How can I change components on my bike?

[lunacycles]

My husband and I were on cape cod, and he had a bike friday with an old shimano 7 speed set up. His sti rear shifter failed, and we couldn't find anything in the local bike shops, and had a trip to P-town planned. I happened to have a set of new 9 speed brifters I had just picked up for another bike I was planning to build when I got home, so we decided to try it. We were also surprised, but it really did work fine. Perhaps it doesn't matter if the spacing is different, since you use the limit screws to tell the derailleur how far to move with each shift.

I think it is fabulous that it works, really! I am just saying it is not common for it to work, nor will it likely work on an 8-speed cassette. The issue is the amount of spacing between the cogs, which is different for 8 or 9 speeds,and the shifters are designed to work with one kind of spacing, tho sometimes you get lucky if you play with cable tension enough.
Limit screws actually only control how far outboard or inboard the derailleur travels. They have no effect on how far the derailleur moves with each shift.

[Triskeliongirl]

I think it is fabulous that it works, really! I am just saying it is not common for it to work, nor will it likely work on an 8-speed cassette. The issue is the amount of spacing between the cogs, which is different for 8 or 9 speeds,and the shifters are designed to work with one kind of spacing, tho sometimes you get lucky if you play with cable tension enough.
Limit screws actually only control how far outboard or inboard the derailleur travels. They have no effect on how far the derailleur moves with each shift.

Wow, thanks for the info. I guess it wasn't the limit screws. I just know that there was a screw we fiddled with until the derailleur threw the chain just the right amount to smoothly move to the next cog. If that's not called the limit screw maybe it is something that adjusts the cable tension (sorry but I am all self-taught so I don't know what its called, I just look at the bike and try to figure out what I have to adjust to make things do what I want them to).

I guess we did get lucky, which is good since our trip would have been ruined if we couldn't make it work. It also surprised the local bike shop guys that couldn't locate a 7 speed shifter for us.

[fidlfreek]

While you're at it you could just upgrade the whole group. For instance http://cgi.ebay.com/Shimano-Tiagra-1...%3A1|294%3A200

You'd need to add new shifter cables/housing and a new bottom bracket (and labor, which I'm guessing would be less than a full bike build, maybe $100, depending on your area) but you'd basically have a bike you could be happier with for a fraction of the price of a new bike.

And yes, I agree with the shop that if you're going to pay full retail on upgrading parts then its probably not worth your time or $. BUT if you can get a deal, then all bets are off