Hi,

The generic seatpost on my road bike calls for 18-25nm of torque for the saddle bolt. The saddle is a Fabric line s elite flat with metal rails, how much should it be torqued? 18-25 nm seems high.

Dave

Can you show a photo as there are so many types, seems unlikely that a manufacturer would make this type of error but that is very high. That said just last weekend i installed a new Litespeed post and it was to be torqued to 10nm.

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What's even stranger is that it has a table of torque values based on bolt sized M6-M10, so first you have to figure out what size bolt they installed, lol! Pic to come.

I imagine they reasonably assume that anyone who understands the concept of torque settings will be able to figure out the relevant bolt size

Yeah, it wasn't too hard, but what a bizarre thing not to have a torque setting for that specific part!

I have seen single bolt torques go as high as 20, don't recall over that. You might search major single bolt manufacturers like Nitto for their max.

Nitto is saying 13 nm for a M8. Looks like single bolt seatposts run with higher torque. I might run 10 NM and see if it holds.

Thanks,

Dave

I had a similar seatpost, years ago. It was a friction fit at the curved area, between the seatpost fitting on the bottom, and the bottom part of the saddle clamp. No ridges on the interface. That made it very adjustable, but prone to major slipping.

At first, it slipped when I rode over a bump, flipping the back down as far as it would go. Cranking down the bolt didn't fix it completely.

I ended up using some wet-and-dry sandpaper on both halves to roughen the curved surfaces, probably 180 or 240 grit, and a coating of Tacx Carbon Assembly Paste -- that was a tube of gel with plastic grit in the gel. (I still have the tube, 20 years later!) Assembly paste is great for aluminum stems to aluminum handlebars, too.

I just use JB Weld. No slip and no future adjustments - ever.

M8 is a pretty sturdy bolt.

For steel M8 with socket head, lubricated torque is 38 Nm, anti-seize torque is 26 Nm.

For stainless steel, 19.1 lubricated.

Pro tip: The torque specs on bike bits is almost always based on the fastener size.

the limitations to that seatpost clamp are the fingers of the aluminum top half of the clamp... being Cast aluminum, they WILL BEND, if over-torqued... and once cast aluminum bends, it is going to break, eventually.

Standard "torque specs for steel bolts" are going to be too much for that aluminum clamp... they refer to the steel bolt screwed into a steel part.

good luck.
i'd think a bit less than half the steel/steel torque might be a good starting point... or less. the length of the clamp fingers will play into it, and keeping seat in position is the only goal, not achieving some torque number.
start light, and work up to the goal.

exactly right. or the threads will strip

The Campagnolo single bolt posts have a heli-coil which helps a lot.

A skilled mechanic will develop a "feel" for how much torque to apply to this fastener. Following a torque spec is fine if you don't have that feel or don't know.

I use the torque wrench on stem bolts and a few other things. Otherwise I use my learned sense of how much is enough.

/markp

sadly, too many follow the steel-to-steel torque charts... which helps keep heli-coil in business.....

i throw out a lot of over-pinched stems. those tiny cast aluminum ears get bent together all too often.
seat post frame clamps too.
BMX bar clamps with stripped out threads...
shifter clamps tightened until the clamp breaks...
etc.

sigh.
my "for parts-only" bins are a roadmap of over-torques, annotated with crashes and rain.
i've learned to just pull the most used bits, and recycle the main bulk.
the derailleur bin is due for a chaff removal again.... one can only keep so many backward-shifting deore and TZ series rear ders. before it becomes crazy. The adjusters and cable pinch stuff gets salvaged.... and newish rollers/bushings. and the plastic washers on TZ hanger bolts too.

I would torque it to 10nm and see how it feels. It should require a fair amount of effort but not too much. Then take it for a good ride and check after returning and for the next few rides. After that you can add a bit more torque if needed but it will probably be fine.