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Discussion Starter · #1 ·
Beautiful hunks of machined, polished stainless steel, looks like they'd have a Vulcan death grip on my seatpost. But on the last epic ride my wife and I did yesterday, hers had slipped 3" by the end of the ride, mine 2"...Here's the story: Had a 410mm length 27.2mm diameter Thompson Elite in my D440's frame. Found out it was 0.2mm oversized for my D440 frame, which actually has a 27.0mm diameter seat tube. No wonder it was so hard to get that sucker down the seat tube! It never slipped, that's for sure. Anyway, my wife needed a longer seatpost than her stock one, Jensen had the 27.0mm ones on clearance (discontinued size, if anyone needs one, get it now) so I got one for my bike, transposed mine to hers, which has a 27.2mm seatpost. Got another Surly seatpost clamp at the same time. Now, BOTH of our seatposts are slipping. I don't have a torque wrench, but I know when it's snug enough. They were snug enough. So, now I've really torqued now on 'em, more than I like. If they slip again, something's wrong here. I'm using the 30mm Surly ring, and they fit the seat tubes correctly. Anyone have recommendations for another seatpost clamp, or are Thompson seatposts 'small for their size'? Thanks in advance to anyone who's had experience with this combo.
 

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Elitest thrill junkie
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Doggity said:
Beautiful hunks of machined, polished stainless steel, looks like they'd have a Vulcan death grip on my seatpost. But on the last epic ride my wife and I did yesterday, hers had slipped 3" by the end of the ride, mine 2"...Here's the story: Had a 410mm length 27.2mm diameter Thompson Elite in my D440's frame. Found out it was 0.2mm oversized for my D440 frame, which actually has a 27.0mm diameter seat tube. No wonder it was so hard to get that sucker down the seat tube! It never slipped, that's for sure. Anyway, my wife needed a longer seatpost than her stock one, Jensen had the 27.0mm ones on clearance (discontinued size, if anyone needs one, get it now) so I got one for my bike, transposed mine to hers, which has a 27.2mm seatpost. Got another Surly seatpost clamp at the same time. Now, BOTH of our seatposts are slipping. I don't have a torque wrench, but I know when it's snug enough. They were snug enough. So, now I've really torqued now on 'em, more than I like. If they slip again, something's wrong here. I'm using the 30mm Surly ring, and they fit the seat tubes correctly. Anyone have recommendations for another seatpost clamp, or are Thompson seatposts 'small for their size'? Thanks in advance to anyone who's had experience with this combo.
So you forced your 27.2 to fit in your 27.0 bike. It's not supprising that it's slipping in the Karate Monkey. I found that I had to tighten the heck out of the surley clamp (not QR) to keep my seatpost from slipping. It's been great now for over half a year, but I did find that it took more pressure than I was used to.

The 27.0 is probably slipping because forcing the 27.2 into your 27.0 frame bulged it out some, especially when you consider all the force that's imparted to the seat and seat post when riding. There are friction-compounds you could try that might help. Go to a hardware store or something similer.

Also, make sure to grease the moving parts of the clamp (cam, threads), that tends to make a big difference in how much force the clamp can supply.
 

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Discussion Starter · #3 ·
Yah, that makes sense. Except my wife's bike never had a (heh..) oversized seat post shoved into hers, and hers is doing the same thing. I usually always apply grease to anything threaded, but this time, I don't remember doing it. I'll do that now, retighten, see what happens. Thanks!!!
 

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Elitest thrill junkie
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Doggity said:
Yah, that makes sense. Except my wife's bike never had a (heh..) oversized seat post shoved into hers, and hers is doing the same thing. I usually always apply grease to anything threaded, but this time, I don't remember doing it. I'll do that now, retighten, see what happens. Thanks!!!
Well, I was also trying to point out that I have to tighten my clamp a lot with my KM, moreso than my other bikes.
 
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