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Old 06-04-07, 10:55 AM   #1
SEAtrain
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Threadless vs. Threaded Headset

I'm building up a new bike with a threadless headset. I was clueless about my spacer stack height so I temporarily set my stem height without spacers by matching existing bike setup (1.75in of drop between the saddle and top of the bar). I am surprised to see 4.5in of fork tube sticking out of my headtube. Coming from steel bike/quill stem, I imagine all sorts of terrible scenarios.

Is this safe? I presume so. Is it more structurally sound than my threaded fork/quill stem setup?

This is a cross post. Sorry.
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Old 06-04-07, 11:32 AM   #2
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Are you using a stem with some angled rise? This would depress the position of the clamp.
Once you are sure of your stem clamp position, the normal practice is to cut your steerer tube but make sure you mark it accurately.
t is probably best to leave some spacer above your stem in case you change your mind. Most setups seem to add about 1cm.
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Old 06-04-07, 11:36 AM   #3
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4.5" of open tube without the stem or 4.5" of bare steerer with the stem installed? Big difference.

Also impt: alloy or carbon steerer?
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Old 06-04-07, 11:40 AM   #4
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Quote:
Originally Posted by vpiuva
4.5" of open tube without the stem or 4.5" of bare steerer with the stem installed? Big difference.

Also impt: alloy or carbon steerer?

4.5in of bare steerer WITH the stem installed and no spacers. This is the distance between the top of the head tube and bottom of the stem.

Carbon steerer.
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Old 06-04-07, 11:45 AM   #5
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Quote:
Originally Posted by MichaelW
Are you using a stem with some angled rise? This would depress the position of the clamp.
Once you are sure of your stem clamp position, the normal practice is to cut your steerer tube but make sure you mark it accurately.
t is probably best to leave some spacer above your stem in case you change your mind. Most setups seem to add about 1cm.
Right now I have my stem installed so that it is angled down. I considered flipping it, but I couldn't come up with a strong enough argument to do so.

Yes, I'm planning to add a spacer above my stem.
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Old 06-04-07, 11:49 AM   #6
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Quote:
Originally Posted by SEAtrain
4.5in of bare steerer WITH the stem installed and no spacers. This is the distance between the top of the head tube and bottom of the stem.

Carbon steerer.
You are lucky you asked before you proceeded. For a 1" carbon steerer the max number of recommended spacers is 25mm (1"). For a 1 1/8" steerer, I've seen 25-28mm as a recommended max. You'll need to flip your stem up or buy a new one with a bigger angle. With alloy steerers the max is usually 40mm-50mm, still less than you're showing.

A little OT: are you sure this frame fits you well? What length stem are you planning to use?
edit: you currently have your stem flipped down, so I feel better about the fit.
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Old 06-04-07, 12:18 PM   #7
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Quote:
Originally Posted by vpiuva
You are lucky you asked before you proceeded. For a 1" carbon steerer the max number of recommended spacers is 25mm (1"). For a 1 1/8" steerer, I've seen 25-28mm as a recommended max. You'll need to flip your stem up or buy a new one with a bigger angle. With alloy steerers the max is usually 40mm-50mm, still less than you're showing.

A little OT: are you sure this frame fits you well? What length stem are you planning to use?
edit: you currently have your stem flipped down, so I feel better about the fit.

Where did you find these specs on the max # of spacers? 25mm is only 1in. I need a lot more that this even if I flip my stem (4.5in = 114mm). My stem is a Ritchey Logic 84/73. I suppose I could get a different stem with substantial rise?

This bike's geometry is very similar to my existing bike.
Old(Serotta - Traditional):
CC 52
TT 53
Stem 10

New(Pedal Force - Semi Compact):
CC 50
TT 52.5
Stem 9

Oops. After looking at these specs and reviewing my notes I see I intended to purchase a 10cm stem but ordered a 90. Nuts! I might need to fix that error. I'm not sure I want my bars quite that close.

Also, the new frame is a semi-compact and has a shorter head tube.
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Old 06-04-07, 01:28 PM   #8
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Quote:
Originally Posted by SEAtrain
I'm building up a new bike with a threadless headset. I was clueless about my spacer stack height so I temporarily set my stem height without spacers by matching existing bike setup (1.75in of drop between the saddle and top of the bar). I am surprised to see 4.5in of fork tube sticking out of my headtube. Coming from steel bike/quill stem, I imagine all sorts of terrible scenarios.
Why of course. The guy who made the fork didn't know what size head tube your bike would have or how many headset spacers you were going to want. Consequently he made the fork extra long with the understanding that you would cut off the excess that you didn't want.
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Old 06-04-07, 02:33 PM   #9
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Actually, Reynolds says 1.5", not 1.125", allowable spacers on a 1 1/8" fork. (1" on 1" fork) Here are their installation directions:
http://www.reynoldscomposites.com/Ou...lation.pdf.pdf
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Old 06-04-07, 03:21 PM   #10
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Quote:
Originally Posted by vpiuva
Actually, Reynolds says 1.5", not 1.125", allowable spacers on a 1 1/8" fork. (1" on 1" fork) Here are their installation directions:
http://www.reynoldscomposites.com/Ou...lation.pdf.pdf
Thank you.

There it is in black and white, but I don't understand. My intuition warns me there should be a limit, but I don't understand the structural reasons behind it.

Also, since the instructions reference the Ouzo Pro fork, I'm guessing the stack up limit might be different for another manufacturer.

I've emailed Pedal Force ... we'll see what that turns up.

It seems like this is a gray area.
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Old 06-04-07, 03:38 PM   #11
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I just spoke with my LBS. Their standard rule-of-thumb is determined by diameter of the steerer. This puts it at 1.125in for the max stack height.
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Old 06-05-07, 08:05 AM   #12
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I wasn't aware of a maximum number of spacers. Is that only for carbon fiber steerers? I'm putting together a Surly LHT for touring (with a steel steering tube.) I want my handlebars able to be set at least as high as my saddle (and I'm 6'4" so all my previous bikes have had a ton of seatpost showing. I haven't started assembling my LHT yet, so I don't know how high the seatpost will be.) I was envisioning the liklihood of using lots of spacers (or a double stem.) I'd be grateful for any advice. Thanks.
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Old 06-05-07, 08:42 AM   #13
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Quote:
Originally Posted by BigBlueToe
I wasn't aware of a maximum number of spacers. Is that only for carbon fiber steerers? I'm putting together a Surly LHT for touring (with a steel steering tube.) I want my handlebars able to be set at least as high as my saddle (and I'm 6'4" so all my previous bikes have had a ton of seatpost showing. I haven't started assembling my LHT yet, so I don't know how high the seatpost will be.) I was envisioning the liklihood of using lots of spacers (or a double stem.) I'd be grateful for any advice. Thanks.
My understanding is that the max number of spacers is different for carbon vs. steel & aluminum steerers. If you poke around on sheldonbrown.com, you will find a method to completely eliminate spacers for an aluminum steerer (clamp at headset, no spacers, stem clamps to steerer). He explicitly warns against using this technique for carbon steerers. I recommend that you consult a reputable shop, and, if available, review installation instructions that come with the fork.

Here are my sources of information for carbon steerers:
Reynolds Ouza Pro Instructions: 1.57"/ 40mm (Thanks vpiuva!)
Pedal Force (frame OEM): 1.57"/40mm
My LBS: Rule-Of-Thumb:Max stack height = steerer OD, unless steerer is AL wrapped.
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Old 06-05-07, 07:21 PM   #14
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I think the amount of safe steerer protrusion should have something to do with the length of the head tube, too - because the main couple that you're worried about, I believe, is between the pair of headset bearings.

In any event, I never cut the steerer on my Surly Karate Monkey (XL) because I wanted things nice and high, and I'm not worried about it. Steel, so...
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Old 06-05-07, 07:34 PM   #15
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While not specifically addressing the OP's question, I'd point out that one huge advantage of threadless headsets over threaded is the fact that you can do a complete and accurate headset adjustment with no more than a 4, 5, or 6mm hex wrench (which are contained in virtually every multitool you can buy). With a threaded headset you need, at a minimum, two very large wrenches - not something you're going to carry in your saddle bag. Plus, threaded headsets are more difficult to do a proper adjustment on. Doing a proper threaded h/s adjustment is a trial and error process and usually requires multiple attempts. Threadless adjustments take less than a minute to adjust properly and lock down.
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