For most moutain bikes from XC race bikes through to DH race bikes (not including dirtjump, street, fourcross, dualslalom, slopestyle etc .. ) there would seem to be a bit of a correlation between stem length and head angle, something that would seem to be usable as a guide toward working out what stem length ought to work with your bike setup
So typically
The shortest stem length available is 40mm* and the longest about 120mm**
The slackest head angles seem to be around 64deg (203mm forked DH race bikes), the steepest head angles seem to be around 72deg (80mm forked XC race bikes)
Okay, so I realise it would seem to be a bit too much of a likely coincidence for it to fit 'so' well and even if it did as a general rule, there would of course be exceptions such as a rider nearing the extremes of height/torso length/etc and wanting to (temporarily?) 'beef' up your bike a bit perhaps for a holiday on the skilifts, or make a bit racier and lengthy perhaps for a bit of XC racing
*I've come across a 35mm before
**I know some are longer, but manufacters don't seem to be including them in there ranges any more (for MTBing)
Some examples in full (probably not 100% correct on the egs):
(assuming the use of stems around say 5-7degrees rise)
72deg ~ 120mm (eg Giant Anthem (80mm forks)
71deg ~ 110mm (eg Giant Anthem (100mm)
70deg ~ 100mm (eg Specialized Epic (100mm), Turner Flux (100mm)
69deg ~ 90mm (eg Ibis Mojo (140mm), Orange P7 (140mm)
68deg ~ 80mm (eg Yeti 575 (140mm), Gary Fisher Roscoe (140mm)
67deg ~ 70mm (eg Orange 5 (140mm), Spesh' Pitch (140mm)
66deg ~ 60mm (eg Orange Blood (160mm)
65deg ~ 50mm
64deg ~ 64mm (eg Orange 224, Specialized Demo)
Right, so tell me why/how this theory falls flat on its face
