NoWhammies

My bike is a BH G7. The bike has a VERY long seat tube (see image below). The way I have my bike setup is the seat post does not extent very much out of the seat tube.

I do not like clamping the clamp from the bike stand on the seat tube for fear of crushing it. But there is not enough seat post sticking out of the frame to use the clamp on.

Anyone have any suggestions? Or am I ok clamping on the seat tube? Don't I need to worry about cracking the carbon?

Thank you.



(Note, while this is a picture of my bike, this is NOT my bike...If that makes any sense)

dsbrantjr

Well, you could mark the seatpost position with a Sharpie or something, raise the post high enough to clamp it and put it back when you are done.

fietsbob

with no round tubes , you would have a repair service stand like this ..

fietsbob

If the seat post is round , you can get a metal seat post to to insert in the frame,

just for placing in the repair stand clamp..

Then put the carbon one back in when you are finished..

Wilfred Laurier

DO NOT clamp on the frame. You will destroy the bike. You could, as suggested, raise the seatpost and clamp there, then drop the post back down when you are ready to ride again.

blakcloud

Just NO. Don't clamp that bike anywhere including the seat post especially if it is carbon. Plus the seat post looks aero so not round, difficult to clamp.

The best way to handle your carbon bike is to use a dedicated stand like the Feedback Sprint Stand or the Park Tool Team Issue Repair stand.

Brocephus

Tell the truth,bro, you just wanted an excuse to post a pic of that bad-ass ride !!!!!!

(BTW, the seatpost doesn't look round, to me. )

blakcloud

Sorry, I should have added, if you already own a typical repair stand you could purchase the Hirobel device from Silca and use it in conjunction with your stand. Saves a bit of money. https://info.silca.cc/hirobel-launch

NoWhammies

Aw crap. Looks like I'm going to have to purchase a new repair stand Although as mentioned, I could start raising and lowering the seat post in the interim.

The seat post is not round, BTW. Hopefully I haven't wrecked the bike for the few times I have thus far clamped it down on the seat tube. Even if it wasn't with a lot of force...

What I have been doing at times, is just hanging the bike by the seat. While this works ok, sometimes though I need the bike to be stable.

@Brocephus thanks for the compliment. I do indeed really enjoy my bike.

sdmc530

I will second the race type repair stand. I have both versions but I use my "race" stand a lot. Very nice for carbon frame issues!

Wilfred Laurier

In my Park PCS-2 (I think), a seapost like that could fit snugly into the open clamp and not need to be closed.

fietsbob

The race stands do have an advantage ... you can walk around, so access both sides of the bike equally..

woodcraft

There's no problem clamping the seat post,

but if you clamp the seat tube with the post inside it, it will be crushed & ruined?

By that logic you should not use a seat post clamp- maybe some tape & don't actually sit on the saddle.

Litespud

Ha! I never thought I would see "Saves a bit of money" and "Silca" in the same post

Metaluna

The area of the frame immediately under the seatpost clamp is designed to withstand the clamping pressure. The rest of the seat tube is not. If I remember correctly, on the carbon frames I have, there's a small relief cut at the top of the seat tube, just like on metal frames (at least for round posts). That allows the frame material to safely flex inward until it makes hard contact with the seatpost, allowing the seatpost to bear most of the clamping load. It's sort of the reverse of how an expansion plug pushes outward to help a carbon steerer withstand the forces of a stem clamp.

Further down the seat tube, the seatpost is not in sufficiently firm contact with the tube walls to allow it to support the tube against clamping forces (if it were, the friction would be so high that it would be impossible to get the post in or out -- that's exactly why seat post clamps work in the first place). So any clamping pressure is going to be borne by the seat tube walls alone. Even if it's a fairly snug fit, the tube would still have to collapse inward some small amount until it contacted the seatpost and the inward and outward forces balanced out. And since there's no relief cut -- crunch. You might get away with it, or not.

woodcraft

And you have direct knowledge of how many of these seat tubes crushed by a repair stand clamp?

Metaluna

Your original premise was that if it's okay to put a seatpost clamp on the seat tube without destroying the frame, then it must also be okay to clamp any other part of the seat tube as long as the post is inside it. I gave a specific example of how the seat clamp area is designed differently from the rest of the seat tube and therefore the same logic can't be applied elsewhere, i.e. the premise is faulty. If that's not enough, combined with warnings from frame manufacturers, etc., then by all means proceed. It's your bike.

Last ride 76 

fietsbob

yes, the Italian company is no more..

Secret Squirrel

Maybe it will fit in the "BontragerUniversal Repair Stand Adapter" or similar?

woodcraft

Not exactly my original premise, but I'll take your post to mean that you have no example of damage actually being caused in this way.

While I mostly just hang the bike by the saddle nose, I've clamped many bikes over many years by the seat tube with no issues.

fietsbob

The accessory in # 8 .. is looking like it was inspired by a trunk rack that would strap on.. the car trunk/boot..

NoWhammies

I am starting to do this more and more with my bike. Hanging it by the saddle nose. I am concerned about squishing the seat tube. Mind you there are times when I do need to secure the bike, and for that I'm at a loss as what to do. I could see about using my Kuat bike rack I suppose. At least for some work.

fietsbob

Consider a low stool so you can sit at the height of the bike on the ground.. or on a low table?

TimothyH

I would not clamp anywhere on a carbon frame. Delamination or cracked fibers could happen under the surface and may not even be visible. .

The top tube just forward of the seat tube junction is commonly clamped but one of the worst places to do so. Carbon fibers at this spot typically run lengthwise - they are very resistant to bending loads but not resistant at all to crushing loads. It only takes 1% or 2% elongation to begin cracking the fibers. Seat tubes are similar.

Ruckus Composites/Silca show some crushed frames at https://info.silca.cc/hirobel-launch.

The Hirobel and other horizontal solutions above are the way to go.

"I've clamped my carbon frame and never had a problem" should be "I've clamped my carbon frame and have not yet seen any damage."

My thin walled True Temper S3 steel frame will never see a frame clamp. I'll crush the Enve seat post before I put the frame in a clamp of any kind.


-Tim-