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#1
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27.0mm seatpost for 27.2mm seattube?
Somebody gave me a nice Thomson seatpost, its 250mm x 27.0 but my
bikes all use a 27.2 seattube. They seem to clamp down ok but I'm cautious. Any problems or issues with this? I'm more comfortable using a 27.2 post in a 27.2 tube. thanks, Rick |
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#2
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27.0mm seatpost for 27.2mm seattube?
"RS" wrote in message . .. Somebody gave me a nice Thomson seatpost, its 250mm x 27.0 but my bikes all use a 27.2 seattube. They seem to clamp down ok but I'm cautious. Any problems or issues with this? I'm more comfortable using a 27.2 post in a 27.2 tube. thanks, Rick What is your frame made of? If your frame is made of CF or aluminum I'd be very cautious. How much of the seatpost is going to be inserted into the seat tube? Does a 27.2mm seat post fit tight in your seat tube? The seat tubes in a lot of steel frames come from the factory out of round or they have high spots that haven't been reamed or honed round so smaller diameter seat posts sometimes provide an easier fit. The seat tube clamps on the circumference of the seatpost. A 27mm seat post is only .2mm smaller in diameter but it's over half a millimeter smaller in circumference - .63mm or .025". So it's a definite maybe. Chas. |
#3
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27.0mm seatpost for 27.2mm seattube?
On Thu, 21 Dec 2006 22:21:06 -0800, RS wrote:
Somebody gave me a nice Thomson seatpost, its 250mm x 27.0 but my bikes all use a 27.2 seattube. They seem to clamp down ok but I'm cautious. Any problems or issues with this? I'm more comfortable using a 27.2 post in a 27.2 tube. I don't think you'll hurt the frame, but you may be more likely to snap the binder bolt. If you have any reason to untighten/tighten if often, a soda can shim is called for. -- JT **************************** Remove "remove" to reply Visit http://www.jt10000.com **************************** |
#4
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27.0mm seatpost for 27.2mm seattube?
RS wrote:
Somebody gave me a nice Thomson seatpost, its 250mm x 27.0 but my bikes all use a 27.2 seattube. They seem to clamp down ok but I'm cautious. Any problems or issues with this? I'm more comfortable using a 27.2 post in a 27.2 tube. thanks, Rick I wouldn't worry about it at all. EJ in NJ |
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27.0mm seatpost for 27.2mm seattube?
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#6
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27.0mm seatpost for 27.2mm seattube?
RS wrote:
Somebody gave me a nice Thomson seatpost, its 250mm x 27.0 but my bikes all use a 27.2 seattube. They seem to clamp down ok but I'm cautious. Any problems or issues with this? I'm more comfortable using a 27.2 post in a 27.2 tube. Others have suggested that this won't be a problem. I'll disagree with them. Although the difference seems awfully small, the clamping force required to adequately clamp the seat post will be MUCH higher than it would be with a 27.2mm post. There's no good reason to risk damaging your frame because you have a nice seat post that doesn't fit. I'd suggest either shimming it, or selling it on Ebay so you can buy a similar one in the right size. Mark Hickey Habanero Cycles http://www.habcycles.com Home of the $795 ti frame |
#7
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27.0mm seatpost for 27.2mm seattube?
Mark Hickey wrote: RS wrote: Somebody gave me a nice Thomson seatpost, its 250mm x 27.0 but my bikes all use a 27.2 seattube. They seem to clamp down ok but I'm cautious. Any problems or issues with this? I'm more comfortable using a 27.2 post in a 27.2 tube. Others have suggested that this won't be a problem. I'll disagree with them. Although the difference seems awfully small, the clamping force required to adequately clamp the seat post will be MUCH higher than it would be with a 27.2mm post. There's no good reason to risk damaging your frame because you have a nice seat post that doesn't fit. I'd suggest either shimming it, or selling it on Ebay so you can buy a similar one in the right size. Yes, lots higher, IME: I once bent a steel lug trying to use a 27.0 post in a 27.2 frame. Didn't really pay attention (not unusual in those days) until after the damage was done. It even closed the vertical slot at the top of the seat tube. Luckily, and I still have that frame, ca. 1980-81, nothing broke when too tight or when things were carefully returned close-as-possible to orig. config. Aluminum doesn't take to being deformed as well as steel. Shim? OK. Better, sell it and get something you want that fits, if for no other reason than ease of adjustment and transplant (you said "bikes"). That Thompson might be a good ebay or Craigslist item due to someone needing a 27.0 post for their bike. Isn't there a cheap, good post made by Kalloy that is inexpensive enough to have more than one, when using multiple bikes? (of course, then you'd want more saddles...) --D-y |
#8
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27.0mm seatpost for 27.2mm seattube?
John Forrest Tomlinson wrote: On Thu, 21 Dec 2006 22:21:06 -0800, RS wrote: Somebody gave me a nice Thomson seatpost, its 250mm x 27.0 but my bikes all use a 27.2 seattube. They seem to clamp down ok but I'm cautious. Any problems or issues with this? I'm more comfortable using a 27.2 post in a 27.2 tube. I don't think you'll hurt the frame, but you may be more likely to snap the binder bolt. If you have any reason to untighten/tighten if often, a soda can shim is called for. Be sure to drill out the shim to save 0.0345gr! |
#9
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27.0mm seatpost for 27.2mm seattube?
On Fri, 22 Dec 2006 10:51:43 -0700, Mark Hickey wrote:
RS wrote: Somebody gave me a nice Thomson seatpost, its 250mm x 27.0 but my bikes all use a 27.2 seattube. They seem to clamp down ok but I'm cautious. Any problems or issues with this? I'm more comfortable using a 27.2 post in a 27.2 tube. Others have suggested that this won't be a problem. I'll disagree with them. Although the difference seems awfully small, the clamping force required to adequately clamp the seat post will be MUCH higher than it would be with a 27.2mm post. There's no good reason to risk damaging your frame because you have a nice seat post that doesn't fit. I'd suggest either shimming it, or selling it on Ebay so you can buy a similar one in the right size. I've sometimes seen it suggested that you can use a knurling tool to increase the diameter of the seatpost. Is that safe and effective? |
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