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Laid back Chromoly seatpost compatible with carbon fiber frame
#1
Hi,

Question about compatibility with a Chromoly Redline laid back seatpost, to be used with a T800 (T1000 reinforced) carbon fiber frame:

 http://www.amazon.com/dp/B0017K75B4/


My potential concerns are:

1) Will the laid back style be too much stress for the carbon fiber frame?

2) The frame uses a 31.6mm seatpost, and the Redline is 25.4.  I have a Shim to convert.  From a strength standpoint, is the shim an issue?

Basically, I do not want to ruin the carbon frame.  I have never owned one before, and I have read some horrow stories about ruining carbon fiber parts (such as handlebars) due to overtightening bolts, using incompatible stems, etc.  I am starting to think that the carbon parts are somewhat fragile.

Advice appreciated, thanks.
rpesq
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#2
Do not use that seatpost. The setback on it doesn't worry me too much. But I would never use an undersized seatpost with a shim in anything other than a heavy duty, non-cromoly steel frame. It concentrates all the stress from the seatpost into a tiny area and could cause frame failure.

If you need to move your seat back farther, there are a number of higher end "setback seatposts" that you can look at. If you can find something with the right diameter, that would be a much better option. I know Velo Orange makes one.

On the safety of using a setback seat in general...probably OK, though I might get concerned if you are heavier or doing anything rough with the bike.
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#3
+1

Though I have used a shim on heavy duty plain gauge Cr-Mo frame - the particular frame is heavier than my plain gauge "Hi-Ten" steel frame....
Nigel
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#4
Great advice, thanks guys.  I actually came to the conclusion that the carbon fiber construction is not for me , I do not have confidence in it.  So I was able to cancel my purchase -- the seller was very gracious.

I'm going to go with an aluminum frame, which is what I am used to, and I feel confident in.  I'll avoid using a seatpost shim, too!

Thanks again.
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