Seat Clamp Size Advice

[rrarider]

You need a micrometer or a vernier. Trying to estimate to 0.1mm accuracy with a ruler is optimistic as is wrapping a tape measure round and dividing by pi - which I've seen suggested

Either borrow a mic or vernier or take the post into a bike shop.

I'd be inclide to pony up for a couple of mics or a vernier on fleabay as they're always handy for measuring bolts and so on even for an occasional dabbler

I'd just get a Vernier caliper, they're only about £12/£13 from screwfix and similar outlets. It won't be the best quality, so you'll need to subtract the zero error offset from the measurement. It's easy enough to read and 0.1mm is fine for accuracy.

Most useful micrometers, like the one I have, measure the range 0 - 25mm. To measure 27mm, you would need the metric equivalent of the 1" - 2", which isn't much use for the small stuff like screws and nuts etc.

 

[EasyPeez]

You should really be measuring the post not the hole

I'm measuring neither the post nor the hole, I'm measuring the tube diameter (as that's what the clamp needs to fit around) and double checking this against the diameter of the removed clamp, as per the pics. What post would you be measuring?

Trying to estimate to 0.1mm accuracy with a ruler is optimistic

Yes, but unless I am misunderstanding something here I don't need a reading accurate to 0.1mm as clamps are not available (as far as I can see) in incremental sizings of 0.1mm. My options are 28.6, 30, 31.8 or 34.9mm so don't I just need to be accurate to the nearest 1.4mm?

 

[Deleted member 26715]

What post would you be measuring

The seat post you have removed? You could measure the gate post but I fail to see the relevance?

 

[Threevok]

Again, the seat clamp size should be in relation to the outside diameter of the seat tube of the frame, not the seatpost itself

 

[EasyPeez]

The seat post you have removed? You could measure the gate post but I fail to see the relevance?

Funny. But there again measuring the gate post would be about as useful as measuring the seat post, for reasons already explained upthread.

 

[Deleted member 26715]

Funny. But there again measuring the gate post would be about as useful as measuring the seat post, for reasons already explained upthread.

Well clearly you know better than us which poses the question why bother asking if you know best!

 

[EasyPeez]

Well clearly you know better than us

Sorry, I didn't realise you represented the group. Is that just on this thread or on the whole of CC? . Also, I'm not sure the 'us' thing really applies as nobody else here is suggesting that measuring the seat post is a sensible way forward.

which poses the question why bother asking if you know best!

Maybe you haven't read the OP/thread properly. I never asked what bit I should be measuring, just for some reassurance (or otherwise) that I had got my measurements right, in light of the contradictory information on the Chain Reaction site and based on other people's experience of changing clamps.

 

[DWM]

Recently bought a 29.8mm Thomson seat clamp for my 2018 Equilibrium Disk (725 version). Fits perfectly. I’m sure a 30mm one will be fine.

Cheers

Dave

 

[PpPete]

I'd just get a Vernier caliper, they're only about £12/£13 from screwfix and similar outlets. It won't be the best quality, so you'll need to subtract the zero error offset from the measurement. It's easy enough to read and 0.1mm is fine for accuracy.

Most useful micrometers, like the one I have, measure the range 0 - 25mm. To measure 27mm, you would need the metric equivalent of the 1" - 2", which isn't much use for the small stuff like screws and nuts etc.

I got a cheapo Vernier - could just recall how to use it, and it was hopelessly inaccurate, and then rusted up.

OTH the £7.99 Digital Micrometer (0-150mm) I got from chinese vendor on ebay has been faultless. Had it for quite a few years and it does get used surprisingly frequently around the family fleet of bikes.

 

[mcshroom]

I'm currently seriously considering buying an equilibrium frameset. They use a 29.8mm clamp as described here - https://www.paulmilnescycles.com/ge...reynolds-frame--carbon-fork---2017-4398-p.asp.

I'd go for the 30mm from your list - it should fit fine.

 

[EasyPeez]

Recently bought a 29.8mm Thomson seat clamp for my 2018 Equilibrium Disk (725 version). Fits perfectly. I’m sure a 30mm one will be fine.

I'm currently seriously considering buying an equilibrium frameset. They use a 29.8mm clamp as described here

Thanks. Those are both Reynolds tubes whereas mine is the Mjolnir/Genesis own-brand steel, so I guess there could be a variation between the two, but given that you've got specs listing 29.8mm and my measurements came in at a whisker under 30mm I'll go for the 30mm clamp with more confidence now.

Thanks again for your help.