Stack height and external headsets
 

Had posted this in the road forum but realized that I'd probably get a faster answer here.

I am trying to figure out the relative HT sizes of a bike with an integrated headset vs that with an external headset.

The latter bike has a 150mm HT - now, if I add a Chris King 1 1/8" AHeadset with a claimed total stack height of 31.4mm, would that result in a setup that is roughtly equivalent to a 181.4mm HT on a bike with integrated headsets (assuming all else is equal)?

Seems to, but I just want to double-check, to make sure I am not missing anything.

Thanks.

Integrated type headset has zero stack height on the bottom,
and in the case of my cane creek one, just a squat ring above the top bearing.
Because the head tube is machined to hold the bearings within it's length..
[AFAIK] Chris King doesn't make an integrated headset,
they machine the aluminum (etc) bearing cups to press onto the frame.. externally .


so your fork's steerer tube is cut too short?

Well no; even integrated headset will have some stack height between HT and Stem. Your 31.4 height is total of headset cups top and bottom plus you are gonna have some sort of seal on top, spacers and top cap that add to headset stack height. Beyond headset stack height you also have the width of stem clamp to get you total stack height. Integrated headsets eliminate the width of headset cups, but you still have spacers and width of stem clamp to consider with regard to stack height in order to determine the length of steerer that will work with any specific headtube.

Thanks for the answer. I am trying to figure out the differences caused by adding headset cups in order to figure out the sizing for a new frame. How much do you reckon is added by this - 20mm (top seal is 10mm, and each cup adds 10mm?).

Reason I ask is this - am planning on buying a new frameset (a Lynskey Sportive) and trying to match it to my current road bike (a Ridley Damocles). Looking at the geo, both the ML and the L can be set up fit me. Depending on how much stack height is added by external vs integrated HT (if atleast 30mm), I will decide upon the size.

Thanks!

The head tube length shouldn't really be on the list of considerations when choosing a frame size... pick the one with the best top tube length.

Using the seat tube length to size frames has always seemed a bit silly to me... effective horizontal top tube length should be the measure. Your seat's height is... you know, adjustable.

And you can put your bars wherever you like via an appropriately shaped stem, so the head tube length should only matter if you're shopping for a new fork.

Well, for most people, head tube length isnt a problem. I have a very short torso and very long legs, and so I need a taller-than-normal headtube and a fair number of spacers in order to get even an aggressive fit. My Ridley has a 175mm top tube and even with 20mm spacers and a non-flipped stem, I still have about 5.5" of saddle to handlebar drop.

As I want to set this bike up in a slightly less aggressive geometry, head tube size is a very valid consideration for me, unless I want to have something like 50 or 60mm of spacers or a full-erection stem (either of which I prefer to avoid, if I can).

So, back to my question :)

I am not getting the focus on headtube and stack height unless you are trying to figure out of your current steerer is long enough for the new frame. Stack height really isnt relevant to fit. I am not familiar with Lynsky geo, but on most frames, HT increases as frame size -- usually measured by ST -- increases. For example, my 58cm Cannondale has 17.5cm HT; a 60cm C'dale has 19cm HT. So I went with the frame that had best TT length for me and took the HT that came with. I agree that a smaller HT with lots of spacers looks kind of odd, however, and based on your proportions, I imagine its kind of hard to find an off the shelf frame that fits well (my height is evenly split between leg and torso so the even proportions of my Cdale -- 58cm ST and 58.5cm TT -- fit me well). With your proportions, it seems to me you need a larger frame vertically speaking with a relatively short horizontal reach, which is not the norm. That would give you less drop without needing a really long steerer and lots of spacers . So if you can make the larger frame work reach wise by going with a relatively short stem with some rise, thats the way I would go. That said, your best bet would be to get a professional to do a bike fit for you. Then you would be better able to dial everything in.

Well, I do know what dimensions I need (I've had my Ridley fitted professionally) and given my proportions, I need a short ETT and a tall stem. With most bikes, if I get the ETT right, the HT is too low and requires a stack of spacers; if I get the HT right, the ETT is too long and requires a short stem.

With the larger frame, I will need an 80mm stem in order to get the bike to fit. That is a bit too short for my liking - I would like a longer stem (I find it helps me with leverage when I am climbing or off the saddle).

And given that I spend a significant portion of the year on a small island and it takes 2 days of travel (by boat and then a flight) to reach civilization, trying out various Lynskey models is not an option. Sadly, my current bike has an integrated headset, so I cant even measure the stack height.

So I would like to try to figure out if I can indeed get the smaller frame to work - which requires getting a rough idea of how much stack height the headset caps add to the HT.

Thanks!

Forget the present (integrated HS bike) and simply measure the headtube of the new frame, and add the headest stack height as per the CK specifications. Add enough for your stem and spacers and compare to your existing fork.

The dimensions of the integrated headset are irrelevant to your situation because you can't transfer it anyway except (maybe) for the crown race.

Size is the seat tube length,
Except as a full custom frame, head tube length is not a separate choice..

sloping top tubes read short, at the seat tube,
I'd go by top tube length then, virtual, as if horizontal

Have the fork steerer left really long and you can put the bars high enough

steel steerers accept this, ... Carbon forks , Maybe a problem..

So, since you prefer a longer stem for performance reasons, it seems like you are kind of stuck with a relatively short HT and a bunch of spacers.

Headset cups vary a bit from headset to headset. But ball park for total height of the top and bottom cups (not counting seals, caps and spacers) figure a bit over 1.5cm on the low end to a bit over 2cm on the high end. For example, the combined height of the top and bottom cups of my Cane Creek S8 headset is about 2cm (bottom is hair over 1cm while top is a hair under); while the aheadset cups on another bike come in at about 8mms each. So if you went with 15cm HT you mentiond (Lynsky Sportive ML?) and used my Cane Creek S8 headset, your total headtube with only cups pressed into the headtube, but before assembling of the rest of the headset, would be about 17cm.

^^ Thanks for that, DOS. That is exactly the info I need to make an informed decision. Appreciate your advice and help.

Cheers,
V.