[jacksonpt]

Can someone explain to me how braking affects the action of rear suspension on most mid grade bikes? I was reading a review on the new Ellsworth Distance (Mark - have you seen this bike... sounds right up your alley), and they commented on how the rear end firms up under breaking. It occured to me that I've read that about lots of bikes, but I have no idea why/how it happens.

So, some education please???

 

[jdcamb]

It is called brake jack. Most single pivot bikes are effected by it. Basically the brakes cancel out the suspension or in some cases (depending on pivot placement) compresses the suspension. Most folks get used to it and it is not a issue. Some D/H bikes use a floating brake to counter this......jdcamb

 

[jacksonpt]

yea... I kind of inferred that much from what I've read. But why/how does it happen. Seems to me that if your weight is centered or over the back, the suspension should work regardless of brakes - I don't see how using the rear brake should have any affect on suspension.

 

[Westy]

Check the DH forum, there seemingling endless discussions on the topic. But my opinion is that weight transfer from braking (brake dive) drowns out any affects that "brake jacking" has, unless maybe your talking about a very long travel rear suspension.

 

[stosh]

GTFO


Hey how's that stuff with your contractor going?

 

[Skookum]

Yah it usually only happens when you're screamin on a downhill section and you slam on the brakes when you're carrying too much speed for some reason. Most of the time if you slow down properly to a corner or downhill rock garden or whatever and lay off the brakes it won't be that noticable, but if you're racing, you're taking risks that put you in that situation all the time.
It basically feels like the rear suspension just dies... and it usually happens to me on a hard tight downhill swithback, or just a chute where i'm carrying way too much speed and there's a corner at the bottom or whatever. To combat this i'll lean back, use more front, and ease off the back brake.
Even my Enduro get's it, but it's less apt to. i don't take it too crazy of trails and the suspension isn't prone to it, but my Bullit succumbs on just about every ride i do with it to some degree.

 

[Skookum]

yea... I kind of inferred that much from what I've read. But why/how does it happen. Seems to me that if your weight is centered or over the back, the suspension should work regardless of brakes - I don't see how using the rear brake should have any affect on suspension.

oh oops...
hmm well, i thought that's why bikes are so expensive, to let knuckleheads in the development room figure that out.

 

[MMcG]

Can someone explain to me how braking affects the action of rear suspension on most mid grade bikes? I was reading a review on the new Ellsworth Distance (Mark - have you seen this bike... sounds right up your alley),

Isn't it essential a derivation of the Ellsworth Joker - and besides - I know a lot of people like their Ellsworths, but from what I've read on various forum I wouldn't touch an Ellsworth with a ten foot pole. I may be overstating things a bit, but I just would never feel comfortable owning a bike like that from a company that seems to have done some shady things over the years.

 

[jacksonpt]

Isn't it essential a derivation of the Ellsworth Joker - and besides - I know a lot of people like their Ellsworths, but from what I've read on various forum I wouldn't touch an Ellsworth with a ten foot pole. I may be overstating things a bit, but I just would never feel comfortable owning a bike like that from a company that seems to have done some shady things over the years.

It's their single pivot trail bike... similar design as the Joker, just in trail bike form, and waaaay cheaper than any of the other ellsworth bikes I've looked at. I've heard that Ellsworth has an iffy repuation for standing behind their bikes, but I'd never heard them called shady before. Though, the price of most of their frames put them out of my reach, so I've never spent a whole lot of time thinking about the company.

 

[BurlyShirley]

Hey Jackson,

Its like this. Go sit on your FS bike and bounce up and down. Notice that when you do that, the rear wheel is moving back and forth. Then bounce up and down with your rear brake on, and notice how the suspension doesnt really move if your rear wheel wont move. Do it on carpet for full effect.
Unless you have a FS design that cancels out brake jack somehow, then forget what i just said.

 

[Echo]

Basically you can think of it like this. The brake caliper is hard mounted to the rear triangle forward and above the brake rotor. On a single pivot bike, when the wheel is rotating, grabbing the brake rotor in that position pulls the rear axle away from the shock. The braking force of disc brakes is stronger than the weight compressing the suspension from above, so therefore the suspension does not move.

 

[Skookum]

Basically you can think of it like this. The brake caliper is hard mounted to the rear triangle forward and above the brake rotor. On a single pivot bike, when the wheel is rotating, grabbing the brake rotor in that position pulls the rear axle away from the shock. The braking force of disc brakes is stronger than the weight compressing the suspension from above, so therefore the suspension does not move.

that makes sense, i'll buy that for a dollar.

 

[JRogers]

Hey Jackson,

Its like this. Go sit on your FS bike and bounce up and down. Notice that when you do that, the rear wheel is moving back and forth. Then bounce up and down with your rear brake on, and notice how the suspension doesnt really move if your rear wheel wont move. Do it on carpet for full effect.
Unless you have a FS design that cancels out brake jack somehow, then forget what i just said.

Or, fiind the steepest section of trail you can that has square edged hits on it (think curbs), grab a handful of brake and go straight down. Aren't your wrists sore now?