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During the last few years, I've had a broken saddle rail every year or so. It always breaks just in front, or just behind the clamp. I wonder what the reason could be, and how I can avoid this.

Here are two pictures: Detail Overview

Some information:

  • I'm ~75 kg (165 lbs), so not exactly heavy
  • I'm only cycling on paved roads, no bumps whatsoever, roughly 12 km (7.5 miles) / day
  • My bike is an ordinary city bike, Shimano Nexus 7 speed, roller brakes, size 37-622 tires, no suspension
  • Most (affordable) saddles over here in The Netherlands are by a single brand 'Selle Royal'. Therefore I expect the size of the rails would be the same for all of them, and shouldn't be an issue
  • Two years ago I replaced the clamp, because the old one looked worn out. This seemed to solve my problem, but today, I found it broke again

I found this question (Saddle Rail Failure?) but was wondering if there could be other reasons.

UPDATE 20 aug 2018

I spoke to the guy at the bicycle shop. According to him it is probably caused by a combination of the rails not being centered properly, and maybe also the way I ride over (speed)bumps. So Andrew, you were right after all, I guess (although I would have to wait another year to be sure ;-) ).

  • What kind of bicycle? Tire size? Suspension? How do you ride over bumps? Do you leave your weight on the saddle or do you take your weight off the saddle? – Andrew Henle Jul 31 '18 at 19:12
  • @andrew, I updated my question. I'm not sure what kind of bumps you're referring to, I can only think of speed bumps, but with a size of say, 2m and a speed of 20 km/h that wouldn't be a problem right? I'm definitely not getting out of my saddle for those 😉. – Berend Jul 31 '18 at 19:51
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    I wonder if you ride with your body all the way forward on the saddle, placing a lot of torque on the rail. This would probably be because the frame is too large for you or the handlebar is offset too far forward. – Daniel R Hicks Jul 31 '18 at 22:27
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    @Swifty This morning I paid extra attention to bumps, and indeed I found a tree root that had pushed the pavement up a few inches. I'm calling the papers :-) – Berend Aug 1 '18 at 14:13
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    I had the same problem once. What solved it for me was to lower the nose of the saddle. When you ride with a high nose, you tend to put a lot of weight on the nose. When you ride with a low nose, you tend to put more weight on the rear part of the saddle. I did not believe that this could help at the time, but time has proven this strategy to be correct. – cmaster Aug 1 '18 at 14:16
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The clamp in your seat post is unusually narrow, and this generates higher than normal high bending forces on the seat rails. A seat post with larger clamp should solve this problem.

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Looks like a cheap clamp with only a single bolt. I think the best option would be to get a proper seat post with two bolts and tighten them to the correct torque with a torque wrench.

Saddle rails usually don’t break. I’m not even aware of any stronger or otherwise reinforced options (e.g. for heavy riders).

  • That may be so, but even a cheap clamp shouldn't break so often. I'll certainly look into a more sturdy type, but I think it will at best only fix the symptoms, not the root cause. – Berend Aug 1 '18 at 14:09
  • It's not the clamp but the saddle rails that breaks. – ojs Aug 1 '18 at 17:18
  • A cheap clamp could have insufficient clamping force on the rails, thus allowing one rail to flex more than the other (e.g. when loaded sideways) which puts more load on a single rail. This could also exacerbate fatigue wear. It’s hard to estimate from the photo but I think quality clamps are also wider/longer and have deeper grooves. – Michael Aug 1 '18 at 17:22

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