Lacie123401

Hi guys,
I have a fork with 19cm carbon steerer.
I currently have a road frame with a 110mm head tube length. Chris king headset 1 1/8 nothread (31.4mm), and a zipp service SL stem with 42mm stack height.
Is this how I correctly calculate how many spacer mm space I have left after they are all installed?
IE: 190mm (fork steerer) - 110mm (head tube lenght) = 80mm
80mm - 31.6(chris king) = 48.4mm
48.4mm - 42mm = 6.4 mm?
Is this a correct calculation and if so does that mean I have only 6.4mm space left?
Thank you for your help!

Camilo

I'm assuming when you list 31.4 for the headset, you're talking about the total stack height: lower bearing cup height + upper bearing cup height. If that's the case, I believe your calculation is correct. It will work, but might require a pretty thin top /compression cover for the upper bearing, and you won't be able to put any spacers under the stem to get your bars up. If you like your bars at that height, you're good to go. But, theoretically, for most CF steer tubes, you could put as many as 30-40 mm of spacers between the upper bearing and the stem if you wanted to raise your bars to that height, so the fork you have will be pretty non-adjustable in that sense.

hueyhoolihan

looks okay to me. for reference i just bought a bike with a 145mm headtube. used a standard threadless headset from richey about 35mm stack height. had a stem with about 40mm stack height. had a compression plug with about 2mm stack height. total stack height was about 145 + 35 + 40 + 2 = 222mm? had a fork with 210 steerer. had to fashion a 10mm steerer extension from a piece of carbon steerer off another bike and use a 5mm spacer on top. perfect!

merlinextraligh

Wut!

This doesn't sound like a good idea. Of what material is the steerer made? Is your steerer extension just placed on top of the steerer tube, or is it bonded to it in some fashion?

hueyhoolihan

carbon steerer, carbon forks. the compression plug holds it all together just fine.

OTOH, in the OP's case, if he or she is concerned that the steerer is not long enough ("does that mean I have only 6.4mm space left?"), and he or she may be, what i have done would not work, IMO.

merlinextraligh

That is a really friggin bad idea.

The compression plug is designed to put the right tightness on the headset. It is not designed to hold the stem on, or to hold the steerer together.

You essentially have your stem bolted to 2 different pieces of steerer stacked together. Your stem is held to the steerer by one bolt, cantilevered out above the steerer. That's got to be putting forces on the steerer that it wasn't engineered for. Any play that develops over time is just going to magnify it.


This has the potential to end very badly.

Personally, I wouldn't risk paralysis or death, to save the hundred dollar or so cost of doing this right.

LowCel 

I'm right there with you. There is no way I would ride a bike setup like that.

LowCel 

You realize that the Chris King 1 1/8 is width and not height correct? The height should be a good deal less than that.

Camilo

Some of the 1 1/8 CK threadless headsets have a stack height of 31.4mm. 1 1/8 would be 28.6, not 31.4 anyway.

Lacie123401

From what I understood from chris king website, the stack height was 31.6mm. Is that wrong?

LowCel 

That is a hell of a stack height, guess I have been away from non-integrated headsets for too long.

LowCel 

I have no idea, ignore my previous post. According to Camillo I was incorrect. It happens.

Camilo

No, you're not wrong. Look at "nothreadsets" on this page https://chrisking.com/specs/headsets_all. It's 31.4 total stack height for a 1 1/8 inch threadless headset.

Just as a big FWIW: this is an important thing to consider when comparing two frames - the stack height of the headset. Two frames with the same length threadless head tube will have very different handlebar height ranges depending on whether they have an integrated or internal (zero stack) head tube vs. a conventional external cup threadless headset.

Campag4life

OP...with your stack, you will likely end up with a spacer a bit taller than 6.4mm. Your calculation is correct...but the steerer shouldn't be placed line to line with the top of your stem...rather about 3mm or so sub flush. This allows for compression tightening of the headset.
You could be able to run a single 10mm spacer OK...or a 5mm spacer under the stem and 5mm spacer over the stem if you want to run a bit more slammed.
I hope you know that working backward like you are is a bit ill advised. Best to start with an uncut steerer. Theoretical stacks also can have a hint of error in them. Most for a bike build...I will generally cut the steerer to about a 30-40mm spacer stack under the stem...then later remove the fork and cut again after I have adjusted my riding position...and regrease the headset then at the first maintenance. Also keep in mind that stems can vary a bit in stack height.
Have fun.