Could I run a 183mm rear rotor on the Slackline? Can the frame handle the braking force?
Secondly, I am currently running 183/160 rotors combo on the slackline. I ride DH on it, and 9 out of 10, the rotors are toasting (sometime even fading!!! It feels so terrifying when you are at high speed!) and my finger is painful holding the brake. As a result, I would like to upgrade my rotors. Should I go 183/183 or 203/183? Any comment will be appreciated. Ta
To go risk going off at a tangent, what's the rationale for putting a bigger disc on the back? 160mm is enough to lock the wheel, and the front does most of the braking effort. Would 203/160 not be better?
Their website shows one of the builds with 183 rotors front and rear so it should be OK.
re: ratherbeintobago
I have been using 160mm for a while. In terms of braking power, it is good enough, as you said "locking the wheel" is easy. However, the problem with fading under high temperature always scare me near the very end or half way of the DH-run I do most of the time. I am hoping a large rotor (183), its large surface, will tackle the overheating problem. Same for the front too. Maybe 183/183?
re: souldrummer
Thanks for the info. I assume it is a YES.
I am hoping a large rotor (183), its large surface, will tackle the overheating problem. Same for the front too. Maybe 183/183?
No, what I'm suggesting is that the back brake does relatively little of the work of braking as your weight (and the grip) is more on the front wheel. A 203mm front would (in theory) give you more power/fade resistance; unless I've misunderstood, increasing the size of the back brake might not help that much.
ratherbeintobago - increasing the disc size will never give greater one off stopping power, as the pad is the same and therefore contact patch hasn't changed. However, the bigger disc will stand up to heat better and will give better sustained braking power on a long descent (within reason, a crap 200mm rotor is probably no better than a decent 160mm rotor).
If you're gonna be riding DH you may as well run a 200mm/180mm set up as it looks super cool and will make you a mega rad rider.
Above was aimed at your first post, ratherbeintobago, as hadn't seen our second post when I posted.
Still recommend going as big as possible for cool factor though. If possible, get some blingy coloured floating rotors (hope/superstar) - they give you the ability to 'shred more gnar'
If possible, get some blingy coloured floating rotors (hope/superstar) - they give you the ability to 'shred more gnar'
Not to mention they make a ticking noise when they cool down?
increasing the disc size will never give greater one off stopping power, as the pad is the same and therefore contact patch hasn't changed.'
Not sure this is right. I thought that the torque (and thus the braking force) generated by a brake was a function of both the friction generated by the pad/braking surface (which doesn't change with rotor size) and the leverage ratio (which does).
I used to have a very scary experience that both rotors smell like "overcooked" and the braking power fade suddenly. Once I realise that, I tested both my brakes on the fly, and end up crashing into a tree due to that distraction. Again, the amount of braking power is not my concern but the overheating issue which leads the drop of stopping power.
I suspect Hardtail DH sort of use more rear brake compare to a full-suss rig? Would like to hear some Hardtail DHer's thought.
On the physics side, I have the following thoughts:
Larger rotor:
-> Larger surface , better cooling, less fading
-> Larger radius of the disc, (further away from the centre), even with a same force applied will generate more torque, in this case braking power. Same as fastening a bolt with a straight Hex key vs a long L-shaped one.
-> Brake pad surface. Yes, I heard you say it is of a constant. However, the circumference of a larger rotor is more. The brake pad actually "travel" more "distance" on a larger rotor, spinning the wheel one circle. I can imagine, the pad will wear faster. But in reverse, that means more energy is put into stopping the wheels in one circle? I am not so sure about this bit. I just think in a logical way.
-> Modulation, I heard someone on the forum saying larger rotor actually provides less modulation, or the another way round? Hope someone could tell me the truth about this bit.
Ta
-> Brake pad surface. Yes, I heard you say it is of a constant. However, the circumference of a larger rotor is more. The brake pad actually "travel" more "distance" on a larger rotor, spinning the wheel one circle. I can imagine, the pad will wear faster. But in reverse, that means more energy is put into stopping the wheels in one circle? I am not so sure about this bit. I just think in a logical way.
Yes, despite what I said above a given point on a rotor's circumference moves about 500mm per rotation for a 160mm rotor, 565mm for a 180mm and 640mm for a 203mm. As such, the disc is moving at a higher 'speed' for a given bike speed; I'd have thought a given pad force would therefore result in more friction?
-> Modulation, I heard someone on the forum saying larger rotor actually provides less modulation, or the another way round? Hope someone could tell me the truth about this bit.
Bigger rotor = more leverage = less pad force required to lock the wheel = less modulation, I think.
