http://www.lidl.co.uk/uk/home.nsf/pages ... aliper.ar6
from thursday. never need to worry about what size seatpost to use again!
from thursday. never need to worry about what size seatpost to use again!
lidl bargains - digital caliper
- Thread starter cce
- Start date
cce":mxq6n4b2 said:
Slight flaw to the logic
Problem is,unless its a plain gauge length of tubing, the diameter changes .It splays at the top,then it narrows to the post size then it opens out again towards the bottom bracket
Plain gauge splays slightly at the top.at its a fair bit thats been splayed there isnt any instruments to easily measure it,calliper jaws are too short.
One of my pet hates :x Why dont they stamp the bloody size on the bloody bottom bracket shell next to the bloody serial number :x
Rocker9455
Old School Hero
do all cycling forums have a lidl bargains topic? lfgss have one too amoung other forums!
dyna-ti":ncm3my2r said:cce":ncm3my2r said:
Slight flaw to the logic
Problem is,unless its a plain gauge length of tubing, the diameter changes .It splays at the top,then it narrows to the post size then it opens out again towards the bottom bracket
Plain gauge splays slightly at the top.at its a fair bit thats been splayed there isnt any instruments to easily measure it,calliper jaws are too short.
The internal diameter at the top of the seatube is the nominal seatpost size - the ID does not increase at the top (unless though damage) - if this was the case how would you ever clamp a seatpost in place and what on earth would be the point :roll: ?.
The external diameter will probably be larger than it is at the front mech mounting position (29.8mm compared to 28.6mm for example) but this is due to the top section of seat tube having a greater wall thickness, not because the ID is larger. External butting, in other words.
The seatube may well have an ID larger than the seatpost size below the area required for seatpost location but never at the top.
dyna-ti":10lg59hd said:
Most seatubes (in other words, those that aren't plain gauge) are butted - and if the ID remains constant but the OD increases in the area of the top tube/seat tube junction then that's what I would call external butting (I guess........)
No seatube on any bike that I have seen displays this "splaying" except where someone has been attempting to fit too large a post or has used too small a post (especially with a binder bolt type clamp) and has slightly stretched the tube wall, or has used too short a post with insufficient insertion which allows the post to rock and bell the end of the tube. I would refer to that as damage.
I have just measured the four bikes that I have here (2x Kona Explosif, 2x Rocky Mountain) - all steel frames and none of the seat tubes have an ID or OD larger at the top than 30mm lower down (if you discount a 1.5mm chamfer, which is all you need to insert an (also chamfered) seatpost easily).
Before you ask - yes, the paint is intact in the clamp area so that's not affecting the results and yes, I do know how to read a micrometer, I've been doing it for long enough.
If you lived just down the road I'd happily invite you round to do the same measurements so that you could see for yourself that I'm not "guessing". Then we could have a cup of tea and a bikkie or go across the road for a beer, since it's such a nice afternoon.
If we had been talking face-to-face would you have basically said to me "Get your facts right and don't guess", accompanied by much eye rolling?
I'm sure that you wouldn't.
