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