Bicycle Mechanics - Bridgestone 300 Seatpost size?

Does anyone know -- authoritatively -- what size seat post a 85 Bridgestone 300 uses?

Trying to get my beater fixie in shape for saddle tryouts: the Selle SMP Evolution demo is on its way back this week and a Koobi PRS Century is on the way for a 30-day see-if-I-like-it ride.

I'd like something that will keep the seat from rocking and is capable of fine tuning.

The authority is YOUR hands. I'd recommend that you get a set of calipers that measure ID and take the measurement from several angles and average the diameters. Tolerances back in 1985 were not as precise as today with CNC machined and faced tubes. My 1985 models were the T700 and 400. The T700 accepts both 26.8 and 27.0 seat posts. The 27.0 is snug. The 26.8 is loose until you tighten a little too much. I've reamed both of them ever so slightly so the 27.0 fits without scratching. The reason is that it gives a tighter fit without requiring one to over tighten the binder bolt.

+1. Would I trust someone over the internet, or just measure what I have in hand? Myself, I am measuring what I have. Or take it to a shop, and have them check. Getting the size right is very important.

My '85 Bridgestone 400 (same frame, different components) came with a 27.0 mm seatpost.

My triple butted 500 uses a 26.8

My triple butted 500 uses a 26.8
IIRC, the 500 was a significant step up from the 300 and 400 of the same year.

there is a step tapered test tool, a Pro bike shop should have one..

But . as an example of variation, I reamed a 27.0 RB1 frame
to fit an American Classic
27.2 seat post, precisely, as described above.
2 other 27.2 seat-posts from other makers are not the same fit.

I bought the AC seatpost 1st, then hand reamed the frame
till the seat post Just Fit.

since you are OK with shipping things back and forth ,
how about harbor freight or someone ?,
for an inside diameter reading dial micrometer that can measure
a ways inside the seat tube.
the prior hands this frame passed thru, someone may have guessed
seat post need, too small and tightened it in there anyhow. :rolleyes:

Thank you to those Bridgestone owners who supplied the helpful replies.

I think it is probably a 27, but I will be taking it into my lbs to confirm. I was just hoping to do some comparison shopping beforehand.

Yes: I know I can take it in to a shop and that I ought to do so, and, no, I don't have the tools myself, and no, -- I wasn't expecting knowledge "from someone over the internet." But thanks for repeating the obvious. It's easy to forget.

I was hoping a knowledgeable someone on the Bicycle Mechanics forum might have an old Bridgestone spec sheet that would say what was used in this frame and be kind enough to share it.

Rock on.

Curly:

Too bad you're not in the Santa Clara area. I have a few spare 27.0 Sakae SR La Prade and CTP5 seat posts off of bridgestones from the late 80's which I've been giving away to a few folks looking for vintage parts. Down to my last two. I have 27.0 and the 26.6 is claimed by someone with a Miyata or Nishiki or something.

I was hoping a knowledgeable someone on the Bicycle Mechanics forum might have an old Bridgestone spec sheet that would say what was used in this frame and be kind enough to share it.
Rock on.
I happen to have the 1985 Bridgestone catalog and, while it give the maker and model of all of the seatposts used through out their line, it doesn't list the diameter of any of them.

I noticed that from the catalogs on the Sheldon Brown site. Just thought the truth might be out there, somewhere.

I had an 86 Bridgestone 200, which I believe is similar frame material (straight gauge cr-mo) and it took a 26.6mm post.

Turns out to be 26.4 mm, but I could probably have slipped in another millimeter or two. The gentleman at the Bicycle Path had a used UNO lying about and hooked me up.

Nice, glad you found one. Enjoy the ride.

Bridgestone (sensibly) used tubing with different wall thicknesses for different size frames, especially in later years, which would explain why they didn't publish seat post sizing.

Well, the 26.4 still sank beneath my Clydeass, so the nice boys at Bullseye in Denton measured everything properly and turns out I needed (as Re-Cycle advised) a 26.8.

Luckily they had a Redline take-off in their box and they swapped me for the 27 I had ill-advisedly bought from them, and I gave them the 26.4.

So it goes.

Giant Defy 1 on the way, so the old Bridgestone Franken-Fixie will be my commuter.

A well equipped bike shop has a stepped test rod, to insert in the seat tube.
a Go/No-Go test .. its machined in 0.2mm increments, so will fit in the tube,
until it won't.

then you get the last size that fit in.