Originally Posted by
cyccommute
Yep. For road use, they'll be adequate. For off-road use, they'll just plain suck. Let's not forget, windchaser, what the Felt Nine-Flow is designed and made for. Sure you can replace the fork, replace the tires, replace all the parts and you'll make it into a commuter bike but why? There are lots and lots of bikes out there that have the right fork, the right tires, the right shifters, rack mounts, fender mounts, etc. at a pretty good price without a whole lot of parts swapping. You can keep the Nine Flow as a mountain bike that is great fun to ride off-road...you can even look for trails to ride it off-road on the way to work...while using the other bike for commuting and/or riding fast.
Upgrading can get costly. Upgrade to make the bike do what it was built to do better. Don't 'upgrade' to make it into something it isn't.
I'm really curious about what he bought this for because, as you suggest, there were likely better options as a commuter than transforming this over to being one. Usually that's something I'd do with a used (cheap) MTB to get a lot of bang for my buck. If he bought this as a commuter, I would change the tires at minimum and gradually add a rack. Maybe he wants a bike capable of both...for a long time I only had one bike; a Cannondale f500 that I put slicks and a rack on. When I went off trail, I'd change tires.