Stack height on CF steerer?
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Stack height on CF steerer?
I was given a bike temporarily (which could turn into permanently), and the owner gave me the green light to make adjustments so it'll fit me. It's a really nice Ti Merlin with CF seatstays and a CF fork from the early 2000's. I changed the stem out and lowered it (borrowed a torque wrench from the LBS and set it at 6Nm), but the steerer is really long, so I had to put a lot of spacers on top. There's 35mm of spacers above the stem and 15mm of spacers below it. CF scares me, so I wanna know if how it's set up is safe. If I end up keeping it, I'll definitely cut the steerer.
Here are some pictures:
A picture of the steerer/stem area:
Pictures of the top cap/bolt:
A picture of the inside of the steerer:
Note there's some sort of expansion plug inside there. The top of the expansion plug is above where the stem is clamped.
Here are some pictures:
A picture of the steerer/stem area:
Pictures of the top cap/bolt:
A picture of the inside of the steerer:
Note there's some sort of expansion plug inside there. The top of the expansion plug is above where the stem is clamped.
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The expansion plug should be centered on the stem. The stem clamp bolts only need to be tight enough for the stem to stay put under hard steering imputes. Did you apply any carbon paste? Don't worry about the spacers above the stem, they're along for the ride and to proving compression transfer. In fact once the stem is set (and the headset adjustment is done) the top cap and above spacers could be removed without concers.
#3
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The setup should be fine, just don't go nuts tightening the stem clamp bolts. 5Nm is plenty.
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Anything above the stem doesn't count except for the risk of getting impaled in a crash. I prefer to keep the stack below the stem at 20-25mm max, and you're well within that. I've seen people with 40-50mm under the stem, and haven't heart (1st hand) of any failures, but of course it depends on how you ride. If you tend to work the bars hard when climbing or sprinting, or ride on lots of Pave, then I suggest you keep the stack short just in case.
BTW- there's no need to ever cut the fork, but cosmetics, or wanting to avoid being impaled may have you cutting it down after you've found your preferred stem height and ridden with a while to confirm.
BTW- there's no need to ever cut the fork, but cosmetics, or wanting to avoid being impaled may have you cutting it down after you've found your preferred stem height and ridden with a while to confirm.
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The expansion plug should be centered on the stem. The stem clamp bolts only need to be tight enough for the stem to stay put under hard steering imputes. Did you apply any carbon paste? Don't worry about the spacers above the stem, they're along for the ride and to proving compression transfer. In fact once the stem is set (and the headset adjustment is done) the top cap and above spacers could be removed without concers.
Anything above the stem doesn't count except for the risk of getting impaled in a crash. I prefer to keep the stack below the stem at 20-25mm max, and you're well within that. I've seen people with 40-50mm under the stem, and haven't heart (1st hand) of any failures, but of course it depends on how you ride. If you tend to work the bars hard when climbing or sprinting, or ride on lots of Pave, then I suggest you keep the stack short just in case.
BTW- there's no need to ever cut the fork, but cosmetics, or wanting to avoid being impaled may have you cutting it down after you've found your preferred stem height and ridden with a while to confirm.
BTW- there's no need to ever cut the fork, but cosmetics, or wanting to avoid being impaled may have you cutting it down after you've found your preferred stem height and ridden with a while to confirm.
How long are expansion plugs usually? I want to know if there is enough of the plug supporting the stem clamp.
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For 1" carbon steerers the usual recommended maximum spacer stack under the stem is about 25 mm. For a 1-1/8" carbon steerer, the most common maximum spacer recommendation is 40 mm but Easton permits 50 mm. You are well within these limits. As noted, what's above the stem is meaningless from a structural standpoint. It just looks odd if it's tall.
The expansion plug isn't needed to support the stem, it just acts as a anchor for the adjusting bolt in most cases.
The expansion plug isn't needed to support the stem, it just acts as a anchor for the adjusting bolt in most cases.
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For 1" carbon steerers the usual recommended maximum spacer stack under the stem is about 25 mm. For a 1-1/8" carbon steerer, the most common maximum spacer recommendation is 40 mm but Easton permits 50 mm. You are well within these limits. As noted, what's above the stem is meaningless from a structural standpoint. It just looks odd if it's tall.
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BTW- nobody does it this way (probably because it isn't needed) but the only place the plug would make a structural difference is halfway down into the headset. This would buttress the steerer at the fulcrum of the bending moments, where failure is most likely.
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They are bad, they look like crap, and can increase the risk of injury in a sensitive area if you crash. Whenever I see bikes set up that way I figure the owners already have as many children as they want.
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As a side note, the tires on it were trash. The rear has flat spots with cords showing through from skids and the front has a sidewall tear. It had a thorn proof tube in the front and a tire liner in the rear. No wonder the bike was so heavy! I'm putting my GP4000S's from my own bike on it so I can take it for a ride. I'd swap wheels and cassettes with my own bike, but I wanna ride the (lightweight when compared to my own FSA wheelset) Mavic Cosmos wheels.
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I haven't seen anybody mention this, but in the second pic down, the cap appears to have a long extension which protrudes down into the steerer and will require locating the expansion plug lower in the steerer. I've only ever seen caps that protrude a very short distance into the steerer. How closely does that cap extension fit into the steerer? Is it conceivable it was intended to help protect the steerer from being crushed by the stem?
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I haven't seen anybody mention this, but in the second pic down, the cap appears to have a long extension which protrudes down into the steerer and will require locating the expansion plug lower in the steerer. I've only ever seen caps that protrude a very short distance into the steerer. How closely does that cap extension fit into the steerer? Is it conceivable it was intended to help protect the steerer from being crushed by the stem?
I took the bike for a ride today, and it rides beautifully! The steering was way different than what I'm used to. It's gotta have something to do with the fact that its geometry is different than my Fuji's racing geometry. It's not horrible, but it'll take a lot of getting used to if I end up keeping the bike. I lowered the stem yet again, leaving the stack height below it at essentially 0mm and the stack above it at 50mm. That periscope sure is ugly!
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