Convert the Rear axle to disc brakes????

Technical questions and answers
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firemanshort
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Convert the Rear axle to disc brakes????

Post by firemanshort »

This forum is filled with posts debating the possibility and feasibility of removing the drum brakes from the front axle and replacing with discs. To date - I do not think there is a clear and easy answer. (But we have our best minds on the task.)

But what about the rear axle? Would that be easier to convert? (no swivel balls or steering) Would Defender Rear Discs just bolt on?

I am thinking that since the brake bias is toward the front - any improvements to the rear would never be realized. BUT... improvements are improvements. This is the academic debate I have in my head.

Has anyone else thought about this?
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Alicerover
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Post by Alicerover »

If you look up the Roam Offroad web site, you will see that they are offering disc brake conversion for both the front and the rear axle.
As I have discussed else where on this forum, there is a little bit of work to do to get the kit to fit the front axle.
Hope this helps
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firemanshort
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Post by firemanshort »

I saw your thing about the front axle. I was just wondering if you did the back and nothing else - left the fronts with the drums.
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Post by Alicerover »

Would not be a good idea to mix up drums and disc's. You could end up with some very interesting, if not dangerous, braking behaviour!!
map1275
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Post by map1275 »

As opposed to just dreaming and everyone else spelling out the facts for you, how about you grab some mechanical physics books and start quoting mass transfer and swept area issues plus starting with the fact that Drums are the more efficient braking system...

Then you can just read a parts book and see that later 110 parts will just bolt on.
harry potter
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Post by harry potter »

map1275 wrote:starting with the fact that Drums are the more efficient braking system....
where does it say that drums are more efficient than discs? l would like to read that publication.

l thought that discs were more efficient as they could disapate heat better, were self adjusting, self cleaning.
why do all new cars have discs (certainly on the front).

but do F1 cars have drum brakes???
map1275
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Post by map1275 »

This is yet another topic that has already been well flogged on this forum already. One of the things we were asking the moderator/administrator to address.

If you read any book on basic mechanics you will see the facts on braking systems. I would suggest 'AA Book of the Car' as a good starting point. Whereas all you have done is quoted select points of your choosing about discs. What you chose to skip was that discs are NOT self energising and have but a fraction of the surface area of drums and all the additional components that are required to compensate for the use of discs such as servo assistance.
harry potter
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Post by harry potter »

map1275. first of all l did not skip that "discs are NOT self energising" and quote only the selective points of discs - l quoted what l understood about discs and what l have read about why manufactures have changed from drum to disc. l had never heard of "self energising"
l do not have the vast wealth of knowledge that you have regarding all mechanical items of the automobile.
l (like many others l am sure) do not have the same mechanical back ground that you appear to have, and l learn by asking questions to experienced individuals, reading publications and research. The joys of a internet forum :) l look forward to reading the AA book of the car.

Discs have but a fraction of the surface area of drums - accepted.

l put "discs are NOT self energising" into google and found a few intersting reads on the subject;
"Due to the nature of SELF ENERGIZING drum brakes there comes a point in brake application that the drums will out brake the discs and lock up. The hinge point backs off the rate of increase so that the rears do not lock up before the fronts. For an all drum car hold off is not need as all four sets of shoes will dig in the same amount and the physical size of the front brakes compared to the rear brakes will account for the additional needed braking capacity in the front, this physical differences is what will cause the fronts to lock first in an all drum car. An all disc cars does not concern itself with this as the brakes are not self energizing.

Self energising drum brakes tend to dig in harder for a given input pressure than non-self energising brakes. It's due to the physical design of the system that allows the shoes to partially rotate into the drum and lever themselves in tighter. This requires less brake pressure for a given stopping force than non-self energised drums"
harry potter
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Post by harry potter »

just like to add where l got that quote from:
http://www.oocities.org/motorcity/2398/ ... valve.html
map1275
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Post by map1275 »

Yes and what you 'appear to do' which is a popular problem on forums in particular but in the non electronic world as well, is to jump to a conclusion 'or present in such a way that represents the data as a conclusion'. Or present a conclusion which is limited. As with your statement on discs you skipped self energisation and surface area and led with the usual statements about 'why aren't discs better...'.

Basic mechanics as taught in any trade school and still taught today, is that drums are the more efficient braking system. Without skipping to the precise detail of higher level physics, discs do not self energise. Drums do. There are still only three basic automotive drum brake designs all with different levels of self energisation.

Some disc designs offer the slightest self-E but it is negligible. As with the first R-Rover with rear discs which forced BL to acknowledge the point in order rectify brake squeal.

As the disc topic has been well flogged it again demonstrates the need for precise and fixed streams to be set in this forum. Opening with simple facts instead of skipping to what the reader wants to see.
For the typical technical level of this and most forums you only need to apply trade level basics. Otherwise; glass is a fluid in temporary suspension and Not a solid in any way.... and where do you stop. Hence why I always used AA Book of the Car as a training aid. Even though it had a few errors and wasn't the approved text, I found it brilliant for entry level (and some advanced) training

Though slightly moving away from the physics side, an extract from Qld. TPT Modification Scheme (copyright Paget 2010) which brings us slightly back to where this stream opened at;

Example build No. 1

In writing this example, the presumption is that the reader wants to do the job properly, if this isn’t you, read no further.

A disc brake conversion was and still is a popular modification. Though converting rear ends instead of fronts may be a notable difference in today’s market. Typically the intent is to fit (or arrive at) a factory optional system and not an aftermarket product. For example; your vehicle has drum brakes to one or more axles but the vehicle manufacturer has a top of the line model which has discs.

Simply purchasing a handful of parts and fitting them will typically result in instant fail. Picking and choosing a handful of parts is creating a home-made braking system. Whether the influence is price, availability or technical knowledge, the result is the same: instant-fail! Typically, the owner/repairer has ignored the rest of the braking system, or allocated a near-enough status to the end result. This doesn’t meet anyone’s minimum standards beyond that of the owner/repairer. So presentation for approval is folly. If the owner/repairer had bothered to follow correct procedures, the end result would have either become self evident through research, or identified by the Approved Person prior to work commencing.

To do the job correctly, the owner needs to have located the relevant parts list/s, assessed the data and worked out whether any of the vehicle’s existing brake components are common with the new system. The common parts can remain. “All” of the rest has to be replaced. Anything less than “all” of the required parts and we venture down the home-made path again. Aftermarket (non genuine) parts are allowed, as long as they are direct replacements for the required items. Used is also OK, as long as they are inspected for wear and damage. Any wearing component will most probably have a wear limit. Your idea of what’s ‘still good’ doesn’t count. Once more it’s a case of research and referring to specifications. Other associated components (steering, suspension, driveline...) may also require changing. Your thorough research will prove or dispel this requirement. All that remains is to fit the components as per the vehicle manufacturer’s specifications.
Using this example, the vehicle is not required to have modification approval (No blue plate). The vehicle has essentially had a factory option fitted. Therefore the design and installation requirements were covered by the vehicle manufacturer. All the owner/repairer had to do was follow specifications instead of creating their own. On a Cover Your Ass (CYA) basis, records should be kept of what has been done. However there is no requirement to do so.
Some owners still choose to pursue modification approval for such changes. This is usually nothing more than a physical confirmation that all is OK. Copies of the owner’s research should make this a fairly quick process, assuming the rest of the vehicle meets all the inspection requirements. Lack of evidence will protract the matter. Wild, fantasy allusions as to what may have been performed, with no hard copy evidence will undoubtedly result in instant failure.

To do something different to the above and to still be approved requires a Design Approval Number (D.A.N.) to be present before commencing work. This may encompass the use of components from other models, vehicles or those specially manufactured. Without the D.A.N. nothing positive will occur, regardless of owner excuses as to how good everything is. The D.A.N. is a means by which a home-made system is legitimised. An Approved Person will formalise the design (accepting all liability) and apply to Queensland Transport for a D.A.N. If sold as a kit for road use, this is what should have been sorted out by the (kit) manufacturer prior to sale. In most cases it isn’t and becomes part of the owner’s sidestepping routine when confronted with failure and evidence of what they should have done before they started modifying their vehicle.
Making matters worse is that QT do not provide a register of D.A.N. holders. E.g. you are contemplating modification XYZ to model ABC; 123 Engineering Co. already has an appropriate D.A.N. and their contact details are... The end user could then have the choice of paying for someone else’s hard work or starting the entire process themselves. But this of course is a service that QT do not provide.
Kiwistage1V8
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Post by Kiwistage1V8 »

ffs... why can't you just let a man ask a question without having to tell him how where when why and on what subjects he can, can't, should or shouldn't post.

A discussion forum is an evolving thing, and it would be totally and utterly boring if no one was allowed to question topics already covered.

it gets tiresome when some know all prick is constantly belittling a persons knowledge, lack of expertise, or forum/internet savvy.

And another thought, map, if this forum is not being run to your satisfaction as you so frequently like to point out, why don't you start your own, and run it how you see fit.
Stop Global Whining.
Jules
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Post by Jules »

At the risk of retaliative posts, may I agree with Kiwistage1V8!
Reading through some of map1275 posts he appears to be "Angry Young Man" and I thought Aussies were "laid back".
Our common interest is the Land Rover (sorry I'm just renovating a S3 petrol at the moment, not a Stage 1) and I thought the idea of the forum was to share info, hopefully, in a pleasant manner without having to resort to Eistein's theory of relativity, after all, we're Land Rover owners with one of the most basis vehicles to work on, however I do like this quote from Einstien:
"Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius -- and a lot of courage -- to move in the opposite direction."
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Geoff
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Post by Geoff »

I don't suppose he cares but, in response to Kiwistage1V8's comments above, I would like to come to the defence of map('Oscar the Grouch')1275. I may be sad but his posts are currently my main and best form of entertainment and I always look out for them especially - I may even be learning something while I smile and laugh out loud. I believe in free speech and that includes map1275. What I like about about the internet is you can say what you want - others can agree, disagree, ignore as they choose. Without entering upon any debate as to anyone's mechanical abilities (and mine are too minimal to judge with any confidence) I just wanted to say there's really no need for anyone to take offense at anything said on a Land-Rover forum and I can't be the only one who trusts that map1275 will continue to contribute to this one in his own inimitable style :D
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mattv8
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Post by mattv8 »

zeues enginerring do a convoersion for both axels, personaly i would rather disc brakes, as brum are only good if both sides are set up well n equal both sides, disc system do not need adjustung in that way so to me offer better braking.. also belive disc are better anyway... the conversion is not cheep though, when i looked at it a few yrs ago it was approx £500 per axle...
why do we do it to our selves!!!
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