I have a tag-along for my son that wants to join me on some rides. It's a great way for father-son bonding. He's 7yo. I've attached the collar of the tag-along to my seat post, and tightened the four bolts. However, without instructions (2nd hand tag-along), I only tightened them hard enough so I cannot move the pinion by hand that's attached to the seat post.

When I connected the tag-along itself, I had to align the holes with the pinion so that I can slide in the quick-release pressure lever and hold everything in place.

However, when we went riding and I started to turn left or right, the whole tag-along "bent" downwards throwing my son off it!

The pinion attached to my seat post was simply not tight enough, and it would turn left or right in the direction we were going, but this caused the other moving parts of the tag-along to follow it, resulting in the tag-along turning on it's side and throwing my son off!

Obviously I've made it tighter, but it may loosen over time.

Any recommendations or tips on how to properly secure a tag-along to the bike itself? I am tempted to drill a 10mm hole through my seat post and the pinion to tighten the lot, with a proper bolt.


  • 3
    Great question. A photo would really really help.
    – RoboKaren
    Commented Feb 1, 2017 at 8:09
  • 2
    Do not be drilling holes - you're adding failure points, expecially in seatposts.
    – Criggie
    Commented Feb 1, 2017 at 9:50
  • 1
    These things have used various attachment methods over the years, so a photo really is needed.
    – andy256
    Commented Feb 1, 2017 at 11:40
  • 1
    Note that (almost all) tag-alongs do tilt alarmingly to the side, and that's considered normal. The only exception is the Islabikes trailer-bike that uses a headset welded to a special rear rack, but you'll only see those in the UK. And they're not manufactured any more AFAIK. The floppy tilty trailer-bikes scare me.
    – Móż
    Commented Feb 2, 2017 at 0:08
  • 1
    The attachment is exactly as shown in the pic as per @RoboKaren answer below.
    – Fandango68
    Commented Jul 19, 2022 at 0:30

1 Answer 1


You mention four bolts, does your seatpost hitch look something like this:

Seat hitch

By design, these can cinch up pretty tight against all size seatposts, in contrast to two bolt models which need the proper size shims:

Two-bolt with shims

However, with the four-bolt there are some caveats:

  • Do you have a carbon or aluminum seatpost? With both, you have to be careful as it's possible to crush the seatpost if you tighten the bolts too much. In these cases, you might want to ask the help of a bike store - they might give you some carbon fiber seatpost compound that will help with friction, as well as tighten the bolts using a torque wrench to prevent seatpost collapse.

  • If you have a steel seatpost, it's next to impossible for you to tighten the bolts too tight. If the bolt heads are stripped, get new bolts at your hardware store and get good quality steel ones (note: bolts with socket cap heads are stronger than the bolts with the button cap shown in the photo). Be sure to tighten in an X-pattern, just as if you were tightening the lug nuts on a car tire or the bolts on a head gasket. Rather than an allen key, you might want to use a hex bit in a socket wrench, you can get much more torque:

Hex bit in socket wrench

  • With the proper amount of torque on the bolts, it really shouldn't twist under normal circumstances. You could drill a hole to pin it, but that would weaken your seatpost. Instead, you may try using some blue loctite on the bolts to make sure your bolts are not backing themselves out and a bit of the same friction compound used in carbon fiber bikes on the seatpost to add just a tad more friction.

p.s. When buying second-hand, always make sure your product isn't subject to a CPSC recall such as this one: https://www.cpsc.gov/Recalls/1998/CPSC-Riteway-Products-Announce-Recall-of-Bicycle-Trailers

  • People use tag-alongs with carbon seatposts? I wouldn't risk it, myself. I hope this is a "just in case" comment!
    – Móż
    Commented Feb 2, 2017 at 0:05
  • 3
    Covering all the bases. :)
    – RoboKaren
    Commented Feb 2, 2017 at 0:29
  • Yes that's exactly the one I am talking about - the pinion I was refering to with the 4 bolts. So in other words, your answer, I just have to tighten it more? If I am not advised to drill a hole through the lot, I am then tempted to create a triangular clamping system to hold that pinion straight! Thanks for your time on this. Much appreciated.
    – Fandango68
    Commented Feb 2, 2017 at 6:40
  • 2
    You should just have to tighten it more. With four bolts, you should be able to achieve much more pressure than the single-bolt that holds up your seatpost, for example.
    – RoboKaren
    Commented Feb 2, 2017 at 6:43
  • 3
    You should be applying blue loctite to anything you don't want moving.
    – RoboKaren
    Commented Feb 2, 2017 at 6:46

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