What comes first, pad fade or fluid boil?
This is a very general question, I know. It depends on the actual brand, pad type, fluid type, caliper type, type of stopping, etc.
Just wanted to get an idea on average, do the guys with hydros ever experience boiling fluid without the pads going.
Do the mechanical guys ever get fade at all with anything other than resin (organic style) pads.
I'm in the middle of building something nice now that I have a year of riding under me. I'm incredibly happy with the 203/185 BB7s in modulation, fade resistance, and power. But I only want to buy once for this one and I'm pretty sure I'm going mechancal but wanted to do this one last poll.
For what it's worth, in my car, a single stop from say 140mph can fade the pads but the fluid won't boil. Repeated stops with short cool downs seems to boil the fluid first.
Thanks for any replies.
I'd say pad's first. I have faded the front brake with a 160 rotor. Rotor turned bright blue. Never faded with 203 rotor. If you're on hydro's, the brake fluid boils easier if it's contaminted with water. So an occasional changing/flushing of the system would help.
The pad will....
always fade before the fluid boils. DOT 4 and 5.1 have very high boiling points as they are rated for automotive use obviously. A single normal stop from 35mph to 0 in an automobile generates way more heat than the same stop would on a bike. Granted we're talking a much larger rotor, caliper etc. on a car, but the heat generated is enormous by comparison. So you'll likely see fade long before you'll boil the fluid. This is assuming the fluid is in good condition and not contaminated of course.
As for mechanicals, yes you can experience heat realated fade with them. It's not uncommon at all. Mechs are just as prone to heat fade as hydros are. My BB7s fade just as readily as my Hayes Strokers if I'm being a chicken and using the brakes too much on a fast downhill run. But even on fast long downhills, though I may have faded the brakes, I've never boiled the fluid. Certainly possible, but not likely.
"I do whatever my Rice Cripsies tell me to!"
I'm pretty anal about my brakes, I use different pads for different course conditions. In the wet, I use sintered metallic pads (both brakes). In the dry, I use EBC Red pads in the front brake, resin pads in the rear brake. I live in NW Florida, we have mud, clear water crossings and sand to pester us.
outside of DH race conditions its pretty rare that you'll ever boil a good quality brake fluid. pad fade is much much more common. Fluid boil has a direct relation to heat transfer from the pad/rotor to the caliper. The braking system only has 3 ways to dissipate heat, either transfer it to the air via the pad or rotor, OR transfer it to a "cooler" object, in this case the caliper/fluid. A cheap/crappy rotor/pad will have both a high fade rate as well as a high heat transfer rate (which could eventually cause a boil) more than likely due to either the material type/dissipation characteristics. Get a good pad/rotor and you reduce heat transfer which will inturn reduce fade and boil.
A good pad/rotor will have dissipation characteristics that will allow it to quickly "vent" latent heat out of the system (in this case the rotor and the pad). 1 factor that plays a role in heat transfer is contact time. Transfering heat to air (or water for that matter) requires a much lower contact time then transferring that heat to another object (say a caliper). So the quicker a pad and rotor can get rid of the heat and recover(larger pads and rotors allow a longer recovery time) the less contact time the caliper will have to absorb that heat. I'm not going to get into why and contact patch size since it really isn't necessary for this discussion.
Mechanicals experience the same fade issues as they are governed by the same heat transfer laws