DIY handbrake conversion

Anyone know exactly what the bolt PCD is on the gearbox end of a Disco II front propshaft? It's about 95mm - but I could do with knowing exactly. Not sure whether it's metric or whether it's actually 3 3/4" imperial. I'd like to use one on the rear output flange (long story) and then attach a brake disc to it; MGB discs have the right bolt hole diameter on a 3 3/4" PCD and would seem to be perfect for the application, but a difference of a millimetre on the PCD would make the difference between success and failure so I'd like to be sure before going ahead!

If no-one knows for sure, I'll do some more careful measuring and try to convince myself one way or the other!

Looks to be 95mm - so metric, not imperial.

Right. I'm using a Disco 2 front propshaft on the rear of the vehicle, so neither the standard drum nor an off-the-shelf disc conversion would fit. I've got a pair of MGB non-V8 brake discs with a view to using one as the disc. Its centre hole is a bit big, so it'll be going on the back of the propshaft flange (i.e. the bolted joint will have the rear propshaft, then the gearbox output flange, then the disc). A friend has kindly agreed to turn a little off the output shaft flange in the thick region that stops the bolts rotating - a couple of millimetres off it will create a shoulder the right size to locate the disc. The bolt PCD is out by about 0.6mm in total, so I'll either slot the flange bolt holes radially by 0,3mm or so, or open them out from 3/8" to 10mm to match the propshaft flange. I've dropped the disc into position temporarily just to get a feel for roughly where it will sit. Looks OK so far.

Dropped the output flange off this afternoon and my friend turned it there and then! Now the brake disc fits nicely. Here's a photo of the disc fitted to the flange. It's a really close clearance, so no worries about it going out of balance when it's running. Need a caliper now.

Very interested in this, I'm going to be doing something similar 'when I get time' ...

I heard that X-eng used to do it (dunno how true or if they still do it) by using the standard drum brake, machining the wear faces off and using the backplate as the disc .. it is only a handbrake after all and doesn't need good wear properties!! No issues with fit or lining anything up then ...

Paddocks also do the full kit too http://www.paddockspares.com/pm085-disc-handbrake-conversion-disco1-and-rrc.html

Like this!
As far as I hear the X eng was an ex-Tractor unit.
What would you be using for the caliper? Would it be cable or hydraulic?

Thanks for sharing.

rathomas said:

Like this!
As far as I hear the X eng was an ex-Tractor unit.
What would you be using for the caliper? Would it be cable or hydraulic?

Thanks for sharing.

Click to expand...

small dumper or similar

I'm not able to use the X-Eng kit as I'm using a Disco 2 front propshaft as my rear shaft - the bolts are evenly spaced in a square pattern rather than the rectangular arrangement of the normal rear propshaft, so neither the X-eng kit or the conventional brake drum will fit.

As for a caliper, I'm just using a normal car rear caliper - they're cheaply available (£15) from the local scrapyard and almost all have cable-operated handbrake systems built in. In theory I could hook up the hydraulics too, though I don't think I'll ever need them. The Mondeo caliper I have is designed for a 10mm thick disc rather than the 8mm MGB disc as I was initially intending to use a thicker Nissan disc but when it arrived it wasn't quite what I needed. I've yet to decide whether the thickness matters; if so, I'll eBay this caliper and get another from the same yard. I'll definitely take care to ensure everything is robustly mounted as the handbrake is obviously a safety system as well as a parking brake; I don't want the bracket distorting when someone's relying on it for their life.

The flange holes needed just a little fettling with a file and then everything went together. The handbrake cable bracket clashes with the gearbox (see third picture - the bracket is in the red box) so since these pictures I've started to modify it. All looks workable so far...

Handbrake cable bracket (and lever) removed, modified and re-fitted so that the cable will clear the gearbox.. I need to fabricate a mount for the caliper and paint everything and it'll be ready to hook up.

Watching with interest - thank for posting

Everything looks better painted (well, possibly excluding the cat). I'll have to pause for a few days until I have steel plate to make the mounting bracket with; I've figured a viable design but don't have anything heavy enough to make it in.

Whereabouts are you? Anywhere near Doncaster I have some 6mm, and 10mm you can have ..

That's very kind - I'm in Derby, which is probably a bit far! Thankyou though. There's a local laser cutter's I've got a decent relationship with; I might offer them double the scrap price for some mild steel plate offcuts from their skip and see what they say.

Success! A bit more than double the scrap price, but a piece 3m x 190mm x 4mm, plus another 1.5m x 180mm x 5mm for £10 seems very fair value. Some quality time with the angle grinder to follow, I think.

What vehicle is the caliper you are using from?

It's a Ford Mondeo rear caliper and carrier. The brake pad part number is PAD1175 which corresponds to a 2000-2004 model. The disc diameter is 273mm and it's about 8mm thick - as long as it has a cable handbrake mechanism, any caliper designed to work with a solid (non-vented) disc of that sort of size should be fine. I did have to take some material off the carrier to clear the bell on the disc; a more careful choice might have avoided this problem.

Investigated getting the gearbox mount laser-cut, but minimum order quantities and the economics of one-offs make it quite an expensive proposition. If anyone else would be interested, it might be worth doing. I've drawn up a circular plate with the right bolt hole pattern, centre diameter etc, as something that could be bolted to the gearbox in place of the handbrake assembly and used as the basis of a fabricated mount. I'm part way through an angle-grinder-and-drilled version, as below, which serves to give an idea of what the laser cut part would look like (only the laser version would be better!)
Anyone interested in a group buy? You could keep it on the shelf until the time comes to do the conversion. I'd be looking for £13.50 each including UK shipping. Made in 4mm mild steel plate. If I get a few, I'll go ahead; if not, then angle grinding will be the way forward!

Do you have the drawing in ACAD .dwg or .dxf format? We do a lot of fabrication work and have various metal punchers, laser cutters and better water jet cutting businesses on the books. Last time we sent in an order I added in all the parts for my custom front bumper...

If you can send me something I could have a look at it for you.