[savo]

Just investigating...
would it be possible to fit a Lefty with its genuine steerer on a 49mm inner diameter head tube? HT length is 110mm.

I know I can buy a tapered steerer converter for the Lefty, but it's not what I'm asking.

Custom made cups would do the work, if there's nothing on the market.

 

[z1ppy]

The lefty steerer has a 40mm OD, so assuming you could get cups made up that fit into your headtube and then find a bearing that fit into them & have an ID of 40mm why not..
[edit] Just checked a C'dale headset bearing and they have an OD of 50mm, so you going to be hard pushed to get a cup inside and an internal/integral bearing setup IMO.
..oh and the 110mm length is fine, as you need a minimum 137mm (gap between std left clamps), though again depending on whether you can the custom headset made with internal (integral) bearings, rather than an external (traditional) setup.

 

[savo]

Thak you z1ppy for replying,

going the custom cup way I'd use Cannondale's bearings on external cups made to the same c'dale stack height of course.

I was hoping to find something on the market but looks like there's no way.

 

[z1ppy]

I can't say I'm any type of expert on these things, but hows about a Hope EC49/40 lower headset, with a stack height of 14mm (Cup F) and get a custom upper headset made up with a stack height of 10 (same as std cup) , leaving the extra 3mm for the standard lefty headset seal

Hang on...

Actually measuring a set of c'dale Headset cups, they are seemingly 49mm (I'd suggest you confirm this), so maybe you can just use the STD ones (though they may need turning down to the fit the internal thoat length (c'dale cups are 9mm), the lefty headset seal and have some spacers made up..

137mm gap between lefty clamps
110mm Headtube on your bike
137 -110 = 27mm
10(x2) Stack of the the C'dale headset
127 - 20 = 7mm
C'dale headset seal = 3mm (aprox)
7 - 3 = 4mm of gap to fill

Hang on again

Or just use the Hope EC49/40 lower headset (14mm), a C'dale top headset (10mm) & the C'dale Lefty headset seal (3mm)

... you might notice I've just been working this though in my head as I typed... I might of course be talking complete rubbish...