4 Pots :twisted:

[madmatt]

Hi All,

Does anyone know of anyone fitting 4 Pots to their 133?
I've got a set of Willwood Superlites that I've had sitting for a while and I've decided to make use of them.

They were ex NASCAR rear calipers (FECKING HUGE) and take a 300x25.4mm disc...
Sooo, anyone know any decent aluminium fabricators/machine shops?
Because I WILL have to either get custom discs made up/go to Tarox for a custom disc or go to AP Racing, buy one (well two) of their discs but I'd still have to get an ally bell made up for them as they're 2 Piece.

Sods law is, I'd also have to get different wheels, 133 Cup wheels don't look great for caliper clearance as is, Rota Boosts/Grids/Torques look good and I know Caliper clearance is great on them (mate has a Turbo Swift Sport with Kido 4 pots on the front).

Cheers

M

 

[Ollie133cup]

Is there any point ? The 133's brakes are pretty awesome anyway .

 

[Matt]

Yeah the standard callipers are mm from the wheel as it is. Going to be an expensive mod lol. Have fun going through the windscreen

 

[Anonymous]

133 brakes over heat and boil braking fluid quite easily if your running a long time on track from completely stock. ask Al hes come close and seen twingos at silverstone carring on after there fluid has boiled nuts.
they def could do with better pads and fluid for track. cooling or grooved discs would help keep them cool/cool down quicker on cool down lap so you can get back out there again faster.
i'd advice getting some new set of rims, if its cutting it close.
also remember what i said, you need to adjust braking bias to have a lot more force at the back, as the force will be too great at the front, either kicking the back end out or nose planting the car. and thats expensive as well getting a rear brake servo or petal box.

 

[madmatt]

Harnesses and Bride seats will be sorted to keep me from going all Superman whenever I tap the brakes :lol:

That was gonna be my next question in all honesty, how do you sort the problem of front/rear brake bias.

I mean, yeah, you get a brake bias valve but where do you tie it into?

Surely, one line goes from pedal master cylinder to servo, then umpteen lines to ABS unit, then 4 individual hard lines out to individual calipers, but how do you sort the bias?

Cheers
M

 

[Daveyb133]

my rs turbo used to have a manual one inside the car i used to turn. looked awful having this valve with copper piping all round the front of the car and going into the back, it sat near my gearstick, like on the carpet bit just by my left foot, will see if i can find some pics

 

[Daveyb133]

this isnt my car but u get the idea

 

[Anonymous]

i was told use a bias but with seperate cyclinders for back and front with the bias acting for the two with force/pressure etc. i'll be looking into petal box, you lose the cyclinder which is a very different feel when driving but least with a petal box and can heel-toe it, near enough impossible to do it with standard pedals.

was told braking should be shifted from 90/10% to 70/30% for big brake kits.

 

[singlespeed]

What size pistons are in the superlites and how does the area compare to the original calipers?

If the difference to the standard calipers is significant, you may need a different master cylinder to move enough fluid as well as sorting any potential front/rear imbalance problems. A propper dual ciruit peddle box with balance adjustment is the best bet

I'm currently running porsche boxter (brembo) 4pot rears over 325mm discs on the front of the Audi fitting inside the 17" rims with about 3mm to spare. These are MGzt 190 discs with the center bore machined to fit and the calipers mounted on a replacement carrier bracket. I also have a the rears fitted with larger 284discs to try and balance the fronts. With Pagid RS14 pads in the front, the ABS has a hard time but it is certainly drivable and so far I haven't managed to get them to fade... They smell bloody awfull but still work

The problem I have found is when the ESP decides it needs to intervene and applies a little bit of brake, which in reality is a lot too much. Switching off the ABS by pulling the fuses is definately not advised.

One option would be to find a disc that has a suitable diameter/thickness. Work out the offset and spacing required and then get a bracket made up to mount calliper. Theres (or at least was) a good brake catalogue on the Pagid website which lists most discs and pads.

 

[Anonymous]

esp was a nightmare with silverstone in wet weather at start, kept applying to much around the bend kicking out the back. been 4-pots god knows what would of happened.

 

[singlespeed]

esp was a nightmare with silverstone in wet weather at start, kept applying to much around the bend kicking out the back. been 4-pots god knows what would of happened.

It's not realy the 4-pots that cause the problem it is the total amount of braking torque developed from friction generated between pad and disc due to the hydraulic force generated by M/C and caaliper. it could just as easily be a single piston sliding caliper or some super sixes. More pistons just spread the force over a greater amount of area, allowing a longer pad to be used without it bending. The "4pots" just look cool and have some tasty pad compounds to fit in them. They also (sometimes) allow a larger disc to be run with a fabricated carrier bracket which gives more heat capacity to the disc and also greater torque as the pads are further out from the hub.

DaveB on the UK-MkIVs forum was the resident brembo hoarder and developer of the kit I used
Pagid catalogue> https://www.pagid.de/eu/downloads-mainmenu-65

 

[Anonymous]

ahh i just thought in general that they would put a getter force on the pads/disc. i was told that the oem cyclinder may need to be upgraded to cope with the force needed to apply the 4+ pots

 

[singlespeed]

it is all a bit of a trade off, between peddle travel and feel...the stock master cylinder has a certain fixed area and has a maximum travel... Therefore it can only displace a set amount of fluid.

Once you press the peddle, the seals and brake lines expand a fraction, any air in the system compresses and the pads eventualy get pressed against the disc to the point they can't move anymore. Now, the same pressure is felt throughout the system of M/C, brake lines and calliper...

Pressure = Force x Area. Therefore, increasing the area must increase the clamping force of the pistons against the pad/disc. The problem with bigger calliper pistons is you need more fluid to acceive the same movement, so your foot now travels further to take up the slack. Hence why 4pots tend to have 4 small pistons when compared to a single piston caliper... Which ends up giving the same clamping force as the original caliper.

For a given rise in temperature, bigger discs can absorb more energy. Therefore the big disc setups can be worked harder before the temp rises to the limit of the pads or fluid. Having the pad further out gives it more leverage, therefore the clamping force of the caliper can generate more braking torque... bugger all use if your tyres and ABS don't let you use it (like my Audi). Forced air cooling would have been more use to me than going from 312mm up to 325mm

 

[singlespeed]

Simplifying the above. If you were to double the area of your calliper pistons from standard (all 4 combined vessus the single), you could double your braking force. However to do that you would need to move twice the volume of fluid. Therefore you need to double the size of the M/C to keep a similar peddle travel

Doubling the M/C size has just negated the 4pots

 

[Anonymous]

cheer for that, very helpful.
seen a place that can do a two piece bell disc set up, although 300mm. wondering if stock calip could be used with new mounting bracket. 20mm shouldnt make a difference in pads used or should a larger one be used?

 

[singlespeed]

Sorry Matt, the thread has drifted a little bit.

With a (normal) lug mounted caliper, the problem in moving the caliper outboard means the mounting holes don't line up anymore. It isn't just a case of spacers and longer bolts. Whilst my rears are standard calipers with a bracket to move them out from 256 to 284, they are actualy taken from a 4wd model which have slightly different mountings

Radial mounted calipers are easier to shim outwards. Theres some pics half way down this thread which can show the difference. https://uk-mkivs.net/forums/t/291763.aspx?PageIndex=2
The new bracket is bolted onto where the original lug mounted caliper went.
The radial mounted porsche caliper bolts onto the new bracket. Note the difference in the direction of the mounting bolts
That is a 312mm set up, wheras I have the same bracket and caliper with a shim between them to run 325's (easily adjusted)

 

[madmatt]

No worries, this is all very ****ing useful =D

I've spent the last 5 minutes looking for the "Thanks" button!

As some NASCAR Techie very helpfully labeled the Calipers with the appropriate Disc size, I'm on the hunt for a 330 x 28mm disc, closest I've found (for a semi reasonable price) is from AP. Alcon discs were a fortune. I'll have a nose at Pagid too.
Pads aren't so much of a problem, constant stream coming from Nascar and suppliers still make motorsport pads for the old cast model.
I'll measure up the pistons tonight before I mock up a disc on autodesk to figure out the mounting bell.

I need to find somewhere that can redo the piston seals as well (just incase), going to replace the bleed nipples myself.

Anyways....

Am I right in saying that a brake bias could be plumbed in, entirely to the front brakes, reducing the flow to them and allowing the car to compensate to the back?
I'm still trying to visualise where the brake bias valve would plumb in, (duh, brakelines) but where in the brake lines??
Dave, the brake lines would be hidden to run to/from the bias valve.

My dad's got a brake bias valve (I think/hope) in both his Xzaras, one with AP 4 Pots in the front, other with Tarox 6 pots, so methink's I'll have to trace the lines back...

Keep em coming guys =)

M

 

[Kam Racing]

one thing to point out is that if you can lock your brakes then you have enough braking pressure and will not brake better with larger callipers or discs you will just decrease the pedal pressure required to lock up. To improve braking you would need to instead improve tyre grip. If you do increase the disc and caliper size it will usually increase unsprung weight which will make the tyres have to work harder to slow down the same amount

'organic' brake pad compounds basically have a short temperature range that the friction level is optimised for. OE pads are set with this being fairly low so that they are better from cold. For track use you can get compounds that can cope with the higher temperatures caused by the harder usage but this is at the expense of performance from cold. CL Brakes use 'sintered metal' compounds (instead of 'organic' ones) and these maintain their friction level from cold to over 1000 Deg.C (higher than F1 cars get up to). The Twingo RS pad shape is in development at the moment but when it is finished by them this will provide the best of both track and road performance.

If boiling the brake fluid is an issue then there are dot 4 fluids such as CL Brakes Race Fluid and Castrol SRF that offer substantially higher boiling points. The CL Brakes dot4 fluid is the best for a dry boiling point 325 Deg.C and is second best on wet boiling point. The Castrol SRF is the best for the wet boiling point but isn't quite as good as the CL Brakes fluid on dry boiling points..

 

[Anonymous]

i have tried CL fluid yet. running SRF and end up costing quite a bit as i have to empty and refil every year at 100 quid a pop. is CL the same where it needs replacing every year?

 

[singlespeed]

As Kam Racing mentioned, theres pads avaliable that can work to extremely high temps. however the low temp friction can be a little exciting to say the least. Pagid RS-14 pads can cope with discs that are practicaly melting and were fine for normal driving during the summer.But, durring the cold winter weather they were quite entertaining or scary at times at the end of the driveway when stone cold, or the end of a long straight section. In future, I will sort some forced air cooling and won't be going for big discs and won't be fitting top end race spec pads again. RS4-2 were ok, but RS14 are severe overkill

Yes, you can have too much of a good thing!


Madmatt. If your serious about 330x28mm discs, theres a few motors with these standard and various offsets for the bells from the Pagid catalogue
Alfa 159/spider with a 39.7mm bell
Various big Mercs with a 46.5mm bell... Grooved or plane
Porch Cayenne/ VW Toureg/ Audi Q7 with 73.5mm bell
The above motors should ring alarm bells when compared to the weight and power of a twingo!