hey everyone, i have a question about piston bore sizes? im planning on running 260mm drilled & vented discs on my car but im a bit confused about
the calipers, i am going for a set of wilwoods, i think that im going to have to go with the midilites (21mm to 25mm) as the powerlites will only
accomadate up to 22mm disc width and my discs are 24mm wide. whilst browsing the Rally Design website, which has loads of technical info, it says at
the bottom that the pistons in the calipers come in four different sizes 31.8mm, 35.1mm, 38.1mm and 44.5mm, so how do i know which one to choose? does
a bigger bore size provide more braking force on the disc and therefore you stop quicker? help me out here guys
thanks Alex
A simple question but with a complex answer 
Caliper diameters are balanced front/rear to provide the correct proportion of brake force for each axle based upon weight transfer during a 1g
deceleration. The weight transfer is dependant upon wheelbase, Centre of Gravity Height (above the road) and vehicle weight distribution.
Bigger calipers will NOT stop the car quicker. If the bigger pistons damage the balance front/rear then the stopping distance will INCREASE.
What rear brakes do you have?
was going to go for the wilwood rear caliper with the hand brake cable mod, with brake bias for the rear.
[Edited on 21/2/06 by omega0684]
Unless you have a massive cast iron V8 or Jag 6 in the front, on a bookish Locost for similar sized discs the the piston area on the front brakes
should ideally be just over 3 times that on the rear.
NB:For opposed piston calipers only count one side of of the calliper --
Working this out a 4 pot 38.1mm or a 6 pot 31.8mm would work but you will need a balance bar for fine adjustments.
Bling to impress the merkins
Of course this won't actually give you any more braking effort than standard Sierra calipers , however fade ressitance will be better but with
decent performance brake pads and standard vented discs you would have to push pretty hard for a long time to fade the brakes.
[Edited on 21/2/06 by britishtrident]
[Edited on 21/2/06 by britishtrident]
so do you think it would be best to get the 4 pot midilites on the front with a 38.1 bore and 2 pots on the back with the same bore size
why use the wilwood rear caliper, unless you want to throw money away (in which case I'll take some!!!)
Just use either the std Sierra caliper or the Golf alloy caliper, both light, though the golf one is much lightER, both work well and both are
standard and thus cheap when/if they go wrong.
I am using Raceleda 4 pot calipers on the front with std sierra 4x4 rear calipers on the back.
possibly upgrading to cosworth engine in the near future, and i have a bit of spare cash to spend, so i thought that a nice set of willy's (chuckle) would go down a treat!
i have unvented drilled and grooved cortina discs on the front with mintex pads, standard calipers, and drums at the back, and it is ridiculous how
fast it stops - seriously, i cant describe it. Its like you're going to to a handstand. I fell out of my seat nearly every lap.
And i never once locked up completely, so maybe i wasnt pressing hard enough anyway.
quote:
Originally posted by omega0684
so do you think it would be best to get the 4 pot midilites on the front with a 38.1bore and 2 pots on the back with the same bore size
just been looking at the wilwood site, getting some of that technical info, just thought of the brake bore size and that fact that people were saying
that it needs to be a ratio of three to one,front to back.
would this be ok, on the front i could have the billet dynalites,these ones
and would it be possible to put these on the rear disc, they are the sinlge pot billet dynalite?
front caliper with 38.1 mm bore size and 31.8mm on the single rear?
dont know whether this would work, please advise?
thanks Alex
Can't see any provision for a proper hand brake on the rear caliper --- this is what you want
http://www.rallydesign.co.uk/catalog/product_info.php?products_id=10563
Rescued attachment vwrear.jpg
my rear discs are 24mm wide they wont fit might have to go with these
[Edited on 21/2/06 by omega0684]
If the rear discs are 24mm wide what diameter are they??
You're either using cossie rears or escort/sierra fronts (these are 240mm dia)
Either way, FAR too much rear brake for a locost, you will have hassle at SVA time getting the balance right.
I used escort front 240mm x 24mm discs on the rear of my RWD Peugeot 205 rally car, and that was to get 50/50 braking for gravel and to have a REALLY
powerful hydraulic handbrake (used Subaru MV pickup FRONT (yes front!) handbrake calipers on the rear of the Pug!!)
Any Locost that isn't carrying numerous bags of cement will need a fraction of this braking effort at the back! Two people can lift the back of a
locost remember!!!!
If you are using cossie rear discs, get some XR4x4 rear solid discs, i you are using escost/sierra fronts on the rear, then fit escort solid ones.
There is no need, even with 500hp, to have vented discs on the rear of a Locost!!!
Whilst we are on the subject of wildwood brakes, I’ve got a pair of these master cylinders and am considering using them on the Velocity, has anyone had problems using these floor mounted (they have the integrated reservoir) and are the sva friendly?
quote:
Originally posted by pathfinder
Whilst we are on the subject of wildwood brakes, I’ve got a pair of these master cylinders and am considering using them on the Velocity, has anyone had problems using these floor mounted (they have the integrated reservoir) and are the sva friendly?
That 3:1 ratio might be closer to 2:1 in practice. (66% of the braking at the front)Remember, two can pick up the FRONT of a locost near as easily as
the back! With two up and a tank of fuel, most Locosts will tend towards tail heavy. (Most definitely with two of me. ) ( No rude comments Mr.
Allanson! )
You can always limit the rears, or use a bias bar. Some problems if you have insufficient rear braking power.
Syd.