Most riders we see are on bikes that are too big for them to ride properly. This is because the bike industry is making bikes longer, but they have not updated the sizing charts.

Before you spend money on a sweet new bike, please follow these steps:

1. Ignore the bike maker’s sizing charts

The critical number when selecting a bike is frame reach. As part of the bike industry’s trend toward longer and slacker and badder-ass-seeming bikes, frame reaches have gotten much longer. A current size small might have a frame reach longer than a size large from a few years ago, but the sizing charts have not been updated to reflect that.

If companies like Yeti and Ibis and Transition were honest about the sizing for their trail and enduro bikes, they’d say:

“If you’re shorter than 5’9″, sorry. Either don’t ride our bikes, or ride one that’s too big for you.”

That’s the current truth. Cross country bikes with more traditional geometry aren’t as long, but you’ll still be smart to ignore the sizing charts.

2. Measure your body RAD

When you are standing tall in a bike stance, with your fists punched downward, this is the distance from the floor to the first (biggest) middle knuckle. Be very careful to get an accurate number. Most people get a number that’s way too high.

The most accurate method uses a RipRow or a handlebar or broomstick.

If you don’t want to bother with measuring, and you think you have average proportions, multiply your height in centimeters by 0.447.

3. Calculate your target frame reach

For a quick estimate of the viable range of frame reaches for you, multiply your RAD in cm by 5.45.

This gives your ideal frame reach in mm. Frame reaches often jump 20-30 mm between sizes. It’s fine to ride a frame 20 mm shorter than your target reach, but do not go longer.

For example, an 81.5 cm RAD gives a 444 mm target frame reach. The best frame for this rider will have 424 – 444 mm of reach.

NOTE: This assumes average proportions. If your proportions are outside the average (many are), you might benefit from a bike selection consultation.

4. Pick candidate bikes

Go to the geometry charts for bikes you’re interested in. Ignore all bikes whose reaches don’t fit you.

Warning: If you’re under about 5’9″ (175cm), it will be more challenging to find new bikes that fit. Open your mind to other brands and models. Don’t be too proud to ride a bike designed for teenagers. And don’t freak out if the bike that fits you has 27.5- or even 26-inch wheels. A proper fit is way more important than wheel size or suspension travel.

5. Dial in the details using the RideLogic calculator

Use the calculator to play with the frame, stem, handlebar and stem numbers until you get the fit you love.

Go to the RideLogic bike calculator.

6. Buy without guesses or regrets

Once you have the bike, if you like, you can chase the final few millimeters using the on-bike check.

Have fun!


5 replies
  1. anna.sut10
    anna.sut10 says:

    I bought a new stumpjumper with 29 inch wheels but after reading this section switched for a size down. So glad i did. First ride was awful but then I spent the afternoon in the garage, complete with the steps. I dropped the bar height, turned the stem the other way around, rotated the bars and bingo! Almost perfect RAD. Now i love it. i just now need to try a bar with more sweep due to elbow and wrist issues and i may drop to a 165cm crank (i used to ride 155’s on my old bike due to my hip replacement) and I might change the rear cassette give me a better range on lower gears. Honestly, so glad i discovered this. Best bit of all is I am now absolutely loving things like logs and drops and can get chest to bars and a really nice hinge to nail corners that were awful on the first ride- in fact, i didn’t do them! I do still like my old 27 from 2015 which co incidentally also fitted perfectly but i find the new bike geometry has given me much more confidence in descents and drops. Interesting, when chatting to folk on trails who have switched from a 27 to a 29, almost all have said they haven’t loved them straight away so i have directed them to your vids for guidance. Most , didn’t drop a size by the sound of it and the complaint is that it feels wrong. Thanks Lee!

    • Lee McCormack
      Lee McCormack says:

      Thank you for this nice note. I’m stoked you’re stoked!!

      Shorter cranks are all pros with no real cons. The easiest/cheapest way to give yourself easier climbing gears is via a smaller chainring.

      Have fun out there!!

  2. Luke Walters
    Luke Walters says:


    Does this target frame reach calculation (RAD * (5.4,5.6)) apply to kids proportions/bikes as well?



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