Brakes and suspension question

bobbydigital

Does anyone know why in the MTB world we don't see these things often,

USD forks, stronger due to the large part of the fork being up at the headset, creating a more rigid structure but I've only seen 1 or 2 models for MTB.

Radical master cylinders, like the M665 design, in motorcycling, they allow "big bore" piston in the brake, giving more power, better regulation and less level travel, but it seems Shimano gave up on that idea and I've only seen a few other companies bother with that design.

Monoblock calipers, these are only seen really on the top end superbike so I guess price is the factor, but for MTB they would be lighter, more rigid and well they wouldn't leak from the center as they are made from a single piece of metal, so could be more durable.

cooldad

USD - because the lowers get crunched on rocks and stuff.

I think you mean radial. As it's a bicycle, and I can lock wheels with my pinkie if I want, maybe unnecessary?

I haven't had problems with calipers not being 'rigid', nor ever had any leak.

02gf74

Are usd more rigid? , they lack the bridge brace that conventional forks have and this means legs can move independently, a right censored when refitting the front wheel, a larger axle is usually employed.

There are one pie e callipers, e.g. Formula, they have a hole in the side covered by a plug so that pistons can be fitted, reason here is cost.

tallpaul_s

USD forks - motorbikes have large bolt through axles with 2 pinch bolts per fork, normal MTB axles are 15mm. They'd need to massively increase the stiffness and size in the fork bottoms to get the same level of stiffness, which would increase the weight. USD forks are stiffer at the top due to the larger diameter stanchions but motorbike forks are also triple clamp - unless they're DH forks all MTB forks will flex at the crown.

Radial master cylinders aren't on that many bikes, normally high end bikes. I have a 140bhp 1000cc bike with non monobloc calipers and axial brake and clutch cylinders and they are far, far from lacking in power or bite.

Monobloc calipers do exist, hope are monobloc. Again they're only on high end bikes and only on high end MTB brakes.

02gf74

TallPaul_S wrote:

USD forks - motorbikes have large bolt through axles with 2 pinch bolts per fork, normal MTB axles are 15mm. They'd need to massively increase the stiffness and size in the fork bottoms to get the same level of stiffness, which would increase the weight.

Indeed, Rockshosx RS1 are probably the most common USD fork:

The RS-1 is only compatible with Predictive Steering front hubs, which have a 110mm axle spacing and use a 27mm oversized aluminum axle sleeve called the Torque Tube to bolster stiffness by resisting torsional forces.

The Rookie

Axle diameter isn't really relevant, its the diameter of the part acting to resist the twist (the torque tube on the RS1) which matters, all the axle has to do is provide the compression force for it to work with and a 15mm axle is more than up to that.

batmo

Cannondale Lefty "forks" are upside down, but solve the axle twisting issue in a different way, I suppose.