Bicycle Mechanics - question about brake pad upgrade

I have 26 year old shimano 600 brakes on 27" wheels. The pads are straight and about 1" long. I'm replacing the pads and wondered if I can use (assuming I find ones that will mount on the brake arms) the much longer pads I've seen in the bike shop? They look to be about 2+ " long with a curve and I'm guessing would have been made for 700 mm wheels?

Sounds like you are describing a brake shoe/pad assembly that is typically found on v-brakes typically on a mtb or hybrid. If that is the case, they will have a stud coming out of the back of the pad/shoe with a nut and some washers. By playing around with the washers and spacers and adding the appropriate toe-in, they will probably work as well as the OEM stuff....maybe better. Give it a try!!!!

I think you should consider that V-brakes probably flex a lot less than those old sidepulls, so the long pad combined with a flexy brake could result in the pad getting pulled up and into the tire sidewall.

It might be safer to replace the pads with modern versions of the same thing. Like this: http://www.biketoolsetc.com/index.cgi?id=6934655383&d=single&c=Repair-Parts&sc=Brake&tc=Pads-Road&item_id=DC-B76G

http://www.biketoolsetc.com/Product_Images/DC-B76G.jpg

I've been using Kool Stop "v-brake" pads for a couple of years now with my old Dia-Compe centerpulls from 1983. A wonderful upgrade, they're not only better pads but they have spherical washers on the posts so toe-in is a breeze. My recommendation is to get Kool Stops in the salmon compound, they're the best brake pads out there in my opinion-

If you want ease of adjustment and the salmon compound, then get these... http://www.biketoolsetc.com/index.cgi?id=6934655383&d=single&c=Repair-Parts&sc=Brake&tc=Pads-Road&item_id=KS-RHD

Maybe i'm overly cautious, but i'd worry about the long pad.

I'd say it depends on the sidepulls. I've got an old 70s schwinn suburban that I replaced the pads with some spanking new Kool stop V-brake pads and have no problems with flex... on the other hand I put the same pads on my girlfriend's 4 speed and her brakes have a bit more flex. She doesn't stop hard enough that it is a worry, but I wouldn't use that combination of pad/caliper on my setup.

Also, most decent V pads have some curve to them so that will help offset the extra length.