Slipping seatpost

[Samuel D]

I have a Ritchey Classic seatpost and Spa Audax frame that worked nicely together for several months. The seatpost fits snugly and smoothly, feeling almost like the piston of a track pump when the clamp is loose. I applied plenty of copper grease from the start – maybe too much.

I recently fitted a new saddle and noticed while riding that I needed to raise the seatpost slightly. I did so despite the whole bicycle being covered in muck at the time. The clamp screw felt rough because of the muck. This may have reduced the clamping force for a given screw torque, but I was afraid to go much above what I remembered 7 Nm to feel like (7 Nm is the limit printed on the Spa clamp).

For the rest of the ride the seatpost slipped down slowly but repeatedly, sometimes going below the original height (presumably introducing muck into the frame), despite my increasing the clamp screw torque each time.

I’m on holiday at the moment (sans vélo) but need to deal with this as soon as I get back. Should I just clean everything and try again? How much copper grease is too much? And is there much harm in going above 7 Nm?

[Brucey]

1) Should I just clean everything and try again? 2) How much copper grease is too much? 3) And is there much harm in going above 7 Nm?

1) yes
2) occasionally a seat pin that is a good fit will slip if it is very well lubed.
3) yes, if the clamp says 7Nm it will probably break if you exceed that by any appreciable amount.

You could try the seat pin dry or with a little grip paste?

cheers

[cromo]

I had the same problem and found it very annoying! I did not want to use excessive force on the seatpost clamp bolt. So, I purchased a seatpost clamp (30.0 mm) and a seatpost shim (27.2 to 30.0mm, as my seatpost was 27.2mm) and cut the shim to fit inside the extra seatclamp. This extra clamp was then tightened around my existing seatpost so that it was just above and in contact with the existing seatclamp. Problem solved!

[Valbrona]

Grease/lubrication is for moving parts. So, by all means, if you want to make your seatpost move within your seat tube ... lubricate it.

[fastpedaller]

I had the same problem and found it very annoying! I did not want to use excessive force on the seatpost clamp bolt. So, I purchased a seatpost clamp (30.0 mm) and a seatpost shim (27.2 to 30.0mm, as my seatpost was 27.2mm) and cut the shim to fit inside the extra seatclamp. This extra clamp was then tightened around my existing seatpost so that it was just above and in contact with the existing seatclamp. Problem solved!

Would an alternative be a 27.2 clamp on the seatpin so it just rested on the existing clamp?

[cromo]

Would an alternative be a 27.2 clamp on the seatpin so it just rested on the existing clamp?

Yes, it would, if you can get one. SJS cycles sell a double clamp that clamps on the frame and the seatpost. My problem was that my bike had lugs that were part of the frame that accepted a bolt, it did not have a separate clamp as such. The cheapest option at the time was to buy an oversize clamp and shim which was then positioned resting on the top of the frame to prevent slippage of the seatpost.
It might be worth mentioning, since seatclamps have a lip at the top it would probably be a good idea to remove the lip using a file if you are using one of the same diameter as the seatpost. If using a shim, then check that the shim is thicker than the lip.

[iow]

I have 'solved' this issue in the past by re-torquing the seat clamp bolt after leaving it over night - I usually find things have settled enough to get another quarter turn on the bolt.

[CREPELLO]

Suggest that you replace the clamp screw with a screw of a grade that will take a higher torque setting. At least the anchor 'nut' on the Spa clamp is pivoting, so that the screw is not bending, as can happen with other seat clamps.

Also, perhaps try Waxoyl instead of grease to protect the interface from water. It tends to go very sticky, except in very warm temperatures.

[Brucey]

a stronger screw won't help if the clamp itself is the thing that is going to fail first.

I've had mixed results with waxoyl, slippage-wise.

cheers

[Samuel D]

Thanks for the range of ideas, all. Will report back next week.

Missing my bike!

[CREPELLO]

a stronger screw won't help if the clamp itself is the thing that is going to fail first.

I'd have thought the M5 screw is the weakest part of the clamp, so therefore a stronger screw could be helpful. Of course, there would be no point in this fix if it's a badly undersized seat post that's the problem.

The other thing to consider would be a stronger clamp.

[Erudin]

"The Constrictor was designed specifically to end slipping seat posts. The extra-thick clamp utilizes an 8mm stainless bolt and accommodates a rear cantilever brake hanger, if you decide to go that route. The Constrictor is machined out of aluminum billet and black anodized. It's available in 30.0mm and 31.8mm sizes."

http://surlybikes.com/parts/small_parts/constrictor

[MikeDee]

Use carbon friction paste.

[De Sisti]

Carbon paste and Jubilee clip worked for me (on a steel 725 frame).

[531colin]

Suggest that you replace the clamp screw with a screw of a grade that will take a higher torque setting. At least the anchor 'nut' on the Spa clamp is pivoting, so that the screw is not bending, as can happen with other seat clamps.

Also, perhaps try Waxoyl instead of grease to protect the interface from water. It tends to go very sticky, except in very warm temperatures.

Oh yes it is!
Its bending in the Surly Constrictor, as well.
Because as soon as you nip it up, the 2 faces of the clamp are no longer parallel, the screw bends as you turn it. On the "tester" bikes in the shop, the screws occasionally fail with fatigue with constant seat height alteration.
Because i need to remove the seatpost to get the bike in the car, I modify the clamp so the bolt doesn't bend....





Drill the pivoting nut, grind a bolt head so it can't turn in the clamp.

However, these bikes aren't "known for" slipping posts....with the clamp undone, you shouldn't be able to wobble the post....if you can, it could be undersize, when it will work its way down.....lashings of grease will make it an "airtight" fit even if its a bit slack.