I'd like to carry 20 - 40 pounds or so in panniers on my rear rack. I've carried that much on my hard tail so it's not a problem for the biking itself.

The cantilevered rack style that is supported only on the seatpost is a non starter. I have a carbon fiber seat post. It can't hold more than 10 pounds (even that worries me)

  • Have you considered replacing the seat post with an alloy one and use a canti rack. You could then mount the canti on the ali seat post with a saddle, and simply swap posts.
    – mattnz
    Oct 3, 2019 at 23:49

2 Answers 2


I recommend against doing this. You will be dramatically increasing your unsprung mass, which will play hell with your suspension's dynamics. You might want to consider a trailer instead, or see if you can carry the load in a frame bag and/or seat bag.

  • 1
    Could you explain why the rack would be unsprung? Seems like if it was attached to the seat post, it would be sprung (based on the 4-wheeled wagon example from the wikipedia article you linked)
    – Paul H
    Oct 3, 2019 at 23:49
  • While useful (and I generally agree), this should be a comment as it does not attempt to answer the question.
    – mattnz
    Oct 3, 2019 at 23:51
  • @PaulH Unless I am misunderstanding, the questioner specifically does not want a seatpost-mounted rack.
    – Adam Rice
    Oct 4, 2019 at 2:17
  • @AdamRice sorry. My comment was unclear. Based on the wikipedia article, it seems like seat post-only rack would be sprung mass. But I don't understand why adding stays to connect to e.g., the rear swing arm would make that into unsprung mass.
    – Paul H
    Oct 4, 2019 at 4:44
  • @PaulH - You couldn't have part of the rack attached to the sprung part of the bike and part to the swingarm, unless you added some kind of articulation system to the rack itself (otherwise the rigid rack will interfere with the suspension). Putting weight on the swingarm is adding unsprung mass.
    – Adam Rice
    Oct 4, 2019 at 17:22

What you'd need is something that:
- only attaches to the seatstay (top of the swing arm)
- attaches to a rear dropout screw eye, mounting point (not sure what it's called) if there is one and the seatstay
And, won't hit the seat when the swing arm moves.

Thule Tour rack (not a recommendation - I've never seen or used this device) is advertised as something that will work for full suspension bikes and only attaches to the seatstay Load capacity 25 pounds on the rear.

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Other racks attach to the rear axle and the top of the swing arm - some are held on by the quick release. Skewers seem too fragile in my mind.

I wonder how the ride would change with 25 extra pounds attached to the swingarm.

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