The beasts are fitted.....some crap pics page 15

Jonny essex said:
...its the size of the calliper that dertermines the amount of stopping power as the size would be the overall pad coverage as well as piston power regardless of size of disc...
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Sorry Jonny, that's incorrect, the size of the discs is very important as larger rotors exert more torque on the wheels for any given clamping force

The overall piston area (rather than the number of pistons) in conjunction with the hydraulic pressure of your braking system dictate the clamping force exerted at each caliper and a 6 piston caliper may not actually provide any greater piston area than a 4 piston caliper (but it may spread the pressure more evenly) so, in the real world, exerts the same clamping force on the brake rotors.

It's important to realise that increasing the size of the pads will not increase clamping force (but will help with brake fade, important on a track, unlikely to be an issue on the road)

I've tried, but been unsuccessful so far, to find out the piston area of the D2 4-pot & 6-pot calipers although anecdotal evidence, based on them being fitted to cars without any changes to the master cylinder, suggests that they only have about the same piston area as the OEM calipers they are replacing - any extra braking torque is being generated by the additional rotor size, not from the calipers.



*If you want the maths behind it

Clamping Force is calculated as Maximum hydraulic pressure in psi x Total effective area of caliper pistons in square inches
NB if they're floating calipers multiply the Clamping Force value by 2

Resultant Braking Torque (ft lbs) is calculated as Clamping Force in lbs x Coefficient of friction between brake pads and rotors (this is a constant for a given type of pad) x (effective rotor radius in inches /12)
NB Effective rotor radius is the measurement from the centre of rotation to the centre of the brake pad

So you can see from this that, whatever clamping force your brakes develop this is multiplied up by the size of the rotors
 
Jonny essex said:
tertius said:
sars said:
They do look good Jonny :thumbsup:

ben g, I think it's a good idea to upgrade both, for road use you really need to keep a similar brake balance set up. putting a much improved front brake will alter bias to far forward and that can be quite dangerous. Having strong rears just means you lock them up, strong fronts can give you a lively rear end and induce instability.
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Hmm, good luck with that ... :D
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Sars is right can you imagine having 358mm rotas up front on 6 pots with the weedy rear OEM 2L 265mm rotas with callipers that are more like paper clips, if im dead in a ditch in two weeks then were see who was right and who was wrong :lol:
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Yes I can actually. Those rears are bigger than the APs I have on my car, and I think you'll find it massively over-braked at the back, unless the pad compounds are very very different front to back.
 
Jonny essex said:
CornishRob said:
How much heavier are they than the standard? Interesting to see how the handling has changed?
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They of course heavier but unsure however they are light aluminium cast callipers and are very light :o its the discs that are bench press weight, but i intend to out weigh that with a Fibre glass bonnet and lighter exhaust.
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It was the unsprung weight I was thinking of rather than the overall weight of the car, so a new bonnet and exhaust wont change that anyway.
 
PerryGunn said:
I've tried, but been unsuccessful so far, to find out the piston area of the D2 4-pot & 6-pot calipers although anecdotal evidence, based on them being fitted to cars without any changes to the master cylinder, suggests that they only have about the same piston area as the OEM calipers they are replacing - any extra braking torque is being generated by the additional rotor size, not from the calipers.
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Piston Sizes

Front 8 POT piston size: φ26、φ26、φ26、φ31
Front 6 POT piston size: φ36、φ31、φ26.4

Rear 6 POT piston size: φ26、φ20、φ20
Rear 4 POT piston size: φ31、φ26.4

That's for K-Sport (and from a few years back, so they may have updated the designs).

Easiest way would to find out for definite would be to speak to Bren or Ann at Apex Performance
 
Jonny essex said:
After a long 4 weeks wait as they are made to order the D2 BBK has arrived....356mm front and rear with 6/4 pot callipers, they are MASSIVE :o and will fill the vast void in my 313s and will help the car stop more when the extra ponys are added but most important as im form Essex....they look beautiful :wub:
Now have to wait two weeks to fit them :cry:
image.jpg1_zpsuoiyztzu.jpg
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And to think they will never be driven in anger or see a track :( :( :(

On the upside they will always be shiny. Looks good Jonny. You fitting them.?
 
Machine monkey said:
Sorry to crash the party JE but i got my discs today. Not as big 330mm but i did swap a set of exhaust tips for them.
First side cleaned up. 3 more to go.
IMG_0552_zpsimlbgc8v.jpg

Hope you dont mind me posting on hear JE.
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Sorry for the hijack. Is that 330 front and rear mat.?
 
No Yorkie just the fronts and bigger calipers at the front only also!!! I will address any issues as needs be if they present themselves :thumbsup:

Good on ya JE Doing it your self i am very proud of you. Just get a hand from someone who has done it before at brake bleeding time. What brake fluid are you using??
 
AnttiO said:
How those big brakes will work with standard brake cylinder, or do you upgrade other parts too?
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Good point. More Pistons, more volume, more fluid to move.!!

Surly that could result in a longer brake pedal if your using the same brake cylinder.??
 
I love reading this stuff and comments made by would be engineers, I get them all day at work and whilst it sometimes gets frustrating with some really interesting questions (and for the record there are no such thing as a stupid question) I try and answer/educate when ever I can.

But seriously guys, Jonny has gone to a professional outfit, told them what he has and they have given him what they believe, in their professional opinion, what he needs. It's not like he's (jonny) gone down to the pub and picked up some dodgy brake parts from bodget and scarper and you're wondering if the master cylinder is big enough :headbang:

So get real, we are talking brakes, do you honestly believe a professional outfit, an American manufacturer with TUV ISO 9001 certification, would supply an aftermarket kit that could possibly kill someone without making sure it is fit for purpose.
 
sars said:
I love reading this stuff and comments made by would be engineers, I get them all day at work and whilst it sometimes gets frustrating with some really interesting questions (and for the record there are no such thing as a stupid question) I try and answer/educate when ever I can.

But seriously guys, Jonny has gone to a professional outfit, told them what he has and they have given him what they believe, in their professional opinion, what he needs. It's not like he's (jonny) gone down to the pub and picked up some dodgy brake parts from bodget and scarper and you're wondering if the master cylinder is big enough :headbang:

So get real, we are talking brakes, do you honestly believe a professional outfit, an American manufacturer with TUV ISO 9001 certification, would supply an aftermarket kit that could possibly kill someone without making sure it is fit for purpose.
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Get off your high horse.!!!!

It's a perfectly ligament question posted on a forum. Are we not allowed to ask questions on here.???????????????????????? :headbang:
 
Nice set.
Dont you have some more pics?
From the rear discs (the inside and the outside (so people can see how the handbrake fits ;))), the rear calipers, the brackets. You know all the stuff the mailman brought 8)

For the rear discs I predict they made an insert in the disk hat to the specific size of the z4's handbrake shoes. I'd like to see how they did that. Or they cast a specific disc for a specific car. that's possible too. I wonder what they did.
 
Indeed you won't have any trouble with the master cylinder.
More pistons doesnt mean more fluid has to be pumped. It means that you can run a larger pad in the caliper. The force from all the pistons is better distributed. The sum of all the pistons is roughly the size of the single stock piston (the pistons in the bbk are a lot smaller; I guess people who think you need a different master brake cilinder never actually seen a piston of a stock caliper and a piston of a bbk). Also I think it's more of a pressure thing than a volume thing, but I'm not sure of that. (total pad pressure=X * piston surface area).

What you'll probably feel at first is that for braking, the padel has to travel a little bit more (1cm or so), but that is because new pads are a bit spungy. They will glaze a bit over time and the voids between the brake pad material will fill up to form a more solid block. Even the various brake in procedures won't change that, it happens over a month or so.
 
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