Josh DB

Jul 1, 2017
Right, this is my first time on here so if something's wrong just correct me ... I've just purchased a second hand dh bike (a giant reign x0 2009 if I'm correct) and it had an upgraded rear shock on it and it happens to be the fox DHX rc4 spring ... now, I'm 200lbs there or there abouts and I can't seem to find the measurements I need for the spring calculators on the web etc .. I've seen a few threads talk about me needing to buy a 2.8" spring and some 3.24" .... my current spring is 450x2.37 and I am hesitant to buy this size spring again as it only goes about 3/5 of the way up the shock ... I want something to cover most of it .... could anyone pleaseeeee help me to decide what I need ... if possible I just want a straight answer ... I'm guessing a 550x3.25 would be ok and I can find them online .... I can't really find stroke length etc either so anyone with any help would be a a massive help !!! Not necessarily urgent as I'm not buying one right now and I'm OK ATM .....


RM Chief Ornithologist
Mar 14, 2005
The spring does not need to cover the whole shock, and the one currently on it sounds like the correct original factory-fit spring.

If you need a firmer rate to suit your body weight, then you just need to increase the 450 to a higher number (eg. 550 or 650) while keeping the x2.37 (which indicates the stroke of the spring) in the range of x2.25 to x2.50.

It's best if you buy a Fox branded spring, but if not, make sure the ID is 1.38" minimum and 1.43" maximum.