Rizal Philippines
4.08.2021
For every 20mm increase in diameter, there is 20% increase in brake power, Hence. the maximum increase can be had for 203 rotor size (from n 160 mm) - 40%
During the last two weeks, my mind was struggling to continue with my planned purchase of P3k ish quad piston brake. (Its review though has been bad)
Some literature even mentions that larger gains can be made by increasing the diameter of the disc rotor say up to 203 or 180. where gains of 30 - 40 can be had.
So I asked a good and experienced mechanics (he grew up in Cuatro Cantos) and he pronounced that if ever it works, ever so slightly compared to two piston brakes. It is difficult to bleed. Some literature mentions that longer pads tend to flex more and result in chatter and brake material separation from backing. This is consistent with a vlogger report for its disappointing performance (Not dramatic stopping power) The gain in quad piston brake is only 10%. Maybe this can be judged from length of brake pad which is roughly that much only: 4 cm single vs 5 cm for quad.
Yes, it’s just the ratio, assuming the same calipers.
A hand-waving calculation would be:
Deceleration = braking force x (rotor diameter / wheel diameter)
The braking force is constant (same caliper), the wheel diameter is the same, so if you increase rotor size you increase the deceleration.
So save your PHP. Invest only in larger disc (may be only in front) better material for the brake pads.
If you dont do downhill, or free fall rides, be content with your 140 mm, 160 mm set up double piston.
