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 16.5 to 22
15 to 22 
Alpha Three 20" 5 to 9 20 to 23 17.5 to 23
Alpha Four 24" 7 to 11 24.5 to 28 23 to 28
Zulu Three 20" 5½ to 9 22 to 26 20 to 25
Zulu Four 24" 8 to 11 25 to 29 23 to 29

Same day shipping for orders placed Mon-Fri by 12 Noon PST.

Wheel Size
24 inches

Approx. Age Range
7 to 11 years


Fast and Free Shipping
Orders in by 12 noon PST M-F ship same day.
(except holidays)

Checked and Tuned
Each bike is checked & tuned prior to shipment.

Easy Assembly
Includes all the tools you need & easy instructions.

  • 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
  • Kickstand

    • Custom sized for the Prevelo Alpha Four
    • If you order a kickstand with a bike, it will come installed on the bike
    • Lightweight aluminium alloy
    • Non-corrosive, solid non-porous casting
    • Dual spring pressure plate and snap action mechanism with hardened steel pivot pin
    • Non-slip clamping surface
    • Made in USA


    Custom Color Grips

    Customize your new Prevelo with grips in the rider's favorite color. Made for Prevelo out of 100% silicone by ESI in Southern California.  We will install the grips on your Alpha Four before shipping.

    custom grip colorsprevelo custom color grips 

    Rider Name Lettering

    • Custom cut out of 2.5 mil vinyl right here at Prevelo HQ in California and applied to BOTH seatstays before shipment.
    • With a bit of work the decal can be removed when it comes time to hand the bike down.




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 (12)

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Shanti A.

This is the bike for us

Hi all, I have been riding bikes for thirty+ years - across a variety of disciplines as well - road, mountain, triathlon... this, along with various sizes of hand-me downs from her older brother, make for a busy garage. When it came time to upgrade my 7yo daughter’s bike, a quick web search brought me to Prevelo Bicycles. Seeing the Alpha Four in person at the Westlake Village showroom sealed the deal. After quickly setting the seat height on the demo bike, my daughter simply climbed aboard and rode away. There really is something to be said about a longish wheelbase, low bottom bracket, low Q-factor (narrow) and shorter crankarms. Jacob let me ride the bike around the parking lot; these bikes are both lightweight and sturdy! Solid frame design coupled with quality components make for a bike she’ll be able to grow with for several years. Yes, these bikes are somewhat more expensive than those you’d find at a big box or dedicated bike shop, but I see it as an investment in my daughter’s riding. She will ride longer and more frequently if the bike is enjoyable. There were some nice touches available to customize the bike, such as handlebar grips and name stickers (both pink) for the seat stays. A third party water bottle and cage round out her new bike. Two thumbs way up for Prevelo!

John A.

Prevelo Alpha Four

We are so happy with our purchase. We were looking for a bike that was made specifically for children. We researched other companies that claimed to make bicycles engineered specifically for children but ultimately decided to go with Prevelo, and we couldn’t be happier. One of the reasons we chose Prevelo is because of their esthetic appeal. The bike is beautiful. Our son loves it! We purchased directly from the owner who was kind enough to help our son on his first test ride. As a father himself, he apparently created this company with a self interest. And that interest is a shared interest for all parents looking to invest in a beautiful well made bike geared specifically for kids.

Alpha Four
Robert B.
United States

Prevelo Alpha 4 v Islabikes Beinn 24

Please see a full review here:

Alpha FourAlpha Four

Nice ride

Bought this for my soon to be 8yr old. Also bough the Alpha Three for my soon to be 6yr old. The Prevelo bikes definitely were an investment, but I figured we could get a lot of use out of them as we have a 2yr old as well. After taking all of 15 minutes to assemble both and fine tune them, I rode both around myself. They're solid. I'm really happy with the build quality. The welds are pretty, the components are decent, and they are noticeably lighter than the bikes my kids were riding. In fact they both commented on the weight when they first tried them out, so it is an obvious enough difference for a 6 year old to notice. The kids are digging the gears. The geometry has them leaning forward more than they were on their old bmx style bikes. And hand brakes with no foot brakes is a new concept for them. So there has been a learning curve. Now they're both riding faster and longer. And my older guy who never liked the easy offroad trails by us tried riding them on his new bike and is itching to go again. Everyone is happy!

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!!