Polo Disc Brake Conversion

[patgarrett]

Hi Lalaw, forgot to ask do you think there is enough clearance to fit a 13" wheel over. I also forgot to add can't wait to hear how it all works when finished and keep up the good work as you could be saving me £s Pat

[lalaw]

I don't think it's possible to use 13" wheels.
There is no problem with studs the disc is only about 2-3 mm thicker.
Br Lars

[patgarrett]

Cheers lalaw I still want to do this conversion and if the 13" wheels don't fit I'll have to go back to the 14" standard ones. There was one thing I was wondering and that is the flexi brake pipe. Where is the interface between morris and polo, ie is it the morris flexi fits the calipper or the polo flexi fits the standard morris brake pipe.

[bmcecosse]

Excellent picture - thank you!! Are you SURE the Minor flexi (3/8" unf thread) fits the Polo caliper correctly ? I would have thought they would almost certainly be m10x1 thread - being a very 'european' car ! The 3/8" thread will go into an m10 thread - but it's sloppy and doesn't really tighten up properly. The flexi also looks quite close to the steering arm securing nut - is it clear in all positions of the suspension and steering lock ? And yes - there doesn't look to be much clearance off the wheel rim - 13 " might rub - would be interesting to try it out though. But it looks like an excellent conversion - and it should end up quite inexpensive. Would be good if someone could come up with a good price to make the brackets! Are there no (semi)retired engineers on here with access to equipment for this ??

[lalaw]

bmcecosse I think youre right about the threads, but it fits and there was no leakage.
But on the other side I bought a flexipipe intended volvo with the same length and the threads seemed to be a better fit. I did this because I thought it was leaking from the flexipipe connection before I found the crack.
On that side I had to change the connection to the brake pipe to fit the Volvo flexipipe.
Br Lars
The flexipipe doesn't rub anywhere I have checked.

[bmcecosse]

Worry about the first side then - it's probably only hanging on by the edges of the threads!!! I would go the Volvo route there too!!

[patgarrett]

Just a thought on the brake pipe thing. You could have a goodridge hose made up with the standard morris 3/8unf fitting on one end and a banjo on the other. That way it would move the flexi away from the steering arm and the threads would match. I would hate for you to be driving along and have to brake hard and the flexi to blow out because of incorrect threads. I've looked on the net and there are sites that sell all the bits and they are very easy to put together. If anyone thinks that a banjo is not suitable look at the back of the master cylinder there's one there.

[bmcecosse]

Yep - this is how the Metro caliper (m10x1 thread) conversion is done on the Mini - the pipes sold for that would be fine - but they are not inexpensive. Provided the flexi is away from the steering arm nut in all positions - then just get flexi pipes with the m10x1 connection - if the Volvo pipe fits, problem solved! Banjo can also only work if there is a dead flat face for it to seal on - if that's not present on the Polo caliper then some work with a hand file may be necessary.

[lalaw]

Testdrive!
I got the calipper today so that I could finish the conversion.
The testdrive went perfect great improvment from the drums.
THe only thing is that they are abit "hard" to press but no problem with locking wheel. (atleast not with my crossply (?) 5.20 x14 tyres)
The force needed to lock the wheels is similar to my father MGB (without servo).
Br Lars ---hmm I think I've earned a beer...

[bmcecosse]

Well done indeed. They will be heavy compared to modern 'softies' cars with over-servoed brakes (my Meriva just about stands on it's nose if I 'touch' the brake pedal!!) - but as you say, same as MGB so should be perfectly ok.

[ratrodmog]

Sorry to resurrect a very old thread but I'm about to start this conversion myself and thought it may be useful for others to see my progress. These are the discs I am ordering http://www.ebay.co.uk/itm/330698446918? ... 1423.l2649 and will turn down the center to fit over the Minor hub. With regards to the stud holes, as they are larger should they just fit over the exisisting studs, only touching in one place? Am I right in thinking that the disc will be held by the two machine screws that normally hold the drum?
In one of the posts, it was stated they will not fit inside 13" wheels however the disc diameter is only just under 9.5" so this inplies plenty of space to fit the caliper within the wheel (Polo wheels were 13" I believe).
Has anyone else done this conversion?

[bmcecosse]

The whole lash up frightens the living daylights out of me........

[ratrodmog]

The whole lash up frightens the living daylights out of me........

Why is that can I ask? Surely if the disc is properly located on the hub and the bracket is accurately made and holds the caliper in the correct position, what is the difference between that and an off the shelf kit? Or have I missed something?

[bmcecosse]

That's exactly the problem - the disc is not well located........

[ratrodmog]

Surely if the correct pcd is drilled then there is no problem. This along with the fact the disc if screwed to the hub meens it cannot move.
It would seem that lalaw had no probelm with this conversion.

[bmcecosse]

Good luck!

[ratrodmog]

Thanks for the helpful advice there

[Alec]

Hello Ratrodmog,

" Am I right in thinking that the disc will be held by the two machine screws that normally hold the drum?"

All those screws are capable of doing is to hold the drum or the disc, in your case, in place when the wheel is removed, they have very little strength. So in my view the disc must fit snuggly onto the wheel studs, not just touch in one spot because the hole is large enough to allow that? It may be possible to redrill the discs to suit the Minor wheel stud PCD, but you will probably also need longer studs as the disc hub is quite a bit thicker than the drum.

Alec

[ratrodmog]

Alec, I think my plan is to re-drill a Fiesta or Polo disc (havn't decided yet) to the 4" pcd and machiine out the center to fit over the hub center. I agree with you regarding the screws not actually performing a structural role and that the disc must fit perfectly on the hub. Am I missing anything else regarding fitting the disc? Not sure about the studs as the disc is only a few millimeters thicher than the drum. Could I use the rear studs as they are longer I believe?

[bmcecosse]

Plenty of longer Mini studs available.