Alpha Four

Size Guide

Prevelo Bike Sizing

Getting your kids the right size bike is important and, fortunately, also easy. You just need two pieces of information about your little rider:

  • Inseam
  • Rider Experience

Measuring Inseam

  1. Have the rider stand against a wall, hold a book between their legs so that it is firmly against their crotch (the same place their bicycle seat will be).
  2. Measure the distance from the floor to the top of the book.

Rider Experience

Children who are learning are more sensitive to bicycle height than children who already know how to ride a bike. For this reason, our recommendations for bicycle sizing vary slightly based on the experience lever of the rider. The chart below takes into account the fact that experienced riders tend to adapt better to a bike that is slightly larger. For this purpose we categorize young riders as either "Learners" or "Pedalers"

  • Learner: riders who either have not yet learned to ride a pedal bike, or are still frequently putting their feet on the ground while riding.
  • Pedaler: riders who can ride confidently and only put their feet down to stop.
Model Wheel
Approx. Rider Age
Learner Inseam
Pedaler Inseam
Alpha Zero 12" 1½ + 12.5 to 16.5
Alpha One 14" 3 to 5 13.5 to 16.5 13 to 16.5
Alpha Two 16" 4 to 6 16 to 18 with short seat post
(21.5 to 24 with long seat post)
15 to 17.5 with short seat post
(20.5 to 23.5 with long seat post)
Alpha Three 20" 5 to 9 18 to 23 17.5 to 22.5
Alpha Four 24" 7 to 11 24 to 29 23 to 28
Zulu Three 20" 5½ to 9 21 to 26 20 to 25
Zulu Four 24" 8 to 11 24 to 29 23 to 29


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24-Inch Wheels | V-brakes | 8-Speed

  • The 24" Alpha Four offers an 8-speed Shimano drive train. The 11-34T wide range gearing is the real deal and gives growing riders truly usable gear range. It features:
    1. Prevelo confidence inspiring low and narrow geometry. Prevelo geometry keeps the rider low, balanced and in control.
    2. Lightweight 6061 aluminum frame with custom formed tubing.
    3. Lightweight aluminum alloy fork with chromoly steerer.
    4. Tektro front and rear v-brakes.
    5. Quick release front and rear wheels for toolless wheel removal.
    6. Three piece crank with squared taper bottom cartridge bearing bottom bracket and ultra narrow Q factor.
    7. Custom made cranks. All Prevelo cranks are sized specifically for each model bike, down to the millimeter.
    8. Shimano ALTUS 8-speed drivetrain. This 8-speed derailleur has a SHIMANO Smart cage. This unique pulley cage permits the use of a shorter pulley cage without comprising gear ratio width. Because kids’ bikes have small wheel diameters, rear derailleurs on kids bikes hang low and close to the ground. The Prevelo Alpha bikes use Smart cage derailleurs to keep things high and away from the ground.
    9. Shimano ACERA RAPIDFIRE Plus Shift Lever. Small hands have a hard time using twist shifters. We use reliable silky smooth thumb shifters. They are easy for small hands to operate, have an indicator display, and operate just like shifters on high performance bikes.
    10. Replaceable derailleur hanger. If the derailleur takes a hard hit, the hanger can be replaced without repair to the frame.
    11. 11-34T wide span gearing gives riders plenty of range to spin up tough hills.
    12. 95% assembled. Just install the handlebar, seatpost, front wheel and pedals.
    Weight (including pedals) 21.2 lbs / 9.6 kg
    Minimum Saddle Height 25.8 in / 655 mm
    Maximum Saddle Height 31.2 in / 792 mm
    Bottom Bracket Height 9.9 in / 252 mm
    Gain Ratio 2.2 - 6.8


    A Wheel Size 24"
    B Wheelbase 38.1 in / 968 mm
    C Effective Top Tube Length 19.6 in / 498 mm
    D Head Angle 69.
    E Seat Tube Angle 69°
    F Chain Stay Length 16.3 in / 415 mm
  • Components

    FRAME 6061 heat treated aluminum alloy custom formed tubing
    FORK Aluminum alloy blades with chromoly steerer tube - 35mm rake
    SEAT CLAMP Aluminum alloy with toolless adjustment
    FRONT BRAKE Tektro aluminum alloy V-brake
    REAR BRAKE Tektro aluminum alloy V-brake
    FRONT BRAKE LEVER Tektro aluminum alloy
    REAR DERAILLEUR 8-speed Shimano Altus double servo with Smart cage
    CRANK SET Prevelo anodized alloy 3-piece square taper with 130MM crank length.
    SPROCKET 32T with double chain ring guard
    BB SET Sealed cartridge
    HEAD SET 1 1/8" threadless
    RIM Aluminum with grinded sidewalls
    FRONT HUB Lightweight alloy 1-piece forged CNC with quick release
    REAR HUB Lightweight alloy 1-piece forged CNC with quick release
    TIRE & TUBE Kenda Small Block Eight Pro 24 ×1.5
    SADDLE Prevelo big kid saddle
    HANDLEBAR Prevelo aluminum big bore - 580mm width x 40mm rise with 31.8mm to 22mm taper
    HANDLEBAR STEM Aluminum 60mm extension
    GRIP Kraton rubber
    PEDAL Composite with 9/16 chromoly axle
  • Trying to decide between the Alpha Four and the Zulu Four? Click here to learn the difference:  Alpha Series vs. Zulu Series


What the bicycle media is saying

two wheeling tots logo

The perfect mix of road warrior and basic all-terrain cruiser, the Alpha Four is built with kid-specific geometry for a precise, comfortable fit.

The Prevelo Alpha series is an exceptional line of bikes for eager young riders. Lightweight with a low-center-of-gravity, the Alphas are fun and easy to ride.


Kid Centric Features

kids sized bicycle crank

Kid Engineered Crank

8 Speed Shimano Drivetrain with Wide Span Gearing

prevelo internally routed cables

Internally Routed Cables

Kid Size Hand Brakes and Easy to Use Shimano Rapidfire Shifters



Sealed Bearings

Quick Adjust Seat Height

Built Kid Tough

Confidence Inspiring Geometry


Prevelo Alpha Four Lifestyle



Customer Reviews

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  • Reviews (8)

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United States

Perfect bike for my inbetweener

After buying two other bikes that drove my son to tears, bad design, we decided to get the alpha 4. He's to big for many bikes and too small for an adult bike. This one is perfect with room to grow. Really great experience with this bike and the folks at Prevelo. Quick delivery, great communication and really awesome bike. My son got right on it and rode for an hour straight. Intuitive and comfortable. Thanx!!

Brian N.

Alpha four

Bought the Alpha four for my daughters 8th birthday. She immediately fell in love with the bike and is having a blast on it! It is a very stable ride and quite easy for her to maneuver. The bike is quite light compared to most of the other kids 24" bikes. We rode 18 miles today and she had a smile on her face the entire time!

Yegi S.

Great experience

My son learned to bike thanks to Jacob! He loves his Prevelo bike and wants to ride all the time! Jacob and the staff at Prevelo are amazing! So glad I found this company right in my neighborhood!

United States

9-year-old LOVES this bike.

My son loves it, light weight, and the trigger-style gears are much easier for him. He asks me to go for rides now, and we're able to go for 8-mile jaunts no problem. He's 9 years old and was late to learn, but this bike made it so easy to learn, and fun to ride.

Jason W.
United States

The best bike for kids!

My almost-9 year old had never successfully ridden a bike before in his life. We bought him a nice bike when he turned 8 and tried to teach him with it. It was difficult for him, he got frustrated and eventually gave up, telling himself he would never be able to ride a bike. We recently had him try a Prevelo bike, which he literally picked up in minutes; it was so much easier for him to learn on. Now he goes out riding without effort. Thank you, Prevelo!