There seems to be quite a difference in headtube length between some of the hardtails I’ve been looking at buying. Some of them seem really low. Like 100mm coupled with flatish bars seems mad.

I like my bars quite high. My current bike has 120mm head tube with internal bottom headset cup, 20mm of spacers, 50mm hope am high rise stem and joystick 38mm rise bars. I’m 6’2 and this feels good to me.

I don’t think I could get my bars high enough on the Chameleon without 40mm of spacers which i’m sure would look daft. But i could easily manage on a 19inch Slackline at 140mm.

New SC Chameleon 100mm and internal headset bottom cup.

Cotic Solaris max 110mm with an external lower headset up.

New Stanton Slackline 140mm and an external bottom headset cup which adds another 10mm at least.

Any thoughts?

You can add height with spacers, bars, stems, headsets etc. You can’t take away much height. So shorter is just better. Yes adding height can look a little silly depending on how you do it but that’s better than people not being able to get the height they want at all

I don’t think head tube length on its own is all that useful – a better dimension is stack height. You can add a lot of height with 40mm riser bars and some spacers but the only way to lose height is with an inverted stem and that can’t deduct much.

Also any angleset adds stack height, through an external lower cup, an external upper cup, or both. I agree that XL bikes shouldn’t have very short head tubes unless they’re paired with long travel 29er forks but generally shorter allows better fit.