18 replies to this topic

[Mudhen]

Hi all,

 

In my seemingly endless loop of trying to get an old rallycar going I ran into yet another issue.  Trying to mount up the calipers onto new vented rotors and they won't seem to fit:

 

 

I put new 'drive flange for vented disc brakes' on so I could start using 12" rims...and it seems to me like they're off by about 4mm, causing the rotor to sit too far out.

 

I measured the distance between the inner surface of the flange to the brake disc like this and got the following numbers:

 

 

Old:

 

 

New:

 

 

I was reading here and learning about Metro vs Mini hubs...these are Mini, correct?

 

 

I'm trying to maintain a 'at least I'm learning' attitude but this fking thing...

 

Thanks

[Spider]

By the looks of it, you can spacer the caliper off the hub using flat washers to get the bridge to sit more or less centred over the disc. It's fairly standard practice to do this with custom set ups.

[nicklouse]

Yes vented original metro vented drive flanges are a different size to the non vented drive flanges.

 

but they can be interchangeable.

 

what was on there before? A modified set of? Or original? What are the “new” calipers off?

[bpirie1000]

For those brakes i beleive there should be an adaptor plate.

https://racecarsdire...-brake-calipers

Please excuse me if i am incorrect...

[Mudhen]

Thanks everyone.  This is what was on it (and is now back on it - still waiting on the 12" gravel tyres I ordered in January, anyway, so will use the 13s until either the cows come home or hell freezes over ):

 

 

The new disc/flange setup has a shallower depth so therefore the disc sits further out - think shimming them is going in the wrong direction.  If I hold the caliper centered on the disc the mount hits the hub:

 

 

What about spacing the flange out from the disc?  Or at that point are things starting to get dangerous or alignment settings getting questionable.

 

Interesting about the adaptor plate - mine don't have anything - they mount direct to the hub.

 

I suppose at this point just take these AP calipers off and go with some new modern 4 pots instead.  I definitely want to move to 12" wheels so getting rid of the existing flanges is necessary.

 

Pat

[imack]

I don't know if this will give the clearance you need, but KAD 7.9" vented discs set up uses standard 8.4" mini drive flanges rather than metro turbo ones.
The mini flanges move the disc inboard (and give standard mini track width/geometry), but you have to machine 80thou from the inner face of the disc bell, otherwise the disc will foul the steering arm.
Another option is to get a 1/4" spacer made to install between the metro turbo drive flange and the disc to move the disc inboard.

Edited by imack, 17 August 2025 - 12:22 PM.

[imack]

These are the spaces I had made that fitted between the disc and drive flange. They were part of the modifications I used to fit metro turbo brakes and 10" wheels. I also had to space the calipers inboard by the same amount. They're actually just under 1/4" thick.

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[nicklouse]

It looks like the original uses the non vented drive flanges. And don’t use those slot head screws get correct bolts.

[Ethel]

The original vented Metro 4 pots used a spacer between the caliper halves, suggesting the datum was the inboard disc face.

 

I've measured up some alloy calipers (I just happened to have in the spare bedroom, as you do) and the hub mounting face to the centre line of the disc is 33.5mm, with a 10.8mm spacer fitted.

 

That tallies pretty well with imack's spacers as half the extra vented thickness. the "throat" of my calipers in vented mode is 25mm

[nicklouse]

Yes but. The discs are the same vented. The flanges (new) are for vented discs. Old flanges look like non vented. Calipers done for old set up not new one with different flange.

 

for example my KAD discs do not use the vented drive flanges.

[Ethel]

I'm just giving the dimensions I've measured to help the OP figure out where his differ.

The (factory) vented & unvented discs should have their inner face in the same place. Because the vented disc is thicker, its centre line is about 5.5mm farther outboard. That has a knock on effect on the drive flanges, but I couldn't say with certainty how much.


Online catalogues state the unvented disc is 66.2mm from flange face to inboard disc face & vented is 69.8mm - suggesting the vented drive flange will hold a disc 3.6mm farther outboard.


....so, yes, if the discs needs to move towards the hub by 4ish mm when bolted to a vented drive flange. Using an unvented drive flange would do that.

The same source states disc thicknesses of 9mm & 20.7mm - I reckon they are wear limits

[bpirie1000]

May just be easier with 8.4 brakes...

Have you actually checked the pistons move on those old calipers first before going to all this length with fitment and so on..

Are thenbrake gains that much to warrant deviating away from 8.4"

[Ethel]

Those are Metro drive flanges, impossible to say if vented or unvented just by looking. The locating lugs can be removed to accept 12 inch Mini wheels.

 

[Artstu]

Those are Metro drive flanges, impossible to say if vented or unvented just by looking. The locating lugs can be removed to accept 12 inch Mini wheels.

 

Those are for vented. Dead easy to tell the difference if you know what you're looking for, not that I think  flanges for non vented discs will work in this instance. Note how the centre section is raised 

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[Tupers]

Those are for vented. Dead easy to tell the difference if you know what you're looking for, not that I think flanges for non vented discs will work in this instance. Note how the centre section is raised

Not quite. Metros came with vented and solid discs with different offset drive flanges but both had the raised hub centric ring in the centre.