My winter commuter is a 1994 MTB with 7 speed STX/LX with slicks. The crank is beat. It is a compact 42/34/24 STX 58mm/94mm BCD. I have a used Sora road group that I could probably sell on Ebay for 40 or 50 bucks, but could I use the Sora road crank 52/42/30 on this bike with the 7 speed STX shifters. The BB is compatible. I am not sure about the STX rapid fire shifters, would they allow the chain to engage into the large ring on the front derailleur ? Would I be better off selling the Sora group and investing in chainrings, cassette (IG60), and a new chain to keep this old 7 speed going.