forks and angles

hi all, my brother is looking at a new bike. he has found a giant trance 2005 model for £500.
http://www.winstanleysbikes.co.uk/produ ... pring_2005
so far he will be changing the brakes, to hydrolics, probs to juicy 3s or 5s. but the forks that come with it only have 100mm travel. and he wants it for hard descents. he is only 13, and is very light, so doesn't want to splash out on an expensive bike. at the moment he has some forks that have 120mm of travel on a saracen he has. would there be any problem in just doing a straight swap as long as the steerer is the same length? would it change the geometry alot?
any ideas.
tom
http://www.winstanleysbikes.co.uk/produ ... pring_2005
so far he will be changing the brakes, to hydrolics, probs to juicy 3s or 5s. but the forks that come with it only have 100mm travel. and he wants it for hard descents. he is only 13, and is very light, so doesn't want to splash out on an expensive bike. at the moment he has some forks that have 120mm of travel on a saracen he has. would there be any problem in just doing a straight swap as long as the steerer is the same length? would it change the geometry alot?
any ideas.
tom
0
Posts
he would do better spending 650 on a decent long travel hardtail bike.
also i do not think the fork from the Saracen would be up to it
Parktools :?:SheldonBrown