Street Trials Geometry

Been wanting to build a custom bike for the longest time, and decided a street trials bike would be a good place to start for some reason. I realize these are strange bikes typically made to the specifications of pro riders. However, I am very curious about the theory behind certain aspects of the geometry so I can make a bike better suited to what I wish to do.

Namely, I have been wondering about the following:

  • Why do most trials bikes have 0 rake, and why is it that some riders (namely Danny MacAskill) prefer some rake?
  • Why are the stems so long? It seems like bike control would be better suited to a short stem.
  • Why does 24" wheels seem to be the standard? I would have expected 20".

Any info on the theory behind this stuff would be great! Thanks!

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I’m not the right person to answer all these questions. But, the stems are long for leverage. The longer stem makes it much easier to exert forward forces on the handlebars and put a ton of weight over the front of the bike. Enough to easily hop on the front wheel. That and the longer stem can bring the handlebars higher, since there may be a limit to how tall you can build handlebars.

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That makes a lot of sense. Being able to pivot on that front wheel must be difficult with a shorter stem. It’s interesting to see how different street trials and “pure bred” trials bikes are. The stems on Inspired bikes and the Canyon Stitched CFR are far shorter then what’s seen in competition. Thanks!

The high bb is also a key part of trials geo.

I think the slightly shorter stems, rake and 24 inch wheels are an effort to integrate freestyle type tricks like tail whips and bar spins into the equation. You can go a little faster and cruise around town. Riding a mod 20 in around town sucks for the position and gear ratio. A street trials bike goes a little less extreme on head angle, bb height and stem length to make it easier to mix styles. At least that’s my take.

The Inspired bikes look like fun!

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Oh, yeah, the bb on those is so high! So, all the parts of these street trials bikes I am confused by are compromises to make them more capable at things a true trials bike can’t do. Also, they look a heck of a lot more comfortable then those pogo sticks of bikes!

And yeah, those Inspired bikes look like so much fun!