear shoe. After this is done, mike the thickness of the total shims on each shoe. Subtract .015 from the shim thickness, using standard mild steel cam scrub plates, you can achieve the .015 minus, by either shimming underneath the scrub plate by slightly loosening the ear tabs by bending, or if the scrub plate is too thick, you can file the aluminum brake shoe flat and rebend the scrub plate for a tight fit.
Now it's time to cam the leading and trailing edges of the brake shoe linings. This is done by using 80 grit sandpaper wrapped around a block of wood. This work is best done by placing the brake shoe in a vise and sanding with the block of wood to achieve uniformity across the width of the shoe lining. It's best to identify leading and trailing edges prior to chamfering, as the chamfering is somewhat different. The reason to chamfer is to provide smooth engagement and smooth release from the drum. Chamfering also prevents inadvertent lock up. You don't have to go to extremes to achieve the desired results. The angle of the chamfer and the depth of the chamfer causes a reduction in the surface area of the brake shoe lining that contacts the drum when increased, and reduces braking efficiency. In lieu of this, it's recommended that when chamfering or relieving leading and trailing edges, that care be taken not to remove too much. For best efficiency during the lifespan of a set of brake linings, as the brake linings wear, it's not uncommon to rechamfer or relieve possibly three times during the lining's life. Doing this allows optimum lining area to drum during the lifespan of your brakes.
The next step is to straighten your backing plates. Chuck up your hollow axle in the lathe and true. Place the tapered bearing on the hollow axle, using it as a spacer, then take the backing plate and nut it on the hollow axle tightly. With the paint removed from the brake backing plate, place a dial indicator on the outboard surface as close to the outboard circumference of the plate as possible. Make sure that you're not hitting anything. Turn the lathe by hand to see if there's any wobble in the plate. If you find the plate is distorted, causing wobble, you'll have to straighten the plate. Don't try to straighten the plate while it's in the lathe or attached to the hollow axle. After straightening, recheck. You're looking for a maximum runout of no more than .005.
The next step is to check the straightness of the brake shoe pivot pins. These can readily be checked with a small machinist' square. Straighten as necessary. Now check to insure that the brake cam has adequate end float in it's backing plate bore for proper operation. When this is done you can paint the backing plate and install any water excluder as required. You can now install the brake shoes. When doing so, insure the brake shoes float nicely in their pivot points. Sometimes it will require a light ream job to achieve freedom of movement. It's a good idea to lightly grease the pins and the backing plate cam boss prior to assembly. Use the grease sparingly to prevent any from finding it's way into the shoe linings. It's always a good idea to assemble with new brake springs. This helps unintended brake drag, which isn't a good thing. It can cause heat build up, lining wear, and brake fade.
After everything is put back together, this is what you should have:
When the brake cable arm is rotated
approximately 15o to 20o, you'll experience full braking,
nearing lock up. Due to the mechanical design of the
single leading shoe, when the brake is applied the front shoe
lining of the front wheel comes into contact at it's leading
edge first. Next the leading edge of the rear shoe lining
comes into contact, but has more lining pressure to drum than
the front shoe leading edge pressure. This is due to
mechanical advantage, as the rear shoe distance between it's
pivot point and the point of contact of the cam is
greater. This is the reason that the rear shoe lining
wears out faster than the front shoe lining. The machining
procedure, which actually offsets the brake shoe lining
circumference to the brake drum circumference is done to enhance
a proper bedding in of the brake shoe lining to the
drum. Max Lambky 2/22/10
A good source for exotic drums
is www.discovolantemoto.co.uk. Most classic bikes in UK
use magnesium replica brakes (Oldani, Manx, or Seeley) made by
Dick Hunt Racing. I wouldn't buy a second hand magnesium brake or plates for reasons explained by Eddie Stevens in KTB. Tom Gaynor 4/18/05
The braking is far better than any very good std or 'racing brake' Vincent but I think it still needs to bed in because I feel 'sponginess' at the brake lever ...especially when hot. I will ride the bike with the brake cables and the balance beam for a few more months and will change for twin lever cables without the balance beam to see what happens!
Several riders asked me to make the same
for their machines. I need to test and improve it more
before to do some copies .
This is not a cheap modification but a complete wheel assembly. Grimeca brake and hub cost about £300 + 36 holes rim + spokes + brake plates castings and machining + spindle + levers + and + ....I don't dare to calculate, may be £500 !
I can suply some photos if you want to make your own. Francois Grosset 1/12/03
1. If the handlebar lever moved more and the actuating lever remained stationary, we can say it is the combined cable mechanism squashing up.
2. If the actuating arm continued to move after you felt resistance and the handlebar lever travelled on, you have to consider that something inside the drum is moving. If the shoe is hard up against the drum, what can move ? Nothing should until the drum is rotating. Then the servo effect may cause the shoe to bite into the drum. That will not be much. Is the shoe material compressing ? Try and squash some under a press. Which leaves you with one answer which is demonstrated by my cutaway hub assembly. You can watch the shoe touch the drum at the pivot end, and then bend itself to form its curvature to fit the drum. How much it moves depends upon the wear. Trevor 12/15/01
The fitting is fairy straight forward. The discs are modified to fit the Vincent hub and are bolted on with a spacer between the disc and spoke flange to enable the calipers to clear the spokes. The calipers are mounted on outrigger plates held in place by the front wheel spindle and a special bolt going through the brake torque mount on the fork legs. The speedo drive is covered by a dummy back plate on the right hand side to carry the drive adaptor.
It works extremely well and is powerful, progressive, with plenty
of feel and feed back. I can E-mail or snail mail pictures if any
one is interested. Please note this mod was designed and
manufactured by Dave Lambert of Derby, UK who is designing a
single disc rear brake along the same lines. For road safety
in modern traffic this is a must-do mod. Whether you do this one
or another one, better brakes are a worthwhile investment. It certainly beats the hell out of pulling the lever back to the bar and praying. Roger Lord 8/5/01
Phone 020 8994 0102 or 6238 or 8484 or FAX 020 8747
1345. A truly fantastic company, but be clear in
what you wish--there are a million variations of size, head style
and material. They can also supply all types of
The other day I posted a note saying that if anybody wanted some of Derek Sayers (non advertised) front brake cables I would be happy to act as internet go-between since Derek is not connected.Many of you seem interested. I do emphasise my only interest is as an entirely satisfied customer of Dels who lives on the front brake. So here is the info and how you can order :- 2 types SHORT and LONG. Originally SHORT was fitted going to RIGHT arm of Balance Beam.No stop.( A,B & some C?) Then changed to LONG going to LEFT arm of Balance Beam with stop.This is the more normal set-up most of us have. Cable type: very large diameter, as big as the rear cable. As original Black with red stripe running down (weird) Some years ago and partly in response to my whinge Del had a batch made which sold promptly. Others may from time to time have had a few bashed out, but Del always has them and seems to me to be the modern reviver and thus deserves our business. ! have the cables on my A, B and C. HAPPY HAPPY HAPPY, but do remember they are PART of the solution. Cost to overseas orderers is £39 all territories of the world, inc air mail/packing in a stout padded bag. Different currency to £sterling is acceptable but only in the form of notes and with a surcharge of £3 to allow for exchange costs Del has no Credit cards facility. Bulk orders by negotiation!! Sales to UK are cheaper of course. Phone him for info. Cheques in £sterling or even notes (left over from International Rally?)are of course welcomed.
Order direct: Mr. Derek Sayer, 75A, Grosvenor Park,
Camberwell, London SE5 0NJ, Great Britain. Phone/Fax (44)
171 703 6205 (change in april to 0207 703 6205)
I'm happy to report that they are very nicely made, and much heavier-duty than the usual cables such as were on my bike. The brake action on my Shadow is substantially less spongy than before, and braking is much more effective with the firmer feel leading to higher pressure at the brake shoes. These cables aren't precisely cheap, but are well worth the investment in my view.
Derek is not on email, but his address is 75a Grosvenor
London SE5 0NJ; phone 071-703-6205. Dave Hartner 4/18/00