Seat Post Clamp Snapped...AGAIN!!

Grenouille

I have a Spesh Roubaix Elite and last month the seat post clamp snapped on a ride (what fun!)





I got a replacement on warranty so that was fine but last night I was putting it on the bike and tightening it with a torque wrench when it happened again!



I will go back to the shop for another replacement on warranty but I don't plan on fitting it as I have no confidence now it its ability to stay in one piece.

What replacement would anyone recommend? These look somewhat tougher:

http://www.wiggle.co.uk/hope-single-bol ... ost-clamp/
http://www.wiggle.co.uk/thomson-seat-collar/
http://www.wiggle.co.uk/chromag-non-qr-seat-post-clamp/

Also, the Spesh seat post collar is 32.6mm - will 31.8mm be ok as they are the closest for the Thomson and Hope collars?

sungod

looks like it failed at the same place, is there burr/edge/whatever at that point on the tube?

if you're replacing, stick to the correct size clamp

Wooliferkins

32.6 is odd by any measure. I doubt the 31.8 will slide over the top of the seat tube. Forgive me for an egg sucking question but you're not getting your Nm and lb/f mixed up on the torque wrench are you?

Grenouille

I forgive you! But no, the torque wrench is set to 6n-m.

desweller

I'd be inclined to find the right size clamp. You might be able to force a smaller one on but it is quite a big size difference. Have you tried calling one of the Specialized high street stores?

Wooliferkins

Grenouille wrote:

I forgive you! But no, the torque wrench is set to 6n-m.

Thanks. Years of working in an environment where, "It just snapped boss" sent a despairing shiver down my spine

andyrr

Max torque is 6.2 ? Does it actually need to be torqued right up to close to that ? Sorry for asking what might seem an impertinent question but if your wrench is a little out and reading low then your 6 could be 6.5 and that, for what is not a particularly sturdy bit of metal, could just tip it over the edge. If it is a carbon post then mabe use some assembly compound which could allow a lower torque on the post clamp.

Wooliferkins

When designing something the loads required to cause failure are usually at least 50% over the user loading

slowbike

Wooliferkins wrote:

When designing something the loads required to cause failure are usually at least 50% over the user loading

Which makes you wonder if the OPs torque wrench is not calibrated. 50% over 6Nm is only 9Nm - easy to apply by hand ...

Monty Dog

Yup, consistent failure would suggest over-tightening, easy with a badly adjusted torque-wrench. I wouldn't attempt to fit a 31.8 in place of a 32.6 either.