soyabean

Anyone here know this vintage?

The previous owner hammered in a 25.4 in there and took a lot of effort for me to twist out. I am fortunute it was only 2 inches in.

It wasn't rust welded seized, just oversized. I can see hammering that flattened the top of the pipe.

I know not all posts are machined equally, so I tried about half dozen 25.4 posts and none of them can even be inserted at their tip unless forced and scratched up as previous.

When I use a 25.2 post, it glides in way too easily with no friction, at the point where I'd have to use some SAC-2.

25.2 is a rare size. I've never seen a bike with one, and I only have one hoarded in my bin of seatposts.

bboy314

Are you positive the one you pulled out was 25.4? I would guess the frame was made for 25.4, but was mangled/misshapened by the post being hammered in.

soyabean

The one I pulled out was a 25.4mm, verified at about 50 areas with my Mitutoyo digital caliper.

It was also cut by the PO so they only had to hammer in the 2" minimal.

I am grateful it was cut, and they did not hammer in a full length 8-12" seatpost.

If I can't get a 25.4's tip to even go in, I'm going to conclude this frame gets a 25.2 .

I verify seattube sizes in the frame with my collection of 100 seatposts. Measuring a tube with a caliper is unreliable because of out-of-roundness and deformations all over the place, not just the mouth.

Hummer

I have a 1985 Norco Bush Pilot. Seat post diameter 25.4mm.

52telecaster

Ream the seat tube to 25.4 and you'll probably be in great shape.

madpogue 

"Hold my beer, while I....."

soyabean

I went thru my bins and new stock of 25.4 on hand and unfinished zinc steel, black painted, steel chrome, anodized aluminum, carbon, I tried them all, none of their tips can get into an otherwise very healthy mouth.

I'm not reaming anything. If that is the only way to get a seatpost to fit, it's almost always too big and a recipe for regret.

My guess is the PO got the bike missing the seapost, they "measured" it and decided it was 25.4, afterall, that's a big box store seatpost prolly found in every housefold.

Vintage bikes are known to have weird seatpost sizes.

I had a similar Norco Bush Pilot that was 26.2 .

I admit 25.2 is rare, but not impossible.

52telecaster

I understand your trepidation but the reamers used for this are adjustable. You try the post with each adjustment. If a 25.2 is going in too loose, your best choice is to go up a tenth of a millimeter on each side. Hence 25.4. of course it's your bike and your call.

bboy314

Reaming is a common way to deal with this issue. From your description, it sounds like 25.2 is too small (and very unlikely the intended size anyway).

soyabean

True, the 25.2 was indeed showing symptoms of "too small", so I excavated out a few more 25.4's from my dumpster finds stored outdoors, and found a 25.4 that "fit".

Barely.

The 25.4 nominal seatpost that fit was actually 25.30-25.33 measured.

I discovered that any 25.4 that was at least 25.37 or more, would not fit in this vintage Norco.

I noticed majority of my collection of 25.4 were 25.40-25.45, with some as much as 25.50 .

Thanks to everyone for all the input.

browngw 

I picked up an 88-89 Norco Bush Pilot last year and just started tearing it down a few days ago. It seems to weirdly have a 25mm seat post. The Norco bike shop in town seemed to think there were some back in the day. Did see one for sale on Ebay.



post. The Norco bike shop in town seemed to think there were some back in the day. Did see one for sale on Ebay.