I an 185ibs, when i sit on the bike it does not compress at all.

 

I am confused. in every post you say you compress the shock, so the shock obviously moves. but when you sit on the bike it does not compress?

One of us is missing something. if you push on the tail of the bike, you are putting your body weight on it to compress--the shock moves correct?
then when you sit on it, you are doing the exact same thing- the shock is moving. If it were not, it would be like trying to compress a table, its solid.

How are you measuring the sag? you are using a friend to help you measure right?

 

When my girlfriend and i sit on the bike it drops about 25mm when i alone sit on it it drops about 12mm. It is stiff and when we jump on it, it rebounds very fast and bangs at the top of the travel. Shouldn't it rebound slower like the front? I tried adjusting the compression and rebound and i feel no difference when we compress and release it - it flies up and bangs at the top as if its only the spring that is working.

 

based on that description, it does sound like something is not working correctly. just so I am clear, when you say it shoots back up and "bangs" at the top of the travel... do you really hear an audible sound? If you rebound is set too soft, the tail will rise and "bounce" at the top and settle a little, but even that is a smooth transition, very much like the front fork.

my guess is that either a) your spring height is set at the max and not allowing the shock to really come into play
(but I dont know if that would even cause the problem youre describing)
or b) you shock has a leak somewhere; there is a hose that runs from the remote rebound resoive back to the shock, possible that
is cut, or damaged?

do you have access to any other bikes? you should compare to see how far out your really is. absolute worst case is that somehow, someway, your shock isactually trashed and you pick one up off ebay for $40

 

Thanks for your time, I will purchase a spanner and release the tension of the spring. If that does not indicate something then I do need a new shock. There is no visible leaks.

 

well, let us know what you find out. If you do have a bad shock, that will be the first one I have ever heard of going bad in such a short amount of time.