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frame too small

Old 12-30-07, 02:48 PM
  #1  
sylentbob3
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frame too small

i recently purchased a fuji comp diamond full suspension mountain bike. being a bit of a newbie, i bought too small of a frame. i went to the local bike shop, where they sold me a bigger seat post, and it started bending after two weeks! i would like to buy a bigger seat post, as the bike would fit much better, can i get something that will work? what can i get and what material do i need? can i get something without spending a hundred dollars on a carbon frame post? thanks!!
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Old 12-30-07, 02:52 PM
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If the seatpost that you have already is bent after two weeks, I'd say you're SOL. Going with anything longer is just asking for a seatpost failure and your expense and is probably too dangerous.
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Old 12-30-07, 11:42 PM
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A carbon post would be weaker than an aluminum or steel post, and would make your problem worse! How many inches of seat post is sticking out of the frame when it is at the proper height?
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Old 12-31-07, 12:13 PM
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i am not sure how much would be sticking out, my bikes away at the moment, but i think around 270 mm would be sticking out when properly fitted. i see that on a 400 or 410 post it says you can put it up to 300. does that sound right?
i know that the frame is a 17" frame and i need a 19".
i think the post that i bought bent because i got ripped off (i bought it for around $30); when i came back to the store to ask him to replace it, he told me to buy a nicer one for $70, so i think one could work.
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Old 12-31-07, 08:18 PM
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Yeah, most MTB seat posts I've seen have the minimum insert line about 100mm/4" from the bottom end. I'm 5'8" and ride a 16.5" frame with 245 mm of seat post (from seat tube to seat rails). I could probably get away with a 350mm post, but I put on a 400mm post anyway. (It's best to have the bottom of the post extend into the seat tube below the bottom of the top tube joint to reduce the likelihood of frame damage).

The fact that there are 400 mm seat posts out there indicates a foot (300mm) of post showing does not necessarily indicate your frame is too small. When it comes to frame sizing, the top tube and stem lengths matter more. So if the reach feel good, then maybe you just have longer legs and a shorter torso/arms than the average person at your height.

A 19" frame will decrease the seat post showing but might stretch you out to the point that you'd need a really short stem. Especially for MTBing, it's generally best to get the smallest frame that allows for the appropriate reach--there have been several times I've had to dismount and was glad I'd gotten the Small frame. If the reach fits, you should be fine. If you feel cramped, even with like a 130 mm stem, then the 19" might be a better fit after all.
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Old 12-31-07, 09:27 PM
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Or rather in this day and age "virtual top tube"
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Old 01-01-08, 09:46 AM
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Originally Posted by JiveTurkey View Post
The fact that there are 400 mm seat posts out there indicates a foot (300mm) of post showing does not necessarily indicate your frame is too small.
What it does indicate is that the current ideas about frame sizing are an utter shambles.
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Old 01-01-08, 10:20 AM
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http://www.lhthomson.com/elite_features.htm

They have up to 410 mm lengths.
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Old 01-01-08, 02:10 PM
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I run a 350mm sp (race face) at the max and have no problems (Giant Trance X) I also have run a Thomson 367mm sp on a Hard tail cannondale at the max and again no problem. If you are bending cheepo sp's, then get a quality aluminum sp like a thomson. Deals can be had on ebay (run around wholesale on ebay)
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Old 01-01-08, 02:15 PM
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Bending a seatpost? How's your ass?

I have a few bikes with compact geometry resulting in long seatpost extension. Usually I use thomson, but my commuter just has a cheapo kalloy(or zoom, or whatever) that is extended ~260mm from seattube to saddle rails and I've never had any trouble with it. FWIW, I weigh about 155
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