3 replies to this topic

[deconstruction]

For quite some time I've been planning to convert the old and tired front brakes on my '65 850 from drum to disc.

It's more or less clear to me what is required and how to do it but I keep putting it off because I get confused and worried   about the steering-arms.

Perhaps the experts could clarify this.

 

part 1 - rack / steering-arms / geometry

​As far as I remember:

- a mk 1 steering-rack is different to that used on mk2 onwards and so requires mk 1 steering-arms 

- the Cooper steering-arm is thicker / stronger (but perhaps that's only the Cooper S)

But is the geometry with disc brakes different to the geometry with drum brakes?

In my case - drum to 7.5" Cooper S disc and 10" wheels - is it really quite simple? Do I just fit the original mk 1 steering-arms on the new swivel-hubs? (In principle there won't be any competition use so no need for the extra strength).

 

part 2 - calipers

Some kits include AP calipers, others pattern / reproduction and others fancy alloy units with multiple pistons.

My preference is for AP as these are nearest to 'genuine'.

Any advice / recommendation here?.

 

part 3 - FAQ

Might this be a good topic for FAQ? 

My question concerns drum to disc for 10" wheels and the difference in rack.

But there are also later drum braked Minis with 12" wheels. And all the 12" disc-braked cars. And the recently popular disc-brake conversion from 12" wheels to 10". Not to forget the use of Metro hubs / brakes.

What happens to steering-arms in all these cases? 

Some of the kits offered by MiniSpares, MiniSport, Somerford etc. include steering-arms and some don't. If they do, I presume that these will be for mk 2 onwards. And there's another thing: does the steering-arm actually change from mk 2 onwards? 850, 1000, 1100, Cooper, Cooper S, 1275GT, SPi, Metro...so many permutations...   

 

Anyway, looking forward to expert advice! 

 

 

P.S.

I haven't forgotten the other jobs which will have to be done:

- wider rear drums and longer wheel bolts (to suit the different offset / ET of the road wheels)

- a new / suitable brake master-cylinder

- optionally a brake servo

   

- Cooper steering-arms are stronger (but perhaps that's only the Cooper S).

[Spider]

Hi and welcome to the forum.

 

Some very good points that you have thought of and bought up here.

 

Part 1.

 

Just swap your arms over from your Drums to your Discs.

The Cooper S did have thicker Arms, but the same geometry as the Drum Braked Arms. The Cooper S Does have a wider track and technically should have slightly different steering arms as a result, but the difference is so small, it's academic. Manufacturing tolerances would be greater.

 

Part 2.

The non-AP branded Calipers that I have seen I know are made under the same roof as the AP Branded types, though, there is some small differences between them, as the Non-genuine types I've seen had metric bolts and a metric bleed nipple.

 

Part 3.

 

The Steering Arms used on the 8.4" Discs (that were fitted with the change to 12" wheels) are the MKII types, though, that has nothing to do with the Brakes but the Steering Rack that's fitted. The Metro Steering Arm is very different in it's geometry and not suitable for a Mini at all.

I haven't looked at all the kits available, but I'd almost certainly say any arms that came with them would likely be MKII as MKI types haven't been made since about 1980.

I'd strongly recommend against fitting Metro Hubs to a Mini. Again, they have very different and incompatible geometry for a Mini. The Brake Caliper from these though, can be fitted to a Mini Disc Brake Hub.

 

This is not 'expert' advise, but just what I've found and worked out over the years.

 

 

P.S.,,,,,
 

One other item that's also often overlooked is the need to change the Rear Wheel Cylinders. You're Mini should have 5/8" (0.625") Rear Wheel Cylinders, but who knows what has been fitted in there over the years. Give the change of many other parts in the System, I'd suggest here replacing the Rear Cylinders with new and they need to be 5/8" in bore size.

While you are in there, if you haven't already put it on your list, I'd also recommend changing out all the Brake Hoses (the fronts are a different length for Discs anyway), and also at the very least, stripping the Brake Limiting Valve that's fitted on the Rear Subframe, however, be cautioned here that kits for these as best I know haven't been made for some time, though they can be found NOS on ebay and the likes from time to time.

[deconstruction]

Thank you Spider 

 

Although I did not mention it, I had already planned to make new rigid brake lines and fit new, suitable flexible hoses. And you have reminded me of the rear wheel cylinders (I think that I read that in 'How To Modify Your Mini') but I had forgotten about limiting-valve so excellent advice.

No point in doing a big job like this and not doing it thoroughly!

 

When I get around to this I may report on it here.

There's a 'difficulty' with a Hydrolastic pipe to be sorted out first   and somehow other projects keep getting in the way...

[Spider]

Cheers on that.

 

I gotta say, while I do really like the appearance of the Braided Hoses, they do have a couple of down sides and these are why I don't use them.

You can't crimp the hoses off (using the right tools) like you can with Rubber Hoses. Of course, this isn't something that's done often, but can help with bleeding, diagnosing or changing that leaking wheel cylinder.

Also, you can't inspect the hose under the Braiding, so it's difficult to determine it's condition.