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Disc brake conversion on a Bedford CA?
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Rick
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Joined: 27 Apr 2005
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Location: North-west UK

PostPosted: Tue Jun 09, 2009 11:33 am    Post subject: Disc brake conversion on a Bedford CA? Reply with quote

CAs seem to be popular right now, this question arrived yesterday. Can anyone suggest suitable parts that would go on to a CA with minimal problems??

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hi, just a quickie to see if there is anyone out there who knows if it is possible to fit disc brakes to a bedford ca? do fb victor items fit or would it have to be a mixture of parts from various sources? i would be very greatful to hear if it can be done or if someone has done it as i plan to get hold of a ca camper but would like to bring it up to date in the safety and reliability departments. thanks. paul.
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danielr



Joined: 27 Jun 2009
Posts: 17
Location: Oxford UK

PostPosted: Sun Jun 28, 2009 10:55 am    Post subject: Reply with quote

This is also something that I'm considering doing to my car.

I know this leaves it un-original, and it'll still have a very tired 53 year old engine. but i can take as long as I like to get places, I'd prefere to stop as and when I want to stop, not when the car feels like it!

The idea that I had was basically to retrofit some modern brakes though ideally without modifying the car too much, (which is rather a tall order).

I think that the best way to do this is pick a car that you already know.

In my case a pug 205, (the reason being that's my daily driver at the moment). So I know it well. it is also a 4 stud attachment fit, although the PCD is different, (smaller on the car) so I may have to machine a disc to have elongated holes to attach the disc to the wheel hub, (basically re-drill the disc to a new PCD size to fit the old car.

The (pug 205) front brakes are bendix calliper disk brakes. the calliper is held on by two bolts, the disk is held on with 2 screws, (then re-enforced with the wheel bolts).
thus I believe that a meaty bracket attachet to the axle/stub axle mount can hold this in place, (wouldn't recommend attaching the baliper to the brake hub of the old disc brakes as this tends to be thinner metal.

By using clamps, (which I'll admit you may have to manufacture yourself) you'll also be able to remove the disc conversion at a later date.
also, you may also find that you're even able to use the front wheel hub of the 'donnor' car (though if the PCD is different you;ll have to get new wheels then Sad)

as I said, my reason for wanting to use pug 205 parts is that I have a pug 205, (thus some spares lying around are twice as useful if I'm using the same braking system on 2 cars). also the price.
at 10 for new discs (each) and 10 for a set of pads, and a mere 50 for the caliper, I can get the whole brake system for around 150, (I know this as I've just had to replace the whole brake system, (started with failed pads and hoses, slightly worn disc, a couple of broken bleed screws later it turns into new pads, new discs, new hoses, new calipers.

I know that deciding on a braking system based on the idea that I can get it cheaply isn't the best idea, (safety before thrifty) but since I'm experimenting with what braking system will work, I'd rather experiment with a cheap system than an expensive one!

(that 150 was part from a supplier, its cheaper still if you have the time to buy through ebay and await shipping).



edit, oh yes, the original question.

whilst I can't say I know a lot about the car in question, I think that the best place would be to look for a car with a simillar amount of wheel bolts/studs and look at the prices involved as well.
also look at the weight!

http://www.carfolio.com/specifications/

is a useful website for this, basically, you have a truck, so we'll say a loaded weight of three tons -assuming that you sometimes load the truck, perhaps don't expect the brakes from a light hatchback (like a 205) to effectivly stop this vehicle! as that braking system is only designed to stop 1 ton.

if you have a 5 stud wheel arrangement then perhaps look at old pug 504 pickup trucks, (reasonably sure that these had discs). or perhaps ford transit vans.

Be aware that disc brakes weren't meant to fit onto your car, so you may have to do some machining, (or get someone else to do this if you cant).

Another thing to consider, is that most of the braking force happens on the front brakes, (this is way a lot of cars -even new cars) have disc front drum rears. to save time/money you might light to look at only converting half the car, (I imagine that the truck is rear wheel drive too, so just doing the front might make it simpler).

(my standard 10 saloon is a full 100kg lighter than the pug, so I think that I'm ok with the stopping power of that system).
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Jim.Walker



Joined: 27 Dec 2008
Posts: 1233
Location: Chesterfield

PostPosted: Sun Jul 05, 2009 5:24 pm    Post subject: Reply with quote

I would be very concerned about front/rear brake balance with this type of conversion. Would it not be better (and probably safer) to consider fitting a (remote) servo to increase braking equally fore and aft?

There is also some mistaken belief that disc brakes are more effective than drum brakes. Obviously if they are larger diameter they will be. Any inadequacy of drum brakes on older vehicles is usually because the drums tend to be smaller because the vehicle was designed to cope with lower average speeds and lighter traffic conditions. All that can be rectified with a suitable servo.

The only real superiority of disc brakes is that they will operate for longer periods in extreme conditions without fade because they are able to dissipate the heat more efficiently and it is overheating which causes fade. Unless you travel at extreme speeds or intend to tackle roads like the Simplon Pass fade is not likely to be a problem. Anyone who has driven something like the 'sit up and beg Ford Popular', which had cable operated drum brakes will know that drum brakes can be awesome!
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Ghost



Joined: 20 Apr 2009
Posts: 75

PostPosted: Mon Jul 06, 2009 12:00 am    Post subject: Reply with quote

Jim.Walker - Can you elaborate on the problem as you see it? The reason I ask is that the conversion to disc front brakes is a regular thing on Morris Minors. I've never heard of problems with this modification. I have driven drum braked vehicles in the Alps and Pyrenees in summer and brake fade was a fact. Very annoying too as the acquired heat takes a long time to dissipate in summer!
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Phil - Nottingham



Joined: 01 Jan 2008
Posts: 1254
Location: Nottingham

PostPosted: Mon Jul 06, 2009 10:05 am    Post subject: Reply with quote

The reason why disk barke conversion on Morris Minors works so well is beacuse BMC/BL developed it on other cars and was used on the Marina which has the same suspension.

Besides front/wheel balance there is wheel offset & wheel bearings to conisder even if PCD stdud can be sorted somehow.

Can you use some system from a later Vauxhall/cars od Bedford vans?
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Jim.Walker



Joined: 27 Dec 2008
Posts: 1233
Location: Chesterfield

PostPosted: Mon Jul 06, 2009 10:59 am    Post subject: Reply with quote

Reply for Ghost:

Front engined rear wheel drive cars generally had around 60% of their weight carried in the front wheels and 40% on the rear. The brakes would be designed to apply stopping power at the wheels in the appropriate proportion for the weight distribution. Too much on the rear can cause the vehicle to spin (which is why unladen articulated lorries tend to jacknife unless some kind of compensation is built in) and too much on the front can be disastrous if the brakes are applied in anything but a straight line by causing the wheels to lock prematurely. In the end, if the wheels can be locked on braking, no amount of increased brake efficiency will stop the vehicle any more quickly. Of course as every driver should know, braking beyond the point of skidding increases stopping distance. A Dunlop Engineer at a lecture once said "If you consider the grip of a tyre to be 100% before it skids, then using 50% for braking leaves only 50% to be shared between cornering and steering forces. At the driving wheels, tractive forces also need a percentage of the grip included". I think that is well worth dwelling on.

A servo will retain the designer's brake balance and reduce pedal effort, but also make it easier to lock the wheels. Servos come in a range of proportional assistance and ones which give too much boost should be avoided. Line (or remote) servos are easy to fit needing only to be connected in the main brake line from the master cylinder with a vacuum pipe to the inlet manifold OF CARBURETTER VEHICLES ONLY.

As far as fade is concerned. It is caused by the gases from overheated (burning) linings forming a gaseous barrier between the linings and the drum, reducing the friction between the two surfaces. Rather like those air tables found in amusement arcades which have discs floating on an air cushion.
As a modern driving instructor once told me "Your driving is old-fashioned!". He meant that I rely too much on engine braking and don't flash my brake lights in peoples eyes often enough! I'll carry on driving like that. My brake pads on my Gentry typically last about 60,000 miles. Which probably accounts for the fact that I only once suffered brake fade, on a drum braked London Taxicab based car, back in the 1950s and that was in the Derbyshire Hills with eight passengers, driving on my brakes much faster than normal, trying to beat the clock in an emergency. In that situation disc brakes all round would have saved a lot of sweat!
Apart from possible brake dust build-up, the only real advantage in disc brakes is their superior heat dissipation. Both types are capable of wheel locking, which occurs after the point of maximum stopping power.
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