hotch

I have a Trek 1100 in perfect condition that came with shifters on the down tube. I wonder what type of agony and cost would be involved with converting it to STI shifters?

pokey

How many speeds on the rear, and what is the rear dropout spacing?

hotch

7 on the rear, triple on the front, der are shimano rx100

pokey

You can look for rsx7 speed STI which shift either a double or triple up front, or you could use a RSX,, RX100 or 105 triple 8 speed shimano STI ,to shift the 7 speeed even though the cog spacing isn't exactly the same. but good luck finding them new and I wouldn't waste my time on used.A 9 speed rear hub for using 9 speed STI requires 130mm dropout spacing and yours may be 126,but you need to measure.Aluminum doesn't like to be bent.You can use 9 speed sti with your hub by getting a 9 speed cassette,removing a cog and a spacer so it fits the hub and use a 9 speed sti shifter to shift the remaining 8 cog.Use a 9 speed chain.You may also need a STI compatible front derailer,but your rear will work.