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I recently broke a saddle rail after 20 months (about 2800 miles). I weigh 170 lb. and ride XC with no big jumps. The rail was not bent. It cracked in two just behind the seat post clamp. I did a search of similar problem reports on the forum and there are quite a few. In addition there are a lot of reports of heavier and/or downhill riders bending rails. The failures occurred with a number of brands, models and rail materials.

I had the saddle adjusted fully back which creates the maximum unsupported length of the rail and the maximum bending stress. I calculated a bending stress in the rail of roughly 16,000 psi. For plain steel or titanium this is about 1/2 of the maximum recommended stress for fatigue. With additional g's of vertical acceleration going over large bumps, the stress will exceed the fatigue limit.

The standard (7 mm) rails flex during a bump to cushion the rider. The drawback is high rail stresses. The DH saddles with 8 mm rails and "I-beam" designs (no rails) seem to hold up well but some reviewers complain of stiffness.

Moving the saddle forward reduces the bending stress. I am looking into an offset seat post so that I can run the seat further forward in the clamp. Anyone have any other solutions?
 

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Doesntplaywellwithmorons!
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No. Bent/Cracked rails are a fact of life with saddles. Only ones that don't particularly suffer them are Brooks (and similar style) saddles with the coiled springs to absorb the impact of a fat ass who forgets to lift it before the dropoff. Of course Brooks also themselves employ a double-rail setup on some models which require a special clamp for your seatpost to work.

Oh and SDF has their I-beam interface that solves the problem of bent rails but only SDG saddles are so far using the design so if you don't like their saddles, yer SOL.
 
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