Mountain Biking - Fork bob while braking
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You know how when you brake, your fork uses some of it's travel. Well a friend said that some company is trying to devise a way to get rid of this. Is there any point and also, how the f*** would anyone stop this? Because when you brake your weight gets shifted to the front, so I don't see how it's possible.
08-24-04, 04:32 AM
I find it useful under hard braking, on my old bike a ridgid fork, braking too hard would throw me over the front. With some suspension it takes some of your body weight and allows you more control when stopping quickly. Of course you can still endo but theres a smoother transition.
08-24-04, 05:36 AM
Only thing i can think of would just lower the sensitivity of the shock so that it doesnt respond to braking like that but would still absorb hard and fast shocks.
08-24-04, 09:37 AM
A lot of the new technology in suspension design is toward inertia valved shocks or SPV (Speed Positioning Valving). The inertia valve activates when the suspension is activated from the bottom pushing up. (like from a bump) When the weight is applied from the top (rider pushing down) it locks out.
Carnutt is the leader in this, but Fox Suspension and Progressive and all the others are following suit. It's still pretty expensive, (figure $650 range for forks), but in the next couple years you'll see the trickle down effect.
08-24-04, 09:42 AM
if the fork was only operated properly from bottom up, when you do a drop would it go rigid and break your wrist, or am i understanding this wrong??
08-24-04, 09:47 AM
When you drop, the impact is on the wheel first which activates the suspension.
it's very technical and hard to explain, but the oil in suspension moves from one chamber to another. The oil flow through a piston with holes in it. Adjusting the rate of flow affects the suspension. An inertia valve has a brass plug that blocks the hole(s) and keeps the oil from flowing into the other chamber. When the piston is activated from the bottom the brass plug moves upwards and opens the hole(s). When the suspension is activated from the top (pushing down on the handlebars on flat ground), the plug remains in place.
08-24-04, 09:53 AM
But if the rider pushed down on his handle bars and the shox locked out than that force would go to the wheel wich than would hit the ground realying the force back up the fork the opisite way. We learned that in science class last year.
08-24-04, 10:18 AM
ITs really technical. But it does realize which way is which (I can't fully explain except that it does work) however there have been complaints on the rear shock of it not working on small bumps, removing some of the sensativity of having a shock. Either that or it seem late to engage while the ball bearing moves out of the way.
I just bought a manitou SPV Evolve (3 or 4th generation SPV from manitou) and am anxious to test it out. Some complaints in 04 about a stiction feeling but it will be neat to see if they fixed it with an spv revamp.
I have an F80x on my XC ride and its like butter. No bob uphill or on braking (esp. not on braking), but at $775 its pretty pricey. Stiff as heck and very tunable.
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