Seat post rotational slip

General
1

I’m having some trouble with slip (rotation) of the seat post on a Nimbus Muni. Those clamps are really tight now, but it still slips. I don’t think I can get them any tighter. I’ve taken the post out and tried to clean it (haven’t tried any solvents yet), but that didn’t help. There’s plenty of post in the top tube, probably 4 inches. Maybe I should try cleaning with something fairly mild like rubbing alcohol? Any other suggestions? My other unicycles don’t have this issue - only this one gives me trouble.

(that’s not rust around the top - it’s Sierra dust from the last ride.)

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2

I recently had an a similar issue with a clamp of mine. I dont know if your clam has had a lot of use…

But in my case my bolts had actually stretched over time due to the tension, could try replacing the bolts and see if its good again.

Alternatively, you could try slipping a bit of a soda can between the rim and post. It just creates a tighter space,

3

Use a double bolt clamp instead which you use an Allen key to tighten and loosen? That should be more secure.

4

Are you using the allen bolts on the other side of the quick release to tighten the clamp, or just the levers?
I’ve personally found the levers on these pretty useless, I prefer to just ignore them and tighten it like a normal seatclamp.

2 Likes
5

have you tried removing the clamp and just seeing what the post fit is like in the frame ? if its a sloppy fit then you have other issues.

6

Lubricate the QR? If the cam of the clamping mechanism is dry, you will get much less clamping force for a given hand force. Obviously take care not to get any grease on the seatpost, but the QR cam shouldn’t be completely dry and it looks like it might be in the photo?

1 Like
7

Agreed with @finnspin, I only like those on a road uni. On a muni, they’re not tight enough.
One thing which could help if you want to keep the “no tools required” aspect is to indeed lubricate the nuts and bolts and the levers, and use carbon fiber seat post grip which is a compound used for, you guessed it, carbon fiber seat posts as those cannot be tightened too much otherwise they’ll fail.

8

I’ve had the same experience with the quick-release seat-post clamp as @finnspin reports above. I have to tighten the bolts with a hex wrench to get them tight enough that the post does not twist. And that, of course, defeats the purpose of the quick-release because it’s too snug to release by hand.

9

That sounds like a poorly designed seatpost clamp if the cam lock is weaker than tightening with the bolt. Once it’s dialed in the cam lever should be able to provide a stronger clamping force than tightening the bolt. Lubrication is key for effectively tightening either way.

10

@jswim788, this should be your first port of call. Just stick a bit of oil or grease on the plastic section, rotating cam part ,and the silver centre sections - you’ll likely find that you can get it much tighter that way.

You shouldn’t have issues with the post slipping even if you greased the post up before putting it in though. I had one for years and once I’d discovered the wonders of a bit of lubrication I never had any issues even with hard riding with bars and some hard falls.

11

Agreed. The one I’m using is the same as the one pictured above (i.e., Nimbus with two levers). Perhaps the cams could be designed differently to create more leverage?