My Soma Double Cross DC just arrived yesterday. I was pretty excited to get it out of the box and take a look. The 60cm frame weighed in at 4.91lbs and the fork was 2.46lbs.
This build has been both exciting and fustrating and I don’t even have any parts together with a frame that only just arrived yesterday. This is my first build from the ground up and luckily there are staff here at Dirt Rag that have spent years in bike shops acumulating a deep knowledge base that I can tap into. Although I try to spend as much time as possible on a mountain bike and commute to work regularly there are things you can only learn in a bike shop.
Next on my list are wheels, a headset, stem and handlebars.
Headset will probably be first since its the easiest of the components to pick up. There isn’t much debate there, 1 1/8" and maybe a color. Since it’s a new build I don’t have to worry about how high or low the stack of the headset is because the steerer tube can be cut.
Stem and handlebars have a lot of options. To start off I’m looking at fairly inexpensive options for a couple reasons. The main reason, I’m not sure what I’ll like. There are several handlebar widths and shapes that can make choosing bars a daunting task. Stems are similar. They come in a variety of lengths and angles which will effect the fit of your bike significantly, not to mention handling. So for the time being, inexpensive. Cheaper on the stem and handlebars will also save me some cash for the fun stuff, like cranks, derailleurs, and shifters. The stem, bars and seatpost will also make nice upgradeable items for cross season when dropping some weight might seem like a good idea.
What has been difficult is the wheelset. The Double Cross is a steel frame with a rear hub spacing of 132.5mm. Right in the middle of road and mountain hubs. I can go either way. This might seem like a great option. Especially since I want to use dics brakes. Well, it’s been the cause of some fustration and has been the reason I’ve spent hours sifting through QBP’s website and the internet. Chainline. The once overlooked principle is defined by Park Tools as: the position of the cogs or chainrings relative to the center line of the bike… For example, a front crankset and/or front derailleur might be designed to have a chainline of 47.5mm. This means it will work best when the middle of the crankset is 47.5mm from the middle to the bike center line.Definitely more of an issue for fixed geared bikes or single speeds but it can effect shifting.
If either the front or rear sprockets are either too much inward or outward relative to the other, there may be certain shifting problems. The following are typical problems that may be caused by chainline issues.
- Chain jumping off large chainring when front derailleur is correctly adjusted.
- Chain riding off lower derailleur pulley when derailleur or hanger is not bent
- Chain rattling on inner faces of front chainrings.
- Chain derailling off inner chainring when front derailleur correctly adjusted.
- Front derailleur cannot be adjusted to stop over shifts while still allowing good shifting.
A ton more about chainline at Park Tool’s site: http://www.parktool.com/repair/readhowto.asp?id=110
The wheels I will likely be using are the Mavic Speedcity wheelset. They are 700c with disc and rim brake capabilities. They are designed as an urban wheelset for mountainbikes, perfect for the potholes and hills of my current urban jungle. Since they are designed for the mountain bike it means the rear hub is 135mm. With a 9 speed cassette I can start to messure the chainline to see what bottombracket width is needed for up front. If the BB is too narrow then there could be problems shifting.