Mansfield Machine

The Mt Mansfield hillclimb, aka Race to the Top of Vermont, is this coming Sunday. Except for the first 200m, this climb is a loose dirt road. The race rules require minimum 2" wide tires, as the post race descent is quite sketchy. I did this race last year, the first time they held it. I raced my hardtail, as-is, with no weight trimming efforts. It is not a light weight machine, weighing in at over 25 lbs. I placed third overall on this bike. I calculated, had I a five pound lighter bike, I could have potentially won the event. There's no way I'll take five pounds off my hardtail. I'm starting with a 3.6 lb Ti frame. It already has an XTR drivetrain. I'm not about to make an investment in a carbon hardtail yet. So tonight I finished cobbling together one of the most bastardized machines yet.

Mt Mansfield is a fairly persistent 12% grade. Sure, there are a couple momentary places the grade levels off, and several section where it is much steeper than 12%, but I'll spend about about 90% of the climb in a single gear ratio. This got me thinking about trimming down my singlespeed for the hillclimb. Stock, it actually isn't much lighter than my hardtail at just under 25 lbs. I have heavy wheels, tires and fork on it.

So I shopped for a good deal on a White Brothers rigid carbon fork. That alone would take 2 lbs off. Then I have these old non-tubeless wheels sitting around I custom ordered eons ago. The disk wheelset weighed in just over 1500g, very light for 26" disk set. Even though I have to add tubes to the tires, this took about another 2 lbs off.

So how do I come up with another pound reduction to reach my goal? I had an old flat bar laying around, silly light aluminum that weighed half the weight of the alloy riser bar I have on the bike now. So I swap the bar over only to realize that the stem is OS (oversize, or 31mm clamp). Argh. Now I have to scrounge for a different stem that doesn't weigh more to fix that problem. Still needed to shed a little more weight.

I pulled the carbon seat post/SLR saddle from my road hillclimb bike. Silly post, it was inches too short. Maybe if I just swap the saddle. The saddle I had on the singlespeed was already a minimalist design, but weighed 250g. The SLR weighed 140g. Perfect, another quarter pound saved. Grab the fish scale, I got 19.95 lbs. Good enough. There are folks out there with fully equipped hardtails out there lighter than this. But this is all I have to work with for now without spending a fortune. I figure the carbon fork will see general reuse from time to time.

I just hope the cobbled up contraption holds up. I'm using a 22x19 gear ratio. That's a 30.1 inch-gear for those that think that way. As you can see, there is no way to test this thing except on a really steep grade. It spins out at 10mph. The test will come shortly after the start of the race. My biggest concern is the chain and chainline. I had to take links out, did not have any spare 8spd chain pins, so I had to reuse the ones in the chain. Bad, bad, bad. The 22t ring had to be mounted on inner BCD too, so I had to move the cog in back closer to the wheel center.

If the Mansfield race were important, bringing an untested rig like this would be hugely risky. Did I get the ratio right? Will I be over/under geared too often? Doesn't matter. The race is not part of the BUMPS challenge. It is just a fun event for me. It would be a riot if a guy on a singlespeed wins it, but I suspect many more people are going to show up this year, making the overall podium a long shot this time. I've always wanted to race my singlespeed. This isn't exactly what I had in mind. A few of us hope to hit trails up that way afterwards to make a complete day out of it. Yes, I will bring a different bike for that.