0

I'm purchasing a new seat-post as my saddle refused to stay at the same angle with my current one; it was a second hand bike (B'Twin Triban 500) with a single bolt clamp. I'm going to switch to a two bolt clamp to try and fix the situation, and hopefully get the right angle!

However, I can't find any information on whether to use grease or threadlock on the bolts. I use grease on most bolts, and don't actually have any threadlock; I believe I'd be looking to get Loctite Blue-243 or Blue-242 if I needed it? Furthermore, is there a difference between threadlock and anti-seize?

Thanks!

  • 1
    Do you mean that the seatpost is staying put in the frame, but your saddle is slipping on the seatpost? I'm not sure you necessarily need a two bolt post, but I agree that good two-bolt posts are less likely to have their clamps slip. You may also wish to check if you torqued the bolt down correctly. A bike store could help you with this. – Weiwen Ng Dec 10 '19 at 21:45
2

A very thin coating of grease will help prevent the threads corroding or sticking together, as will a specific anti-seize product. You definitely want something on the bolts as water and crud gets thrown up into the bottom of the saddle by the rear wheel.

You can use thread locker, but if you have been having trouble with the seat bolt coming loose you are probably not tightening it enough. You can try taking the bike to a repair shop and having them use a torque wrench to tighten the bolts properly.

|improve this answer|||||
1

Are you sure you are using the correct size seatpost? You can increase the width depth of the slot in the back of the frame where the seat post goes in to make it easier to tighten the seatpost more firmly. seat tube slot: seat tube slot

The play between seatpost and frame should be just barely noticable when wiggling the seat post back and forth without the bolt clamped down. If the play between seat post and frame is quite substantial you could consider using a piece of beer can (or other similar material) as a spacer, but this is not a very elegant solution. enter image description here

You could try using some sandpaper on the inside of the seat tube to make it rougher/ make it harder for the seat post to rotate out of position.

Is the problem that the seat post clamp bolt loosens up by itself? or will the seatpost rotate/move even when the seatpost bolt is tight? If the bolt loosens up then I would suggest using locktite or another similar threadlocker, I don't believe anti-seize has thread locking properties but I could be wrong on this. Also make sure the currently installed seat post clamp is the correct size for the frame/seatpost.

When using non-carbon frame and seatpost you shouldn't worry too much about overtorquing in my experience. As long as you don't strip the head of the bolt(s) or threads of the clamp there should be no issue. 5-9Nm should suffice according to the following website: http://www.bike-manual.com/brands/trek/om/cross/torque_spec.htm but if you make sure your bolt can handle it without stripping/ruining the bolt head you can go a bit higher if needed.

On 1 bike I had a a seatpost which had the same issues as you describe, I thought the clamping was the issue but as it turns out the top piece of the seat tube (which clamps to the seat itself) was rotating inside the tube-part of the seat tube. Unlikely that this is the case for you since you ordered a new seatpost though.

|improve this answer|||||
  • 1
    I think his problem is it's flopping around on the top where the clamp between the seat post and the seat is, not the actual seat post clamp (which can certainly be problematic especially if the frame has not been reamed to just the right size) – user68014 Dec 10 '19 at 20:44
  • @user68014 yes you might be right about that. In that case I'd suggest loctite. Perhaps a stronger kind than loctite blue for instance loctite Red (high strength thread locker). – Maarten -Monica for president Dec 11 '19 at 0:35

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for?Browse other questions tagged or ask your own question.