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Seat Post QR Clamps

By Brian - Posted on 16 May 2010

NB: Originally posted elsewhere on the Global Riders Network and appears via syndication.

When buying a QR seat post clamp. Is the dimension of the clamp the inner diameter of the clamp (outside dimension of the seat tube)?

It's the seat tube outside diameter.

Reason: Seat tube wall thickness can vary, giving a different required seat post clamp size for the same seat post diameter. You should take the measurement at the point the clamp is fitted, with a vernier.

If you're around Manly Dam today you're welcome to drop in to my place this arvo and I can measure it accurately.

Thanks for the offer. The bikes at the shop at the moment but I have some verniers to measure it.

front derailer size Brian it should be the same ..

Trap for young[1] players: the material your seat tube is made of is probably closer to 4mm thick than 0.2mm thick.

Eg. 31.6mm seatpost probably needs 34.9mm clamp, not 31.8mm.

[1] And old: Eye-wink

I wasn't sure if the sizing factored in the in the tube thickness and whatever size you bought it was actually bigger if measured. Obviously not the case Eye-wink

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