Bicycle Mechanics - i think i'm going to shoot my frame

ok, i've no idea what size seatpost my frame takes, so i was thinking of buying a micrometer-thing to measure it. but then i realised that even with the proper tool, i might be screwed, b/c we're talking about very small increments here, and no real way of knowing if the thing is measuring the exact diameter of the seat-tube. what is a boy to do? does anyone, per chance, know what size seatpost an early 80's nishiki custom sport takes?

tia,
-rob

take it to a bike shop. that way you dont have to drop the coin for a caliper. I didn't know mine for my bianchi. I took it to the shop and told them I wanted a new seatpost, but I didn't know the diameter. they measured for me, and I bought a seatpost from them...it went well.

do you know the type of tubing? double butted tubing from the 80s was like 27.2 (i think), but straight guage was 25.4. Just rules of thumb though

A dial caliper should be more than accurate enough to measure the seatpost diameter. However, have you tried removing the post, wiping any grease off and looking for the size stamped into the post? Many posts have their size marked on them. Cheaper than buying a caliper for one measurement.

A dial caliper should be more than accurate enough to measure the seatpost diameter. However, have you tried removing the post, wiping any grease off and looking for the size stamped into the post? Many posts have their size marked on them. Cheaper than buying a caliper for one measurement.


problem is, i picked up the frame/fork cheap, but all i got was the fork/frame. no seatpost, no headset (which is 27.0, the old japanese standard). the frame was made in japan, and the tubing is the cheapest of the tange stuff. i'm thinking it's gotta be reallllly narrow (25.4 might be right), b/c i trashpicked an old rusty japan-made bike from the same era, and tried the rusty 26.4 seatpost from that, just to get an idea for fit (i have some old 27.2 seatposts lying around, and had realised that they were waaaaaaaay too big a loooong time ago.) even the 26.4 was too massive for my seat-tube. i'm thinking i might, alternatively, wait for a similar bike to show up on ebay, so i can ask the seller to yank his seat-tube out and tell me what diameter it's got.

or, i could do as phatman said, and take it to the lbs. but my favorite lbs is massively incompetent, and the rest of 'em tend to fleece their customers way too hard. i imagine the one spot would charge me $5 just to measure the seat tube. arg.

thanks for your help, everyone.

-rob

A set of dial calipers will measure the inside diameter of you seat tube just as easily as the outside diameter of a seatpost.

Yeah, seatpost diameters vary in 0.2mm increments. 0.2mm is about 8/1000 in, so a 1/1000 in. dial caliper (or, obviously, a metric one) will measure it closely enough.

or, i could do as phatman said, and take it to the lbs. but my favorite lbs is massively incompetent, and the rest of 'em tend to fleece their customers way too hard. i imagine the one spot would charge me $5 just to measure the seat tube. arg.
$5 for services rendered is cheaper than buying calipers...

$5 for services rendered is cheaper than buying calipers...

that's a powerfully good point. but, forget all that; i'm just gonna haul the frame down to this real good bike shop in philly, and do it up like a normal, non-stingy guy.

the guys at trophy bike wont charge me to measure, and i might even probably buy the post there!! wow.

still, i hate spending money on a frame that might not live.

-rob

We use a stepped piece of bar stock for sizing seat tubes. Just about any shop would have one and I wouldn't think anyone would charge for the two seconds it takes to drop it in and read the line. While the tube can be measured with a caliper, that requires someone who knows how to correctly read one(Not implying anyone here can"t :) ) The sizing "stick" is always right.