Double leading rear brakes?

[TurboFource]

The Jensen Competition Manual mentions converting the rear brakes to double leading shoe brakes
by using another wheel cylinder, has anyone done this? If it was good enough for racing it should work
on a street car I would think....

[BDA]

Unfortunately, the Jensen manual doesn't say anything about where they got the parts. I've never heard of any sources for that stuff. Dave Bean has stocked some esoteric parts and they may know something about how to implement the dual leading shoe setup.

On the other hand, there are several ways of doing rear discs now. I think I might quickly jump to the rear disc upgrade if the dual leading shoe setup doesn't work out quickly.

[jbcollier]

It's in the manual:

http://www.lotus-europa.com/manuals/misc/jensen.pdf

They fit the backplate and cylinders from the front of an early Hillman Imp.  It's not a bolt on modification as they used 1.5" shoes.

Remember they did this to balance the fact they fit GT6 uprights, spindles, discs and calipers at the front.  They also fit dual master cylinders with an adjustable balance bar.

Please be careful with brake modifications.  The stock system is well balanced and was lauded in its day.  Things of course, have moved on so I understand the desire to improve the braking system.  Brake system mods must be done to both the front and the rear.  Simply fitting more powerful front brakes will lead to the front wheels more easily locking, more difficult modulation and longer stopping distances.  Boosting the rears alone may well lead to the rears locking first which will cause the car to slew sideways in hard braking.

Myself, I find the brakes excellent but fade-prone in heavy use.  Pedal pressure is on the high side for modern practice but that gives excellent modulation which I appreciate.  I'm experimenting with different pads.  So far stock and green-stuff.  The green-stuff works great on the street.  Not so much down a twisty mountain pass.  Trying Mintex M144 next but there is 3 feet of snow on the ground right now.

[BDA]

JB is certainly correct to warn you about balance. I can only speak about my brakes. I have Richard's vented front and (solid) rear discs and I use the stock master cylinder size. They are very well balanced in my opinion and they do a very good job of stopping the car. There are several rear designs for rear discs out there and my advice would be to investigate how they worked in real life and consider using a brake preportioning valve (just in case).

[Lotuswins]

My Friend, Topper Kang has the rear setup you describe, and is detailed in the Jensen Manual.  His is a full race TC, and its a legal mod for his vintage race group.  However, it has no emergency brake and the parts are hard to source.  Two little tiny slave cylinders per drum, and they can overheat easily, so its recommended to vent by drilling the backing plates, which is kind of scary.  And you have to source race pad material and get the shoes specially 'retread' by a known brake vender.  Not cheap.  I have a spare setup, from a Metropolitian Nash (same setup as the Herald) that Topper ran across in a pick a part and he picked up for my S1 racer I intend to build, if I ever get around to it.  I believe the backing plates have to be offset to suit the Europa axle setup also, which is tricky.  I think they were 1 3/4 wide shoes though.    Anyways, they are difficult to setup, hard to source parts, and with no emergency brake makes them a poor choice for a street car. 

Jerry Rude
4005R

[EuropaTC]

One snag about using the Hillman Imp (or any other) dual cylinder drum brake is the handbrake system. I'm sure it can be done but it's an added complication because the twin cylinder backplates were only on the front of the car. 

Not a problem for racing/track cars but over here you'd not get away with it on a road car, we've got to have a separate emergency braking system.

Given the standard rear brakes don't contribute that much to the Europa's braking performance (roughly 25%) then I doubt you'd make sufficient difference with a twin leading shoe backplate to lock the rears before the fronts, even if you left the front discs as standard.  BUT.... I haven't done the sums so don't take that as anything other than a guess.

If you want better brakes then there's a well worn path with rear disc conversions and if you're prepared to go to larger wheels, then you can fit bigger discs and calipers all round. With careful selection you'll get a more balanced system than OEM (prone to locking the front, especially in wet conditions) which will stop you quicker overall and even feel like a modern car, but it's got to come as a designed package.

Brian

edit to add - Jerry beat me to it !

[TurboFource]

Saw it in the manual so I thought I would ask about it. Thanx for the replies!

[Bainford]

I have Richard's vented front and (solid) rear discs and I use the stock master cylinder size.

Are the vented front discs suitable for a 13" wheel, or are they an oversize disc? I've been keeping an eye out for a vented disc that will work with the stock 13" wheel, and still retain the fixed calliper.

[jbcollier]

AFAIK, none of the current disc kits work with the stock wheels except using GT6 parts (not a good idea with out doing something at the back as well).

[EuropaTC]

I think the Triumph folks use Ford Capri vented discs at the front, re-drilled to suit on Spitfire/GT6 big brake conversions.  You could probably get away with these by spacing out the type 14 caliper plus a custom mount or GT6 calipers suitable spaced ? Don't know to be honest but if I wanted to retain a 13" wheel that's where I'd start. 

But as John says, increasing the front discs without doing at least a larger drum or disc at the rear wouldn't be a good idea, it would just magnify the difference between F/R.

Brian

[BDA]

I have Richard's vented front and (solid) rear discs and I use the stock master cylinder size.

Are the vented front discs suitable for a 13" wheel, or are they an oversize disc? I've been keeping an eye out for a vented disc that will work with the stock 13" wheel, and still retain the fixed calliper.

I think that Richard's front vented disc kit included GT6 hubs. I measured the distance from the outside of the caliper to the center of the dust cap at about 135 mm (5.3") so they should fit under 13" wheels.

I would take JB's advice about brake balance. Richard's caliper is a floating type rather than the stock static caliper with two pistons.I am pretty sure the pressure developed at the pads is greater than stock but I've never measured the piston diameter so I don't actually know. If you're interested in them, it would be worth a phone call to get all the particulars.