32 replies to this topic

[Paul Wiginton]

I had the disk bells/bearing carriers CNCd from 7075 T6 alloy, the disk is a meonite one from an F1 Kart, the callipers are Wilwood PS-1s. The handbrake is hydraulic which technically is illegal but the MOT states 'cars built after (I think) 1967 must have a seperate mechanical handbrake' Since my car is 1960 I get away with it.

Paul

[LukeH]

I had the disk bells/bearing carriers CNCd from 7075 T6 alloy, the disk is a meonite one from an F1 Kart, the callipers are Wilwood PS-1s. The handbrake is hydraulic which technically is illegal but the MOT states 'cars built after (I think) 1967 must have a seperate mechanical handbrake' Since my car is 1960 I get away with it.

Paul

Did you have a drawing to base the bells/bearing carriers on or was it a one-off fabrication by someone/you? I had considered using some sort of Kart setup as I recall that the rear disc setup on my 2-stroke race kart would stop me very quickly from around 80-90mph. I think I will certainly explore that a bit further.

Unfortently my car is a 1979 so I'll have to use a mechanical handbrake of some description.

Luke.

[Paul Wiginton]

I designed them with a friend who has them on the back of his Speedster also

[LukeH]

I designed them with a friend who has them on the back of his Speedster also

Impressive! You have have certainly given me something to think about. Thanks for replying to my topic.

Luke.

[duff6.lawson3]

I realize that I am a little bit late to the party for contributing to this thread but I'm going to throw in my 2 cent opinion anyway to give another view.  

 

Beginning with, yes you are all absolutely correct.  Drum brakes on the rear of a Mini are absolutely adequate when properly adjusted.  There are two big statements there though.  "Adequate" and "properly adjusted".  

 

Drum brakes are adequate, but disc brakes are a step above "adequate".  

 

"Properly adjusted" is not an easy task and doesn't last for long and then should be adjusted again.  To be "properly adjusted" they need to be right on the edge of drag.  Too much adjustment and drag is excessive, along with too much heat, and to little drag and reaction time is increased.  In racing, proper adjustment should probably be checked before every race and in street use it should probably be checked every 2,500 miles.  Also, based the the cars that I have worked on, the shoe to drum fit, just isn't very good.

 

So, for me, the case for rear disc brakes, in combination with a adjustable proportioning valve and a residual pressure valve, is that after installing and adjusting once, they never need to be adjusted again.  FOREVER!!  And forever is a very long time to not even need to think about adjustment.

 

 

 

 

[tiger99]

That is precisely why I am hoping to fit rear disks to my next Mini. Purely to minimise maintenance, along with other similarly motivated mods, maybe even modern all in one hub assemblies to solve the bearing crisis that seems to have existed ever since the spares suppliers found a cheap Chinese source. I think that means new fabricated radius arms (the originals were fabricated for a while), which gives an opportunity to install proper, safe toe and camber adjusters and improved suspension bearings, and so on...

 

There is a very significant problem which must not be overlooked. The volume of fluid displaced to fully apply a disc brake is much larger than that needed for a small diameter wheel cylinder. In a dual line system, there must be sufficient pedal travel to get one set of brakes fully applied while the other circuit has failed. That fundamental safety requirement is difficult to satisfy with large diameter pistons. The pressure limiting arrangements do not help, it is volume that is the problem. So, ideally callipers with a very small cylinder bore will be used, which also nicely reduces the braking torque at the rear. A small disc diameter helps too, of course. The other way is to increase master cylinder diameter, which unfortunately increases the necessary pedal pressure, and if there is a servo, may violate another safety requirement, that the servo must always, with the lowest likely amount of vacuum, be able to develop sufficient pressure to lock the wheels.

 

I am not sure that parts can be found that will do the job properly in the simplest way. So it may come down to using an alternative means of proportioning, not a limiter. Something like the reverse of the "intensifier" fitted to early Coopers might do the job, or of course a stepped bore master cylinder, or twin master cylinders and a very asymmetric balance bar.

 

I am very interested to see what, if anything, people have actually done.

[Dusky]

Drum brakes on the rear Are much More than adequate. They lock my 13 inch supersoft slicks on hot tarmac if they Have to. If you're worried about maintenance you bought yourself the wrong car.

[tiger99]

You completely miss the point. I intend to cover a high mileage again, and like a brake pedal that has a nice short travel without having to do adjustments every few weeks.

[Dusky]

You miss your own point. Unless you neglect the greasing and oil change intervals the 10 minutes it takes to adjust the drums really wont make a difference.

[mini13]

i put kads on the back of mine for the lack of maintenence, they were a complete PITA, kept dragging and munching pads and discs, flogged them in the end and went back to shoes and minifins and gained a handbrake that works in the process.

[tiger99]

I would expect that with the KADs. High cost does not necessarily mean high quality or fit for purpose. There are also questions about the fatigue life of the calipers. They are really only suited to low mileage competition use.

Dusky, I never would neglect greasing or oil changes (I used to get phenomenal mileages from ball joints and radius arm bearings), but I would most probably fit an automatic greasing system and reduce the regular service to mostly the oil change and normal safety checks. But you only have to pay attention to this forum to see how much misery is caused by the rear brakes, which is why I don't want the standard setup. Also as I have said elsewhere I will be intending to address the issue of proper front/rear balance.

[lrostoke]

Wouldn't it be simpler to modify a self adjusting mechanism off a more modern car ?

 

No messing with balance then??

[Spider]

I did a conversion on our Mokes back in the mid 80's, for a number of reasons, some were maintenance and another was to get a decent handbrake. I found it didn't take too many creek crossings before the drum brakes need major work. I'm just about to do another in fact.

Edited by Moke Spider, 11 August 2016 - 06:38 PM.

[tiger99]

Frankly, the continuing problems many people have with Mini handbrakes at MOT time are in themselves a very good reason for fitting discs with modern calipers.But I hope no-one will be misguided and fit one of the abominable electric handbrake systems used on certain modern cars.

[Carlos W]

Frankly, the continuing problems many people have with Mini handbrakes at MOT time are in themselves a very good reason for fitting discs with modern calipers.But I hope no-one will be misguided and fit one of the abominable electric handbrake systems used on certain modern cars.

 

If those problems are caused by lack of maintenance then rear calipers wont solve the problem, proper maintenance however will!