When I got the cycling bug this summer the only bike available to me was my son's 5 year old Marlin 5, very similar to the 6 (in 2015 it has a 12-34 cassette). After a few rides I too thought I was a bit slow on that machine (about 12-13 mph average on hilly roads). The first thing I realized was that the cheap spring forks were sapping my energy - especially if I had to get out of the saddle. Since my son had moved out and left the bike at home, I felt completely OK modifying to my immediate needs (most of my mods are reversible). So I replaced the spring fork with a solid carbon (375mm) fiber fork (this also allowed me to raise the stem length a good 30mm). With this change I picked up 1 mph on my normal loops. Next to go were the 29er 2.20" tires. They were replaced by 700c x 32 Continental GP Four Season tires - and with that change I picked up an additional 2 mph. Now my rides were in a more respectable 15 to 16 mph range. Next I cut 1.50" off each end of the bars to make them shorter, replaced the 100mm stem with a 35mm stem, added Ergon bar-end grips and raised the seat to the proper height to make the bike more comfortable and to get my power to the wheels. Another 1+ mph were added. With all of the changes I made to the bike, I reduced the weight over 6 pounds and could easily cruise 17-18 mph on the flats.

The next change was to get a proper road bike, which added further to my speed, comfort and joy of riding. But now that Marlin (with 40mm Continental Terra Speed tires) is a good gravel/trail bike. I think if my son wants it back...I'll buy him a new bike.