Somewhere along the way, I've become a weight weenie.
I took my trusty Seshin BMX out yesterday for a workout at the Brooklyn Banks. My bike is built to 2005 spec, with 14mm 48H wheels, heavy forks, and mostly overbuilt parts. I did that intentionally at the time, knowing I would be crashing the bike repeatedly. I wanted it to hold up to my hack riding.
Now I'm feeling like the bike could stand to lose some weight here and there. I ride with a little more grace than I did back then, and I am not doing any massive drops to flat. I weighed it yesterday and it came to 28.2lbs. That's not terrible, but its still pretty high up there when compared to today's street machines. Even some completes weigh in less than my bike.
Thinking about it a little more, I wanted to know just how much difference some new parts would make. So I devised a little spreadsheet
I thought about the heavy parts of my bike, what I thought I wanted to change, and compared weights, and prices. I know the front of my bike is overbuilt for what I use it for, but my cranks and rear wheel are not. BMX technology is evolving pretty fast. New materials and manufacturing processes are being employed to make parts that would once be considered light for race application, become the norm for "street" use.
The spreadsheet is actually fairly straightforward, if one can trust the weights for each component published online. The hardest part was finding the weight figures for some of my "obsolete" parts. I had to scour internet archive for a few of them.
I did it in two sections, the front end, and the drive train. One of the nuances of upgrading my front end to a lighter fork, is that it means going to a smaller front axle, which means I need a new front wheel. So some of the items had to be lumped together which can get costly.
Some of the items that make the biggest single difference in mass, would be the tires. I currently have heavy steel bead tires on my bike, that are quite worn down. Switching those to newer Kevlar beaded ones would save over 100grams per wheel. Add some .6mm thickness tubes in there, and its now at 150grams per wheel. That makes quite a difference when its all rotating weight.
The bright blue highlighted parts on the table are items that exceeded 5 grams difference per dollar. And strangely, they are small parts. Tubes and Bar ends, and a light weight chain. The purple highlighting shows the total differences on the two different areas of the bike. To upgrade all of the front end of my bike would cost $404, and save me .75kg.
To upgrade my drive train (including rear tire) to a smaller gearing, would cost just over $100 and save me about half a kilogram. Of course, in doing the drive train gearing swap, I don't NEED to change the chain, as moving to a smaller gearing will allow me to remove some links and take mass off my current KMC 510HX chain.. but I would need to change the sprocket to a smaller one if I do so with the driver. I didn't put a price on the driver, because a friend has already donated one to me. (I've also been warned against using the KMC 710 Super Light)
So.. after it's all said and done, I could shave nearly a kilogram off my bike, for the low low price of $512. That would put the entire exercise at 1.94 grams per dollar. Its not really a priority for me at this point, as I've got hubs to worry about. Still, it was an interesting look at what it would take to bring my bike up to speed with today's parts.
Since the tires are wear items, I probably WILL be replacing them, and who knows, maybe that will make enough of a difference for me to be happy with it.
I would hate to think about the grams / dollar figure of an already lightweight road bike.
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