Avid codes 09 or avid elixir cr 09 ?

PB Forum :: Downhill
Avid codes 09 or avid elixir cr 09 ?
  • Next Page
Author Message
Posted: Apr 12, 2010 at 8:27 Quote
but the code's 4 allow it to have a much bigger pad, and this is what gives a break its power. its not the amount of pistons, its the surface area of a pad on a rotor

respectfully I'd have to disagree, its a common misconception about disc brakes...


a hydraulic disc brake gets its mechanical advantage (leverage) from 3 aspects:

1 . the volume ratio between the master cylinder (brake lever) and pistons

2 . the efficiency of the brake system in transferring lever action to piston stroke

3 . the size of the brake rotor (each jump up from 160mm to 180/185mm to 200/203mm give additional 20% 'power' increase)


more pistons, or larger pads do not actually give any more "power" (large pads actually mean less friction / mm2 of pad material)

the reason more pistons are used, is to give a smoother modulation by giving the brake pads a 'leading edge' (similar to a rim brake rubber brake-pad being "toed in" at a slight angle)

you will often see multi-piston brakes have different sized pistons


Hope have previously admitted they only made their 6-pot brake with vented rotors because of fashion - there is no need on a pedal cycle to have anything more than a 2-pot (piston) brake with standard rotors

however, if customers ask and want to spend their money...its good business sense to provide the goods!


YES, on a road motorbike that can hit 150mph+ you need multi-piston calipers and vented rotors, to give smoother modulation and improve thermal performance, but not on a 40lb push bike Wink

Posted: Apr 12, 2010 at 9:09 Quote
i got the elixirs cr , but have now changed them to new saint ones . which i find much better wi both modulation and power

Posted: Apr 12, 2010 at 9:34 Quote
hampsteadbandit wrote:
but the code's 4 allow it to have a much bigger pad, and this is what gives a break its power. its not the amount of pistons, its the surface area of a pad on a rotor

respectfully I'd have to disagree, its a common misconception about disc brakes...


a hydraulic disc brake gets its mechanical advantage (leverage) from 3 aspects:

1 . the volume ratio between the master cylinder (brake lever) and pistons

2 . the efficiency of the brake system in transferring lever action to piston stroke

3 . the size of the brake rotor (each jump up from 160mm to 180/185mm to 200/203mm give additional 20% 'power' increase)


more pistons, or larger pads do not actually give any more "power" (large pads actually mean less friction / mm2 of pad material)

the reason more pistons are used, is to give a smoother modulation by giving the brake pads a 'leading edge' (similar to a rim brake rubber brake-pad being "toed in" at a slight angle)

you will often see multi-piston brakes have different sized pistons


Hope have previously admitted they only made their 6-pot brake with vented rotors because of fashion - there is no need on a pedal cycle to have anything more than a 2-pot (piston) brake with standard rotors

however, if customers ask and want to spend their money...its good business sense to provide the goods!


YES, on a road motorbike that can hit 150mph+ you need multi-piston calipers and vented rotors, to give smoother modulation and improve thermal performance, but not on a 40lb push bike Wink

Eek See i would agree but my saint 4 pot for sure had more power than my friends old saint 2 pot with goodridge hosing,could be purely less effort needed to apply the power i'm not sure but different.

Ok i'm 16 stone and hes around 12 but he also found the 4 pot to much for him.

Posted: Apr 12, 2010 at 11:18 Quote
hampsteadbandit wrote:
but the code's 4 allow it to have a much bigger pad, and this is what gives a break its power. its not the amount of pistons, its the surface area of a pad on a rotor
respectfully I'd have to disagree, its a common misconception about disc brakes...
a hydraulic disc brake gets its mechanical advantage (leverage) from 3 aspects:
1 . the volume ratio between the master cylinder (brake lever) and pistons
2 . the efficiency of the brake system in transferring lever action to piston stroke
3 . the size of the brake rotor (each jump up from 160mm to 180/185mm to 200/203mm give additional 20% 'power' increase)
more pistons, or larger pads do not actually give any more "power" (large pads actually mean less friction / mm2 of pad material)
the reason more pistons are used, is to give a smoother modulation by giving the brake pads a 'leading edge' (similar to a rim brake rubber brake-pad being "toed in" at a slight angle)
you will often see multi-piston brakes have different sized pistons
Hope have previously admitted they only made their 6-pot brake with vented rotors because of fashion - there is no need on a pedal cycle to have anything more than a 2-pot (piston) brake with standard rotors
however, if customers ask and want to spend their money...its good business sense to provide the goods!
YES, on a road motorbike that can hit 150mph+ you need multi-piston calipers and vented rotors, to give smoother modulation and improve thermal performance, but not on a 40lb push bike Wink
While you're not entirely wrong, you are wrong that more pistons dont equal more power in terms of braking performance. The dual pistons allow force to be exerted over a greater distance which, as you pointed out, actually minimizes force per unit of measure. So, if you double pad size, you halve the friction being exerted by a given area of pad. However, in reality, smaller pads have a much smaller "window" for the point between which heavy friction occurs and lockup occurs. Doubling the size of the pad therefore doubles the effective area of braking power available to the rider before lockup occurs... resulting in a more powerful brake. This is exactly why, as you point out, motorbikes benefit from larger pads and multi piston systems.

Posted: Apr 13, 2010 at 12:02 Quote
Doubling the size of the pad therefore doubles the effective area of braking power available to the rider before lockup occurs... resulting in a more powerful brake.

thanks for the information and clarification


modulation is everything in a brake, and a softer modulation (from having extra pistons working longer pads) does make for a more "controllable" braking system before lock-up (skidding) occurs

this does not mean the brake is more "powerful because of extra pistons", just more "controllable" from having increased modulation to allow the rider to feather the brake

power and modulation are different aspects of a braking system, and its all debatable because a skilled rider will learn to use any brake system given time (look how many riders did well on Hayes HFX-Mag and HFX-9 brakes) - we are trading terms here Wink


a consideration about braking:

-perhaps a more grabby back brake is beneficial on a mountain bike, as 80% of your stopping power is found on the front brake

can a more "grabby" back brake with less modulation could be a benefit to allow the rider to slide the back wheel more easily to setup the bike going fast into corners and turns?

-and then run a brake with better modulation on the front, to give smoother control with less tire slip from locking the brake up?

  • Next Page

 


Copyright © 2000 - 2024. Pinkbike.com. All rights reserved.
dv65 0.008930
Mobile Version of Website