& spped tp 8 speed conversion
 

I have a 1991 Specialized Allez with a Shimano 105 group that I've upgraded with an indexed 8 speed Shimano brake shifter...now , of course I have an extra click on the shifter with the 7 speed hub (its driving me crazy). Can I purchase a 8 speed freewheel and use it on my current set up. Many Thanks...for any recommendations

Does the bike have a freewheel or a cassette? For a '91 Shimano, I suspect that you have a cassette rather than a freewheel. If you do have a freewheel, it's simple. Just take off the old freewheel and put on the new one (you may need spacers on the drive side). Cassettes are only a little more complicated but do able.

Since 7 and 8 spd cassettes have the same spacing you can't get an extra gear onto the cassette but you can transplant a body so that you have an 8/9 body on your existing wheel without too much trouble. Sheldon Brown tells you how to it. It actually pretty simple. I've done it to a couple of bike that I own and it only took an hour or so for both of them.

Thanks cyccommute for the tips...I'll move towards a 8 seed soon...Gizmo

To upgrade to 8-speed you will have to replace the 7-speed freehub body with a wider 8-speed body. Your frame may be spaced 126 mm and 8/9/10-speed hubs are 130 mm so the wheel will require some effort to install. You will also have to redish the wheel.

If your frame is steel, it could be cold-set to 130 mm. If it's Al, don't even consider cold-setting it.

You may also luck out and find your frame is spaced either 128 mm (a compromise between 7 and 8-speed spacing) or even 130. My 1992 Trek was spaced 128 and takes either width hub easily.

Check around on the web for a 9 speed hub. I got 3 that I used the cassette bodies for replacement on clearance for cheaper than I could get the replacement freehub body for just one. Jenson, Price Point, Nashbar, etc. often have clearance Shimano rear hubs for cheap.