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Clydesdales/Athenas (200+ lb / 91+ kg) Looking to lose that spare tire? Ideal weight 200+? Frustrated being a large cyclist in a sport geared for the ultra-light? Learn about the bikes and parts that can take the abuse of a heavier cyclist, how to keep your body going while losing the weight, and get support from others who've been successful.

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Old 06-20-11, 06:03 PM   #1
Mithrandir
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The Incredible Sinking Seatpost!

So does anyone else have this problem? As you ride a couple of miles, your seatpost starts to sink lower into the seat tube? I've tried tightening the bolt as much as it can go, and I've ended up stripping off the nut a few times (I now carry spares in case such a thing happens during a ride), but nothing seems to hold the seat in place over a period of 10 miles or so. It's especially noticeable if I unexpectedly hit a bump and wasn't prepared for it, so most of my weight is on the saddle.

Any suggestions? Besides "lose more weight", that is
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Old 06-20-11, 06:26 PM   #2
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I've had that problem on QR seat post clamp binder bolts and after none of the usual fixes did it for me (cleaning the post, sanding the post, greasing the post, talc'ing the post), I finally gave up on the QR feature and just cranked the bolt down with an allen wrench. But if your post clamp doesn't have a quick release, and you've already tightened the bolt to the stripping point, I'm not sure what to suggest. I've heard of people cutting aluminum cans into shims they can put around the post, but I never tried that.
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Old 06-20-11, 07:11 PM   #3
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You would be surprised how little it will take to stop this. The above mentioned remedies will work, but a simple addition of a seat post clamped tail light can stop the problem (attached to the seat post, not the seat tube, at the union of the two).

I had that problem on the GT Peace (notorious problem with this bike). I and my shop tried everything and this was the only thing that helped.

Good luck

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Old 06-20-11, 08:21 PM   #4
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Get some of this: http://www.performancebike.com/bikes...ssembly+grease . Though it is designed for use on carbon parts, it will solve your problem.
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Old 06-20-11, 09:21 PM   #5
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Quote:
Originally Posted by Mithrandir View Post
So does anyone else have this problem? As you ride a couple of miles, your seatpost starts to sink lower into the seat tube? I've tried tightening the bolt as much as it can go, and I've ended up stripping off the nut a few times (I now carry spares in case such a thing happens during a ride), but nothing seems to hold the seat in place over a period of 10 miles or so. It's especially noticeable if I unexpectedly hit a bump and wasn't prepared for it, so most of my weight is on the saddle.

Any suggestions? Besides "lose more weight", that is
what kind of bike and what type of binder bolt? I had the same thing happen with some of older road bikes.. I ending up going with a campagnolo qr seat binder instead of using the bolt and it has worked like a charm. And you do not have to worry about stripping or breaking the binder bolt..

http://cgi.ebay.com/Campagnolo-Quick...item1c1c074098
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Old 06-20-11, 09:27 PM   #6
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Do you have the right size seat post? Bikes have two (generally) different size seat tubes. I imagine it would be very obvious if you had the smaller seat post in a larger seat tube, but hey.
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Old 06-20-11, 09:47 PM   #7
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Quote:
Originally Posted by jboyd View Post

I have this same seat. I didn't think I would when I got it but I like it.

The modern external whatever-they're-called seatpost clamps seem fragile to me. I'm afraid to tighten them down as hard as on my 1984 531 frame. I'm sure they're fine, it just freaks me out because I don't have an extra and they look so tender. That's why my seatpost sinks or so I tell myself.
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Old 06-20-11, 10:34 PM   #8
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Originally Posted by davehbuffalo View Post
The modern external whatever-they're-called seatpost clamps seem fragile to me. I'm afraid to tighten them down as hard as on my 1984 531 frame. I'm sure they're fine, it just freaks me out because I don't have an extra and they look so tender. That's why my seatpost sinks or so I tell myself.
If it's an external clamp that you have, replace it with a Salsa Liplock and be done with it forever. By far, it is one of the best sub-$20 components I've sank money into. Instead of just having a threaded side and a bored side for the bolt head, the threaded side is a threaded pivoting insert, allowing a consistent straight angle for the bolt to thread into as it tightens down. It's never 'out of alignment' at the threads, and you can get much better clamping force with it.
And they come in a gazillion kick-ass colours.

The other option is to put a hose clamp on your seatpost, just above the collar junction.
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Old 06-21-11, 12:52 AM   #9
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My new Bike friday came with a Cane Creek thud buster LT seat post..

it moves thru a parallelogram, rather than telescopic mech.

the black elastomers, are for 200 pound riders , purple for more , blue for less..

you might try a Surly Stainless steel clamp band , a more strong metal to thread into..

Last edited by fietsbob; 06-21-11 at 12:56 AM.
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Old 06-21-11, 04:42 AM   #10
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What worked for me was clear nail polish on the post where it was clamped down. Hasn't budged in the past 3 months after a month of dropping 1cm every 20km.
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Old 06-21-11, 08:59 AM   #11
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Being a big guy myself I kept having this problem. The solution I found was hitting up the Home Depot and putting a couple hose clamps on the post. Hasn't budged since and I no longer pedal with my knees at my ears!
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