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seat post size on old roadie (and other questions)....(4 posts)

seat post size on old roadie (and other questions)....Hu-man
Apr 3, 2003 8:19 PM
fixing up an old road bike frame- Guibilato (Italian), 20+ years old (I'm guessing). Light, steel and lugs, Campagnolo headset and horizontal dropouts. Don't know if the frame was low, medium or high quality for its day.

1) What are the typical seat post sizes for a frame like this?

2) Bottom bracket has 4 oval slots cut in the underside. There is an inner liner, but what are the slots for?

3) Suggestion for good value reasonable cost brakes?

4) Rear wheel is 27 inch and front is 700. Any thoughts on going with one size or the other for both wheels?
Semi-informed speculation . . . .Silverback
Apr 4, 2003 9:13 AM
Somebody's bound to pop up with answers to all these things, but I can give a couple of them with reasonable certainty....
Only way to be sure of the seat post size is to measure it, which any shop should be able to do. A common size used to be 25.4, but around the late '70s a lot of high end bikes switched to larger diameters. No way to tell from here.
The slots are probably drain holes, to let out the water that inevitably oozes in or condenses inside the tubes and runs down. The liner keeps out splash and spray from underneath. Used to be common. You don't see it much anymore (costs more, for one thing), but I've seen people drill holes in the bottom of their BB shells to let water out.
Before you go shopping for brakes, check either www.sheldonbrown.com or www.rivendellbicycles.com for information on "reach," the distance from the brake bolt to the actual braking surface. You'll have to match the reach of the brakes to fit your wheels, which of course is affected by whether you use 700c or 27-inch. If you can make the 700s work, they'd be a better choice just because 27-inch wheels and tires are getting hard to find.
re: seat post size on old roadie (and other questions)....toomanybikes
Apr 4, 2003 11:25 AM
Agreed with above, get the post measured, probably 25.8 but be sure. The frame is proabaly double butted Columbus SL or if you're really lucky may be SLX. Either way nice frame.

The Bottom bracket drill outs are for drainage but I'll bet they are decorative as well!

One of the advantages of the older frames like these is that you can use either 27 inch or 700c rims and tires and the brake shoe adjustment is very minor, so the issue of what brakes you use will be easy - get some nice retro Campys off eBAy.

I have both 27 inch and 700C rims which I interchange depending on the trires I want to use. If I were doing a re-build like what you are doing I would go with the 700's as, again, agreeing withh the above - 27 inch rims I think will be impossible to find now and 27 inch tires are becoming harder to find. I fear that when I run out of my stock of tires I may have to rebuild my 27 inch wheels into 700's.
4 answersKerry
Apr 6, 2003 4:53 PM
Despite the other posters, I'm thinking that 27.2 mm was a standard seat post diameter in higher end frames of that era. The point is, you'll have to get a measurement or try different posts until you find the fit. Your LBS probably has some old posts in their parts box for your trial and error procedure.

BB cutouts are to allow drainage and to give a distinctive look to the bike, in that order.

The best value is in the eye of the beholder, but brakes from C or S low line groups will work just fine.

Something is goofy about the wheels. Bikes were not built for two different sizes of wheels except TT specialty frames. Someone may have put a 27 and 700c wheel set in there, but the bike is most likely built for 700c.