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CF frame in a home workstand - best way to clamp?

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CF frame in a home workstand - best way to clamp?

Old 07-01-16, 09:03 PM
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CF frame in a home workstand - best way to clamp?

What's the best way to put your CF bike into your home workstand? I tried clamping it by the seat post, but there wasn't enough seatpost showing to clamp it. The seatpost is also CF, though.
I ended up clamping it lightly on the top tube - just enough to keep it from swinging, really. All I was doing was putting on some bottle cages and a saddle bag.

I hear horror stories about about clamping and crushing and whatnots - thanks for any info!

I have a Parktool PCS-10 stand.
Bike is a new Specialized Roubaix SL4 Sport.
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Old 07-01-16, 09:11 PM
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I would just extend the seatpost so you had enough purchase to clamp on the post. You can clamp a CF post, and it's for sure lower liability than clamping your frame.
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Old 07-01-16, 09:12 PM
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Originally Posted by the sci guy View Post
What's the best way to put your CF bike into your home workstand? I tried clamping it by the seat post, but there wasn't enough seatpost showing to clamp it. The seatpost is also CF, though.
I ended up clamping it lightly on the top tube - just enough to keep it from swinging, really. All I was doing was putting on some bottle cages and a saddle bag.

I hear horror stories about about clamping and crushing and whatnots - thanks for any info!

I have a Parktool PCS-10 stand.
Bike is a new Specialized Roubaix SL4 Sport.
Either tape/mark the seatpost so you can draw it out to have enough clamping area....or get a stand that uses fork dropouts.

I really would not do what you're doing.
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Old 07-01-16, 09:18 PM
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Top tube is bad, much cheaper to replace a crushed seatpost. I use a stand that clamps front fork and frame is supported by BB.
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Old 07-01-16, 09:20 PM
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Originally Posted by TMonk View Post
I would just extend the seatpost so you had enough purchase to clamp on the post. You can clamp a CF post, and it's for sure lower liability than clamping your frame.
This.
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Old 07-01-16, 09:21 PM
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I've read that you can buy a cheap alloy seatpost to use for this purpose. Just do do any sort of heavy duty wrenching work on it.
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Old 07-01-16, 09:23 PM
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Originally Posted by mcours2006 View Post
I've read that you can buy a cheap alloy seatpost to use for this purpose. Just do do any sort of heavy duty wrenching work on it.
this is a good option too.
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Old 07-01-16, 09:56 PM
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Originally Posted by TMonk View Post
I would just extend the seatpost so you had enough purchase to clamp on the post.
Originally Posted by Marcus_Ti View Post
Either tape/mark the seatpost so you can draw it out to have enough clamping area.
Ah - good combo idea. I think I'll do that.
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Old 07-01-16, 10:25 PM
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I just clamp my bike lightly on the top tube, any heavy wrenching I would rather do with the bike on the floor.
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Old 07-01-16, 10:53 PM
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i use "yakima top tube adapter". google it to see.
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Old 07-01-16, 10:58 PM
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^
that probably works too.

Really, anything BUT routinely putting a tight clamp on a CF Frame should work just fine.
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Old 07-01-16, 11:18 PM
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I'd imagine it would be pretty hard to actually crush any tube on the frame with the force of a workstand clamp but I also clamp my bike by the seat post regardless of frame material
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Old 07-02-16, 12:05 AM
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Originally Posted by john00 View Post
i just clamp my bike lightly on the top tube, any heavy wrenching i would rather do with the bike on the floor.
+1
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Old 07-02-16, 05:48 AM
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Perhaps a question of more interest is why your seat post has so little extension. Since most CF frames are compact design with sloping top tube, and you only need about 4 inches exposed for the clamp, that suggests the frame is considerably too large for you. Not a definitive conclusion, but that is my first guess.
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Old 07-02-16, 07:02 AM
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Originally Posted by rpenmanparker View Post
Perhaps a question of more interest is why your seat post has so little extension. Since most CF frames are compact design with sloping top tube, and you only need about 4 inches exposed for the clamp, that suggests the frame is considerably too large for you. Not a definitive conclusion, but that is my first guess.
It could be that the clamp itself is quite long. My clamp is 4.25" long. The clampable length of my 54cm carbon bike is 4.5", so it's a pretty tight fit to begin with.
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Old 07-02-16, 07:48 AM
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Originally Posted by rms13 View Post
I'd imagine it would be pretty hard to actually crush any tube on the frame with the force of a workstand clamp but I also clamp my bike by the seat post regardless of frame material
+1 I'd have to be surprised if carbon tubing is really too fragile to clamp in a bike stand that is made to service bikes. Wouldn't Park Tool for example be the first to have disclaimers? OTOH most ParkTool videos always show the seatpost being clamped. Are seatposts generally considered stronger tubing than the frames?

I've never thought about this much before. I've always clamped on the seat tube, and my bikes are Ti with CF seatpost, and Steel with alloy seatpost.

This attached snapshot from the PCS10 PT video makes me cringe a bit.. Maybe it's just me, but I'd would never consider clamping on the seatpost if working on a bike clamped at this angle.
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Old 07-02-16, 08:00 AM
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Originally Posted by rms13 View Post
I'd imagine it would be pretty hard to actually crush any tube on the frame with the force of a workstand clamp but I also clamp my bike by the seat post regardless of frame material
Combine carelessness, with high mechanical advantage, add in some country boy biceps and you'd be amazed at what you can break. Had it happen at work yesterday.
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Old 07-02-16, 08:03 AM
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Originally Posted by Sy Reene View Post
+1 I'd have to be surprised if carbon tubing is really too fragile to clamp in a bike stand that is made to service bikes. Wouldn't Park Tool for example be the first to have disclaimers? OTOH most ParkTool videos always show the seatpost being clamped. Are seatposts generally considered stronger tubing than the frames?

I've never thought about this much before. I've always clamped on the seat tube, and my bikes are Ti with CF seatpost, and Steel with alloy seatpost.

This attached snapshot from the PCS10 PT video makes me cringe a bit.. Maybe it's just me, but I'd would never consider clamping on the seatpost if working on a bike clamped at this angle.
Yes. Seat posts are designed to survive clamping forces, specifically the collar clamp. Frame tubes are designed to survive normal riding forces, not being crushed in a clamp maw
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Old 07-02-16, 08:07 AM
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Originally Posted by Marcus_Ti View Post
Yes. Seat posts are designed to survive clamping forces, specifically the collar clamp. Frame tubes are designed to survive normal riding forces, not being crushed in a clamp maw
Ok, but eg. look at this video (at approx. 1:40 into it). "Clamping forces" don't appear are really supposed to be all that great.
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Old 07-02-16, 08:13 AM
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You're not going to crush a CF frame by clamping it hard, but you could induce some micro fractures that propagate over time.
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Old 07-02-16, 08:34 AM
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Originally Posted by mcours2006 View Post
It could be that the clamp itself is quite long. My clamp is 4.25" long. The clampable length of my 54cm carbon bike is 4.5", so it's a pretty tight fit to begin with.

I have a cheap amazon work stand, one of the $80 or so ones, I just cut down my clamp and the soft plastic end pieces to suit my Supersix Evo. I used a slide miter saw to cut the stuff, took all of ten minutes.

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Old 07-02-16, 08:44 AM
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Originally Posted by Marcus_Ti View Post
Yes. Seat posts are designed to survive clamping forces, specifically the collar clamp. Frame tubes are designed to survive normal riding forces, not being crushed in a clamp maw
Agree that seat posts are thicker and stronger than most tubes on a bike but seat post clamps are designed to provide uniform pressure on the seat post. Depending on the clamp you could end up with much higher pressure focussed on a small portion of the clamping surface.
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Old 07-02-16, 09:16 AM
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Originally Posted by Sy Reene View Post
Ok, but eg. look at this video (at approx. 1:40 into it). "Clamping forces" don't appear are really supposed to be all that great.
[u rl]https://youtu.be/MfRx0D3iPVc[/url]
Many bike major CF bike labels (all of them?) have clauses in warranties/warnings about not clamping the frame members in workstands. That might be a relic soon to pass-like warranty-voiding clauses about not using CF frames in stationary trainers...or it might not.

IMO, the extra 15 seconds of seatbag removal is worth it to use the post. Course I ride a Ti bike anyway
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Old 07-02-16, 12:46 PM
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I don't clamp my CAAD 10 frame, especially the top tube. Don't want to do that, the top tube is very thin walled. I do, however, regularly clamp my CF seat post. If the seat post is designed to support 200+ lbs, I don't think it's really an issue to suspend an 18 lb bike from it. I try to keep the center of gravity of the suspended bike in line with the upright of the workstand, which is perpendicular to the floor in my case. I raise and lower the bike on the stand, depending on which part of the bike I'm working.
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Old 07-02-16, 01:43 PM
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sci guy, when you are trying to clamp the seat post, and having trouble finding enough length for the clamp, are you aware you can safely clamp around the upper part of the seat tube where it extends above the top tube? Since the seat tube is supported by seat post inside it, you don't have to worry about crushing it there. On many bikes that will give you another inch or so of area to clamp onto.
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