My current off-road machine is my Blue Triple Top Tube 29er. This bike was the first in a lot of ways for me. It was the first time I felt that I had really nailed the fit and handling of a bike. Flying down the trails it just felt like it hugged the turns and I never once felt out of control or even a little sketchy on it. I put a relatively slack head tube angle on it which gave it an incredibly stable feel but was not sluggish in the tight stuff at all. And the actual fit of the bike was near perfect, spending all day on the bike was never a issue (at least comfort wise, being in shape enough to spend all day on the saddle is different story). Simply put the design of this frame was near perfect for me. With this bike I also built my first 29er suspension corrected fork (the axle to crown distance was designed around a Fox f29 with twenty five percent sag) that I have been riding for a little over a year now. While I will never give up my front shock, I could definitely see the advantage of having a rigid fork. Climbing up hills seemed much more efficient and while on smooth trails I felt much more in control.
One of the most distinctive firsts with this bike would have to be the use of the triple top tubes. Without a doubt this bike was visually distinctive and no matter what was a conversation piece at the trail head. Unfortunately what made this frame distinctive also made it extremely heavy. Each of the top tubes weighed in around 300 grams while the True Temper top tube I would typically use is listed as weighing 287 grams. While I would never count myself as a weight weenie (I do ride steel after all) having almost 700 grams (over 1.5 lbs!!!) of unnecessary weight is a little much.
With this next 29er frame I am looking to take what I learned from "Blue" and tweak the geometry a little as well as lighten up the frame a bit. There were two changes to the geometry that I wanted to make that hopefully will give me an even quicker handling bike while maintaining its stability. Both changes are in the rear with the first being shorter chainstays. Previously I went with 440mm chainstays (the distance from the rear axle to the center of the bottom bracket) and with the new bike I am going with 420MM chainstays. With the shorter chainstays you run the risk of the tire interfering with the seat tube and you then are forced to either have a segmented seat tube (not the best idea with mountain bikes) or go with a curved seat tube. Having a decent tubing bender with the correct dies I went with the later option.
The other change is a steeper seat tube. On "Blue" I eventually moved the seat pretty far forward to so I could be a little further over the bottom bracket. With the new frame I went with a head tube angle of 73 degrees from the previous 72. This will allow me to place the seat back centered on the rails.
There are also going to be some other changes to this frame from my previous builds. While I am going with the 44mm inset headtube I am also having some headtube rings fabricated to stiffen up the head tube as well as give it a much cleaner transition from the head tube to the headset. Also a fellow frame builder had fabricated some direct mount front derailleur mounts (redundant?) that I am extremely excited to try out. The other change will be the low mount rear dropouts. Buy using these I can mount the rear disc caliper on the chainstay instead of the seat stay thus eliminating the need for the chainstay brace. Also the dropouts are stainless so they are going to look extremely slick!