Awesomeguy

I have a carbon frame and with a aluminium seat post and seat clamp says 6-8nm torque spec.
im still waiting for my torque wrench to come in , but I’ve been using 5nm torque wrench and it hasn’t slipped , should I be concerned ?

will I damage something by being off by the torque specification ?

SoSmellyAir

If the seatpost has not slipped or twisted, then you are fine at 5 Nm.

Did you use any grease between the seatpost and the frame?

Awesomeguy

so the bike is only couple months old and bought from a trek dealer, so Im assuming they did everything that should be for preventative care , then the question becomes , when my torque wrench comes , should I torque it at 6nm (the spec says 6-8nm) or leave it at 5nm?

SoSmellyAir

If you feel comfortable resting on that assumption, then just leave it at 5 Nm.

Camilo

The torque spec is maximum, not minimum. If it doesn't slip, it's fine. If it slips it probably won't be "catastrophic", but merely noticeable. FWIW, I use my 5nm torque key for almost everything with a low torque unless it doesn't hold. Only then I use my beam-type torque wrench.

soyabean

I always use some Park Tool SAC-2 on all seatposts, carbon or not.

Bike Gremlin

As far as I know, in most industries, torque specifications are the optimal torque. Because for bolted connections, going under the optimal torque can also put more stress on the parts (especially the bolts).

With cycling, there is more marketing and nonsense than engineering.

Having said that, if the torque spec. says 6-8 Nm, in a carbon frame, I would use some carbon mounting paste and tighten it to 6 Nm.

My 2c on tightening torque and torque wrenches.

P.S.
A thing to look out for with a carbon-aluminium connection is the galvanic corrosion.
It would probably be a good idea to remove the seatpost at least once every 6 months, clean, re-apply the carbon-assembly (mounting) paste, and put it back (of course).

Relja

Crankycrank

My take is that if it's not slipping it's probably fine but if I just purchased a new torque wrench to check something I'm worried about (plus, I can't resist trying out a new tool) just go ahead and re-torque it and you can relax about it and concentrate on just riding. You've got nothing to lose except 5 mins of your time.

SoSmellyAir

Does CF assembly paste also prevent galvanic corrosion?

Bike Gremlin

As far as I know - no.

Anti-seize paste does, but that's not a good idea for carbon parts (as you need to increase grip and friction, since carbon doesn't take much compression very well - and anti-seize paste is "greasy").

Relja

SoSmellyAir

That is my understanding as well, which is why I recommended grease to the OP originally.

Exactly. I only use anti-seize when installing pedals (and spark plugs, for my car).