heres one for the brake specialists.i currently have Ap 6 pots with 356mm discs up front,and AP 4 pots on rear.i am thinking of changing the fronts to some AP 4 pots with the 330mm disc,mainly to reduce weight and rotating mass.am i going to sacrifice my stopping power by doing this or will the AP 4 pots just do as good a job at stopping the car,bearing in mind i will still have the 4 pots on the rear.

 

I would have thought that when your 6 pots are working at there hardest they are good enough to make your rear brakes "almost" un important? By lessening the braking force at the front (4 pots) you will increase the work that the rears are doing, but thats because the front wont be working as hard = you will not be stopping as quickly?

Just a thought?

Lee.

 

yeah,i had thought along the same lines as that myself,but i was just thinking that maybe i could get as much stopping power as i need with both front and rear 4 pots and be carrying around a little less weight too.

 

Probably stating the obvious that I aint no expert but, I believe that having the weight bias to the front of the car when braking actually aids turn in, I had thought of getting AP 4 pots for the rear of mine (I am on AP 6 pots at the front with only DS2500's) but I reckon I would not notice the difference???? Saying that if I wasnt short of pennies they would be on straight away I read an article about suspension this week (I think it is on the KW web site) and they reckon a cars weight bias can be as much as 90% at the front when heavy braking

Unfortunately (and I am sure your aware of this) the only way to maintain the stopping power and lower weight is to spend a fortune on AP/or other competition stoppers

 

Larger brakes are always better , there is no substitute for size , the obvious down side the larger you go is more weight , if you are looking for the ultimate performance and use it all the time , as in track or competition use , then the extra braking you get far outweighs the downside of the extra weight , for competition cars , you can fine tune the suspension to deal with it.

The 330mm 4 pot kits work very well , and would cope with most driving styles on the road , the extra braking power you would get by fitting the larger 6 pot kits would be better braking down from three figure speeds , and track use ,

Why do you feel as though you need to reduce weight ?

Cheers Ian

 

it is more for the quarter mile side of things really.the car is used for track,fast road and will be doing quite a bit of drag when the weather picks up.it has already proven itself on track with the brakes but i have just got it into my head that every time i look at the size of them fronts i think thats a whole lot of weight to have to spin round.i know when it comes to stopping these cars from hairy speeds that bigger is always going to be better.i think what i need is to borrow some 4 pot 330mm fronts and try them out and if they are good enough then fine,if not i'll give em back.anyone care to borrow me a set.

 

I had Alcon 6 pot calipers and 365mm discs on the front of my old 2005 STI Type UK and that set up weighed less than the Brembo's with oem discs.

Keep them, big brakes are cool

 

Arf do we need to talk about some AP six pots ?

dunx

 

it seems that all the parts i searched for years to find i have now sold to you dunx.

 

Apart from the tein's and your not having them back mate

 

 

The main benefit you will get by going to a smaller size for drag racing is better selection of wheel/tyres.

What is the caliper model? The current calipers may well be compatible with a 330mm disc anyhow.

 

So ? Make me an offer...



dunx

 

i have the 7040 calipers on the front at the moment which i beleive is only for use with the 355mm discs(i may be wrong).the wheels i use on track are rota g force 18-8.5 with toyo r888.

 

CP7040 will work with smaller discs also.

 

Just a thought > what is the weight difference between 6 pot APs with 355mm's and 4 pot AP's with 330mm discs? you may get the same weight saving from ditching the 4 pot rears and going for some old 2 pot rears? that way you will still have the benifit of the big anchors on the front and loose the weight your looking for on the drag strip

 

Arf i have the AP cp5570 , 6 pot caliper but with the 330 mm disks,they are awesome,they are off the car at the mo,can weigh them if you like ?

 

I'll vouch for that.....Best braking set up i've ever driven with

 

@ 555EFC, That would not be the best idea.
It's remarkable how much bigger rear brakes do,not only for total braking performance, but also for stability.
Because of the large front brakes going back to 2 pot rears could result in a car that will want to come around with the backside on heavy braking.

Maybe custom bells, made from lighter materials can save you some weight,
Going smaller imho is only an option if your disk sizes limit you in wheel/tire choice.
But If you are dead set on 330 all round it can be done with your current caliper.
Maybe someone on here wants 356mm, and you can swap disks/adapters (if they are in similar condition)with some cash your way.

With 330 all round there could be some balance problems, so maybe a different pad front/rear could be advisable.

 

i had the cp5570 6 pots with the 330mm discs on my old car and yes they are exellent.right then, seeing as money grows on trees around here alately(or so it would seem).i have bought a set of ap 4 pots cp5200 with 330mm discs and ferodo ds2500 pads, to compair the difference if any in braking between the 2 sets.if they still give me the stopping power i want,then i will sell the 6 pot set up.if they dont then i'll just sell the 4 pots on.

 

Give me a pm bigarf when you decide which one's you don't won't please fella
ps i see you thought the banny avatar was gay and funny to

 

will do mate.
p.s i thought the avatar was of a 70's **** star

 

, i just couldn't let it go when i saw it,needed to be told i say
I see he has changed it back now to.
I'd be very interested in either of the brake setup's arf cheers

 

Hey fella your best bet would be to ring pete collen at AP racing very knowledgeable guy and very helpful.

Good luck

 

fair point, I am still running the standard 2 pot gold sti callipers on the rear and with a geo set up it runs ok, however I bet the AP 4 pots with light weight bells are a lighter set up

 

Fair play to you mate, look forward to hearing your thoughts after you have tried em

 

So you you've bought some four pots already ?

I was preparing to suggest a sideways move your large six pots swapped for mine !

dunx

P.S. I hope the four pots will do... as I quite like these

 

i might be intouch with you yet dunx,gunna see what difference the 4 pots make first.

 

update.
right then. seeing as the weather has warmed up alittle,i had some time spare this morning so i swapped from these


and a few hob *** biscuits later, to these.


to be fair my old pads were quite worn and the ones i have just fitted came with as new pads which i was told were the ferrodo 2500.before i took my old setup off, i took the car out for a little test.i did a few stops and recorded the times just so i knew roughly how to compair both sets.obviously without proper recording equipment its not bang on but it will give me an idea of differences.these were done one after another so brake to a stop then back up to speed then brake to a stop and so on.
from 80mph to 0 = 4 secs
from 110mph to 0 = 5.09
from 110mph to 0 = 5.36
from 110mph to 0 = 5.16
all pretty much similar.
so i fitted the 4pots and took her out for a test.there is a noticable differance in pedal feel as if you need to push a little harder to get the same responce as the 6pots.obviously this will be down to the 6pots giving a better clamping load on the disc.so first i took her round the twisties to see wether it would be over braking on the rear now due to me having 4pots on the rear as well.all seemed normal there and it felt just as confident into the corners as it did with the 6pots.so onto the braking down to zero test.i must admit that i didnt think this would come out as good.the results were.
from 80mph to 0 = 4.1 secs
from 110mph to 0 = 5.26
from 110mph to 0 = 5.04
from 110mph to 0 = 5.18
again all pretty much the same.even though i thought i had to push the pedal a bit harder the car is actually stopping pretty much the same at speed.what i have also found is with the 6pots they used to overpower the abs a little and get the odd bit of locking up but the 4 pots even when stamped on gives a smoother stop.i weighed both sets before fitting and there was approx 7lbs each corner differance,so all in all there is a saving of around a stone in weight.carnt actually feel any differance but surely it must account for something.so to some it all up for the time being i can still stop the car as good in every day use,will just have to see how it fairs with a few hours on track,and if my right foot feels like its having to do to much work to stop the car then itl be back to a set of 6pots.

 

Nice one arf,so it would appear that the 4's are as good as the 6's then with less weight so better really