Whats the rule of thumb for suspension travel, i.e. front / rear balance. does it have to be even 100mm front 100mm back can you have 130mm front 100mm rear or 100 front 130mm rear and how would this effect the bikes handling or geometry? I,m looking for a new frame but i like my marathons forks there 100m travel and the frames I like the look of seem to have more travel on them. Bloody bikes why aint nufink straight forward!!!?

Most manufacturers will tell you what the recommended fork length is, theres normally a range that you can use.

Putting a longer for on the front will make climbing more difficult, as the front will want to lift and wander around, but descending will be easier as you'll have more travel and a slacker head angle.

100rear/130front you can get away with, but i'm not sure how well it would work the other way round.

If you've got a specific frame in mind then look up the spec, ask in the shop, or here :)

hth