What actually happens if you over-tighten your seat post clamp?

General cycling advice ( NOT technical ! )
Jd843
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Joined: 20 Feb 2020, 7:48am

What actually happens if you over-tighten your seat post clamp?

Postby Jd843 » 22 Nov 2020, 10:47am

Possibly daft question...!

What are the potential consequences of over-tightening seat post clamp bolts? Damaged frame, seat post, or both? I always assumed both, but in most discussions online about seat post torque, people seem more worried about damaging carbon seat posts but not frames. Damaging a carbon seat post would be annoying, but at least it's more straightforward to fix - buying a new seat post, vs repairing or replacing a carbon frame?

I've got a torque wrench and I usually go for around the 5-6Nm range, but I am very paranoid about the torque wrench being faulty and accidentally breaking something by unwittingly going to 10Nm or something.

rotavator
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Location: North Wales

Re: What actually happens if you over-tighten your seat post clamp?

Postby rotavator » 22 Nov 2020, 3:03pm

Well I managed to snap the (Campag) clamp on mine :oops: ...I suppose that was better than damaging the frame or seatpost.

De Sisti
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Re: What actually happens if you over-tighten your seat post clamp?

Postby De Sisti » 22 Nov 2020, 3:10pm

[quote="Jd843" question...!]
What are the potential consequences of over-tightening seat post clamp bolts?
[/quote]
It will eventually snap (mid-ride), as in my case. Actually, it was within a couple of miles of my house.
No damage to frame of seat post.
Last edited by De Sisti on 23 Nov 2020, 4:25pm, edited 1 time in total.

pwa
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Re: What actually happens if you over-tighten your seat post clamp?

Postby pwa » 22 Nov 2020, 4:47pm

Damage to the clamp itself is the most likely. But carbon posts do come with a recommended limit, so the makers must foresee damage. Do carbon frames have any figures printed in the clamp zone?

Jdsk
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Re: What actually happens if you over-tighten your seat post clamp?

Postby Jdsk » 22 Nov 2020, 4:51pm

Jd843 wrote:I've got a torque wrench and I usually go for around the 5-6Nm range, but I am very paranoid about the torque wrench being faulty and accidentally breaking something by unwittingly going to 10Nm or something.

The margin of error on the recommended torque would probably be OK for that overload.

You can test a torque wrench with fancy equipment... or some jury-rigged levers and a known mass.

Jonathan

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foxyrider
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Location: Sheffield, South Yorkshire

Re: What actually happens if you over-tighten your seat post clamp?

Postby foxyrider » 22 Nov 2020, 7:34pm

In my case, the result of overtightening was an immediate failure of the Ti bolt - annoying but no damage to anything else.
Convention? what's that then?
Airnimal Chameleon touring, Orbit Pro hack, Orbit Photon audax, Focus Mares AX tour, Peugeot Carbon sportive, Owen Blower vintage race - all running Tulio's finest!

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The utility cyclist
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Re: What actually happens if you over-tighten your seat post clamp?

Postby The utility cyclist » 23 Nov 2020, 1:14am

You can crack the uppermost part of where the post inserts on a carbon frame if you overtighten significantly. You might if again going way over the amount you need to tighten, be able to crush/crack a carbon post, more so if it's wafer thin/el cheapo.

Cyclewala
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Re: What actually happens if you over-tighten your seat post clamp?

Postby Cyclewala » 24 Nov 2020, 9:53am

Bolt broke on a late night commute once. Had to ride the remaining 9 miles stood up all the way. Quads were hurting for days.

On another occasion, bolt broke whilst moving briskly and could have been nasty. Thankfully, I had a rear reflector about two inches above the clamp and it stopped a sudden dropping of the seatpost.

Also, damaged a carbon seatpost on another bike and changed it to an aluminium post.

Joys of being a lardy rider and the extra strain on the components.