Dangerous suspension seat post. Don't buy this!

[John F]

The single bolt attaching my suspension seat post has just broken during a ride, resulting in the saddle coming away and crashing on to the road. How I avoided a nasty accident I'll never know. The saddle was fixed correctly and I would guess to the correct torque (though not with a torque spanner)

Conclusion is that the bolt was not up to the task. The stresses imposed on that single fixing must be considerable. Worringly most of the posts that I have seen for sale also have only one bolt. How can I trust any one of these now?

There are however a couple that I have seen that have the saddle fixed with TWO bolts. This tells me that some manufactures have decided that a single bolt fixing is potentially dangerous and that two bolts are preferable.

Has anyone had this frightening experience?

What are peoples thoughts?

 

[oyster]

You could be right about two bolts. But it seems just as feasible that they decided it was cheaper for them to do it that way. Obviously next to impossible to assess without a detailed understanding of their factory and sourcing of parts!

I know that the difference between a quality high-tensile bolt and a cheapo mild steel thing is dramatic.

 

[DanD]

I had the same shock on my bike with its single seat clamp bolt shearing off suddenly a couple of years ago. Luckily I was using the bike on an indoor trainer at the time so no serious injuries. I'd been using the post for a few years and the failure was totally unexpected.

I've not had much luck with seatposts/saddles as I've also recently had both saddle rails shear on my Brooks saddle which I believe is a known problem with their chromed rails. Their customer support was good and the saddle was repaired under warranty.

I'm now paying more attention to regular checks of my bike's components, but not confident that I'd spot anything that might indicate an imminent stress failure.

 

[RogerA]

I had the same thing happen a few years ago on a Dahon that I got through the cycle to work scheme. When I checked, I discovered there had been a manufacturer recall but that the cycle supplier hadn't told me even though they had all my details. In my case the bolt failed as I entered a roundabout, and the saddle was only held on by the saddlepack tool bag.

 

[John F]

I had the same shock on my bike with its single seat clamp bolt shearing off suddenly a couple of years ago. Luckily I was using the bike on an indoor trainer at the time so no serious injuries. I'd been using the post for a few years and the failure was totally unexpected.

I've not had much luck with seatposts/saddles as I've also recently had both saddle rails shear on my Brooks saddle which I believe is a known problem with their chromed rails. Their customer support was good and the saddle was repaired under warranty.

I'm now paying more attention to regular checks of my bike's components, but not confident that I'd spot anything that might indicate an imminent stress failure.

I also like to check my components, but hard to tell whether that single bolt is made of super strong steel or not. Your Brooks story isnt helping my optimism either!

 

[John F]

The CNC Suspension Seat post (Amazon) has 2 bolts and looks like a more reassuring option0.

 

[Andy-Mat]

How awful, a possible serious accident and or damage to the nether regions, or both. My thoughts are low quality bolts out of the far east, but just guessing.....

Having built a kit car in the early 1990s here in Germany, and having to abide by the requirements of the German TÜV (Pronounced almost like "Toof" by the way), I bought only 8 series metric bolts or higher quality and never had a problem with either the bolts or the TÜV!

So I looked around for an easy way to help everyone here to be able to purchase high quality bolts, and I found this video, which should help a bit, though many will need to watch the whole video till the infos they need come up. Look under "How do you identify a bolt? ":-

bolt markings for use on cars? - Google Search

Regards
Andy

 

[AndyBike]

Pretty nasty, last thing you want is a seatpost enema. A lucky escape

Sure its not just down to overtightening rather than a product defect. Shouldnt really exceed 10nm as its putting too much pressure on the rails.
Suspension posts have a habit of being wobbly due to needing that bit of play to function correctly, and it can be a temptation to hand tighten too much trying to avoid that.

 

[Andy-Mat]

Pretty nasty, last thing you want is a seatpost enema. A lucky escape

Sure its not just down to overtightening rather than a product defect. Shouldnt really exceed 10nm as its putting too much pressure on the rails.
Suspension posts have a habit of being wobbly due to needing that bit of play to function correctly, and it can be a temptation to hand tighten too much trying to avoid that.

I think that you have a good and valid point, but one that might be better addressed with a top quality bolt, which are cheaper and easier to repair. than the enema you mentioned. OUCH!!!
Regards
Andy

 

[AndyBike]

Thats always been one of my irrational fears, but from the post type thats just a post and the saddle has the clamp built on, and held with nuts/bolts. 99% of the time its the super cheap ones. I keep thinking of how an apple corer works

 

[DanD]

Thats always been one of my irrational fears, but from the post type thats just a post and the saddle has the clamp built on, and held with nuts/bolts. 99% of the time its the super cheap ones. I keep thinking of how an apple corer works

I think I was lucky that I was clipped-in to my pedals on the trainer as I immediately stood up on the pedals when the seat bolt sheared and the saddle disappeared. If my feet had slipped off the pedals.....I don't want to think what might have occurred! The downside of being clipped-in was that trainer also tipped over, but I was only left with a couple of bruises. The rail breakages were more gradual and just left me confused .

 

[AndyBike]

Rail breakages can occur if the saddle is too far back and the weight on it while sitting puts a tremendous shear strain onto the rails. It's not a wholly unusual thing to happen.

 

[guerney]

This thread of got me thinking about getting a Cane Creek Thudbuster again... might reduce big sudden forces acting on the rails.

 

[John F]

Pretty nasty, last thing you want is a seatpost enema. A lucky escape

Sure its not just down to overtightening rather than a product defect. Shouldnt really exceed 10nm as its putting too much pressure on the rails.
Suspension posts have a habit of being wobbly due to needing that bit of play to function correctly, and it can be a temptation to hand tighten too much trying to avoid that.

I like to think I have a bit of a "feel" when tightening bolts thanks to rebuilding a Vincent and Norton many years ago. But of course you could be right, I didn't use a torque wrench.

My new seat post as referred to earlier has arrived, and I must say I'm not overwhelmed by the quality. It does howver have 2 bolts, though they are smaller diameter than the broken single one.. I do have my seat as far back as is allowed as I'm tall, which would indeed put greater stress on the fixing bolt(s) as mentioned previously.

The saddle is the cheap Lidl one, and looking at it closely the seat rails are not exactly in a straight line, i.e. where they start to bend is roughly where the extremity of the safety markings are, so something else to consider and worry over!

 

[John F]

Rail breakages can occur if the saddle is too far back and the weight on it while sitting puts a tremendous shear strain onto the rails. It's not a wholly unusual thing to happen.

I have mine right back. Puts more of a strain on the bolt

 

[John F]

How awful, a possible serious accident and or damage to the nether regions, or both. My thoughts are low quality bolts out of the far east, but just guessing.....

Having built a kit car in the early 1990s here in Germany, and having to abide by the requirements of the German TÜV (Pronounced almost like "Toof" by the way), I bought only 8 series metric bolts or higher quality and never had a problem with either the bolts or the TÜV!

So I looked around for an easy way to help everyone here to be able to purchase high quality bolts, and I found this video, which should help a bit, though many will need to watch the whole video till the infos they need come up. Look under "How do you identify a bolt? ":-

bolt markings for use on cars? - Google Search

Regards
Andy

Looks interesting, will check this out thanks.

 

[John F]

Looks interesting, will check this out thanks.

Just invested in a torque wrench. Sticker on new post says 10n/m so at least I should get that right! Next action check out the bolt strength!

 

[Andy-Mat]

Just invested in a torque wrench. Sticker on new post says 10n/m so at least I should get that right! Next action check out the bolt strength!

A good idea, but it still does not shield you from a bolt breaking, unless you know the exact quality/type of bolt.....even then, poor qualty may still fail, and you get the steel enema.....
10n/m may or may not be OK......
For instance, if the bolt you have is of cheap Chinese quality, it may even cause the bolt to break even sooner than without......the bolt has to be of a quality that can both accept the torque fully and always.....
Just saying!
Andy

 

[guerney]

A good idea, but it still does not shield you from a bolt breaking, unless you know the exact quality/type of bolt.....even then, poor qualty may still fail, and you get the steel enema.....
10n/m may or may not be OK......
For instance, if the bolt you have is of cheap Chinese quality, it may even cause the bolt to break even sooner than without......the bolt has to be of a quality that can both accept the torque fully and always.....
Just saying!
Andy

This is all rather interesting - What should a buyer of bolts - intending prevention of steel enemas - look out for specifically? Who sells the best bolts for this very important purpose? How is bolt quality quantified?

 

[Andy-Mat]

This is all rather interesting - What should a buyer of bolts - intending prevention of steel enemas - look out for specifically? Who sells the best bolts for this very important purpose? How is bolt quality quantified?

I noted for all, in this post only a few days ago, where to find a video showing all the different qualities and their markings.
For metric bolts for car construction (here at least) are marked 8.8 (from memory), which is the lowest "strength" allowed. But the video appears to cover them all far better than I could.
This may also help, though I have not checked it in detail:-

Screw - Wikipedia

en.wikipedia.org

You best buy high quality bolts, from companies that you can trust, going there in person if possible.
May I suggest stainless or zinc coated, to prevent rust, which may not cause the strength of the bolt to fail, but may prevent easy removal, later
Do not forget to get new nuts (locking?) of the same high quality as well, where needed.
regards
Andy