jedck

Like a complete moron, I put my carbon top tube (cannondale synapse) into my feedback repair stand. I was just tightening the clamp and not really paying attention/thinking when (with headphones in, so very indistinctly) I heard a sound. Maybe creaking? I am not 100% certain if it came from the frame of the clamp. I immediately realized I should not be clamping carbon and loosened it. My questions:

(1) What are the chances I damaged the frame?
(2) How could I tell / do I need to take it to a bike shop to have someone check for damage?
(3) Should I not ride it until I figure out if it's damaged?

AlmostTrick

How tight did you clamp it and what song were you listening to?

diphthong

that's what seatposts are for...

diphthong

sounds like a deep purple thing. maybe burn. perhaps deep purple in rock. quite possibly fireball but i'm going with machine head and "space truckin."

second guess...the cult and "sweet soul sister" from sonic temple.

KLiNCK

If you don't see any visible cracks and, when gently tapping on the suspect area, you don't hear any "dead" spots you are more than likely "good to go."
If in ANY doubt - take to LBS.
As mentioned above, best to clamp from seatpost.

Russ Roth

If you don't see any physical damage in the surface it's probably fine, there's nothing wrong with clamping by any tube as long as you don't do it too tight. I've seen seatposts crushed by dopes clamping too hard, with carbon its best to creep up on the right pressure till its just snug enough not to flop around.

dsbrantjr

https://www.parktool.com/product/int...be-clamp-isc-4

squirtdad

many bike manufacturers reccomend not clamping carbon on top tube or even using bike racks where the bikes are hanging from hook things. not all carbon bikes are the same (mtn vs road etc etc) but the top tube of a racy road bike is going to be about the most fragile part of the frame.

Buzzkill53120

I bought this adapter to clamp my Madone (by the seat post) in a Park stand, works great: https://www.trekbicyclesuperstore.co...r-166250-1.htm

easyupbug 

For 26 years I routinely lightly clamp my Trek 5500's round carbon TT for light work like tuning, flat repair, etc. but never anything more forceful like a BB change. I would never clamp a shaped tube such as yours probably is. Round tubes have the advantage of hoop strength which is significant, so I can not imagine an issue with hanging a carbon bike with a round TT but again might easily be an issue, as squirtdad points out, with a shaped TT hanging for even light work. I keep my Park 102L hidden in the back of the shop to prevent disaster with the kids.

cpach

This is why you don't do that. Also most bike shops don't really have any tools for serious carbon inspection--they do have more experience so are better than the average consumer, and can inspect closely visually and tap test the area, but to really know what's going on with carbon it requires a carbon repair specialist with access to things like ultrasound, xray, etc. If you live somewhere close to a carbon repair company you may want to get into contact with them, but a lot of companies require bikes to be stripped to the frameset.

The safe thing to do would be to get the frame inspected by a specialist--while it's not unlikely that the bike is fine, I don't really feel comfortable advising anything else, ultimately its your call. A top tube failure would be one of the more likely failures to lead to a loss of control.

ljsense

I have a Feedback repair stand, and my guess is that the clamping mechanism made the noise, not your frame.

Does it have a ratcheting slide, and then you turn the handle to tighten it up? If we're using the same model, that clamp doesn't really get very tight -- it pings back to the last ratchet with enough force.

If you broke your frame, you'd know it -- there'd be a big ol' crack, maybe even with carbon hairs jutting out of it. There'd be some stomach churning scene. This can defnintely happen with shop clamps, where you wrench down a heavy lever. But if you're using the same Feedback clamp style I am, my guess is your frame is just fine.

revcp 

Buy a cheapy seatpost for using the stand. Take the existing seatpost and saddle out when it's time to do some work, stick the cheapy in and crank that baby down.

fietsbob

Do it a lot ? https://www.parktool.com/product/tea...egory=Portable

_ForceD_

I like this idea/tool. However won't work with aero seatpost.

Dan

JohnDThompson 

At least a crushed seat post is easier and less expensive to replace than a crushed frame tube. Use a steel post for clamping and it's unlikely you'll crush it.

I don't like clamping on frame tubes regardless of the tube material. Too easy to damage paint and/or decals if you're wrestling with a stubborn component. This is particularly true with new bikes, when the paint may not have had sufficient time to fully harden.

Russ Roth

I've seen this damage frames from over tightening and bulging the frame.

Aero posts don't always fit the clamp and my most recent build started by waiting for a post to arrive

vespasianus

This. Tap (gently!) to top tube with a nickel and listen. The tone should be similar over the top tube. It might change a little bit when you get to the ends of a tube but otherwise, similar. If you hear a thud or a dead sound, that will indicate some damage.

And yes, don't clamp carbon. With my carbon bike, I remove my carbon post and put in a cheap aluminum post to hold the bike.

cxwrench

Do NOT clamp carbon frame tubes. Period. Even if you are extremely careful w/ tightening the clamp bad things can and will happen. The one that happens often goes like this: Mechanic carefully clamps bike in the stand. At some point during the repair/build he decides the bike needs to be at a different angle and rotates the frame up or down...but the stand is adjusted a little too tight...crack. Use the seatpost or a beam stand.

ljsense

An awful lot of people sit on their shaped carbon top tubes, sometimes even as they are descending a mountain road. They hold up to that.

I agree that it's best not to clamp frame tubes. That goes for any bike. Triple butted titanium or Columbus SLX doesn't like a clamp any more than carbon does.

That said, from my experience with the Feedback clamp that the OP is using, here's how I'd answer his questions directly:

What are the chances I damaged the frame?

Less than 5 percent.

(2) How could I tell / do I need to take it to a bike shop to have someone check for damage?

Look for a crack. Cracks in carbon rarely can hide under paint. But in those cases, tapping the tube with a penny will indicate whether there's a crack -- instead of it sounding tight and solid (ping, ping, ping) it will be dead and muted where the carbon has delaminated or shattered. (tuff, tuff, tuff).

(3) Should I not ride it until I figure out if it's damaged?

Yeah, I would take a look at it and just see if it's obviously broken, then do the penny test. Next, just stick something in your clamp and tighten it until your clamp makes a ping. Then you will probably rest easy that that was the sound you heard.

fietsbob

3D print * a filling wedge to transition from round to that V side..

*or old handicraft DIY era, carve it out of wood.


see # 14, bike stand doesn't use a frame tube, clamp replaces 1 of the wheels, & supports under the BB..






....

79pmooney

Or ... slide the seat nose into the loop of a rope tied to the overhead. No, you cannot wrestle with the bike with both hands, Gotta set the bike on the floor leaning against the bench. But taking the bike off and on the :stand" is so quick and easy. I set the bike on the floor every time I put a wheel in to seat it in the dropout. No big deal..

Other advantages - cheap. Takes up zero floor space. Disadvantage - cheap.

I've worked in bike shops and volunteered at coops. I've used good stands. Nice, but I don't want one in my garage. The rope has worked really well the past 30 years.and I've never hurt myself on it in the dark. Love that it isn't an obstacle I have to get large items past.

Ben

cxwrench

You're kidding, right?

As for sitting on top tubes...I've seen 2 frames in the last year (carbon) cracked because of that.

vane171

That's what I do with my old bike, even if it has steel tubes, because I am cheap, I don't have proper bike repair stand. You can improve stability by having a separate, second loop of the rope go around handlebars near the stem, or under the stem. That is OK for light jobs but not for serious wrenching.

For that, if you got CF, maybe it is better not to be lazy and take wheels off and mount the bike on some stand by the skewer levers and maybe if you do BB, use also the seat clamping as a third clamping point... no idea if some stands come like that, but should be easy to make it as a DIY project.

It is more involved but for major jobs it gets absorbed in the work time anyway. For a chain job, tune up gears, wash bike, I'd use the rope suspension outlined above. BTW I use two inch wide straps that have length adjustable plastic do-dads on them and plastic clips like those you find on backpack straps. Or just about any straps like those you use for strapping down a load would do.

You mean sitting on them while riding or sideways sitting as people do when they stop to chat or take in the view?

JohnDThompson 

Keep a round post of the proper diameter available for clamping purposes. Or use something like the Park "internal seat clamp" tool to fit a range of diameters:


https://www.parktool.com/product/int...be-clamp-isc-4