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Old 07-29-14, 04:31 PM   #1
DaveLeeNC
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Routine (??) Saddle/Seatpost Questions

I have a couple of questions that (I hope) are simple.

What are the considerations when mixing various saddles with carbon rails and differing seatpost clamps? Are (for example) scandium/titanium (ala' some HCNC products) seatpost clamps OK to use on carbon rails?

When company X says that their saddle is 130 mm (for example), is this the width at the widest points? I thought that a simple Google search would reveal this, but it gets all balled up in proper saddle/butt matching techniques. I just want to be sure that I know what, for a given saddle, 130mm means.

Thanks.

dave
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Old 07-29-14, 04:44 PM   #2
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130 mm = 5.11811023622 in

I have a couple steel rail saddles they are 40_45 ish apart to rail Centers ..

Last edited by fietsbob; 07-29-14 at 05:02 PM.
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Old 07-29-14, 05:02 PM   #3
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And for completeness it is .642 millifurlongs.

dave

ps. Somewhere in reading a bunch of posts from somewhere I got the idea that this measurement was something other than the obvious. But I don't recall where or what that was.
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Old 07-29-14, 07:57 PM   #4
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Most saddles have 7 mm round CrMo or Ti rails that fit almost all saddle clamps. There are some carbon rails that are 7 mm round, but most are oval 9x7 mm that only fit on top clamp types, but not on side clamps. Ritchey does sell side clamps to fit the ovalized rails though.

Care must be taken when installing carbon railed saddles and ensure the clamp bolts are torqued to spec. Too tight and you risk cracking the carbon. Full clamps are better on carbon than the minimum yoke-cradle types because it spreads the clamping forces on a larger portion of the rail. With the yoke-cradle types, the forces are focused only on certain points along the rails producing stress raisers, and produces a "bowing effect" on the rails if the bolts are overtightened.

As for the saddle width, it is usually at the widest part of the saddle. But again, it may vary from manufacturer to manufacturer.

Last edited by e_guevara; 07-29-14 at 08:06 PM. Reason: Additional info
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Old 07-29-14, 08:13 PM   #5
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Make sure you use a clamp designed for carbon rails the shape you have or you'll have an expensive and not very effective paperweight.
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Old 07-30-14, 06:07 PM   #6
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It would appear (based on what I can tell) that the oval shape of some (all??) carbon rails require (usually?) rail clamps of the same shape that don't clamp across the small diameter of the oval. But that is hardly clear on the vast majority of the documentation supplied via online sources.

If you are going to use carbon railed saddles, apparently you have some serious detective work to do WRT the right seatpost.

dave
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Old 07-31-14, 09:58 AM   #7
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Carbon rails are often oval with the long axis vertical. The radius of the oval ends is the same as for round rails so clamps that grab the rails from the top and bottom will work on oval CF rails. Clamps that grab from the sides won't unless they are specific to the oval rails. With any of these and even when using metallic rails the edges of the ends of clamp where the rails pass should not be sharp or have a burr.

On saddles I have, the widest point on the saddle agrees with the specified width.
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