I'm interested in learning more about trials bikes. I've seen them in pictures and videos with the riders doing really impressive stuff on them; incredible balancing, huge jumps, etc.

This type of riding is new to me and seems very fun (sort of reminds me of bmx riding as a kid). My regular routine consists of mainly road and cx riding on normal frames with 700c wheels.

I like to do balancing work and jumps on my cx bike, but there is a limit. The wheels are large and harder (I imagine) to get off the ground than a smaller wheel. Also, although I treat my cx bike pretty rough, and bang it around, I don't want to crack a carbon frame trying to land a big drop (or jump, or whatever).

I'd love to start riding one of these trials bikes, however, I don't know much about them or what even makes a "trials" bike.

I basically know that:

  • they don't have a seat post or saddle
  • The wheels are smaller than a 700c wheel, some 20", some 24", some 26"?
  • they look superficially like a bmx bike

So my question is what makes a "trials" bike, and, what are the most important features to consider when either buying a used one, or building one myself? I'm specifically interested in the wheel sizes ( why choose one over another ), dropout types and rear spacing.

2 Answers 2


This is a fairly lengthy history at biketrials.com, so I'm going to talk more about my experience. Early trials riding typically used BMX bikes and was modelled on motorbike trials. They used 406 wheels and caliper brakes, because that was what was available. Where I was we used leather-insert brake pads to get vicious braking at low speeds (trials typically peaked at running speed, and only that for very short distances).

Mountain bikes first became important for the brakes. They made cantis affordable and available, and U brakes were invented. Around this time I started to see ISO 387 or ISO 388 wheels and tyres, which would fit into most 406 frames but allowed a fatter tyre (they were still 20", because as Sheldon reminds us, inch sizes traditionally measure the outside of the tyre, not the rim). Originally these were sold as ISO388, but looking around now they seem to have "standardised" on calling it ISO387. Whatever :)

Much later, as mountain bikes became light enough to use for trials riding we started to see people doing trials riding with longer, faster sections as well as the usual technical sections. Standards also rose, these days using shipping containers in sections is fairly common, mounts and drops off a vertical pallet are considered routine.

Today we're seeing people using cyclocross and even road bikes for trials, because lightweight wheels and frames are now strong enough, and the brakes good enough, for that to be possible. There's also unicycle trials riding and a few people doing crazy stuff on recumbents... crazy by recumbent standards, because even riding no-hands is hard on most recumbent bikes). The days when getting a bike under 10kg meant you had to start with a BMX are long gone. We're also seeing a wide variety of trials-type riding, from flatland to the exxtreme sportz TV spectacular stuff with people doing backflips off cliffs.

If you want to get started I suggest buying a cheap-ish BMX with strong wheels and decent brakes. Just looking for one with V brakes should get you out of BSO territory. Expect to trash it, but it will let you learn a bunch of basic skills (riding on either wheel, track standing, riding backwards, hopping, simple lifts and jumps). Once you have trashed by watching instructional videos and experimenting you'll have a much better idea of what you want to do, and that will lead you into the bike you want to buy.

  • 1
    +1 for the cheap thrash bike on which to learn. No point wasting big money on something you might not suit/enjoy.
    – Criggie
    Oct 21, 2016 at 3:53
  • 1
    Note you can get started on a cheap-ish 26" MTB as well, imo that has some benefits over a BMX: bike/parts are usually more readily available, will be easier to find with V-brakes, has the benefit you can figure out which gear suits you best for lifting the bike on it's backwheel and of course for those forward hops which are after all one of trials' key points. Learning that stuff with standard BMX gearing is making things unnecesary hard.
    – stijn
    Oct 21, 2016 at 8:05
  • What about the 24" wheels, is that a thing in trials?
    – ebrohman
    Oct 26, 2016 at 17:18
  • @ebrohman apparently so: trialspads.com/articles/20-24-and-26-trials-bikes.html
    – Móż
    Oct 26, 2016 at 20:31

Trials bikes were originally just mountain bikes, at the time most mountain bikes had 26" inch wheels and 135mm rear dropouts (trials is basically shorthand for mountain bike trials). Trials bikes of this design usually fall into the "stock" category.

When people started modifying bikes to be even more well suited for obstacle courses, the 20" wheels and 116mm rear dropouts were introduced, this is when the bikes started to closely resemble bmx bikes. Trials bikes of this design usually fall into the "mod" category.

"Stock" bikes and "mod" bikes make up the two officially recognized categories of trials bikes, so, plan for 20" wheels or 26" wheels. The 20s are generally more nimble but the the argument for 26s is probably more clearance and better balance.

There's quite a bit more information on the subject:



  • this is only correct if you ignore the entire history of trials riding until well after the invention of mountain bikes.
    – Móż
    Oct 20, 2016 at 21:52
  • @Móż Are you referring to the motorized variety? Can you link to some examples? Oct 20, 2016 at 22:50
  • 1
    According to biketrials.com the first US "world championships" were in 1980. The first MTBs appeared only just before then. But in the late 1970's there were contest explicitly called "trials" where I lived, using BMX bikes, and by the time we started seeing actual mountain bikes in the mid 80's were old news.
    – Móż
    Oct 20, 2016 at 23:55

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.