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Hydraulic drum brake

Howard

Well Known and Active Forum Website User
VOC Member
Has anyone converted motorcycle drum brakes from cable to hydraulic?

I'm contemplating modifying the Laverda front brake on my Egli, and I'm trying to work out the pitfalls and advantages before I start.

H
 

BigEd

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VOC Member
VOC Forum Website Moderator
Has anyone converted motorcycle drum brakes from cable to hydraulic?

I'm contemplating modifying the Laverda front brake on my Egli, and I'm trying to work out the pitfalls and advantages before I start.

H

I have not done this myself but a friend modified an Ariel full width hub to hydraulic operation but did not find an improvement. I think that one of the things you need to look at is the leverage aspect, i.e. the ratio of master cylinder diameter to slave so that enough pressure is applied to the shoes. This perhaps is why his mod did not improve on the standard lever/cam set-up.
 

Howard

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VOC Member
Thanks Eddy, you've gone straight to the point I was worried about, if I increase the cylinder ratios, I decrease the amount of movement available at the wheel - perhaps I can only use 1:1, and then the extra force advantage is lost.

H
 

BigEd

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VOC Forum Website Moderator
Thanks Eddy, you've gone straight to the point I was worried about, if I increase the cylinder ratios, I decrease the amount of movement available at the wheel - perhaps I can only use 1:1, and then the extra force advantage is lost.

H

In theory there should be be none or less "lost motion" in a hydraulic system so that should work in your favour. I may be seeing a few motor cycle friends this evening including the one who did the Ariel mod. I will ask around as I think that there might also be someone there with a hydraulically operated Norton drum brake.
 

Pushrod Twin

Well Known and Active Forum Website User
VOC Member
Howard, interesting question. I havent converted an existing brake to hydraulic, but I did fabricate an entire 4 leading shoe hydraulic drum & wheel set up for a side car outfit in the early 80s. I used 2 Triumph Herald front drums & brake plates mounted onto a steel disc centre with a 14" Morris Minor rim welded to it. A Japanese M/C master cylinder was used to actuate it all. Dont even know what size the cylinder was but it worked well with moderate pressure. Was extremely heavy of course.
This was all in exchange for the genuine ex Egli Grimeca set up which graces the front of my Egli replica.
Why the interest in hydraulics to the Laverda wheel? Is the current lever action too heavy & short of feel? The old 4L/S Guzzi wheel on my Sport is possibly one of the most maligned drums built, all the road testers bagged them for being heavy & having the feel of sqeezing a 4x2! I have learned to exploit it, it is a very safe brake, difficult to lock, but can be warmed up, the oft discussed "servo effect" felt & the tyre made to squeal controllably with practice. It has 500 lbs of bike to slow without my weight being added. I believe it could be "improved", given more feel & less lever pressure, by changing the bar lever fulcrum. This may be an option for the Lav brake if this is the issue. There was some good articles in MPH a few years ago detailng brake lever fulcrum points, may be worth a look if you can track them down.
Cheers, R
 

Howard

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VOC Member
Hi Roy

I don't know if the brakes are a problem or not to be honest (they weren't when I didn't know any better). I've just got used to two finger stopping with Japanese discs. The MoT tester was very impressed with the brakes, so perhaps it's just retraining I need.

I'd thought it may be simple to replace the cable operation with a jap lever master cylinder and a slave cylinder to pull (push) the lever at the wheel end, then juggle the piston sizes to give increased force at the wheel end. I'm not sure that the master cylinder would move enough fluid - disc brake pistons don't have as much travel as drum brake levers

H
 

ET43

Guest
Hi Howard,
The Awful Dave Williams converted his Ariel twin to hydraulic operation and I think that he used cut down Austin Mini shoes and other bits, so it can be done.
Cheers, ET43
 

davidd

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VOC Member
Howard,

A friend of mine who copied my disc brake set up for his Prince could not fit the lever with master cylinder under the cowl. I urged him to go to a radial cylinder lever and his brake system had much better feel than mine. Along with the ratios, you might want to look at the pros and cons. Also, I seem to remember BMW using a cable that went to a master under the tank. I am not certain that would be useful to you but if you are handy a hybrid system might offer some advantages.

David
 

bmetcalf

Well Known and Active Forum Website User
VOC Member
Howard,

A friend of mine who copied my disc brake set up for his Prince could not fit the lever with master cylinder under the cowl. I urged him to go to a radial cylinder lever and his brake system had much better feel than mine. Along with the ratios, you might want to look at the pros and cons. Also, I seem to remember BMW using a cable that went to a master under the tank. I am not certain that would be useful to you but if you are handy a hybrid system might offer some advantages.

David

Disc brakes are bad enough, but a radial master cylinder? That's going too durned far!
 

Howard

Well Known and Active Forum Website User
VOC Member
Oh dear! What have I started. Cut down Mini shoes I understand, but what's a radial master cylinder?

I had a BMW with the cable hydraulic system, I didn't quite see the point, but it worked ok.

It may be easier to join a gym, and increase my grip strength.

H
 
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