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BMX seatpost seat clamp slipping - solution

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BMX seatpost seat clamp slipping - solution

Old 02-02-16, 09:58 AM
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fiataccompli
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BMX seatpost seat clamp slipping - solution

I have a circa late 1990s/early 2000s Mongoose BMX bike with a rather useful very-setback seatpost, but as it exists currently it will not tighten enough to not slip/rotate. Anyone familiar with these and is this common? Maybe I'm missing a shim or rubber grip here?

thanks in advance




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Old 02-02-16, 10:12 AM
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ask at a local bike shop that can see it in person, your 2 pictures dont do it.
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Old 02-02-16, 10:18 AM
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well, uh, yeah...but I was asking here to see if anyone has first hand experience & since this is generally mechanically-minded folks. I hate to waste my friends' time at shops when the culmination of them fiddling around with some POS BMX seatpost is pretty much zero business for them, if you know what I mean.
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Old 02-02-16, 10:49 AM
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Take it apart and show all the Pieces , If Its Not too Much Work.

Bene Sugg, Pay them at the shop, for their Time.
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Old 02-02-16, 11:03 AM
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Rubber - no.
It'd simply squash and smear.
Shim - can't tell from here. Depends on fit and on how well the seat tube slit closes up.
You can try an assembly paste, either improvised. Toothpaste, valve grinding compound, something specific.
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Old 02-02-16, 11:58 AM
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I'll just take it apart (I mean, I have to anyway ) and get photos. I just happened to take a photo of it the other day while I was playing with my son in the driveway and goofing around on it...and I had it handy and a few minutes to pose the question. Again , mostly hoping it was a rote thing for someone here...if it involves much thinking about it I can figure it out but I'll close the loop on the thread anyway. Thanks again

added: and it seems like this is (obviously hard to tell from the above photos) an unlikely variant of a clamp style I have seen on a number of road bikes. But on the road bikes, it's actually two bolts holding an upper & lower clamp that clinches the center cylinder (that in turn clinches the seat rails), whereas this one is built like the bar clamp on a quill stem. I figured it was some BMX standard (along with proper adjustement) that I was oblivious to....or it was a design tool to keep the rider from actually sitting on the seat!

shim-wise, it would seem a sliver of aluminum can would be ideal. Anyway, more later with photos. Be sure to have your popcorn queued up, 'cause you won't want to miss this, right?

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Old 02-02-16, 12:46 PM
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Either shim the seat rails or two pieces that make the aluminum cylinder that clamps the seat rails with a piece of soda can and tighten. Add shims until it holds fast.
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Old 02-02-16, 01:35 PM
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In the process of multiple times of slipping Undoubtedly the aluminum parts got shaved a little smaller.

I expect the clamp uses 1 bolt to make a round piece of steel smaller .
maybe the bolt is bad ,? maybe the threrads are galling , from not getting greased and still being wrenched on to tighten it,

maybe the slit closes Up to nothing when tightened. and no amount of further tightening works then .

In which cas the drinks can shim may help ... Uber Guessing.. Film at 11..
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Old 02-03-16, 08:21 AM
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so, this is what it looks like. many years of wear on aluminum. An aluminum can shim seems like the appropriate 'fix' after proper cleaning.

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Old 02-03-16, 11:54 AM
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Is that the original seat? Not all rails are the same diameter.
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Old 02-03-16, 01:08 PM
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I didn't buy the bike new, but it's a Mongoose saddle that appears to be original, matches the trim on the bike, etc. I think it's just not a great design.
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