Upgrading to 4 pots, why and how!
Turbo Mini Forums

I have just done the conversion to vented 8.4 disks and metro turbo 4 pot calipers and I thought I would sum up exactly what is involved and why I did it.

So how do brakes work? By turning kinetic energy into thermal enery through friction. In other words the momentum of moving forward into heat by friction (pad to disk) Like all things there are limits to what your equipment can handle. I found after repated heavy braking I was getting brake fade with my old set up. This is when your disks and pads are too hot to work efficently. To over come this you can start by uprating your pads (green stuff worked well for me) But they were still fading when I really pushed them so vented disks are the way forward. Unlike their solid counterparts they are "vented" down the middle. This allows them to disperse heat more effiecently (cool down quicker) due to their larger surface area (thanks to the inner core).
Remember the heavier your mini is the more inertia it will have when moving - as my mini is a normal full fat mini I decided vented were definatly for me.

So why did I chose 4 pot calipers, mainly because to convert to vented I had to run them! Multiple piston calipers have beter contol on the pad as taper developes from top to bottom from disk speed and from outer edge to inner edge from disk rotation direction, keeping more of the pad surface on the disk (very important to create friction!) Multiple piston calipers are also better than their 2 pot cousins due to more effiecent torque arm effect. Basically the center of each piston if nearer the edge of the disk - where it moves the fastest.

*Also Note* There are two types of metro caliper available. They are both 4 pot for the metros split breaking system however some are vented and some are solid. Yyou tell which type of disk the calipers are designed for by the width as the calipers for vented disks have to be bigger for the disk and both pads to still fit in. (Spacers are available to convert sold calipers for vented disk)
Im not sure what model metro from what years had which (any info guys???) But the turbo metro definately has vented.

What you need:

1, Metro calipers
2, Metro disks (vented or solid -your choice!) The metro drive flanges have sticking out lugs used to locate the wheel onto the drive flange, these need to be machined off as they will not fit onto most mini wheels (apparantly some of the big 13" wheels will fit over) It cost me ?10 by a local machine shop to do this.
3, Metro drive flanges to match your disks (again vented or solid)
4, The metric nuts that connect disk to drive flange
5, ERA caliper bolts to fit your metric calipers to your imperial mini hubs. The metro bolts have bigger mounting holes so the era bolts have a bigger shoulder to fit the calipers on snugly (i personally wouldnt want mine lose!)
6, Mini wheel studs (metro wheel studs are a different length and thread)
7, Hose conversion kit to allow your mini to spread its fluid into both caliper resoviors for all 4 pistons.
8, New pads and new split pins to hold the pads in place - these are very important on the metro set up as they directly hold the pad in place by going through a hole on the pad backing.
9, New split pins for your hub bolts. Remeber to do these up tight nearly 200lbs (I think must check haynes manual) for a late model hub with taper bearings.

Fitment is easy - identical to normal calipers. Just put em on as you took the old ones off! I personally did one side at a time so I had an example to refure to if needed.

Dont use the metro hubs! This really muffs up your suspension settings!

I think thats it....

Ill add anything else if i think of it, feel free to point out any errors etc.

Dan

Edited by SumpNut on 14th Jan, 2005.

you'll need to remove the tabs off the metro drive flanges to fit most wheels too

ah yea - i knew there was something, ill edit that now

can you not use mini solid discs with the metro solid 4 pots?

Not seen any of them for a long time... Aren't they also more expensive to re-build?

Dan - how about a before / after driving comparison? Can you really (honestly) tell the difference at low/high speeds, emergency braking, etc?
I know the torque-arm is ever so slightly longer on 4-pots (hardly anything though), but the piston area is (to all intents) the same between two and fours...

I think all calipers after mid '86 were the type B (vented turbo) type. These will be 99% of them still around probably!!!

Does this mean that there is a caliper out there with four pistons that's going on solid discs??
Hmpf. Never heard or seen...

I'm changing AWAY from the vented ones now. They are just too heavy, and if historic racing Minis don't need them neither do I.

I have some calipers from a Metro which i used with solid discs, infact they're still in the garage somewhere.
Aren't the calipers for the vented discs the same but with a spacer added to allow for the wider vented disc ?


Phil.

WWW.TURBO-MINI.COM

Aren't the calipers for the vented discs the same but with a spacer added to allow for the wider vented disc ?

in my experience some are and some arnt. iv had ones that are a complete (2-part) casting for vented as opposed to 2-parts + spacer.

also the braking feels no differnt to a solid 2-pot 8.4 setup (imho) BUT iv had the solid disks fade before, and iv never had the vended setup fade. that piece of mind alone outweighs any disadvantages over weight/cost for me :)

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

just wanted to say i've got vented on my estate, brilliant braking :)

I have a 4 pot caliper somewhere with spacers fitted, ill try and dig it out of my junk when im next home.

I know Mr T Bo on this site uses 4 pots and solid 8.4 disks, the reason he did it was that on the lightweight mini the disk and pads would not get hot enough to work to its max potential with sporty pads, so he decided to go for solid disks. I belive he has had some very good results from his brakes.

My brakes were great, big improvement over the old system RE fade and general stopping power.

My car is off the road at the moment, one of the things i need to do is to replace my passenger side pads due to my fan throwing tonnes of oil into the wheel arch and all over my disk, doh...the pads were brand new!!!!

I think the type - A caliper was the one that designed for solids, and the vented's with a spacer and longer bolts.
The type - B caliper was only available on the vented discs when they were standardised (86ish?)




Could be totally wrooooooong!!!

Edited by TurboDave16V on 17th Feb, 2005.

my mates just bought a set of 4 pots n there solid disc type, they look exactly the same as the vented ones bar the spacer

are these quite rare now then????

Hi,
I think they were quite rare ten years ago, never mind now!
Cheers,
Gavin :)

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hahah o well

Does the fitment of vented discs (which requires the fitment of Metro Turbo drive flanges) increase the track width as compared to a standard 8.4" disced Mini?

Type A & B were fitted to MK1 Metros (up to Oct 84). From then on it was all vented Type A. Looking at the parts list it appears Type A was available in vented and solid, Type B was solid only. I think Type B is the rarer of the solid type.

Edited by metroturbo on 12th Mar, 2009.

Increases track either side by about an inch I think.

I converted my 8.4 in Injection Cooper discs, drive flanges and callipers to Vented 4 pots in 1993 and I recall they defo came out further under the Sportspack arches after the conversion.

Had to grind the 4 lugs off each drive flange lugs to fit the wheels on.

Minivanless, but reluctantly happy living with the decision. There'll be another one day.
http://www.youtube.com/profile?user=minimadmotorman#p/u

Sportspack arches weren't invented till 1996!!

If you have two pot callipers you only need to upgrade to 4 pot vented if your engine allows you to achieve some interesting corner entry speeds which will give you the most adrenaline packed 5 seconds of your life if your brakes are not up to spec. Or if you still have drum brakes fitted and that 1275 motor in the corner of the garage is calling you.

Own the day

if you have drum brakes after the first corner you no long need a fast engine to achieve those adrenaline packed five seconds.

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!