Build your own

Bikemagic Bikemagic

There’s a well-established progression to bike ownership. You start by buying an inexpensive bike. You ride it. Gradually you begin to feel the need (or want, which is to all intents and purposes the same thing) for better bits. So you start to upgrade – tyres here, bars there, forks, cranks… Sooner or later you find yourself with an entry-level frame with components that are deserving of something spanglier.

It’s at this point that what you should really do is buy a nice frame and then assemble it yourself. Sounds a bit daunting, but it’s no harder than fixing them and by putting a bike together you’ll find you’re much more au fait with how it works and how to sort it if it goes a little bit wrong.

So, fairly straightforward then? Yes, but there are some potential pitfalls that are worth avoiding before you start. Not least of which is making sure all the bits will actually fit. Fortunately most parts are entirely interchangeable, but there are a few that you need to watch out for…

byo_bb (11K)

First up is the bottom bracket. The first thing you need to do is check how wide the shell on the frame is. On mountain bikes it’ll be either 68 or 73mm unless you’ve got something exceptionally odd. Simply measure between the two faces to find which one it is. Having established that, you’ll need to get the right length axle. This depends largely on what cranks you’re using, although wider shells need correspondingly wider axles. If you’re using cranks off another bike and the shells are the same width, chances are the axle will need to be the same too. Otherwise refer to the instructions that came with your cranks.

byo_brakes (10K)

Once upon a time it was hard to find a frame that you could bolt disc brakes on to. Nowadays it’s hard to find one that you can’t, and some frames can’t have V brakes fitted to them… Make sure that your frame has the right mounts for the brakes you want to use. If you’ve got an IS mount (like this one here) you’re laughing. Don’t lose hope if you find yourself with a Hayes mount (two threaded bosses close together on the chainstay), though – adapters or alternative calipers are available to sort out most things, although sometimes you’ll find a caliper that just won’t fit in the space available. The easiest way is just to run Hayes brakes, which are actually rather good.

byo_frontmech (9K)

The front mech (if you’re going to use one) is a potential minefield. For a start, there are three different clamp diameters in common use. And then the cable may be routed along the top tube and meet the mech from above (top pull), or go under the bottom bracket and meet it from below (bottom pull). And finally, Shimano mechs come in top-swing (where the mounting clamp is below the cage) or bottom-swing (with the mounting clamp above the cage) variants. They’re usually interchangeable but some suspension designs get in the way of top-swing ones. The easy way around most of these issues is just to get a Shimano Deore front mech. They come with a system of spacers to fit any seat tube and you can route the cable in either direction. And they’re cheap.

byo_headset (9K)

The vast majority of MTBs use a 1-1/8in fork steerer tube, while most road bikes use a 1in size. Threadless headsets are pretty much universal now, so just pick one you like. There are some other headset sizes out there, though. For instance, this Giant needs a 1-1/8in steerer but the frame is designed for a recessed headset rather than the more familiar type with the bearings outside the frame. Or you may encounter a frame built for a 1.5in steerer. You can put a 1-1/8in fork into a 1.5in headtube with a special reducing headset, but not the other way around. Then there’s Cannondales which have another size again, although they usually have a Cannondale fork in so it isn’t much of a problem. The other thing to watch with headsets and forks is that the fork steerer is long enough. If you cut the steerer down to fit a frame with a short head tube and a shallow headset and stem with no spacers, there might not be enough steerer to fit something with a longer head tube or a taller stem.

byo_seatpost (10K)

Finally, there’s the seatpost. The only real issue here is with diameter. There are dozens of sizes, although most frames need one of the three most common – 26.8mm, 27.0mm or 27.2mm. Those differences may sound small, but trying to jam a too-large post in, or clamp up a too-small one, will end in tears. If you need one of those sizes you’ve got plenty of choice – if you find you need a 30.9mm or some such, you may find that there’s only two posts that’ll fit. The only other seatpost issue is whether you get one with layback or an in-line clamp. If your new frame is about the same length as the old and you’re happy with your riding position, use whatever the old frame has. In-line posts let you move the saddle further forward than layback posts, so if you end up with the saddle pushed right forward on a layback post think about getting an in-line and vice versa…

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