Possibly stupid Quesstion, re. seatposts, clamps etc..

[Sparrow]

Now this might seem a bit of a dim query. But how best to tell which dia seatpost to get for an older MTB (or even road) frame. And which size clamp? I have a digital caliper thing. Do I subtract a certain amount from the id of the seat-tube? (And how do I edit my horrible spelling in the title?)

 

[ishaw]

Re:

To get the seat post diameter, measure the inside diameter of the seat tube. For clamp size, it's the outer diameter of the seat tube.

 

[JoeG]

Re:

For the seatpost diameter, this is the best tool. Most bike shops should have one of these; way too expensive to buy for one use.

https://www.steintool.com/portfolio-ite ... zing-rods/

Looks like there's some cheaper competitors available now, too.

https://www.sjscycles.co.uk/tools/cyclo ... s/?geoc=US

https://www.universalcycles.com/shoppin ... gJa_vD_BwE

 

[Sparrow]

Simple as? Surely not? Thanks for the reply but I am "Hmm scepticalish" Surely not?

 

[Sparrow]

Thank you JoeG.

 

[Sparrow]

And deffo would want one of those, but as you say, plenty dollar for one or even (blush) nine uses..

 

[Dr Dremel]

Measuring OD of a tube with calipers is usually accurate. Measuring ID not so much as you have to wiggle the caliper to get measurement in the middle of the tube. I usually just try to fit different diameter seatposts.

 

[Splatter Paint]

Re:

It can be difficult to measure the tube id correctly but, you’ll get within 0.2 mm of what you need. Often the top 50 mm gets worn I’ve had frames where 27.2 mm goes in a bit, then jams and had to buy a 27.0 mm.

Between the members on this site, we’ve pretty much had every bike going, so you can always ask!

SP

 

[Graham_hkr]

Re:

If you wanna go a bit deeper to make sure the diameter doesn't reduce further down, as SP suggested, you can always purchase a Telescopic Gauge Mic, sure their not expensive.. :idea: