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jefnvk 03-06-17 09:32 AM

Measuring Threaded Stack Height
 
Sorry if this has been answered before, I can't seem to find an answer searching.

I am rebuilding an old bike. The headset is indexed and needs replaced, but I am not sure how to determine the proper stack height. What exactly do I need to measure to figure out what the old one is? I know it is a 1", just need to figure the height.

SquidPuppet 03-06-17 09:37 AM

Two halves. Top and bottom.

The bottom measurement is from the bottom of the crown race to where the lower cup meets the head tube.

The top measurement is from where the upper cup meets the head tube to the top of the lock nut.

Add them together for total stack height.

jefnvk 03-06-17 09:43 AM

Awesome, thanks!

JohnDThompson 03-06-17 09:46 AM

Stack height = measurement A plus measurement B:

http://www.os2.dhs.org/~john/stack-height.jpg

Note that you can replace your headset with one of shorter stack height and just use spacers to take up the extra space. But you can't replace your headset with a taller headset than what you currently have.

If you have removed the headset cups and crown race from the frame and fork, you can measure the length of the frame head tube and the length of the fork steer tube from the race seat to the top. The difference between these two measurements is the maximum stack height your frame can accept.

jefnvk 03-06-17 09:53 AM


Originally Posted by JohnDThompson (Post 19421996)
If you have removed the headset cups and crown race from the frame and fork, you can measure the length of the frame head tube and the length of the fork steer tube from the race seat to the top. The difference between these two measurements is the maximum stack height your frame can accept.

Also good to know, because it is currently in pieces :)

coupster 03-06-17 10:31 AM

The above answers to your question are correct. But it would be better to fit the replacement headset to the bike than try to accurately measure the old headset.

First, measure the actual head tube of the bike. If the headset is currently out of the bike, great. If not don't take it into account. You want the measurement of the frame of the bike. Second, measure the length of the steerer tube of the fork. From the bottom of the crown race - if its still on the bike - or the top of the fork crown - if not - to the top of the threaded steerer tube. Subtract the head tube measurement from the steerer tube measurement. That is the maximum headset stack height you can use with that bike and fork combination. If you have any required spacers; brake hangers, accessory brackets, etc, measure their thicknesses and subtract them from your previous total. Any headset with a published stack height of <= to your measurement will work. If its less you can make up the difference with some spacers or cut the steerer tube. (I'd go for spacers) If its more you will need new fork.

Moe Zhoost 03-06-17 11:04 AM

Coupster's method is spot on. I've found that it is a bit easier to insert the fork into the head tube with the race seat touching the bottom. Then all you have to do is measure the length of the steerer tube protruding from the top. You want a bit of room between the steerer tube head and the lock nut so subtract about 2 mm and you are in business. As others have said, you can always add spacers if your stack height is a bit low.

jefnvk 03-06-17 11:42 AM

Are these spacers something that are generic and purchased separately from a headset, or would they be included? Most of what I am seeing when I do a search are marked for threadless.

bradtx 03-06-17 12:38 PM


Originally Posted by jefnvk (Post 19422307)
Are these spacers something that are generic and purchased separately from a headset, or would they be included? Most of what I am seeing when I do a search are marked for threadless.

In all of the headsets I've bought, none had any additional spacers. Just the keyed washer. Nashbar had some nice CF 1" spacers if you want something a little different.

Brad

fietsbob 03-06-17 12:49 PM

Often the Keyed washer is forced to turn by the lock nut turning, , Digging into the fork steerer thread,
(I have used an aluminum <c> 'super record' spacer, the thread scored the tab instead)

Adding a non keyed spacer is fine, [Maybe better as it will spin rather than the keyed one] It just has to be close to 1" inside diameter..

I have used steel tubing, as spacers... and even used the Shop fork threading die to cut more thread..








...

dedhed 03-06-17 05:59 PM

Any co-op or LBS will have spacers often for free or nominal $. Just make sure to get 1"


I've found on old bikes the biggest problem is finding a short enough stack height headset. Tange Levins always seem to end up being what I use.

jefnvk 03-06-17 09:33 PM

OK, thanks for the assistance. From what I measure, my steerer tube is 144mm from bottom of crown race to top, my frame head tube is 104mm, so that gives me 40mm. The brake cable mount and spacer that was on the old one come out to 5mm, the Tange headset calls out a height of 30.8mm, so if I add 4mm of spacer to that headset, I should be right in the ballpark, correct?

JohnDThompson 03-07-17 07:16 AM


Originally Posted by jefnvk (Post 19423662)
OK, thanks for the assistance. From what I measure, my steerer tube is 144mm from bottom of crown race to top, my frame head tube is 104mm, so that gives me 40mm. The brake cable mount and spacer that was on the old one come out to 5mm, the Tange headset calls out a height of 30.8mm, so if I add 4mm of spacer to that headset, I should be right in the ballpark, correct?

Yes, that would work. Or, you could use a taller headset. 40mm gives you a lot of options.

jefnvk 03-07-17 08:21 AM


Originally Posted by JohnDThompson (Post 19424162)
Yes, that would work. Or, you could use a taller headset. 40mm gives you a lot of options.

I'm not looking to drop tons of money on this, all I've found in the <$30 range is the Tange at 30.8, and the Velo Orange at 41. Thought about the VO, but once I add that brake line bracket back in that is up to ~43, and I am assuming 3mm is a bit too much extra height.

wschruba 03-07-17 09:44 AM

I don't really have anything to add, other than the Tange Levin is a solid, dependable headset, for relatively cheap. One of the few headsets still made that is "right" with an inverted top cup that sheds water over the bearing, rather than relying on sealing. Over pack the bottom, and spin the fork a few times, wiping off any excess grease that comes out, especially if you aren't running fenders.

Just make sure you buy the right one (measure your bike) as they make it in ISO and JIS sizing.

By the way, if a headset is close to fitting, but needs a bit more room, the included spacer can be substituted with a paper thin shim, or removed entirely. The top nut can also be swapped (or modified) for one with no lip on it, to allow it to be turned down the steer tube, regardless of the length. You may be able to find some old parts, which sometimes substituted a low-profile lockring for a top nut, if you are coming up short on threads...useful especially since a nut's threads don't actually start for a short distance from the end of the nut.


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