54 replies to this topic

[firstforward]

carlukemini, on 03 Nov 2014 - 10:40 AM, said:

My only experience of rear disc brakes has been on small cars in the past (wife's car), most recently a 1.4 polo. I hated them for one simple reason - they were doing such little work that they basically just corroded extremely quickly. The calipers were in good working order, no binding, no laziness, just didn't do enough work to keep the disc cleaned up. I put 3 or 4 sets of discs on the back of that car in the space of 6 years.

 

I have to suspect that the same situation could arise on a mini, if the brakes need to be setup to do very little. Do look very smart though, and it's an interesting engineering undertaking to do what you are doing. Be sure to feedback after a while how you find living with them. I think with all these things the proof comes in use. If they work well and turn out to be zero maintenance as you hope, then that will prove them to be a good idea as a conversion.

 

I have purchased many cars from new and never had rear brake disc corrosion until I replaced the original disks with aftermarket junk then I agree the disks on the edges tend to corrode somewhat. I have had a fair share of motorbikes with rear disc brakes and never suffered corrosion, as you will appreciate the rear brake on a bike does very little, its mainly on the front. There is only about 190Kg of total weight with the bikes I had but the disks perform really well at slow speed and high speed so I am not sure where the point mentioned here that brakes need heat to work fits in with how well motorcycle brakes work, because work they do.

 

If there was a choice of fitting disc or drums on the rear of a mini for the same price for me it would always be disc because of a maintenance point of view but then again I use my mini a lot, unfortunately rear discs are expensive and the mini drums work to a fashion so I keep with drums.

[spiguy]

Each to their own I guess. I'd much rather have drums on the back of any car really, most of my cars over the years have been drums and I have found them to be reliable, very low maintenance items. I see lots of small cars with rear discs parked in car parks etc and if you have a look at the back discs there's only about 30% of the braking surface left with the rest corrosion. Maybe it's a Scottish thing due to our climate. I have replaced many a rear disc but I can honestly say I have never had to replace a rear drum, just shoes once in a while. And between my last mini and my current daily, I've done just shy of 200,000 miles.

 

But I don't really understand people who are saying that drums on a mini are hard work, in need of constant attention etc. The occasional nip up of the adjuster which takes all of 2 minutes and that's you.

 

I do think it was very misleading of the earlier poster (sociopath?) to lead people into a debate about the pros and cons of rear discs on a mini without being upfront about what he was actually doing (ie electric mini with a sh*t load of batteries in the boot!)

[Pete649]

And, I would never bother with KAD calipers, considering the excessive cost, and that we don't know the fatigue life for which they were designed. That matters very much for all alloy components that are cyclically stressed. A steel caliper lasts for ever, unless badly designed, an alloy one will eventually fracture.

 

Did a bit of reading up on this. Interesting from what little of it I understood as a lot of it was beyond me. I think the gist of it was that alloy products can be designed to have a useful design life but without knowing what the design criteria is then you have no way to predict failure. One would hope that alloy component manufacturers have taken this into account in their designs, but that is all you have - hope. Have I understood this correctly?

 

[Sociopath]

Each to their own I guess. I'd much rather have drums on the back of any car really, most of my cars over the years have been drums and I have found them to be reliable, very low maintenance items. I see lots of small cars with rear discs parked in car parks etc and if you have a look at the back discs there's only about 30% of the braking surface left with the rest corrosion. Maybe it's a Scottish thing due to our climate. I have replaced many a rear disc but I can honestly say I have never had to replace a rear drum, just shoes once in a while. And between my last mini and my current daily, I've done just shy of 200,000 miles.

 

But I don't really understand people who are saying that drums on a mini are hard work, in need of constant attention etc. The occasional nip up of the adjuster which takes all of 2 minutes and that's you.

 

I do think it was very misleading of the earlier poster (sociopath?) to lead people into a debate about the pros and cons of rear discs on a mini without being upfront about what he was actually doing (ie electric mini with a sh*t load of batteries in the boot!)

No, no, no, I didn’t mean to mislead anyone. I wouldn’t keep standard mini rear brakes set up regardless. Even if they paid my to.  Brake disc conversion is a must have for daily used modern classics, everywhere. I just don’t get hostility of mini owners towards the idea.

Of course, many new cars are fitted with drum brakes. Mind thou, these are self adjusting set ups. And this refers only to the  lower-medium segment cars. Meaning cheap. Good cars have always disc brakes all around. So, by what logic are they worse than drum brakes? Don’t be ridiculous mate.

[Tupers]

Brakes need to heat up and maintain that heat for optimum performance. Even though a Mini doesn't use a huge amount of rear breaking force they are still there need heat to work correctly. The advantage of a rear drum in this situation is that the drums traps heat inside and allows the shoes to stay warm so that they can bite when you need them. 

 

It is quite hard for a disc to retain head due to the fact that it's friction face is open to the air as it the pads to a certain extent. If they are loosing heat at a greater rate than a drum then they will struggle more then when it comes time for them to bite. 

 

Another part of the reason for a Mini not needing lots of breaking power at the rear is it's light weight. You could expect a weight difference of 300KG or more between classic Minis a most modern cars. 

 

When you're adding that much more weight to a vehicle having rear breaks that apply more pressure is a great help. It's also worth pointing out that most every car now has ABS that will cut pressure to the rear if you are over breaking. You obviously don't have this on a Mini unless you are willing to put in a lot of work. 

 

 

It would certainly be interesting to do some back to back tests between drums and varying thicknesses of discs as there is no doubt you could eventually match the breaking performance.

Ultimately though any rear disc conversion on a Mini should be done with the aim of reducing weight rather than adding unnecessary breaking force. 

Edited by Tupers, 03 November 2014 - 07:42 PM.

[nicklouse]

Tuppers but why?

When I slam all on. My rear wheels leave the ground.

How would we do back to back with that?

[Tupers]

Tuppers but why?

When I slam all on. My rear wheels leave the ground.

How would we do back to back with that?

 

Why what?

 

 

Don't get me wrong I'm not saying any of us need to convert to rear discs. I'm perfectly happy with the performance and operation of standard breaks and would only look a changing if I was building a crazy hill climb car where I'd want to loose a ton of weight. 

 

If I wanted to do back to back test I would create a rear disc set-up and test it against a drum set-up on an airfield at varying speeds and breaking distances. I suppose it would also be advisable to have a system set-up to monitor wheel speed vs vehicle speed and brake temperature. 

[spiguy]

"Good cars have always disc brakes all around. So, by what logic are they worse than drum brakes? Don’t be ridiculous mate."

 

Eh? never said they were worse than drum brakes. By "what logic" are you putting words in my mouth? All I said was that I have always found rear drums to be perfectly adequate on all the cars I have had with drums on, and that I have found them to be low maintenance. Also said that on the small cars (which a mini also is) that I have experience of, disc brakes were in fact more hassle than benefit, particularly due to increased maintenance. Maybe you should use quoting to avoid confusion.

 

"Brake disc conversion is a must have for daily used modern classics, everywhere"

 

And yet, in the case of the mini, several race series using minis, including high power modified variants manage to blast around race tracks with rear drums, but you think that as a road car disc brakes are a "must have" modification for all classics including minis. I fail to understand that logic. But again each to their own, and maybe in your specific application rear discs will have significant benefits. I would have thought however that if they were so essential to the safe use of minis, that there would be a number of off the shelf solutions by now and you would see this modification being done frequently, which you don't.

 

If you were saying that you had experienced real life problems with lack of braking force on a mini with rear drums, brake fade etc and therefore you had found it to be neccessary to convert to discs, that would be a good logical argument for doing so, but to say that basically all cars need them because it's only 'cheap' cars that don't have them is a very primitive argument.

 

 

 

Edited by carlukemini, 03 November 2014 - 08:33 PM.

[timmy850]

I have a 51 year old mini.

It's been upgraded to twin cylinder drums at the front, it had the single cylinder ones originally. The brakes were designed before the cars were launched, which was 1959, and the cars all had 848 engines.

It stops fine, locks up the wheels under heavy braking too.

The front brakes on minis were changed numerous times over the cars production lifetime, but the rear ones stayed essentially the same.

Does it matter I need to adjust the brakes? I don't think so... I also need to check the oil, coolant, grease things, check tappets, etc. If I can't find an extra minute or so each time I give the car a check over to do the brakes too then maybe I shouldn't own such an old car? The front ones take more than twice as long anyway, because it has two adjusters and they are harder to reach than the rear ones.

Minis - they are all old cars, from an old design, and they all need things checked and adjusted every now and then

[Sociopath]

 

"Good cars have always disc brakes all around. So, by what logic are they worse than drum brakes? Don’t be ridiculous mate."

 

Eh? never said they were worse than drum brakes. By "what logic" are you putting words in my mouth? All I said was that I have always found rear drums to be perfectly adequate on all the cars I have had with drums on, and that I have found them to be low maintenance. Also said that on the small cars (which a mini also is) that I have experience of, disc brakes were in fact more hassle than benefit, particularly due to increased maintenance. Maybe you should use quoting to avoid confusion.

 

"Brake disc conversion is a must have for daily used modern classics, everywhere"

 

And yet, in the case of the mini, several race series using minis, including high power modified variants manage to blast around race tracks with rear drums, but you think that as a road car disc brakes are a "must have" modification for all classics including minis. I fail to understand that logic. But again each to their own, and maybe in your specific application rear discs will have significant benefits. I would have thought however that if they were so essential to the safe use of minis, that there would be a number of off the shelf solutions by now and you would see this modification being done frequently, which you don't.

 

If you were saying that you had experienced real life problems with lack of braking force on a mini with rear drums, brake fade etc and therefore you had found it to be neccessary to convert to discs, that would be a good logical argument for doing so, but to say that basically all cars need them because it's only 'cheap' cars that don't have them is a very primitive argument.

 

 

 

 

I don’t think I need quoting anyone. All of you here say, in choral voice, that drum brakes  in mini are great, and  converting it to discs would only make things worse. Listen to yourself.


Back in  80’s  I had a car. Fiat Uno 1.4 Turbo. Quite tiny car. Bit bigger than mini, but I wouldn’t say its rear end was  heavier than mini’s. If it was, not by much. It was suicide car. And believe when I say this, I wouldn’t be here today, have I kept it a week longer. It had discs on rear axle. When I researched components for this conversion, I’ve looked up fiat uno turbo set up. Disc are bigger. Pads are bigger. Calipers are… way bigger. 

[spiguy]

No offence, but you have done it again... 

 

"All of you here say, in choral voice, that drum brakes  in mini are great, and  converting it to discs would only make things worse. Listen to yourself."

 

Nobody has said that. People have said that they don't believe a mini requires rear discs, as the drums are adequate for the job they are designed to do on a normal mini. Also an experienced racer has said that he believes they are also adequate for use on minis in motorsport. That is totally different to saying discs would make it worse. It is a very interesting project that you are undertaking, and it looks like alot of work and thought has gone into it, and I -  and I'm sure every other poster here - wish you well with it and hope that it meets your needs well.

[Cooperman]

This topic has strayed and is getting stupid.

The Op asked for 'thoughts and criticism'.

He got that, but doesn't like what he is hearing. So now he wants to tell everyone who has, quite correctly, stated that as the rear brakes on the Mini do only about 20% of the total braking, thus rendering discs unnecessary at best and at worst giving a less safe braking system, we all don't know what we are talking about and he is correct.

Unless we are looking for another DILLIGAF' situation I suggest that this thread be closed now.

[Tupers]

 

Back in  80’s  I had a car. Fiat Uno 1.4 Turbo. Quite tiny car. Bit bigger than mini, but I wouldn’t say its rear end was  heavier than mini’s. If it was, not by much. It was suicide car. And believe when I say this, I wouldn’t be here today, have I kept it a week longer. It had discs on rear axle. When I researched components for this conversion, I’ve looked up fiat uno turbo set up. Disc are bigger. Pads are bigger. Calipers are… way bigger. 

 

 

It's worth baring in mind the the brake system on the Uno would have been designed from scratch to suit that car. The correct valving, pad compound and size would have been taken into account during the design and testing of the vehicle.

 

According to wiki (not always reliable I know) a MK1 Uno could have weighed between 700 and 900KG.

You're starting at the very heaviest of Minis there and then adding 200KG. I would imagine the Turbo would have been closer to the 900KG weight and being a faster heavier car it would have required larger brakes that were properly designed for the task at hand? 

[timmy850]

This topic should be more like:

 

Hey guys, I'm building an electric powered mini. I'm making a disc brake setup for the rear because I'll need extra braking performance to counter extra weight from all the batteries I've added behind the rear wheels. It's now as heavy as a Fiat Uno Turbo with the extra weight I've added so I'm using some rear disc brakes from that. What do you guys think? I'm open minded to your thoughts, as I've posted this on a classic mini forum, which mainly deal with standard A-series engines minis.

 

And then we all say: 

"cool",

"looks nice",

"we don't need that much rear brake performance on our standard minis because they are so light at the back",

"we'd like to see more photos of your electric conversion"

[Tupers]

/\ Give that man a cake and a medal. /\