Dawes Galaxy Seat Post Size?

[Chris Jeggo]

The two 531PG bikes are a Falcon and a Hateley, and both have 26.6mm seat posts.

[Wilhelmus]

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[Jdsk]

Regarding the method of dividing the circumference by pi, all very well in theory, but I imagine that the slightest error, of which I'm more than capable at my age, would be disastrous. Anyway, to how many decimal places would you take pi?

Work to one more place than you're interested, so if that's 26.4 mm use 3.142 for π.

Jonathan

[slowster]

Regarding the method of dividing the circumference by pi, all very well in theory, but I imagine that the slightest error, of which I'm more than capable at my age, would be disastrous.

Rather than imagining what error you might make, just take some measurements and see what the results are. I would suggest you take two or three measurements. If all three are identical/close to identical, and if the resulting calculated diameter is exactly or very close to one of the standard increments, e.g. 27.0mm, 28.8mm or 28.6mm, that would give you confidence in the result. If you get a result of 28.9mm or 28.7mm, that would be the time to think about other options for measuring the seatpost.

Anyway, to how many decimal places would you take pi?

I always use six decimal places, simply because the mnemonic I learned pre-internet is 'May I have a large cup of coffee', i.e. 3.1415326.

[Jdsk]

3.1415326

It's not going to affect this calculation... but was that a large container of coffee?

; - )

Jonathan

[slowster]

3.1415326

It's not going to affect this calculation... but was that a large container of coffee?

; - )

Jonathan

Oh dear. It has been a long time since I used pi in a calculation (and evidently that is just as well). Thank you for the correction and reminder, although I fear I will have forgotten it again by the time I next need to use pi.

[Jdsk]

How I wish I could calculate pi...

; - )

Jonathan

[nsew]

Thanks for doing that, especially on such a morning (unless it's somewhat warmer down there than it is up here). This morning was the first time this year that we've had to defrost the car windows. It intrigues me to see the neighbours pouring kettles of hot water over their windscreens. Long may their luck hold. We have a convector heater in the rear compartment, which we attach to an extension lead and plug in for a few minutes, whereupon the ice melts like magic while the toast is doing. Also nice for Herself to be able to drive away in a lovely warm car. But I see I'm digressing. I shall order an inexpensive 26.6 mm post from a certain online emporium and, should it be too large to fit comfortably, get a 26.4 mm one, maybe a little more expensive. Regarding the method of dividing the circumference by pi, all very well in theory, but I imagine that the slightest error, of which I'm more than capable at my age, would be disastrous. Anyway, to how many decimal places would you take pi? It reminds me uncomfortably of maths at school, at which I was a duffer.

If purchasing a painted (or cheap anodised?) 26.6 seat post it will be possible to get 26.4 with sandpaper. Just take away the section needed. I was able to fit a 27.2 seat post to a friends 27.0 seat tube this way. The fit was perfect.