Bicycle Mechanics - Seatpost binder eyelet broken

Hi all:

In trying to tighten the seatpost binder bolt a bit too much on my Al frame, I cracked the "eyelet" on the frame. :eek: :( Is my frame toast?

The frame may be salvagable by grinding the broken lug smooth and removing the other side too. Then get a separate seatpost collar clamp that goes completely around the top of the seat tube. Something like this:

http://www.nashbar.com/profile.cfm?category=117&subcategory=1189&brand=&sku=11701&storetype=&estoreid=&pagename=

Depends on the frame. You might be able to cut off the other eyelet and retro fit a seatpost coller type binder.

It might be possible to find an internally-expanding post, too. Example: http://www.bikeville.com/seatposts.html Go down the page to the internally-expanding American Classic post.

Thanks for the suggestion. However, I am not sure there is enough room to mount the collar. Here is the pic... What do you think?

Maybe a skilled welder could repair the fracture.

Thanks for the suggestion. However, I am not sure there is enough room to mount the collar. Here is the pic... What do you think?

Toast. Send frame to me ;)

-Kurt

You're right, there isn't enough room above the clamp to fit a collar. Also, don't even think about welding the tab back on. The main tubes are carbon and the heat would absolutely destroy the bike.

The internal expanding seat post mechBgon suggested is probably the only way to get around this problem.

BTW, Trek has a "lifetime" warranty on their frames for the original purchaser. You do have your sales slip don't you? I'd contact them about a warranty claim and see what they say. They may replace the frame or give you a very good replacement price.

The internal expanding seat post mechBgon suggested is probably the only way to get around this problem.

Would something like that work okay on a carbon fiber seat tube? It looks like the expanding mechanism is down at the bottom of the post, so it would be putting the pressure inside the carbon fiber tube, not the seat tube collar. I don't know much about carbon fiber, so I'm wondering if it can take a pressure point like that.

I would sure suggest looking into the warranty first of all. Good luck, and don't feel bad, most of us have overtightened our binder bolts at some point! :(

Would something like that work okay on a carbon fiber seat tube? It looks like the expanding mechanism is down at the bottom of the post, so it would be putting the pressure inside the carbon fiber tube, not the seat tube collar. I don't know much about carbon fiber, so I'm wondering if it can take a pressure point like that.(
Good point. The expander would have to be at the bottom of the seatpost and would load the seattube (even steel or Al but particularly carbon) in an area not intended to take an outward radial load. Probably not a good idea. I'd ask American Classic but I agree there is likely to be a problem with this appraoch.

Thanks for the replies. I bought the bike used a couple of years ago. No warranty for me. :( The bike is from 1992/93 and it came pretty much stock to me when I bought it for $150. I guess the silver lining is that I don't need to shed tears of blood at my mistake.

I tried to see how firmly the seatpost still held. I held the saddle and jumped up and back down with all my weight (160lbs) on the saddle. The seatpost did not budge. I jumped down a curb and there was no play in the post. I guess I will check for play before every ride and just ride it. The failure mode is going to be my seatpost descending down into the seat tube. That is probably unlikely to be catastrophic, right? :eek:

I'd say that's correct, the failure might only be catastrophic if it allowed the seat post to turn or drop unexpectedly and made you lose control of the bike.

Here's a thought. If this were my bike, I would try an inexpensive fix like this. In your picture, we're looking at the end of the binder bolt, and a nut that fits flush into the recessed area of the collar tab. What if you used a slightly longer bolt, and a larger nut with a flat washer that would NOT fit into the recessed area, but rather would overlap the perimeter of it , and would apply pressure to the entire area around the recessed opening? That way, you'd be distributing the pressure over a much larger area to close the collar, not just relying on the cracked portion of the weakened tab. You could even use an aluminum flat washer so it would conform to any contours on that part of the collar, if necessary. The bolt would still be held in place by the original hole in the tab, but the larger nut and washer would apply the pressure outside the recessed area, so it would be much stronger. Let me know if I'm not explaining this very well. Sure, it wouldn't look as good, but who cares! It would be strong and would allow you to keep riding, and that's all that matters. Right?

And of course, you're right about the silver lining, and the other good news is that this is a lesson you'll never forget about seatpost binder bolt torque! Many of us learn that the hard way! :)

Another thing I could do is attach a smaller collar directly to the seatpost itself. If the post were to drop because the eyelet finally gives out, hopefully the collar will prevent the post from dropping all the way.

Another thing I could do is attach a smaller collar directly to the seatpost itself. If the post were to drop because the eyelet finally gives out, hopefully the collar will prevent the post from dropping all the way.

Hose clamp would work. But wouldn't prevent the seatpost from lifting up, just from dropping down.

Bob

Also wouldn't prevent it from turning, which is a more likely scenario.

I just had a thought: would drilling a hole right through the alloy part of the seat tube and seatpost, and then pinning it in place with a bolt and nut of appropriate size weaken the frame too much? It wouldn't be very adjustable, but if you have the seatpost height really dialed in it might not need to be.

It has been done before to junky bikes with broken eyelets. It's a possible last resort if the situation gets desperate.