brakes calculation

[vandit]

due to limitation of resources and books am not able to check my brake calculations.....whatever i learned about calculating was through this forum only and hence can somebody please just cross check my calc for the following data:

total weight of the car=340kg(750lbs)
weight distribution= 45:55(front:rear)
max decceleration assumed=1.6g
centre of gravity height=13"
whellbase=61"
rims diameter=13"
tire profile=60x185
caliper-->dual piston;24mm dia each
brake disc diameter=215mm(front:2 disc, outboard)
rear brake disc diameter=280mm(inboard;1 disc on diff)
coefficient of friction for pads assumed=0.4
driver input force to pedal=34kg(75lbs)
pedal assembly mech advantage=5:1
________________________________________
my results
master cylinder(for front) bore=.887"
master cylinder(for rear) bore=1"

somebody plz check and tell me if am going wrong somewhere.......

[vandit]

due to limitation of resources and books am not able to check my brake calculations.....whatever i learned about calculating was through this forum only and hence can somebody please just cross check my calc for the following data:

total weight of the car=340kg(750lbs)
weight distribution= 45:55(front:rear)
max decceleration assumed=1.6g
centre of gravity height=13"
whellbase=61"
rims diameter=13"
tire profile=60x185
caliper-->dual piston;24mm dia each
brake disc diameter=215mm(front:2 disc, outboard)
rear brake disc diameter=280mm(inboard;1 disc on diff)
coefficient of friction for pads assumed=0.4
driver input force to pedal=34kg(75lbs)
pedal assembly mech advantage=5:1
________________________________________
my results
master cylinder(for front) bore=.887"
master cylinder(for rear) bore=1"

somebody plz check and tell me if am going wrong somewhere.......

[Homemade WRX]

I can run this through my excel sheet when I can manage to get to the lab...stupid exam/frame building week

[vandit]

thanx for the help......i will be waiting for ur reply

[Homemade WRX]

I can only calculate the brake torques front and rear along with % F&R
and what is your effective diameter for you rotors?...

[flo]

Hi,

i have put your numbers in my excel sheet, but i dont get even close to your numbers.

bore sizes of 13mm front and 15mm rear should be ok.

Which caliper you want to use?

cu

flo

[vandit]

thanx flo.....i will check my calculation tonight .......and i think i hav little discreption in understanding the effective rotor diameter.......if its (total dia - the caliper piston dia) then my effec dia for front comes out to be 191mm and rear comes out to be 256mm.......

[Homemade WRX]

from my understanding and reading it is actually part of your piston diameter/pad height...just was wondering what number you wanted me to run with...oh well...I should be able to run it this afternoon being exams are finally done, until thur. at least

[Ryan Colton]

Just a question? Isn't 1.6g's a little high to use for sizing your brakes? With both our 04 and 05 cars we consistently are hitting 1.2-1.3g's but not over that.

Let me know how you guys came up with using that please?

[Homemade WRX]

yeah, I'm shooting for 1.6 myself to be on the safe side...UTA hit 1.8 with there aero package and we are just running an undertray...<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Ryan Colton:
Just a question? Isn't 1.6g's a little high to use for sizing your brakes? With both our 04 and 05 cars we consistently are hitting 1.2-1.3g's but not over that.

Let me know how you guys came up with using that please? </div></BLOCKQUOTE>

[Matt Gignac]

I wouldn't design the braking system around your maximum possible braking potential, but where you'll be spending more of your driving.

For instance, let's say you size everything for 1.6g decelleration, and it ends up you spend most of your time braking at 1g. Basically, you totally overestimated your weight transfer, so you will be overbraked at the front and underbraked at the rear. The result is locking the front brakes way before the rear (and some funky turn-in response).

Take a look at g-g plots, and look where most of the braking occurs. If I saw g-circles like the ones UTA posted, I'd probably set my brakes up for 1g braking as a baseline.

Matt Gignac
McGill Racing Team

[Homemade WRX]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Matt Gignac:
I wouldn't design the braking system around your maximum possible braking potential, but where you'll be spending more of your driving.

For instance, let's say you size everything for 1.6g decelleration, and it ends up you spend most of your time braking at 1g. Basically, you totally overestimated your weight transfer, so you will be overbraked at the front and underbraked at the rear. The result is locking the front brakes way before the rear (and some funky turn-in response).

Take a look at g-g plots, and look where most of the braking occurs. If I saw g-circles like the ones UTA posted, I'd probably set my brakes up for 1g braking as a baseline.

Matt Gignac
McGill Racing Team </div></BLOCKQUOTE>
I calculated maximum possible braking to be sure that we can do it. At our local autocrosses we will often are hitting 60-80 mph depending on the driver and the course. For slower courses (i.e. competition) the brakes will be adjusted accordingly...
I do agree though, not to overlook the lowe speed braking.
-Micah

[vandit]

flo
i think i got the reason why ur and mine nos. were not matching regarding the size of master cylinder........i gave u the mech advantage of 5:1 .....from my side it was actually the ratio after dividing equally by bias bar........and i think u made it further half ,takin bias bar........