San Marco Aspide, Broken Rail

Discussion in 'Cycling Equipment' started by gpriatko, Jul 25, 2008.

  1. gpriatko

    gpriatko New Member

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    I've broken the left side rail on my last two San Marco Aspide saddles.

    The most recent saddle lasted almost two years (10,000 miles). I’m not sure how long the previous one lasted.

    FWIW, I’m about 185 lbs. and I do about 2000 feet of climbing every day.

    I’m using a Bontrager seat post. They have decent looking clamps:



    http://bontrager.com/model/06096/en



    The rails always crack in the middle of where they’re clamped. If they were cracking at the edge then I’d say that the clamp was biting into the rail.



    Am I doing something wrong with the way that I’m clamping these saddles?
     
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  2. CAMPYBOB

    CAMPYBOB Well-Known Member

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    At 185 Lbs. and lots of climbing, you might want to try going to a steel rail saddle for increased durablity or just try another Ti rail brand that is similar in shape to the Aspide. You will incur a weight increase, of course. but I don't see 10K miles as a particlarly good life cycle.

    Still, I know how it is when you find a component that just works particularly well and it's cost and durability be damned sometimes. I'm getting so-so rear tire wear out of the FortezzaTri Comp and they are not inexpensive. They stick like glue, roll nicely an are the most puncture resistant tire I've used..so I keep mounting a new rear evey 1200-1500 miles.
     
  3. gpriatko

    gpriatko New Member

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    Yeah I've thought about finding a saddle with steel rails but I've delayed because I'm comfortable with the fit of the Aspide. My new saddle is an Aspide Arrowhead and I like it as well or maybe better -- and of course the rails are Ti.

    I'm still puzzled as to why the rail breaks in the center. I'd expect the rail to break at the edge of the clamp. Always the left side, always the center. Kind of makes me think that I'm doing something wrong.
     
  4. kdelong

    kdelong Well-Known Member

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    I'm not an expert on seat posts, but it sounds like possibly the seat post is to blame. If you were putting enough pressure on the rails to break them, the break would occur outside of the area being clamped on. Since it is breaking inside of the clamp and it has broken in the same place multiple times, I would suspect that either the ends of the clamp are not aligned or that the rail is not meant to be clamped in that type of clamp. I beleive that I would try a different seatpost and see if that makes a difference. Good luck!
     
  5. CAMPYBOB

    CAMPYBOB Well-Known Member

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    I'm still puzzled as to why the rail breaks in the center.

    The Ti rail is flexing on both sides of the clamp. The movement 'may' be transferred thru the clamp pressure pads to the rail area in between the pads. I notice that during long, hard rides with lots of climbs I have a habit of losing form and slamming my weight back down on the saddle after climbing out-o-the-saddle. I've had a Campagnolo carbon seatpost come un-bonded at the aluminum clamp-carbon tube joint. I'm explaining this one with a faulty bonding operation taken to failure mode by lots of intense climbing (I'm at about 170 lbs.).

    As kdlong said, you might want to check the alignment of the clamp and also your clamp pressure. His other idea was a good one: For the price of a new seat post from another manufacturer, a change out may solve the issue and allow you to keep your favorite saddle.

    Good luck!
     
  6. gpriatko

    gpriatko New Member

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    I'm not sure what you mean by 'the ends of the clamp are not aligned'. Do you mean an unequal rotation of the clamp end relative to the bolt that runs left-right through the head of the clamp or do you mean that the clamp end is not parallel to the main axis of the bike?

    The pressure pads have a shelf for the seat rail to rest on. In theory, the seat rail is supported along the full length of the portion of the rail that is inside the clamp. So it seems like any break should happen outside of the clamp.

    It's like the clamping force is being concentrated at the center of the clamp rather than being spread out along the length of the clamp end. That might happen if the diameter of the seat rail is too small for the clamp. I could try glueing a piece of rubber to the rails. Something like the inserts that go between a handle bar and a cycling computer.
     
  7. alienator

    alienator Well-Known Member

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    There are other reasons for the rail to break as yours has. If the seat rail has a different cross-section than the inner surface of the clamp, there will be increases in stress somewhere along the rail, in the clamp. Sure, the rail outside the clamp flexes, but there are also changes in stress distribution in the rail, in the clamp, that come with that flexing. As a result, the rail inside the clamp can still get worked and made to exceed critical stress.

    It's not uncommon at all for their to be failures like yours, and in those cases, a change of seatpost is usually what resolves the issue.
     
  8. swampy1970

    swampy1970 Well-Known Member

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    You might be overtightening it slightly.

    I never really liked the look of the brontrager seatpost clamps. They're a little too lacking in clamp area. I've been using a Thompson post (masterpiece) and have had no problems with my rather svelte Specialized Toupe. For reference I'm in the 175 to 180lb range. The clamp area on that post is significantly bigger.

    Here's the clamp off the masterpiece - I believe the cheaper Elite model is very similar.

    [​IMG]

    I don't know why people think that climbing puts more stress on a seatpost. I would have thought that equivalent saddle time on the flat, at a higher average speed with more potholes encountered, would have given more stress. Again as reference, I regularly put in about 7,000ft in a weekend and my last ride was almost 16,000ft of climbing. I killed an American Classic CR-420 rim but the saddle and seatpost were just fine and dandy...
     
  9. gpriatko

    gpriatko New Member

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    Could be. I haven't been able to find the spec for torquing that bolt. I'll keep looking.

    That looks like a much better setup than the Bontrager.


    Maybe it doesn't; I don't know. I put down the most torque when I'm climbing there's some rotational moment about the axis of the seat post. Push with the left leg and the seat wants to rotate CW. Push with the right leg and the seat wants to rotate CCW.
    I do about 500 climbs a year. Multiply that by 2000 pushes per climb and you've got 1,000,000 stress cycles per year. In my case It looks like some where around 1.5 million it goes "ping!"

    I don't crank very hard on the flats.


    The roads are fairly smooth here and I'm out of the seat for any major jolts. I ride the same circuit every day so I've gotten real good at knowing where they are.
     
  10. gpriatko

    gpriatko New Member

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    Just got back from a ride.

    Everything I said about rotational torque on the saddle -- that's just nuts.
    It may not have been the dumbest theory I ever had but it's a contender.

    As far as I can tell the only stess that I'm putting on the saddle when I'm climbing is the verticle stress from shifting the work between the right and left leg.

    My best guess is that the clamp end is concentrating the stress at the bolt.

    Why did it break on the left side both times? Don't know. It might not be a systematic kind of thing. It's got a 1:4 chance of doing that just by dumb luck.
     
  11. 531Aussie

    531Aussie Well-Known Member

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    fair enough that certain posts may be better than others, but the bottom line is, ti rails break more often that steel rails.

    I've seen about half a dozen saddles in the last couple of years with busted ti rails, but I can't even remember ever seeing a busted steel rail
     
  12. Albert 50

    Albert 50 New Member

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    the price you pay for 48.74 grams of weight saving :rolleyes:
     
  13. dhk2

    dhk2 Active Member

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    +1. The "mounting and use" instruction sheet that came with my last SI Flite saddle about 3 years ago recommended replacing the saddle at a specific interval (~10K miles IIRC) to avoid fatigue failure of the ti rails.

    Have never had a ti rail break, but I generally replace saddles at or before 10K miles since the foam and support tends to break down after a couple of seasons, leading to a major loss of comfort. My theory is that all the heat, humidity and sweating of summer riding here tends to degrade the foam and ruin the comfort.

    In my (limited) experience, saddles with a "lorica" cover (eg, SSM Era and Aspide) seem to hold up better than the leather ones (eg, Arione, Flight, Fly).
     
  14. 531Aussie

    531Aussie Well-Known Member

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    jee, I didn't know that. That'd be less than 6 months for some people, even some club-level riders. I'm still using some Vetta saddles which are over 10 years old.
     
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