The gear chart is pretty easy to work with. Since the IRD FW's are not listed on the pull down menu, you can just type in the ones you have. While the chart is pure numbers, it is a tool to use to see what changing your gears may feel like. In half stepping, your jumps between gears can be 4-5 gear inches, this is essentially splitting a jump of the traditional what now is called "crossover gearing" (like 26-36-46 rings)

You'll only need a new chain because it will need to be longer with a 32 or 34t cog, and with this a new chain is needed.... as opposed to just adding some links.... which would result in the chain skipping. When you change the FW to completely new gears, it's always best to get a new chain. No special chain is needed, these days you'll see them labeled a 8 speed, 9sp, 10sp. etc. What you want is an 8sp chain, which works for anything from 5-8 speeds. The exception to this are the Suntour Ultra 7 FW's, which work best with a 9sp. chain, but you're not using those. I use SRAM PC-850 chains myself, they're inexpensive and work as they should. Installing them and taking them off is simple with the quick connect Power Link.

I spent some time in Flagstaff in 1983/84 while going to NAU. I bought my Stumpjumper at Cosmic Cycles. I don't remeber much about school, but I sure remember the great rides around Flagstaff on the Stumjumper! Great fire road trails. My favorite ride had to be going up Lookout Road to the TV towers in Fall. What a view... I'll never forget that . The Pine trees..... wonderful smelling pine trees everywhere.