Every material has a limited life span- where it can handle so many fatigue cycles. Those bolts are probably stainless and could only take so much. With a twenty year old bike I would consider hanging it on the wall and finding something with less hours on it, or at the least carefully inspect it after each ride.
Seat Bolts Failed - Pic
I have 2003 Intense FS and was riding a rocky trail when bam the two bolts clamping the seat wires to the post fractured.
![Hand tool Plane Wrench Scrub plane Wood]()
Fortunately I found the two castings that clamp on the two seat wires. If you look at the right casting, the stubs of the fractured bolts are still there, very clean fracture.
Riding back with seat "balanced" on the post was tricky.
Is this a common occurrence?
Are there steps I should take to prevent this?
Any thoughts?
Fortunately I found the two castings that clamp on the two seat wires. If you look at the right casting, the stubs of the fractured bolts are still there, very clean fracture.
Riding back with seat "balanced" on the post was tricky.
Is this a common occurrence?
Are there steps I should take to prevent this?
Any thoughts?
1 - 19 of 19 Posts
Itd be unusual for those to be stainless, ss has less strength. You could go to harware store and find replacement, but you want as high a grade as u can find. Might have to look a bit to find the stronger than standar metric bolts.
That makes sense. Curious, is the hardware in my photo part of the bike (20 YO) or part of the seat (? YO). If part of the bike then the failure after 20 years is no big deal. Planning a trip to the hardware store tomorrow.Itd be unusual for those to be stainless, ss has less strength. You could go to harware store and find replacement, but you want as high a grade as u can find. Might have to look a bit to find the stronger than standar metric bolts.
Thanks for the reply.
The bolts would have come with the seatpost. If the seatpost orginally came with the bike, the bolts are 20 YO. If the seatpost was purchased and installed later on, they would be younger.That makes sense. Curious, is the hardware in my photo part of the bike (20 YO) or part of the seat (? YO). If part of the bike then the failure after 20 years is no big deal. Planning a trip to the hardware store tomorrow.
Thanks for the reply.
I'm surprised that they both sheared off at the same time. Those bolts only supply clamping force to keep the seat in adjustment (fore-aft and tilt), they don't support your weight in any way. Had you recently tightened them and possibly over torqued them? Was your seat making any strange noises prior to the bolts breaking?
Good questions. I asked myself those same questions on the slow ride back.The bolts would have come with the seatpost. If the seatpost orginally came with the bike, the bolts are 20 YO. If the seatpost was purchased and installed later on, they would be younger.
I'm surprised that they both sheared off at the same time. Those bolts only supply clamping force to keep the seat in adjustment (fore-aft and tilt), they don't support your weight in any way. Had you recently tightened them and possibly over torqued them? Was your seat making any strange noises prior to the bolts breaking?
IIRC the last time I tightened the bolts was my last fore/art & tilt adjustment many months ago ~spring. While I swapped seat post very early, I added a spring seat post, not because it needed it but leftover from a hardtail. So my guess the seat hardware is the OEM pieces.
What most surprised me about the shear was how clean it was.
Thanks for the reply.
Time for a new seat post...
Sent from my SM-G991U using Tapatalk
Sent from my SM-G991U using Tapatalk
At the hardware store this morning, had the threaded part with me M6. Purchased 2 30mm socket head bolts at ~$2 each. Installed and did a a 5 mi test ride, rock solid.
Thanks for all the suggestions.
Thanks for all the suggestions.
Did you get the 10.9 grade bolts? Those are the higher strength from usual.At the hardware store this morning, had the threaded part with me M6. Purchased 2 30mm socket head bolts at ~$2 each. Installed and did a a 5 mi test ride, rock solid.
Thanks for all the suggestions.
I did not, I was happy to find SS socket head bolts. I live in the sticks, more elk and deer than people. If these go 10 years they'll outlast me.Did you get the 10.9 grade bolts? Those are the higher strength from usual.
actually, in old seatposts similar to the one OP posted those bolts DO support your weight.....Those bolts only supply clamping force to keep the seat in adjustment (fore-aft and tilt), they don't support your weight in any way....
I disagree, the left casting (convex with groves) sits in a concave grooved portion of the seat post. The screws thread into the right casting and clamp all four pieces together. In order top to bottom: 1 casting with threads, 2 seat wires 3 bottom convex casting 4 concave seat post.
To my mind while the screws bear no weight, they are under considerable stress as the riders weight moves fore/aft under normal riding. Nothing is static while riding. FWIW
To my mind while the screws bear no weight, they are under considerable stress as the riders weight moves fore/aft under normal riding. Nothing is static while riding. FWIW
Seat rails. They’re called seat rails.
Thanks, fellas. Carry on.
=sParty
Thanks, fellas. Carry on.
=sParty
I expect that they didn't fail simultaneously. One probably broke a while ago, but the other held the seat in place well enough that you didn't notice. Then the increased load from suddenly having to do double the work shortened the remaining bolt's life.
That's certainly possible, the test ride with 2 new bolts sure felt solid.I expect that they didn't fail simultaneously. One probably broke a while ago, but the other held the seat in place well enough that you didn't notice. Then the increased load from suddenly having to do double the work shortened the remaining bolt's life.
Exactly. Come to think of it, I can't think of ANY seatpost where the bolts carry the weight of the rider.I disagree, the left casting (convex with groves) sits in a concave grooved portion of the seat post. The screws thread into the right casting and clamp all four pieces together. In order top to bottom: 1 casting with threads, 2 seat wires 3 bottom convex casting 4 concave seat post.
To my mind while the screws bear no weight, they are under considerable stress as the riders weight moves fore/aft under normal riding. Nothing is static while riding. FWIW
And yeah, "seat rails".
you are correct. i guess they don't technically support weight in a shear direction, but there is a lot of constant force being applied to them. not just from shifting weight, but every bump hit while seated goes straight thru them...I disagree, the left casting (convex with groves) sits in a concave grooved portion of the seat post. The screws thread into the right casting and clamp all four pieces together. In order top to bottom: 1 casting with threads, 2 seat wires 3 bottom convex casting 4 concave seat post.
To my mind while the screws bear no weight, they are under considerable stress as the riders weight moves fore/aft under normal riding. Nothing is static while riding. FWIW
I've had more trouble with those kurled post clamps than any other type (usually just single bolt, but I've never had the bolt fail). The knurls get mangled and then the seat won't hold an adjustment.
The style that Thomson popularized is my strong preference. I dunno if the bolts are under any less strain, but I've had posts from multiple brands using this type of clamp and they've all been far less troublesome.
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The style that Thomson popularized is my strong preference. I dunno if the bolts are under any less strain, but I've had posts from multiple brands using this type of clamp and they've all been far less troublesome.
I had a Nitto 2-bolt post on my all-purpose road bike for years. One afternoon I'm pedaling down the street and one of the bolts snaps. My fault - I overtorqued it. But I got away with riding it in the overtorqued state for quite a while before the bolt broke.
I replaced the post with a 2-bolt RaceFace... and made sure to use a torque wrench when I installed the saddle.
I replaced the post with a 2-bolt RaceFace... and made sure to use a torque wrench when I installed the saddle.
1 - 19 of 19 Posts
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