Radial Brakes

[cd52]

Hi,

Relatively new to the whole bike/mechanical side of motoring and was hoping someone could explain the differences between a standard braking sytem and radial brakes.
I guess it will probably be pretty simple but all the magazines keep going on how the new radial brakes improve stopping power but never go on to actually say what they are for the totally clueless like myself.
Any info greatly accepted

[craigs23]

Greater power due to a more direct feel on the lever - the piston moves in the same way as the lever travel. Down on the calliper end, apparently radial mounted callipers have more rigitity (less flex or something, allowing a more powerful setup).

Goes to show my limited knowledge on the matter....they look rather trick though.

[spakmitten]

they press the pads from both sides instead of just the ouside i think

[feef]

Grabbed from various techie brake sites and mashed together....



A radially mounted caliper is stiffer, and is better at maintaining alignment with the rotor. This means the pads stay in alignment better, making better contact with the rotor and exerting less lateral force on the rotor while generating less heat for a given pad pressure.

With traditional caliper mount points on the trailing end of the caliper, pad pressure at the leading edge of the caliper has considerable leverage to misalign the caliper in relation to the rotor. Radial mounting takes care of that. Putting a mount at both the leading and trailing end of the caliper, leverage at the leading edge of the pads is reduced to a level that it becomes insignificant.

The magazines and testers will all tell you that radial brakes make the bike stop quicker. Not true - they have nothing to do with stopping power and everything to do with the design of the front forks of the bike. More and more bikes are coming out with upside-down forks. ie. instead of the fat canister part of the fork being at the bottom of the assembly, it's at the top. This means that the fork pistons are now the part of the suspension with the wheel attached to them. It also means that it's impossible to put a stiffening fork brace down there now because the brace would need to move with the wheel, and the length of the fork pistons precludes that.

The stiffness of the front end is now entirely dependent on the size of the front axle. Bigger axle = stiffer front end. A side-effect of this design was that traditionally-mounted brake calipers could cause a lot of vibration in the steering because of flex between the wheel (with the brake disc bolted to it), and the fork leg (with the caliper). The slight tolerance allowed by floating brake rotors couldn't compensate for the amount of flexing in the forks. To reduce the brake-induced fork vibration, the brake calipers were moved around the rotors so that they fell into the radial line of the wheel. This is because there is less lateral flex at that point, which means less or no vibration. It's interesting to note that car brakes have been radially mounted for decades.
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[Kickstart]

Hi

Not sure there is any true benefit. They might well be more rigidly mounted, but they are also larger and require larger mounts. There is still a twisting force on the forks. Suspect the main advantage is just gained from the heavy duty mountings.

Main advantage I have heard and that I believe is that for race use you can easily change the size of the brake disks when it rains, just using a couple of small and simple spacers to move the caliper out / in.

All the best

Keith
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[cd52]

Thanks for the quick replies folks
Gives me a better idea of something else now