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Tuning Front Brakes?

BlackLightning998

Well Known and Active Website User
VOC Member
Hi,

I picked up from the 5-speed gearbox thread a couple of members like me looking for guidance on how to tune the front brakes. There was one reply and an offer of a telephone number on top of that.

Any chance we can start this dedicated thread and seek the guidance of experienced Vincent owners for their tips on tuning the front brakes for maximum effect?

Replies and tips gratefully received.

Stuart
 
Last edited:

Tom Gaynor

Well Known and Active Website User
VOC Member
Brakes

Try this website: http://www.francescobazzani.com/freni-e.html

I have a 210 mm Menani on my race bike, functionally identical to the better known Fontana, and slightly cheaper. My (racing) experience of big Japanese brakes (250 mm four shoe) is that they aren't as good as 210 mm Italian ones. On the road it probably wouldn't be noticeable. The 250 mm Fontana would probably stop a speeding locomotive.


If the standard brakes are to work efficiently, both levers should be parallel when both are hard on. Captain Vincent has a neat way to achieve this.
But. Vincent brakes are 7" drums, very resistant to fade ( a 7" brake with 2" wide linings) but lacking the diameter or design features ever to be very powerful. Rudges had 8" drums in 1934. Diameter for stopping power, width for fade resistance.......
Stiffening them up is worthwhile, classically by brazing triangular braces inside the steel plates or by buying "Lightning" plates.
If you stick with the balance beam, put an outrigger plate on. Going to twin cable levers removes the balance beam as a source of lost motion.I've tried both. Functionally it makes no difference. A given pull at the lever results in half that pull at each drum with both methods.

However even with ribbed drums, Lightning plates, turned linings and all, mine were fade resistant but not responsive, particularly in traffic. Discs are (IMHO) the best and cheapest option, a big four-shoe the next best. Both require the contrivance of a speedo drive. So I bought PV 2ls brakes: expensive (compared with making up a double disc system from a breakers), not as good as disc(s) or a big four-shoe, but perform very, very much better than I could ever get my standard brakes to perform. The bicycle still looks like a Vincent, and i didn't have to make my own arrangements for a speedo drive.
 

Vincent Brake

Well Known and Active Website User
VOC Member
Vincent 4LS brakes

Hi out there,
Indeed the only way to brake decently in style in nowadays traffic is possible with those 2 sided 2 LS brakes. I produce them myselve and use them well.
But I have bought an Egli with a D casing, in the front wheel is a YAM (I dare not say the complete word) TZ 350 hub measuring 250 mm. would it be best to go to (what Egli most used I guess) a ceriani 230 mm hub and a Vin rear hub (I could build in me own) or go to menani front 210 rear 180 mm (who have seen this on an Egli (not the Godet) I like to keep parts (seen) on the machine to its time (1969)


Vincent Speet
 

BlackLightning998

Well Known and Active Website User
VOC Member
Hi out there,
Indeed the only way to brake decently in style in nowadays traffic is possible with those 2 sided 2 LS brakes. I produce them myselve and use them well.
But I have bought an Egli with a D casing, in the front wheel is a YAM (I dare not say the complete word) TZ 350 hub measuring 250 mm. would it be best to go to (what Egli most used I guess) a ceriani 230 mm hub and a Vin rear hub (I could build in me own) or go to menani front 210 rear 180 mm (who have seen this on an Egli (not the Godet) I like to keep parts (seen) on the machine to its time (1969)


Vincent Speet
Thanks Tom, Vincent.

For some strange reason I want to try and keep the set up original. I have modern roadbikes, Japanese, Italian and US - so stopping power on discs is well understood - but I am sure that I can get the original twin drum's tuned better for good stopping. The bike has a strengthening plate on the front balance beam that my father and I made for it 30 years ago before the bike was sold - that was one of the ways I identified it from photographs when I found it again.

I'm managed to get the brakes adjusted so they stop the bike, but I now suspect the cables have too much flex in them as the handle just comes back to the bar.

I've picked up a useful tip from Russ at Vinparts about turning the brake plate cam to take up the slack, so that's next on my list to try.

Thanks for your interest.

Cheers

Stuart
 

Tom Gaynor

Well Known and Active Website User
VOC Member
Spongy brakes

Flex (call it lost motion) in the hub can be multiplied eight times, because the radius of action of the cam (say 1/2") is 1/8 the radius of action of the lever (say 4"). Or whatever. This already multiplied lost motion is then multiplied again by the handlebar lever, by about five times. So 1/40" of an inch of lost motion at the cam will amount to 1" lost motion at the hand lever. The greater the mechanical advantage, the greater the potential for sponginess. (True also of hydraulic brakes...) My guess is that you are losing motion in the drum, thus gaining the full 40-fold magnification.
I haven't ever suffered from cable stretch, which isn't to say that others haven't, but compression of the outer is common. Just watch the cable trying to straighten itself out when you pull the lever hard on. Then multiply the change in length by five.
 

BlackLightning998

Well Known and Active Website User
VOC Member
Flex (call it lost motion) in the hub can be multiplied eight times, because the radius of action of the cam (say 1/2") is 1/8 the radius of action of the lever (say 4"). Or whatever. This already multiplied lost motion is then multiplied again by the handlebar lever, by about five times. So 1/40" of an inch of lost motion at the cam will amount to 1" lost motion at the hand lever. The greater the mechanical advantage, the greater the potential for sponginess. (True also of hydraulic brakes...) My guess is that you are losing motion in the drum, thus gaining the full 40-fold magnification.
I haven't ever suffered from cable stretch, which isn't to say that others haven't, but compression of the outer is common. Just watch the cable trying to straighten itself out when you pull the lever hard on. Then multiply the change in length by five.
Hi Tom,

This would sit comfortably with the advice that Russ has given me to take up all the free play on the cam before the shoes hit the drum and then fit the arm and cable onto that - this would minimise the lost motion in the assembly.

I'll keep having a fiddle around and see how I get on - I can sense an improvement since I have been dabbling, so I may get there in the end.

Right now I just don't fancy what it'll be like once the bike is run in, doing 100mph and deciding I need to stop in a hurry!

Thanks for your help.

Stuart
 

Tom Gaynor

Well Known and Active Website User
VOC Member
Brakes

Hi Tom,

This would sit comfortably with the advice that Russ has given me to take up all the free play on the cam before the shoes hit the drum and then fit the arm and cable onto that - this would minimise the lost motion in the assembly.

I'll keep having a fiddle around and see how I get on - I can sense an improvement since I have been dabbling, so I may get there in the end.

Right now I just don't fancy what it'll be like once the bike is run in, doing 100mph and deciding I need to stop in a hurry!

Thanks for your help.

Stuart

What I found was that the problem was the delay between grabbing the lever and getting a result. The result was not sensational, but it was OK. But while from touring speeds I was able to allow for the delay, in traffic I wasn't. The guy in front slows, you need to slow too, immediately, not after 1/2 or 1 wheel revolutions. That was what I could never achieve.
 

BlackLightning998

Well Known and Active Website User
VOC Member
Hi Tom,

Exactly, I find that my riding style has to change and become more anticipative leaving a larger gap in front of me, town riding is not a lot of fun and filtering through traffic is almost a no-no. Mind you, trying to read other drivers behaviour is no bad thing but I would like the welcome reassurance that I could stop rapidly if I really need to. I've been riding modern machinery for the last 20 years so I guess I've been a little spoilt. The good thing is it has saved me some money - I was going to have the master cylinder changed on my Ducati 851 as I thought the brakes weren't brilliant - well compared to the Vincent they are stunning - so they can stay the way they are for now!!!
Glad to see the Scottish Section is so active on the Forum - it is 30 years since I used to go, first Monday of the month, to Carfin and the Church Hall where we met. I was lucky enough to have my first ever ride on/in a Vincent in the Steib chair on George Ramsay's outfit. I've got some super pictures of his Egli at the Kenmore Rally where we used to go for several years - Rab Smith was usually in his tent sleeping off the night before - great bloke and you could not ask for nicer, (Bike was a bit oily though in those days but it ran well).

I always remember a guy called John (King, I think) who has an immaculate Shadow (he had the Steib for it from new) and he had done some tidying up on it including replacing the oil lines - but didn't want to damage the ferrules at the end so had not crimped them. He came with it on a trailer. Started the bike to let everyone hear it - it soon wasn't so shiny as uncrimped ferrules aren't very good at keeping the oil in!!

Happy days for a teenager.

Cheers and thanks again for your interest.

Stuart
Cheers for now
 
Last edited:

tonythecat

Well Known and Active Website User
Non-VOC Member
Tuning Front Brakes.

I am suprised no one has mentioned the heavy duty front brake cable as supplied by Conway Motors this transformed the brakes on my Rapide, it is a really strong outer cable which does not compress at all, so all the energy is trasferred to the brake arm.
 

john998

Well Known and Active Website User
VOC Member
Front brakes.

Hello, I have always felt that nearly every Vincent that I have ridden had better brakes than my own. This disqualifies me by and large from this discussion.
That said I once spent a lot of time on a set of front brakes, AM4s turned to fit re-machined drums, stiffened plates, heavier cables, the whole 9 yards. On the road they where an improvement, one race at Cadwell and I was back to normal ie. Passable.
The mention of the Kenmore rally, just before my first attendance, called forth a smile. Rab is well described, and both he and George Ramsay will be missed. We do not seem to have produce characters like them now.
John.
 

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