Hello all – I want to replace my allan key seatpost clamp with a QR job. The old clamp says 34 on the back, but all the clamps I can find seem to jump from 33 to 34.9.

Am I being daft? Does anyone know what size I need to buy?

TIA,

Jamie.

The 34.9 one will do.

Grand. Cheers man – off to spend some hard-earned……

Hmmmm – further advice required please – bought a shiny, gold, 34.9mm Hope quick release clamp as advised above and the bl00dy thing is way too big. I’ve screwed it down as far as possible with the wee knurled nut but it’s just plain too big – the clamp closes at the back of the seatpost but doesn’t hold it securely.

The old 34mm one sits very snugly so I reckon the 33mm one would be too small. Does anyone know where I can find a quality 34mm quick release clamp? Or want to buy a slightly scratched 34.9mm one…..?!

what frame is it? 34mm is a very weird size. Try CRC and just search through. Alternatively, depending on the shape and design of your seatclamp you might be able to get a QR adaptor for it.

Also thinking about it, 34mm might be an outside diameter size instead of an inside diameter size…get your Local Bike Shop to measure it.

Cheers for the responses dooge – it’s an ’08 Boardman MB Pro frame – I’ll take it (the clamp) into work with me tonight and borrow the fitter’s calipers.

Also – no offence to nickc for advice given in good faith – just me being unlucky (and or daft…).

If it’s any help, the seatpost itself says 27.2 – does that mean I should be buying a 28.6mm clamp do you think? Just had a quick look at the wife’s seatclamp which has the same basic Halford’s seat clamp. It also has 34 stamped on it, so I’m wondering if this might be a part number rather than a size (blushes..).

The clamp should have an internal dimension on the wider, lower, step approx the same dimension as the outside of the top of the seatube. The internal dimention the of the upper lip of the clamp should not be smaller than the outside dimension of the post.

I use a 34.9mm clamp on a Ti29 frame that takes a 27.2mm post.

Well, phoned Halfords and asked them eventually – the bloke in the bike hut reckoned I needed a 31.8mm clamp (!?!). Just one of life’s little mysteries I reckon….

Ordered from WHS and hopefully with me before Inners / GT this Friday.