seatpost measurement
- Thread starter brady37
- Start date
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Biker Joe
Über Member
- Location
- Nr Harlow, Essex.
I use vernier callipers.
Your LBS will also measure it for you.
Your LBS will also measure it for you.
MrJamie
Oaf on a Bike
I shall share my ingenious method I used this week, if only for amusement...
Rather than try to measure the diameter to within 0.2mm without the proper callipers, especially given the tapered end to the post, I opted to measure the circumference. As circumference is Pi*diameter each 0.2mm step is a 0.62mm step in circumference which is much easier to measure to the nearest likely value. Wrapping the post in a piece of paper (as an actual tape measure would be too thick) and then measuring that a few times until I had a fairly confident figure seems to work fine. It only gets sillier as when I held the old seatpost next to the new under the bright kitchen halogens, I noticed it actually had the diameter measurement stamped on it, which I hadn't been able to find when I looked in the garage, but at least it was correct
Check for a stamp on the post if you haven't already and maybe check if the bikes still listed on the web.
Rather than try to measure the diameter to within 0.2mm without the proper callipers, especially given the tapered end to the post, I opted to measure the circumference. As circumference is Pi*diameter each 0.2mm step is a 0.62mm step in circumference which is much easier to measure to the nearest likely value. Wrapping the post in a piece of paper (as an actual tape measure would be too thick) and then measuring that a few times until I had a fairly confident figure seems to work fine. It only gets sillier as when I held the old seatpost next to the new under the bright kitchen halogens, I noticed it actually had the diameter measurement stamped on it, which I hadn't been able to find when I looked in the garage, but at least it was correct
Check for a stamp on the post if you haven't already and maybe check if the bikes still listed on the web.
Profpointy
Legendary Member
Unfortunately seat posts sizes vary by fractions of a milimetre, so near-enough isn't good enough in this case. Even calipers is a bit of a struggle (and I can read a vernier), so micrometer is better.
I suppose some kind of go / no-go arrangement might work if you can lock it to the size, then compare against the "new" one.
Or take the old one to the shop and say "same size please"
I suppose some kind of go / no-go arrangement might work if you can lock it to the size, then compare against the "new" one.
Or take the old one to the shop and say "same size please"
biggs682
Touch it up and ride it
- Location
- Northamptonshire
i think Aldi had verniers for about a £10 last week
02GF74
Über Member
I was going to suggest the paper method too. It should be possible to measure to within 0.5 mm with a steel rule - use a blade to make the marks as a biro or pencil will lead to error due to the thickness of the mark.
0.5 mm in cricumference translates to 0.5/pi mm or 0.16 mm in diameter - less than the seat post increment of 0.2 mm so is accurate enough, beaing in mind that not all 0.2 mm increments exist - just find the nearest size.
quite often the post is stamped with the diameter or look up the frame on google or sheldon brown's list or give frame details on here.
0.5 mm in cricumference translates to 0.5/pi mm or 0.16 mm in diameter - less than the seat post increment of 0.2 mm so is accurate enough, beaing in mind that not all 0.2 mm increments exist - just find the nearest size.
quite often the post is stamped with the diameter or look up the frame on google or sheldon brown's list or give frame details on here.
