Classic & Vintage - 7sp vs. 8 sp question- Cannondale R700

Not exactly vintage but I am wondering what my options are with this road bike. I picked it up on craigslist a while back ($100 with full 105!!!) and it needed work, but finally it has new cables, housing, and tape, Easton drop bars and stem, CF seatpost, Terry Saddle, and Ultegra 8sp bar-end shifters. Right now I just use the friction shift mode since the bike is a 2x7.

I am wondering if I can just buy an 8 sp cassette like this one (http://www.google.com/products/catalog?oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&q=8+speed+road+cassette&um=1&ie=UTF-8&tbm=shop&cid=5315827289850721522&sa=X&ei=O2LETsXHFI-4twfUgdXODQ&ved=0CEEQ8wIwAA) and just swap it out? Derailleur is a shimano105.

Basically I'm just not sure if the spacing is right, the rear dropouts are 126mm or thereabouts.

I am also curious about this because I'm interested in eventually getting brifters, but I don't know of any 7 speed brifters.

Thanks!

You cannot spread the rear drops on a aluminum frame.......

I use 8 sp brifters on a 7 sp Shimano 105 RD and freewheel. The spacing is the same, between 7 and 8 sp, I just adjust the stops so it'll never travel beyond the 7th cog. It runs fine. This is the setup for my 86 SR400.

IMO, you don't need to do anything to the frame. 130mm is just 2mm per side and the triangle won't protest from being spread.
As mentioned you can't cold-set a Cannondale Al frame.

The current wheel can't take a 8 speed cassette. The spacing is too short and the freehub body is too small. You must swap axles and add the appropriate spacer(s) and replace the freehub body with one for 8/9/10 speed. Then redish the wheel.
Or you buy a replacement 130mm wheel if that's cheaper and you don't care to preserve the 105 group/rim.

7 speed brifters are rarer than hen's teeth. 8 speed is still available and the recommended buy. You can run 8 speed brifter with a 7 speed cassette. Including your current bar-ends. I've done it, you just need to fine tune it.
When you move up to brifters, PM me, I may be interested in buying your bar-ends, as I'm not a brifter guy.

You can easily put a 130OLD rear wheel in there, no need to cold set. Works fine, no problemo. Done it a zillion times. The 105 RD (which 105? without pics, I'm guessing 1055) will be fine to 8 speed.

I've done both. I put an 8 speed wheel and ran 8 speed 105 on a Cannondale that was originally 7 speed, and I ran a 7 speed system with 8 speed brifters, just stopped out the highest gear. Found it much better to stop out the highest gear, than to stop out the lowest gear (biggest rear cog). Shifter liked that a lot better.

I use 8 sp brifters on a 7 sp Shimano 105 RD and freewheel. The spacing is the same, between 7 and 8 sp, I just adjust the stops so it'll never travel beyond the 7th cog. It runs fine. This is the setup for my 86 SR400.

"The stops" as in the stops on the derailleur? I've never had brifters so idk if they also have some sort of stops as well... Is it better to use the upper 7 shifts or the lower 7 shifts? Does it matter?

You cannot spread the rear drops on a aluminum frame.......

You are right about coldsetting, but many throw in a 130 wheel without a problem. Myself included!

You are right about coldsetting, but many throw in a 130 wheel without a problem. Myself included!

+1 A piece of cake.

Are you going to put on a new rear wheel to use with the 8 speed cassette, because 8 speed cassette and 7 speed free hub are not compatible. Shimano RSX brifters are 3x7.

take a LH spacer off the axle, that 4mm , then re-dish the rim, centering things.
then it will be a snap, relatively, to change the puncture.
Spreading the stays after fixing a flat is a PIA...