15 replies to this topic

[morley]

i've got myself a hold of some metro 4 pot calipers, but they are for use with solid discs.

at the moment i have some 2 pot standard calipers, i was wandering if me putting on the 4 pots would be a worthwhile upgrade as they are only for solid discs?
i've heard that you can convert them to accept vented discs do anyone have any more info on this?

and what else is neede for the converision would i just need hoses, era caliper bolts, metro drive flange with lugs cut off? and do the discs need to be turned down at all?

thanks!

[bmcecosse]

If you have discs already - just recondition them and carry on! The supposed 'improvement' with these 4 pot calipers is just not worth the hassles! Standard discs are fine for sane road driving - IF they are in top condition with decent pads.

[In-a-mini]

If they are for solid i think you may be able to fit them to the disc's and flanges from the mini (i have been told this but not tried) if not then the drive flange may need the lugs cut off depending on what wheels you are using. you will also need the bolts as you have said and the conversion hose set.
I personaly think they are a worth while upgrade for low cost and vented can be a little overkill. They are not the best brake option out there but unless you want to pay £250-£300ish for a pair of aluminium callipers they are worth a go

[MRA]

4 pots in this case will give you a minimum of 11% advantage over standard 8.4" calipers with comparable pads.

This could be the difference between stopping or running some youngster over

[moocoow]

Slight thread hi-jack but on the same theme.

I assume with fully working standard two pot calipers and decent pads you should be able to lock the wheels?
If so, what advantage do the metro calipers give?

Also does the extra unsprung weight of the heavier metro calipers have a noticeable effect on handling?

One last question, do the vented disks require maintenance to clear road crud that may get stuck in them?

[Dave33]

The metro 4pots on vented calipers are a good cheapish upgrade compared to say kad or any alloy 4 pots,they also stand up to all weather use,it all depends on your driving and how quick your mini accelerates,if you just use it as normal transport then originals are fine,if you got a quick motor and do alot of b road blasting then i have no probs with the 4pots.
As for handling,yes there heavier,and in theory you want lightness,but in practice driving you wont notice the difference,I think they used to use them on miglias,for those who couldnt afford the alloy type.
The vented discs do not clog up,and they cool down quite quick compared to solid type.wether they give you better braking i doubt it.
If you get some make sure you use a good quality disc like ebc and a decnt set of pads,am using yellow ebc in mine,and i couldnt ask for more,originally had blackstuff and was not impressed.
if you get some secondhand ones,make sure you change the pistons and seals.
Hope this helps
dave

[moocoow]

Thanks Dave, very helpful

[MRA]

The vented discs do not clog up,and they cool down quite quick compared to solid type.wether they give you better braking i doubt it.

Solid or vented........ the only action that brakes have is to turn kinetic energy in to heat energy by the medium of friction.... that is the bottom line.

Therefore if you can radiate more heat, or if you have a combination of events your brakes will in theory be better, ie higher friction material, more cooling larger mean diameter more calipers, more discs etc....

Generally on a Mini we can increase the friction but by doing so reduce the low speed braking EBC Greens are in this ball park, we can increase the mean radius by fitting multiple piston calipers, we can extract the "Q" (heat transfer) value or heat value quicker by fitting vented discs......

There are thousands of Mini drivers out in the real world who have fitted 4 pots with vented discs to do just that, and for the majority it wasn't done to look good it was done because it works

Now just going back to my first line, "solid or vented" if you brake hard using either solid or vented initially the brakes should not be any different (if all else is identical) it only starts to show up once the amount of heat "stored" cannot dissipate to the surrounding atmosphere, at this point brake fade occurs and until the vented discs get to a similar point they will continue to work without fault.

I personally know what I would prefer, and please note that unless someone knows different I can't think of a new car with solid front discs fitted

So in essence, whilst I can see what Dave33 meant by his statement above, I hope that I have now explained the main difference between solid and vented discs and the reasons for having them.

Edited by mra-minis.co.uk, 12 June 2010 - 08:23 PM.

[mljb59]

The vented discs do not clog up,and they cool down quite quick compared to solid type.wether they give you better braking i doubt it.

Solid or vented........ the only action that brakes have is to turn kinetic energy in to heat energy by the medium of friction.... that is the bottom line.

Therefore if you can radiate more heat, or if you have a combination of events your brakes will in theory be better, ie higher friction material, more cooling larger mean diameter more calipers, more discs etc....

Generally on a Mini we can increase the friction but by doing so reduce the low speed braking EBC Greens are in this ball park, we can increase the mean radius by fitting multiple piston calipers, we can extract the "Q" (heat transfer) value or heat value quicker by fitting vented discs......

There are thousands of Mini drivers out in the real world who have fitted 4 pots with vented discs to do just that, and for the majority it wasn't done to look good it was done because it works

Now just going back to my first line, "solid or vented" if you brake hard using either solid or vented initially the brakes should not be any different (if all else is identical) it only starts to show up once the amount of heat "stored" cannot dissipate to the surrounding atmosphere, at this point brake fade occurs and until the vented discs get to a similar point they will continue to work without fault.

I personally know what I would prefer, and please note that unless someone knows different I can't think of a new car with solid front discs fitted

So in essence, whilst I can see what Dave33 meant by his statement above, I hope that I have now explained the main difference between solid and vented discs and the reasons for having them.

if brake fade on solid discs occurs so fast why do modern cars not have vented discs on the rear?

[lorry]

Because most of the braking is done by the fronts so they get the hottest

[bmcecosse]

The main problem with standard Mini discs - is the horrible caliper and miserable small pad. They will easily lock the wheels (if in good order) so that child is safe! But -the horrible calipers and the small pads soon lead to problems . The best solution I found was the Fiesta Mk I caliper conversion - which gave me excellent brakes with never a hint of fade despite several attempts to induce it - no sticking on, no daft squealing or pulling to one side, no servo required, nice big cheap pads - AND it allowed me to fit my 10" wheels. All done very simply for very low cost - fantastic conversion. By all means fit the ghastly Metro 4 pots - with all their complications of piping up the 4 pots, and the need to overhaul 4 pistons and seals - instead of just the ONE in the Fiesta caliper - but they still won't allow you to fit 10" wheels after all that hard work!!!!!!!!!!!!!

Edited by bmcecosse, 12 June 2010 - 09:22 PM.

[Dave33]

I havent tried 4 pots with solid discs,so cant speak from experience,and i know the reason for vented is to allow better heat dissipation.
i also note that bill sollis ran solid dics and vented on his miglia,and couldnt notice any difference braking wise,he used solid in the end as they are quite a bit lighter than vented and this is obviously important on a race car.
I think that in theory vented should be better,by stopping discs overheating but in practice this obviosly isnt the case on a mini according to guy who raced minis at top level for many years.
modern cars are alot heavier and run much larger discs than minis so theres obvoiusly a need for vented here.
as for complicated brake line setup this isnt the case,it couldnt be simpler,and replacing the pistons and seals is not expensive or hard to do.you dont really need a servo with metro calipers,as long as the whole braking system is all working as should be and you use good discs and pads they work brilliantly.
The only downside i can see is like said the fitment of 10" wheels,saying that though im sure miglias use 10" so maybe there is a mod to allow fitment,but they wont fit straight on.
dave

Edited by Dave33, 12 June 2010 - 09:43 PM.

[MRA]

I havent tried 4 pots with solid discs,and i know the reason for vented is to allow better heat dissipation.
i also note that bill sollis ran solid dics and vented on his miglia,and couldnt notice any difference braking wise,he used solid in the end as they are quite a bit lighter than vented and this is obviously important on a race car.
I think that in theory vented should be better,by stopping discs overheating but in practice this obviosly isnt the case on a mini according to guy who raced minis at top level for many years.
modern cars are alot heavier and run much larger discs than minis so theres obvoiusly a need for vented here.
hth
dave

Interesting...... unfortunately I can point you in the direction of people with road going Minis that have swapped from solid to vented because of brake fade, on a race car using race pads fade isn't such an issue.....

Race pads have a higher co-efficient of friction therefore they have "increased" one of the prime items within the braking system.

in pracrice vented discs ARE better than solid as I said once you get to the maximum capacity for heat, if the solid cannot get rid of the heat quick enough a vented disc WILL help...

to quote "modern cars are alot heavier and run much larger discs than minis so theres obvoiusly a need for vented here." absolutely wrong, heavier cars do need better brakes, agreed, however bigger discs get rid of heat quicker so with your theory they wouldn't need to be vented..... and as you stated they tend to be vented, so bigger and vented discs add 2 pluses to the system.. as I said before brakes have to have the following......

1) A disc of mean area
2) A swept surface area
3) Friction co-efficient (pad material)
4) Number of surfaces
5) Pressure applying them to the discs
6) Number of pistons applying the pressure through mechanical means.

Increase any of the above and you Will increase the performance of the brakes this is simple facts based on dynamic and theoretical testing.

I have fitted more 4pots to 10" systems than I can remember.

I have been running 4 pots with vented discs since about 1987, so I have the experience to know that vented discs are a bonus which cannot be touched by any solid system of the same size.

If you think that by fitting race pads to a road car will improve your brakes, forget it as they take too long to warm up and often don't work unti l they are warm

Edited by mra-minis.co.uk, 12 June 2010 - 09:54 PM.

[Dave33]

like i said was not from personal experience,and as you say race pads can be quite different than a road use due to the extreme use they get,but have you tried ebc yellow pads?
these are designed for race use but can also be used on the road ,they work very well from cold,the only downside is a bit more brakedust than greenstuff.i currently run vented and use this setup and couldnt ask for more.
But for road use with the odd blast are vented really necessary?
dave

[MRA]

Yes I have used most all of the e bc range, and prefer to stay well clear of them now, in preferrance I use Mintex and or Delphi which for a standard pad offer much better braking than any of the colours.

You could also ask the same for drums...... at the end of the day if you drive within the capability of the vehicle (ie slowly) then no vented are not required, thi sis not a turn around on my part as I will continue to use vented on my own cars and advise customers to follow suit when I feel it necessary, ie high power or simply a fast driver...