Frame is designed to run 120mm forks with integral headset in 44mm headtube. This gives 69.5 ha. If I want to run tapered forks it will need an external bottom cup giving an extra 15mm of stack height.

Am I right in thinking this would now work best with a 100mm fork as the extra stack height will already increase effective fork length and slacken ha?

Anyone?

Assuming that the axle to crown length is also reduced by 20mm (some don’t) then yes you should have roughly the same head angle. Keeping the 120 travel and an external bottom cup will slacken the head angle by about 1/2 a degree.

ta

17mm = 1 degree, so closer to 1 degree.

So to keep with original geo I’d be better off with 100mm?

I guess (caveated by toppers comments re A-C) but I’d try it before buying new forks

You also gotta tell wot you bought Clink 😉

I’ve bought a Voodoo Bizango 29er frame only to run ss. Geo is spot on for what I want and it was cheap 🙂

What? Cheap? Didn’t Halfords at least do it in Titanium? 😉

Cheap and the geo I want with sliding drops for ss.

Looks very like my Voodoo bokor. Spot on with 100mm sids and an external bottom cup.

The sliding dropouts are brilliant, had SS bikes for years and by far the best solution I’ve used.

To be ott accurate, 21mm is 1 degree using parametrics and that range of forks, HA, wheelbase etc. 20mm is the general rule. 17mm, near enough anyway )
120mm fork will sag more %-wise than a 100mm, so taking that into acc and if the lower cup really is 15mm more than the internal, it’ll be about right on the ride height angles. Close enough.

Hmmm.

I calculated it at 17mm using trig and everything. I have no idea what parametrics means though 😛 so you may know more than me.

Getting too technical for me! 🙂

So you reckon the extra stack height and 100mm will be ok?

Another new frame….

Al, not necessarily knowing more, just how to use certain tools to get answers )

depends on what sag you like running 20% 30%…….?

Just to update this thread riding with 100mm and seems fine. I also e-mailed Voodoo for help and the man himself (Joe Murray) replied!