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So I have an issue now that my head angle is far too steep. But I'm trying to be scientific rather than just buying new forks which are bigger.
I've put a longer shock on my Stumpjumper 120, an increase of 10mm shock length and 3mm stroke.
A 47mm stroke shock gives 120mm travel, so an extra 10mm of shock length pushes the rear wheel down by around 25mm, as well as an increase in BB height and steeper head angle. To counteract this I would like longer forks which will give a known output.
I'm currently using 2009 Revelations (130mm). I believe these have an axle-crown of 509mm. Using sketchup and some photo's, it appears I'm running a head angle of 72 degrees.
I'm working on an output of 68 degree head angle, to produce this I need to move the headtube upwards around 73mm, ready reckoning of 0.5 degrees per 10mm gives me a near-as-dammit confidence check on that too.
Any arguments against my theory? If not, I just need to find a nice bargain fork (probably 160mm)!
You will end up with a bike on stilts,high bb'ed,slack seat angled behemoth (if the headtube does'nt get ripped off first).
i think you are over thinking it. go for a ride...
yeah, change your frame, I think
160mm forks on a 120mm frame?
Are you serious?
A frame change is in the workings, but pennies are limited!
Stock setup of the bike is 70.5, so I only need to find a couple of degrees from the look of it....
I have a nice 165mm travel frame for sale. Cheap. This would be a much more sensible approach!
slackset headset?
or offset shock bush?
Would have been better off with original shock,offset bushes and a works components -1 angleset.
Pennies may be limited, but you can't buy braincells~ please try and use the ones you have left and realise this is not the greatest idea~ surely if you can accept that a dodgy head angle will affect your riding, you can also grasp that a BB height requiring a ladder to mount the bike might not do you any favours, combine that with the additional leverage on the headtube and you're well on your way to a Darwin award... nonetheless, please post pics when you prove us all wrong and have a wealth of happy customers for your aftermarket upgrade kit.
why are you doing this?
Cheap fix to fubared original shock?
Seriously, give it up, your BB will be too high, and that's only the start.
Offset shock busings would get you part the way there with the standard shock. Whack in a 140mm fork and you'd be close to the desired head angle. And it has a chance of still being nice to ride.