how much to tighten a brompton slipping seatpost?

[velosam]

My seatpost is slipping - how much do I need to tighten it? I realise its till it doesnt slip - but given that I can take cackhandness to new levels I am wondering if there is a level of effort on the QR I should aim towards.

thanks

[mrcharly-YHT]

In all my time of riding a B, I never had this problem. Never massively tightened the seatpost QR.

So I suspect something odd is happening.

Is something preventing the clamp from squeezing the post?

[LittleWheelsandBig]

Shall we meet up soon to check this? Some things are easier in person than virtually.

[Kim]

IIRC there's a torque rating.  It not being immediately obvious how to use a torque wrench with a QR, I opted for loosening it off, closing the lever and tightening the bolt to the rated torque.

First thing to try with a slipping seatpost is cleaning it with alcohol...

[velosam]

Shall we meet up soon to check this? Some things are easier in person than virtually.

We could but the bike is at my mum's!  Will contact you directly.

I have checked the post and its pretty clean and very annoying to have it fall down all the time.

[Bromptonlad]

quarter of a turn should be enough

[drossall]

General advice is not to tighten much (assuming a starting point at which it did not slip when new). So, if a Brompton seat post should start to slip, look at replacing the sleeve (which is a consumable item). But best to let LWaB look, I would think.

[velosam]

Yes I think so too. The bike is only 2 years old so a bit disappointing.  I just stop and pull the seat back up, ita easier than damaging the bike

[Pickled Onion]

It's not unusual for it not to be quite tight enough from new, and not be a problem for some time.

As BromptonLad says, try a quarter turn or less if that makes the clamp hard to push. You don't want to do this repeatedly, once or twice is fine before looking at a new sleeve.

[hubner]

Mine started to slip yesterday, it's a new refurbished A Line. I've only ridden it 5 or 6 times.

At first, the qr needed a fair amount of force to close it but today it seems it needs less and seat post was slipping.

I don't know if the nut had loosened itself, anyhow I tightened it until the qr lever needs about the same amount of force to close it like before.

[LittleWheelsandBig]

Nylon tends to creep under load, particularly at first. It is also hygroscopic, so changes in humidity can affect its dimensions.

[hubner]

It started to slip again and I was tightening the nut quite a bit and was worried about damage to the frame. The lever needed a lot of force to close it, the bolt was protruding past the nut at about 2.75mm, which is quite close to the 3mm limit acccording Brompton.

Then I remembered I had cleaned the seatpost and the inside of the seat tube with a rag that might have had some oil on it from cleaning some other parts of the bike. So I cleaned it all with some meths/lighter fluid and now with the clamp set to a fairly amount of force to close the lever the seatpost doesn't slip. I also rotated the post by 90 degrees.