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I am going to make a custom fixie bike (possibly with a front brake) that I will use to race on tracks and even commute with.

I have been looking at a Planet X frame, and they seem to have very high quality frames for decent prices. But I am not sure if I should get the track frame or the time trial frame. What are the differences between these style of frames? The time trial frame is $150 more than the track frame, is it actually that much better?

I am going to put time trial handlebars on the bike. I also plan to use a belt instead of a chain to cut down on weight and maintenance.

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3 Answers

up vote 9 down vote accepted

You seem like you want three different bikes all smashed up into one, and the result is not going to be good.

First, the time trial frame is not intended to be a track frame. If you're going to race at the track, use a frame and components that are designed for the track. For starters, the time trial frame will have a lower bottom bracket, dramatically increasing your likelihood of a pedal strike, which can be disastrous.

Second, bikes at the velodrome are not allowed to have brakes. Period. You will also likely not even be able to mount brakes on the Planet X Track frame.

Third, a belt drive won't really improve the reliability of a track bike. Track bikes use significantly thicker chains due to not having to fit between tightly-packed cogs in a rear cassette. Having raced a few years at velodromes, I have yet to see anyone snap a chain.

Fourth, you probably won't even be able to install a belt drive. Belts can't be disconnected/reconnected like chains can, so you will have no way to route the belt through the frame to mount it around the chainring and cog.

Fifth, aero bars are explicitly disallowed from any mass-start events at the velodrome. Unless you only plan on riding pursuits, you will need standard drop handlebars.

My advice? Save the creativity for your second bike. The fact that you have to ask this question tells me it's probably your first build, and you're very likely to end up with a frankenbike that's not actually what you were hoping, not race legal, and likely not even possible to build given the requirements / parts you've named.

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This is indeed my first build. I currently ride a pre-made road bike. I've replaced many of the parts, but always with the equivalent. I've never gotten creative. I thought I might be able to this time. I really just want to make a fast, light bike. Thank you for your answer - it definitely got me thinking in a different direction then I was! –  Keegan McCarthy Jul 10 '12 at 22:51
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Two very different animals.

The TT frame is built up with road components, the brake handles and shifters are a bit different but the front/rear derailleurs, crank, etc are all regular road components.

The track frame is a single speed frame and many do not have holes to mount brakes...for Planet X you'll have to ask if the fork does or does not have them... there are no pictures or specs on the fork.

Belt vs Chain : you need a custom frame for this (or the ability to customize the frame) as belts don't break like chains do. In frames made for belts, there is usually a piece that unscrews to reveal a gap in the wheel stays. On some CrMo or Aluminum frames you could probably do the customization, but I'd be hesitant to try this on a carbon frame.

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For your purposes, the biggest difference is the rear dropout (where the rear axle connects). The track bike will be much easier to set up as a fixie.

I suspect the pricing difference has to do with features like bottle bosses, attachment point for derailer, cable routing stuff, etc, not from the TT frame being "better" in any other way.

The TT frame has a vertical dropout, designed for a bike with a rear derailer. The track frame has a rear-facing horizontal dropout. If you want to set the bike up as a fixie, you need some way to tension the chain. With a horizontal dropout chain-tensioning is relatively straightforward. With a vertical dropout, you'll have to use a chain tensioner or something else to take up the chain slack.

The geometries are different. The TT has a top tube about 1cm shorter in the same frame sizes. They have different angles which affects handling. Basically, the TT is a better geometry for TT-style bars.

Both frames are better for what they're made for. The TT frame is better as a geared bike with TT bars, the track frame is better as a fixed-gear bike with drop bars.

Unless they're hiding something pretty well, you won't be able to put a belt onto either bike. A belt requires that there be a reconnectable split in the rear triangle on the drive side of the bike (I've seen it in the dropout and in the seat stay, but it could be in the chain stay, too). If you're racing, you may want to reconsider the belt drive idea, anyways. I've heard belt drives tend to have a subtle "squishiness" to them (from the material coating the carbon compressing) that's annoying when you're trying to push hard.

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+1 for horizontal dropouts –  Mac Jul 11 '12 at 0:19
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