4 Pot Calipers

[Bob Tucker]

I'm having one hell of a job getting a firm brake pedal on Ray's Vette.

Hes insisting I get if fixed before he drives it. (Wimp!!!)

 

It has Wilwood 4 pot calipers front & back.

The upper bleed nipples face straight up, the bottom ones face straight down.

Ive bled & bled & bled but still have a spongy pedal.

 

So far Ive bled them in situ, do I need to remove the calipers & turn them upside down to bleed the bottom pistons before refitting them?

 

I know that would seem sensible, but does anyone have hands-on experience of 4 pots?

 

Ta Bob.

[Guest rizla]

id give marc a bell at mnr,they have fitted 4 pots on a few of the race cars,im sure he would give you sound advice

[Bob Tucker]

Ta mate,

Ive also realised that my old favourites, Rally Design sell Wilwood brakes.

I'll buzz them too.

 

Good luck tomorrow !!!

[Guest rizla]

nerves have set in already bob

[Guest salty_monk]

I reckon you could be right, you'd have to put something in there to keep the pistons apart though... (although maybe not with an Eezibleed)

 

My friend fitted his callipers upside down on a Golf with exactly the same effect...!

 

On the Moggy when I used the silicon brake fluid it helped to leave the pedal compressed (lump of wood between seat & pedal) for a couple of days.

 

[ibrooks]

Those look very like a big version of the AP four pots on my.....

 

 

 

 

 

 

 

 

 

 

 

 

 

 

wait for it......

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mini!

 

They are actually from a Metro Turbo so it may be worth looking at a Metro manual (every Metro from B-Reg onwards got what had previously been the Turbo brakes). They also have an assortment of bleed nipples facing in various directions and from memory there's a quite specific order to bleed them in.

 

Iain

[Guest docter fox]

so a C reg bog standard metro will have 4 pots?

[Guest TerryBarry]

The Metro / Princess 4 pot calipers were set up as part of the dual circuit hydraulic system. Thus the upper and lower pistons were fed by different sections of the master cylinder.

The process was to bleed the rear brakes first.

Then starting on the caliper furthest from the master cylinder - open both lower nipples on the caliper and bleed these simultaneously, next switch to the upper nipple and bleed that. Repeat the process on the other caliper

[Bob Tucker]

Just as I feared & expected!!!!

Loads of different answers, all of them perfectly feasible!!!!!

 

I also spoke to Rally Design, who import Wilwoods. They said....

 

The calipers are not handed, so they fit 4 bleed nipples so you have an upper pair of bleed nipples whichever side you fit them.

Use a power bleed set up, leave the lower ones alone, bleed the inner top nipple first, then the outer upper. The fluid chambers are all connected, so bleeding the uppers evacuates the lowers.

 

Just off to the garage....I'll report back tomorrow.

 

Many thanks Bob.

[ibrooks]

so a C reg bog standard metro will have 4 pots?

Yep.

 

Little rider to this one - B-reg is a rule of thumb. It was actually cars made after eighty-summat. It's not unknown to find an earlier car on a later plate (I was once offered an L-reg Sierra but have never seen another one later than K-reg). Basically B-reg on is fairly certain with the chances of finding anything other than 4-pots on later cars steadily decreasing as they get newer. If you pick a c-reg Metro at random I'd bet a pint it's got AP 4-pots. A d-reg I'd bet two pints and if you find an e-reg with the older twin pots I'll nail jelly to the ceiling.

 

And yes the Metro ones are split so may add complications to this problem. On a brighter note it means I've seen them used on rear brakes where 2 pistons brake along with the fronts and the other two are connected to a hydraulic hand-brake (not strictly legal for the road I believe but how many MOT testers would realise or check is another question).

 

Regarding nailing jelly to the ceiling - you put it in a polly bag and freeze it around the nail then remove the bag and work quickly and carefully on a ceiling above a floor you don't have to clean. A penny washer on the nail helps.

 

Iain

[Guest docter fox]

do you have much more useful information like that? I may have to try that at some point

 

would metro 4 pots fit a sierra based hood? would i just need some new mountings? I'm guessing they wouldnt be easy to make? and most important of all, would they be much better over standard sierra?

[ibrooks]

Metro four pots on a Sierra disc - maybe. Anything is possible. They are designed to work on an 8.4" vented disc. On a Sierra disc they would therefore only cover the outer few inches of the disc leaving the inner part with nothing grabbing it - but then the lever advantages say that forces applied to the outside edge are more effective so.....

 

Dunno whether they'd be better or not. You'd have to size them up and see how much of the disc would actually be between the pads.

 

Aren't the Sierra brakes good enough though? I know mine are if anything a little OTT.

 

Iain

[Guest docter fox]

they just don't seem to have as much clamp as I'd like at higher speeds but perhaps it's just mine

 

how's the bleeding going bob?

[Guest Kieran]

...also 1984on Skoda Rapid / Estelle also have 4 pot calipers on the front, and lots of pad grades are available too.....

 

Kieran

[Guest docter fox]

has anyone retro-fitted some sort of 4 pot caliper onto a hood then? as the wilwood ones are definately out of my price range