Zeus rear disc brake conversion

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Well i've been out in the landy all day and the brakes are great but what i have noticed is that under normal braking it feels like just the front brakes are working but if i give the pedal just one pump then it feels like all the brakes are working so not sure if there is still air in the system or if i need a bigger master cylinder so i will give them another bleed at the weekend and see :)
 
Looks great:)
Wonder why they didn’t use the same callipers fitted to the defenders? After sales I guess;)

J
 
Sounds like air in the rear lines, you need a smaller not larger master cylinder for disc, no self servo means you provide all the effort so you need more pressure.
 
No, disc brakes work on higher pressure than drums. For a given pressure or in this case pedal effort a disc wont produce as much braking effort as a drum so you get around this with a smaller master and bigger servo.
 
Citizen Kane said:
No, disc brakes work on higher pressure than drums. For a given pressure or in this case pedal effort a disc wont produce as much braking effort as a drum so you get around this with a smaller master and bigger servo.
Click to expand...

Thanks. I know you have a lot of knowledge, but I need to think about that as an explanation.

keeps the grey cells working:)

J
 
The formula for sliding friction is the product of the coefficient of friction between the materials and the force. In this case its the friction material on the metal disc or drum and the pressure you supply. The disc and drum are comparable in diameter, I guess you could argue that the drum is a larger diameter but the big difference is the self servo force enjoyed by the drum. The leading edge is "grabbed" by the drum and that drags the shoe harder onto the drum adding to the force.
 
Citizen Kane said:
The formula for sliding friction is the product of the coefficient of friction between the materials and the force. In this case its the friction material on the metal disc or drum and the pressure you supply. The disc and drum are comparable in diameter, I guess you could argue that the drum is a larger diameter but the big difference is the self servo force enjoyed by the drum. The leading edge is "grabbed" by the drum and that drags the shoe harder onto the drum adding to the force.
Click to expand...
So would adding a servo work or not :confused:
 
Its both. A servo to cut pedal force for the same pressure, but also you need to get the fluid volume right. Callipers have a bigger cross section than wheel cylinders so they do produce more force, but they move a much shorter distance so I think overall the volume for discs is less. While you do get some non-servo disc set ups its very rare and I've only seen it on small light cars, not something the size of a Series. I'd be surprised if you can just put callipers on with the drum master cylinder and get the correct brake balance. I would expect to have to fit a disc master that was matched to the callipers. If you are fitting a servo then I would go for the 9" early 90 one and mate it to a Defender master, but this takes some work and I would want Zues' opinion first. I have the 9" servo on my S2a on the series pedal box and it works well but you need to make some adaptors.
 
Agreed, Zeus should be able to advise on the correct master cylinder but I suspect they may leave you hanging. Heystee have recommendations for their disc conversions but they use Defender callipers and disc so its straight forward.

If you are prepared to do a bit of work I think you can fit the Discovery 1 dual diaphragm servo. Defenders soon moved on from the 9" servo to the type 80 servo which I think is 11" and more than a little challenging to fit to a series. The Discover one can be persuaded to fit, it looks about the same diameter as the type 50 servo but obviously being dual diaphragm its deeper. I know some of the Defender or Discovery master cylinder are quite a bit shorter than series ones so you win back some space but I suspect you may need to have some adjustment to get the braking correctly balanced.
 
Thanks guys for all this info but i'm going to see if there is any air in the system first, just waiting for a brake bleeding kit to arrive me and Son bled the brakes but i don't always have him to hand and i just want to re-check just incase there is some in there then i will check to see if the rod on the master cylinder needs adjustment and if that doesn't sort it then i will start searching for a better master cylinder, a decent servo and a servo pedal box and anything else i would need :)
 
I have just emailed Zeus to see if they can advise me what master cylinder I need and anything else I would need as well, so will just have to wait to see what they say :)
 
cornish rattler said:
I have just emailed Zeus to see if they can advise me what master cylinder I need and anything else I would need as well, so will just have to wait to see what they say :)
Click to expand...
By the sounds of your experience with them, they should get back to you by June! Hope you sort it soon.
 
If you get no luck from Zeus there is some information here http://www.expeditionlandrover.info/#brake

While it doesn't mention a suitable MC for the Zeus conversion this is what another manufacturer of conversion kits has to say.

"Which master brake cylinder:

Question: The calipers are 2 pot and the 88 master cylinder is designed to push fluid into a single cylinder at each front brake.
Does an 88 master brake cylinder pump enough volume for the disc brakes & get good pedal height on the first try or do you recommend switching to 109 master cylinder?

Reply: During application, the pads in a disc brake system are displaced much less than the shoes on a drum brake system so a smaller volume of brake fluid must be moved by the master cylinder. This is offset to some extent buy the larger cross sectional area of the disc brake caliper pistons as compared to the drum brake cylinders but a disc brake system in good condition will have less pedal travel and the pedal will "feel" firmer than in a drum brake system. Note that "pressure" is as important a design consideration as "volume" in choosing a master cylinder. I recommend upgrading any Land Rover to a dual braking system for the significant additional safety margin the dual system provides. Power boost is helpful (and commonly used) in disc brake systems which do not have the same "positive feedback" characteristics as drum brake systems."

The site also has some information of servo upgrades. Having said all that, if you get the system bled and you are happy with the pedal effort then you don't necessarily need to do anything.
 
No one has yet mentioned a pressure limiting valve in the system. I seem to remember the late series three 88" with 11" drums had one but it has been a long time since I ran one.
 
Citizen Kane said:
If you get no luck from Zeus there is some information here http://www.expeditionlandrover.info/#brake

While it doesn't mention a suitable MC for the Zeus conversion this is what another manufacturer of conversion kits has to say.

"Which master brake cylinder:

Question: The calipers are 2 pot and the 88 master cylinder is designed to push fluid into a single cylinder at each front brake.
Does an 88 master brake cylinder pump enough volume for the disc brakes & get good pedal height on the first try or do you recommend switching to 109 master cylinder?

Reply: During application, the pads in a disc brake system are displaced much less than the shoes on a drum brake system so a smaller volume of brake fluid must be moved by the master cylinder. This is offset to some extent buy the larger cross sectional area of the disc brake caliper pistons as compared to the drum brake cylinders but a disc brake system in good condition will have less pedal travel and the pedal will "feel" firmer than in a drum brake system. Note that "pressure" is as important a design consideration as "volume" in choosing a master cylinder. I recommend upgrading any Land Rover to a dual braking system for the significant additional safety margin the dual system provides. Power boost is helpful (and commonly used) in disc brake systems which do not have the same "positive feedback" characteristics as drum brake systems."

The site also has some information of servo upgrades. Having said all that, if you get the system bled and you are happy with the pedal effort then you don't necessarily need to do anything.
Click to expand...
Yeah to be honest when i
bought the two kits i was expecting the front kit to have larger discs and the rear kit to have smaller discs like most disc brake systems and also i wasn't really expecting the rear callipers to be 4 pot like the fronts but was expecting 2 pot but it seems both the front and rear kits are egzackly the same as each other, obviously there must be a reason for that :confused:
 
When I spoke to Zues when I was considering a kit I found they were very helpful. Same size front and rear with same size master cylinders may not work without a reducing valve or a change of master cylinder to one with different piston diameters..
 
Yeah i am looking into this but its not as simple as replacing the master cylinder as i would need to replace the pedal box, fit a servo to fit to the pedal box, and buy a suitable master cylinder to fit to the servo as well as fit and pipe up a pressure valve, everything seems easy enough to get its just getting the right pedal box do i go for a series pedal box or a defender pedal box and depending which pedal box i go for buying the suitable parts :)
 
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