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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 06-22-09, 03:10 PM   #1
passerby
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Schwinn madison seatpost diameter...wtf?

well i had checked every possible website giving the specs of the 08 madison and all of them said that the seatpost diameter was 27.2. so i bought a 27.2 kalloy seatpost and it was too small!!! does any1 know if the specs are incorrect or did i just recieve a seatpost that was smaller than 27.2? could the seatpost be 28.6 or 29.2?
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Old 06-22-09, 03:29 PM   #2
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The seatpost is 27.2 i have a madison
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Old 06-22-09, 03:33 PM   #3
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What? That the first I have heard. They seem to vary between 27.0 and 27.2. Mine came with a 27.0 and it was cheap. So I bought a 27.0 DA but it slipped a bit. So I sanded the inside a bit and got a 27.2 Velo-Orange post in there.

Now, are you SURE the post you bought is 27.2? Even Schwin tecks told me their frames vary form 27.0-27.2
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Old 06-22-09, 03:36 PM   #4
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okay then i probably did get a smaller seatpost on accident...man, this sucks. thanks for everything guys
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Old 06-22-09, 03:50 PM   #5
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Digital calipers.
Seriously, everyone should have a pair in their toolbox. They're cheap as hell now; you can get a pair for under $30 at Home Depot, or under $20 at Harbour Freight Tools.
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Old 06-22-09, 04:11 PM   #6
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I have an "Old School Blue" Maddy and I don't know how or why but I can use either a 27.0 or a 27.2 with no problems at all.
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Old 06-22-09, 08:15 PM   #7
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Originally Posted by CliftonGK1 View Post
Digital calipers.
Seriously, everyone should have a pair in their toolbox. They're cheap as hell now; you can get a pair for under $30 at Home Depot, or under $20 at Harbour Freight Tools.
Or stop being lazy and learn to read standard calipers.
Measuring a seatpost diameter (or much of anything on a bike) does not require a digital caliper. And if you really needed to get exact measurements, you would get a dial caliper.
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Old 06-22-09, 09:36 PM   #8
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Or stop being lazy and learn to read standard calipers.
lighten up, gramps. precision measurement is precision measurement. digital gets the job done as well as analog.

PS...is that a digital watch you're wearing?
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Old 06-22-09, 09:59 PM   #9
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Or stop being lazy and learn to read standard calipers.
Measuring a seatpost diameter (or much of anything on a bike) does not require a digital caliper. And if you really needed to get exact measurements, you would get a dial caliper.
If I really need exact measurements I'll bring home my calibrated NIST traceable digital calipers from work so I can measure seatpost diameter and how many nanometers of grease are still on it.

At home, I'll take the lazy route and use my $25 cheapo pair from the hardware store.
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Old 08-23-09, 11:50 AM   #10
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I took my seatpost out today and it says 27,0 on it. i double checked it by measuring with a nice metal ruler and it is indeed 27.0.

and indeed, its about 380mm long and quite heavy.
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Old 08-23-09, 12:14 PM   #11
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Digital calipers.
Seriously, everyone should have a pair in their toolbox. They're cheap as hell now; you can get a pair for under $30 at Home Depot, or under $20 at Harbour Freight Tools.
+1, I insist that everyone order this now
http://www.dealextreme.com/details.dx/sku.2306
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Old 08-23-09, 12:41 PM   #12
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when you measure the inner diameter of the seat tube with ANY calipers, your reading will have an error. The error is usually larger than how precise the caliper is. The reason for this is that the measurement you need is when the bolt, or skewer, is tight against the seat post. When the bolt or clamp is open, your measurement will be too large. The seat tube flares at the top a bit when it is open. Also, when the collar, or clamp is open, the opening is not perfectly round. You could very well get different measurements depending on which way you measure.

with this said, choose whatever caliper you want, how precise a reading is depends on the flared status of the top of the seat tube.

The best way to get this measurement is to either try a bunch of different common seat post sizes, or use a seatpost sizing tool. A bike shop will usually have both.
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