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Old 07-26-05, 07:12 AM   #1
slowpedal53
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Question on Measuring Stack Height

I'm working with a threadless (MTB) headset for the first time and, before I buy a fork, want to make sure I'm measuring it correctly. It's an Aheadset, marked "Manufactured by FPD for CANE CREEK."

Using a caliper, I measured the bottom half from the bottom of the crown race to the top of the rounded part of the frame cup, right where the head tube makes contact. This measured 12 mm.

On the top, I measured from the bottom of the rounded part of the frame cup (again where the head tube makes contact) to the top of the bearing retainer. I did NOT include the cap or the lock ring directly under it. This also measured 12 mm.

So, I arrive at a stack height of 24 mm. I wanted to check this because it seems small compared to most headset measurements I see discussed here. Also, I have a frame with a huge headtube (7 1/4") and I won't have much leeway in finding the right length steerer.

So, did I miss anything or am I OK? Thanks.
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Old 07-26-05, 07:35 AM   #2
sydney
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Originally Posted by slowpedal53
I'm working with a threadless (MTB) headset for the first time and, before I buy a fork, want to make sure I'm measuring it correctly. It's an Aheadset, marked "Manufactured by FPD for CANE CREEK."

Using a caliper, I measured the bottom half from the bottom of the crown race to the top of the rounded part of the frame cup, right where the head tube makes contact. This measured 12 mm.

On the top, I measured from the bottom of the rounded part of the frame cup (again where the head tube makes contact) to the top of the bearing retainer. I did NOT include the cap or the lock ring directly under it. This also measured 12 mm.

So, I arrive at a stack height of 24 mm. I wanted to check this because it seems small compared to most headset measurements I see discussed here. Also, I have a frame with a huge headtube (7 1/4") and I won't have much leeway in finding the right length steerer.

So, did I miss anything or am I OK? Thanks.
I'd give myself more room,even if you measured correctly. 7.25" = 185 for the HT. Figure 30mm for the HS and another 40 for the stem and look for a steerer at least 255mm or longer. A too short steerer is money down the toilet and a PITA.
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Old 07-26-05, 07:57 AM   #3
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Originally Posted by sydney
I'd give myself more room,even if you measured correctly. 7.25" = 185 for the HT. Figure 30mm for the HS and another 40 for the stem and look for a steerer at least 255mm or longer. A too short steerer is money down the toilet and a PITA.
Thanks, sydney. That's exactly what I'm trying to avoid. Problem is that this is a cheapo project bike and it's tough to find used or otherwise inexpensive forks with steerers much longer than 10" (255 mm.) My stem is 45 mm so, using the exact stack height, I'm at 254 mm for the whole assembly, minus the 3 mm clearance mandated by the headset instructions. This cuts it extremely close on a 10" steerer so I'll do my best to find a 10 1/2"-er, which are rare but not impossible to find.
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Old 07-26-05, 08:17 AM   #4
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Originally Posted by slowpedal53
Thanks, sydney. That's exactly what I'm trying to avoid. Problem is that this is a cheapo project bike and it's tough to find used or otherwise inexpensive forks with steerers much longer than 10" (255 mm.) My stem is 45 mm so, using the exact stack height, I'm at 254 mm for the whole assembly, minus the 3 mm clearance mandated by the headset instructions. This cuts it extremely close on a 10" steerer so I'll do my best to find a 10 1/2"-er, which are rare but not impossible to find.
I always factor in the possibility of having to use a HS or stem with greater stack at some point down the road.
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