univega.duder

Dear Bike Forum Mechanics-

I'm trying to determine the correct size seatpost diameter for my old Univega Specialissima. The existing post appears to be a 26.6. I thought this was the original post but when I loosened the binder bolt the post slid to the bottom which seemed strange. I tried a 26.8 post (Daija brand) from another bike and it fit without too much trouble. I tried measuring the inner diameter of the seat tube but couldn't get consistent results with the calipers. I'd like to order a Nitto 26.8 seat post that would have a little more setback but am nervous it my not fit. Does anyone have any seat post wisdom they can share? Thanks!

Thruhiker 

Nice looking bike! I think 26.8 is the size you want. Nitto is good quality and in my experience there stems and seatpost are true to the size they say they are. You could also maybe get some fine grit sand paper and sand some of the paint off inside the seat tube. A dowel rod or any thing similiar wrapped with sandpaper then put in a drill makes it a pretty simple chore job.

Charliekeet

Sheldon Brown’s seatpost database says this:
Univega
Specialissima
1981
26.8

So I don’t know about the accurate dating of your frame, but given this and that your measurements indicated on the higher side (plus that the smaller 26.6 behaved the way it did) it seems likely to be the slightly larger size.

Iride01 

You aren't going to get a good measurement on the tube diameter at the clamp area of the tube. So don't try to judge anything by that. If you don't have some inside measuring calipers to get further down, then just go with your trial and error method which you said had you putting a 26.8 mm down the seat tube.

fietsbob

Too small .. you need a 27.0, not a 26.6 ,, if your measurement is accurate..

I have used an adjustable reamer & shaved out 0.1mm from the inner tube wall ,

& was able to precisely fit a 27.2 seat post in a formerly 27.0 frame ..

looks like you've compressed the ears against the rear cable hanger..





...

Ronno6

According to Sheldon Brown, 26.8
https://www.sheldonbrown.com/seatpost-sizes-m-z.html#u

Iride01 

Was there an issue with your first seat post that bothered you as far as it rocking or slipping in the clamp when riding? If you get a seat post that fits like a glove, then you might be posting about how to remove a stuck seat post several years down the road.

If a smaller diameter than original works without issues while riding, then why not use it?

univega.duder

The current seat post functions fine but I'm mainly hoping the Nitto S65 will have more setback and will allow me to position my saddle further back. I don't know how to accurately measure the setback of the current post but visually it doesn't look like it has as much setback. The current post also doesn't seem like it's clamping the saddle rails quite right. It seems like it may be marring the saddle rails and not supporting the saddle quite as it should.

Thanks! That's really helpful.

I don't think the ears are compressed - I think it's just the angle of the photo (at least I hope so!)

Great! I didn't realize Sheldon had a seatpost database. I haven't been able to accurately date the frame but 1981 seems close and 26.8 is fitting. Thanks!

Thanks! I ordered the Nitto S65. I also noticed some rust further down inside the seat tube. Do you have any suggestions for dealing with the rust? I'm wondering if your sandpaper on a dowel would be a good place to start? Or maybe a wire brush on an electric drill?

Thruhiker 

Are wire brush on a drill works good. Sporting good stores and even walmart sell wire brushes for cleaning guns. They work pretty well. If you get a cheap firearms cleaning kit it will have a rod to thread the brush into and then you can put the rod in your drill chuck.

panzerwagon 

I have couple of specialissimas (1983 and 1984) and both still have their 26.8 seatposts. The miyata 1000s I’ve seen in person from the 80s have all taken 26.8 (Miyata was the manufacturer of the specialissima). There’s no way that is anything but a 26.8.

If you could measure from further down the tube, you’ll find the inner dia fits a 26.8. I had the same problem on my univega grand touring when I purchased it. Previous owner had put in thinner seatpost and clamped it down hard. I simply took a large screwdriver and gently twisted apart the cinch eyelets (only touching the seat tube with the tip/edges of the screwdriver). Then 26.8 went right in all the way.

Cleaning advice with drill and brush is spot on, but make sure all scraped surfaces are covered in grease afterwards.

ps. Great looking bike you have!