Cannondale Headshok - damping slow? broken lockout?

[Julian]

I have a Cannondale Headshok Ultra Fatty on a 2000 Jekyll.

On a ride yesterday it started making a loud "THUNK" when coming off a
log, or rock. It's like the rebound damping is super-slow and not
letting the fork return quickly enough. When it does pop back out, I
hear the "thunk" as the fork tops out. At least, that's what I _think_
is going on in there.

I also noticed that the lockout doesn't, anymore. And if I turn the
lockout "on" then the damping is even slower, with an even louder
thunk.

Any thoughts on what might be causing this?

It's going to the shop in a couple of hours, but I'd like to get 2nd,
3rd, etc. opinions.

Thanks all for your help.

[S. Anderson]

"Julian" > wrote in message
...
> I have a Cannondale Headshok Ultra Fatty on a 2000 Jekyll.
>
> On a ride yesterday it started making a loud "THUNK" when coming off a
> log, or rock. It's like the rebound damping is super-slow and not
> letting the fork return quickly enough. When it does pop back out, I
> hear the "thunk" as the fork tops out. At least, that's what I _think_
> is going on in there.
>
> I also noticed that the lockout doesn't, anymore. And if I turn the
> lockout "on" then the damping is even slower, with an even louder
> thunk.
>
> Any thoughts on what might be causing this?
>
> It's going to the shop in a couple of hours, but I'd like to get 2nd,
> 3rd, etc. opinions.
>
> Thanks all for your help.

I'm not an expert on Headshoks, but it's possible your damping
cartridge/fluid/valve/whatever is shot. With no rebound or compression
damping, it could top out very easily and make a clunk when it hits full
extension. Same thing on compression..you might bottom it out because you
no long have compression damping. Bottoming out isn't solely a function of
compression damping, it's actually controlled mostly by the spring. But you
might not have noticed before because the compression damping was slowing
things down enough to not let the spring bottom. Easy test: if you stand
beside the bike and push down on the forks, they should not immediately
bounce back up like a pogo stick. There should be SOME delay..if you don't
have any, and if your rebound adjuster makes no difference in how fast the
forks come back up, your rebound mechanism is toast in some way.

Cheers,

Scott..

[Charles Beristain]

Julian;
"thunking" - more than one potential cause for "topping out" or
"thunking".

1) bearing migration .. cannondale has a tool that measures migration
and brings them back into spec.. easy to use/quick

2) spring in the air piston has worn bushings/torn o-rings. .. easy to
inspect once the cartridge has been removed.

3) the cartridge itself... many different things.. leaking around
o-ring seals, cracked shim, inadequate oil charge, etc.

If your shop has lots of experience with headshoks.. it will be
easy/quick to fix.

the fact that your lockout no longer works indicates to me the problem
is with the cartridge itself.

I'd be interested in knowing what the fix was.

charlieb

On Wed, 09 Jul 2003 14:41:41 GMT, Julian >
wrote:

>I have a Cannondale Headshok Ultra Fatty on a 2000 Jekyll.
>
>On a ride yesterday it started making a loud "THUNK" when coming off a
>log, or rock. It's like the rebound damping is super-slow and not
>letting the fork return quickly enough. When it does pop back out, I
>hear the "thunk" as the fork tops out. At least, that's what I _think_
>is going on in there.
>
>I also noticed that the lockout doesn't, anymore. And if I turn the
>lockout "on" then the damping is even slower, with an even louder
>thunk.
>
>Any thoughts on what might be causing this?
>
>It's going to the shop in a couple of hours, but I'd like to get 2nd,
>3rd, etc. opinions.
>
>Thanks all for your help.