Midget disc conversion.

Post by **paulhumphries** » Tue Dec 05, 2006 3:05 pm

Today I decided to remove the hub and brake back plate from a spare Miror upright to see how Midget parts will fit.
The Midget hub fits straight onto the Minor stub axle without any problems.
Trouble is the disc is then almost touching the upright

I now understand why the caliper mounting bracket is "J" shaped - it fits behind the upright.!
To be honest I'm not happy with this set up.
Looking at an application guide I can see the Midget discs off a wire wheel model should be a better fit (86mm against 99mm hight when laid flat on bench) and thus allow caliper mounting to be between disc and upright rather than behind upright.
The Midget discs are quite small in dia (210mm) so before I try the wire wheel discs route I'm wondering if Marina discs (248mm dia) will fit straight onto Midget hubs.
Anyone know the PCD of the Marina disc mounting holes (not hub wheel stud PCD) ?

Thanks.

Paul Humphries.

Post by **paulhumphries** » Tue Dec 05, 2006 6:52 pm

I can answer my own question !
Marina discs won't fit onto Midget hubs (without modifications)

The hub to disc bolt PCD is different.
If I need to redrill then I'd choose something easier (than Marina) to source.
Mondeo has been suggested - 260mm dia compared to Marina 248mm so probably only suitable for 14" wheels.

Paul Humphries.

Post by **Packedup** » Tue Dec 05, 2006 7:07 pm

If you think the hub is held on the stub axle by the bearing and hub nut, might it not be possible to find a hub/ disc combination of one size and use the correct bearing to fit it to the Minor stub?

Would seem to be the simplest way of getting a disc on the upright, then it's "just" a matter of making a caliper bracket and gettign it all to clear the wheels (oh, and finding wheels that fit the PCD, or finding disc/ hubs with the Minor PCD, or getting the new ones drilled...).

Post by **bmcecosse** » Tue Dec 05, 2006 8:08 pm

It all sounds so much easier to follow the Polo disc route!! I'm not familiar with how the Spridget disc fits to the hub - but could it be machined slightly on the mounting face to move it away from the upright ? And of course - it really is very much easier (amidst all this disc frenzy) to just fit nice big Wolseley 9" front drums and backplates - it takes less than an hour per side - job done! And far better than the rather small spridget discs will ever be - they were barely adequate when new for the much lighter spridget.

Post by **IslipMinor** » Tue Dec 05, 2006 10:56 pm

they were barely adequate when new for the much lighter spridget

Mmmm!!

Standard Midget discs, steel wheel hubs and bearings, combined with Metro 4-pot calipers, Mintex 1155 pads, 2.2:1 boost servo etc. can be made to be very much more than adequate!!

The high boost servo gives a good 'feel' to the pedal, but the basic braking design is completely fade-free under any sort of road and track conditions, however extreme. The end of the Parabolica at the Hockenheim GP circuit is a 100mph+ down to 25mph for the hairpin - even a race-prepared 944 Turbo who overtook through the curve, came out second after the hairpin! Half way down the next straight bit and he was gone!

The disc is quite close to the upright, but on mine never less than 6mm away. The caliper needs to be used in combination with the steel wheeled disc, as it sits behind the back of the hub. Even then the caliper is very close to the back of the hub. There is not enough room between the wirewheel disc and the steel wheel hub.

The Midget caliper has more or less the same piston area as the combined piston areas on the 4-pot, so will give the same initial result. It's a simple kit to fit, if you have all the parts, pads are plentiful, discs are around £25 per pair. A servo will make it much nicer to use, as without it the pedal is very heavy.

PS Haven't forgotten about the Metro caliper drawing, cannot find it so will make another over the Xmas period.

Post by **bmcecosse** » Wed Dec 06, 2006 7:13 am

You have extensively'improved' the original braking system - better pads/calipers and a massive servo! As standard - they were of course an improvement over the old drums - but still barely adequate. My main worry thouigh would be the J bracket - is yours a solid type bracket Richard ?

Post by **IslipMinor** » Wed Dec 06, 2006 11:26 am

Yes it is a 12mm thick 'J' bracket that fits behind the original drum mount on the upright. It is fitted with 3 high tensile 8mm Allen screws and Nyloc nuts.

The original Midget caliper mount adaptor is also solid, and about 10mm thick.

Post by **IslipMinor** » Tue Jan 02, 2007 3:13 pm

Please see my reply in the post 'Midget/Sprite Brake Discs' for detail on the Metro and Midget caliper brackets.

Post by **brian19614** » Thu Jan 25, 2007 7:13 pm

IslipMinor wrote:Please see my reply in the post 'Midget/Sprite Brake Discs' for detail on the Metro caliper bracket.

hi,just read your article on midget disc brakes,i have just picked up a midget disc brake assembly,can you tell me what back plate/caliper mount bracket you used. thanks brian.

Post by **IslipMinor** » Thu Jan 25, 2007 7:34 pm

There is no back plate used on the Midget conversion. Also no stone guard as there is not enough room between the back face of the disc and the lower trunnion.

The mounting bracket is a 'J' shape and used to be quite commonly available as part of a complete conversion kit - they are still available from Mini Mania in the USA, but probably a bit expensive to post over to the UK.

The design of the bracket is shown in the other post on Midget discs for Minors - 'Midget/Sprite Brake Discs'.

While changing to discs, it's definitely worth considering fitting a servo to keep the pedal pressure down to 'modern' standards at the same time.

Post by **picky** » Thu Jan 25, 2007 7:52 pm

the riley brakes are much heavier than the standard morris ones, would this extra unsprung weight affect the suspension slightly? I imagine the midget setup is slightly lighter.

Post by **bmcecosse** » Thu Jan 25, 2007 8:23 pm

Riley/wolseley brakes are not 'much' heavier - ceratinly the drum is an inch bigger in daimeter - but the weight difference is not much. Compared to an MG Metro 4 pot caliper (which weighs a Ton !) the bigger drums are lightweights! Any suspension effects will be negligible - the Minor not being exactly a F 1 car in the first place!

Post by **brian19614** » Thu Jan 25, 2007 9:01 pm

IslipMinor wrote:There is no back plate used on the Midget conversion. Also no stone guard as there is not enough room between the back face of the disc and the lower trunnion.

The mounting bracket is a 'J' shape and used to be quite commonly available as part of a complete conversion kit - they are still available from Mini Mania in the USA, but probably a bit expensive to post over to the UK.

The design of the bracket is shown in the other post on Midget discs for Minors - 'Midget/Sprite Brake Discs'.

While changing to discs, it's definitely worth considering fitting a servo to keep the pedal pressure down to 'modern' standards at the same time.

thanks for your reply,any chance you could post the design again as i cant find it, thanks brian

Post by **bmcecosse** » Thu Jan 25, 2007 9:17 pm

The 'POLO' disc brake conversion is also well worth reading.

Post by **brian19614** » Thu Jan 25, 2007 9:28 pm

found the conversion kit on mini mania web site,already have everything else,so the kit looks the best option for me,

brian.

Post by **IslipMinor** » Thu Jan 25, 2007 11:51 pm

It's under the thread 'Midget/Sprite Brake Discs'. You can find it in the first page of the older 'Mechanical' threads.

Mechanical

Goto page 1, 2, 3 ... 44, 45, 46 Next

Click on next and you will see it there.

Fri Jan 26, 2007 7:27 pm

hi, i have a marina disc brake conversion fitted, with standard minor wheels, would it be possible to fit the metro calipers and pads straight to this, and more importantly, would it be advantageous?