Guardian 16 Inch ETHOS and AIROS Bike Review

Scoring high in style and performance, the Guardian ETHOS 16 and the AIROS 16 kids bikes offer fun designs that appeal to kids, and safety innovations that appeal to parents. Win-win!

With a semi-upright body position, lightweight frame, no coaster brake, and Guardian’s innovative SureStop braking system, Guardian’s 16 inch bikes simplify the riding experience for first-time pedal bike riders as well as more confident riders already cruising the neighborhood.

In our review, we’ll cover why the SureStop braking system makes Guardian Bikes so unique, and how the AIROS (previously called Original) and ETHOS lines are different.

Child riding Guardian 16 inch bike across a bridge and making a funny face

Guardian 16 inch Overview

RATING: Exceptional (AIROS), Highly Recommended (ETHOS)


BEST FOR: Kids 4 to 6 who will be doing neighborhood and paved trail riding. The SureStop braking system is ideal for timid riders who need the security of an easy braking system, as well as adventurous riders who need extra stopping power.


SEAT HEIGHT: 18.25″ – 22.6″
WEIGHT: 17.1 lb. (AIROS), 18.6 lb. (ETHOS)
BRAKES: Surestop Dual Hand
FRAME: Aluminum Alloy (Airos), Steel (Ethos)


  • Proprietary SureStop braking system for faster and more controlled braking, and NO coaster brake
  • Comfortable upright positioning for young riders
  • Lightweight, durable frame
  • Eye-catching designs – fun, colorful graphics and colored rims
  • Insanely easy assembly


  • Upright design not ideal for aggressive riders

Guardian 16 Inch Video Review

Want to see the Guardian bikes and their proprietary SureStop braking system in action? Check out our video summary which details the main reasons why parents and kids love Guardian bikes! Please note that Guardian’s Airos line is referred to as “Original” in this video.

Guardian ETHOS 16 and AIROS 16 Put to the Test

A well-designed bike is helpful for any child riding a bike, but it’s especially important for young kids who are still developing their gross motor skills and muscle strength. Perfectly sized for the small frames of 3 to 5-year-olds, Guardian 16 inch bikes are built to work naturally with young riders.

young boy riding a 16 inch boys pedal bike

While more expensive than the average kids bike, the kid-friendly weight and geometry of a Guardian 16 inch bike make the process of learning to ride (or progressing your riding skills) significantly easier. We’ve watched a sea of kids try to ride cheap bikes as well as Guardian bikes. There’s no contest here – a Guardian bike is worth the extra money.

Every time we put a rider on a Guardian 16 inch bike for the first time, it’s a hit straight out of the gate.  Built on a lightweight frame with a low center-of-gravity design and complemented with upright handlebars, the Guardian 16″ is easy to balance and easy to maneuver, especially for beginners or more timid riders. It’s a smooth ride that immediately builds confidence.

Child riding down grassy hill on Guardian Airo 16 inch kids bike

But of course, there are several amazing kids bike brands on the market that also offer lightweight bikes with kid-friendly geometry. So what makes Guardian bikes shine among these other shining stars?

The SureStop braking system of course!  Guardian’s proprietary braking system stops the bike using the power of two v-pull caliper brakes, just like many high-end kids’ bikes. However, it simplifies the process for kids by requiring them to pull just ONE brake lever to activate both brakes in sequence.

With SureStop, the difficulties that can arise with coaster brakes, as well as the confusion of dual-hand brakes for young riders, are both eliminated.  How does the SureStop system work?  Not to worry, we’ll cover the details later in the review.

Guardian Bikes 16 ETHOS vs. AIROS (Original) Line

Guardian bikes are available in two different quality tiers – the higher-end “Airos” line (previously called Original), and a more budget-friendly “Ethos” line.  The 16″ bikes from the two lines are the same size, come in almost identical designs, and both feature Guardian’s SureStop braking system.

Where they differ is in components.  The Ethos line runs about $100 cheaper and is built with a heavier steel frame versus an aluminum frame, as well as a threaded headset versus the more high-end threadless headset on the Airos line.

Guardian 16 inch AIROS and ETHOS Bikes

Side by side comparison of 4 year old boy riding the Guardian 16 inch Ethos bike and Guardian 16 inch Airos bike down the sidewalk

Visual differences can be seen in the image above. On the left, the Airo has thicker aluminum tubing with more intricate graphics. On the right, the Ethos has thinner steel tubing with a simplified graphic design.

Both the Airos 16 and Ethos 16 come in two colors – bright pink with polka dots, and a black blue geometric design. All bikes feature a complementary pop of color on the rims.

Girl on pink Guardian Airos 16 bike, boy on blue Guardian Airos 16 bike

So which Guardian 16 inch bike should you get? Do you really need to spend an extra $100 on the Airos versus the Ethos? The lighter Guardian Airos is ideal for lightweight and timid kids (as well as those who simply want the best). The Guardian Ethos is a great choice for those riders who can handle a slightly heavier bike as well as families on a tighter budget.

Compared to cheap 16″ bikes as well as the Specialized Riprock 16, the Ethos 16 is still pretty light as it is a couple of pounds lighter.

16″ Airos16″ Ethos
Seat Height18.25″ – 23.5″18″ – 23.5″
Weight17.1 lb.~18.6 lb.
BrakesSureStop, no coasterSureStop, no coaster
DecalsUpgraded Heat Bonded GraphicsTraditional Water Transfer Graphics

Guardian’s Unique SureStop Braking System

Girl riding Guardian Airos 16 inch bike down paved trail

Our favorite feature of all Guardian Bikes, no matter the size, is their proprietary SureStop braking system.  Unique to Guardian, the SureStop system allows riders to stop faster and with more control.

We’ve seen time and again that SureStop allows kids to feel more in control on their Guardian bike, and as a result, their confidence level increases.  With less anxiety about stopping the bike, many kids are more willing to ride more adventurously.

Our 6-year-old testers on the 16″ Guardians both mentioned the brakes without being prompted.  They accelerated and then stopped over and over again because they thought the brakes were “fun”.

Having tested out SureStop brakes myself, their description of “fun” is understandable.   Braking with SureStop brakes provides a similar feeling to braking in a new car with an advanced braking system versus an older car with a standard braking system.  Not only is it easier to brake faster, you feel MUCH more in control of the car.  As a result, you’re more confident while driving a car with advanced brakes.

In our experience, the same applies to kids using SureStop brakes.  With much of the anxiety of braking gone, many kids are more confident in their riding. This also applies to adventurous and aggressive riders who really appreciate the extra stopping power SureStop gives them.

How does the SureStop system work?

Guardian’s unique braking system allows both the rear and then the front brake to be activated sequentially with the pull of ONE brake lever.  When the lever is pulled, the back brake is activated first.

Activating Guardian’s Single Brake Lever

single brake lever on Guardian 16 inch kid's bike

Once the rear brake has engaged, the SureStop system on the rear brake pad then activates the front brake.  This sequential stopping system allows the bike to stop faster and with more control.  It also prevents kids from going over the handlebars when accidentally braking with just the front brake.

SureStop Rear Brake and Front Brake

brake cables and pads on Guardian Bikes 16 inch bike

No Coaster Brake – Hooray!

While many parents think coaster brakes are just a normal part of 16″ kids’ bikes, we absolutely love that Guardian’s 16″ bikes do not have a coaster brake (back-pedal brake).  Coaster brakes can be very confusing for kids new to pedal bikes.

When learning to balance a bike, both kids and adults naturally pedal backward when they lose their balance.  Upon doing so on a bike with a coaster brake, the brake is unexpectedly activated, which often causes kids to fall. This process can be very frustrating for young riders which can then delay their mastery of a pedal bike.

On a bike without a coaster brake, a child can naturally pedal backward without activating the brake. Once they regain their balance, they can continue to pedal forward without a break in the momentum they just gained on the bike.

No coaster brake also allows kids to easily set the pedals to “start” position, and allows more confident riders to quickly re-position pedals to “do tricks”.

Child riding down dirt path on Guardian 16 inch bike, standing up on pedals

What size child will fit on the Guardian 16 inch bike?

The seat height on both 16″ Guardians ranges from about 18.25″ to 23.5″. If you’re trying to get the seat height as low as possible, you will need to take off the rear reflector.

FIRST PEDAL BIKE: If the Guardian 16 is a child’s first experience riding a pedal bike (without training wheels), they will need an inseam of around 18″ to fit on the bike (usually kids’ in 4T pants).

First-time bike riders need to be able to place their entire foot on the ground when sitting on the seat in order to comfortably start and stop the bike while they are learning to balance, pedal, and use a handbrake.

EXPERIENCED ON A PEDAL BIKE: For experienced riders who are already comfortable riding a pedal bike without training wheels, they only need an inseam of about 16″ to fit on a 16″ Guardian.  Experienced riders are comfortable starting and stopping a bike without using both of their feet, so they only need to be able to touch the ground with their tip-toes.

Keep in mind that both lines of Guardian 16″ bikes are not compatible with training wheels, so kids under 40″ will not fit on the bike.

Guardian 16″ Sizing Overlap With 14″ and 20″ Small

Guardian Bikes 14, 16 and 20 small lined up next to each other. Child sitting on the Guardian Bikes 16.

When choosing the right size Guardian bike, be aware that the Guardian 16 inch has some overlap with the smaller Guardian 14″ and the larger Guardian 20″ Small.

Guardian 16 Inch or 20 Inch Small?

Think your child is a bit on the sizing fence and might be able to fit on the 20 inch small? Here you can see how our 4-year-old tester fits on the Guardian Airos 16 and the Guardian Airos 20 small. She is 43″ tall and has an inseam of 19″ with shoes on.

Guardian Airos 16 and Guardian Airos 20 Small

Side by side comparison of 4 year old girl on Guardian 16 and Guardian 20 small

The Guardian 16 is an excellent fit for her right now and does provide some room for growth. (She has the seat height set to 21″.) The Guardian 20 small is more of a “stretch fit”. She can reach the ground with her tip toes when the bike is at its minimum seat height (21.25″), and has considerable room for growth.

As an experienced rider, the 20 small is a better buy as it will provide much more room for growth. But if this were her first pedal bike, the 16 inch would absolutely be the way to go. The 20 small is manageable for her, but even as a very experienced rider, it’s still a lot of bike for her to handle.

For example, the higher handlebar (on the 20″) in relation to her body will make it more difficult for her to manuever. It would be very difficult for a new pedal bike rider of her size to learn on the larger bike.

Like with any bike brand, kids typically grow out of their first pedal bike faster than you would like because you need the minimum seat height to be lower to allow them to reach the ground with flat feet.

Can you skip from a 14″ to 20″ Small?

If your child is already on a Guardian 14″ bike and you’re looking for their second pedal bike, can you skip the 16″ size and go straight to the 20″ small? Although there is no overlap in seat height, if you’re on a budget, this certainly is an appealing option.

Here you can see our 4-year-old on the Guardian Ethos 14″ at its maximum seat height (20.25″) versus the 20″ small at its minimum seat height (21.3″). We also raised handlebars on the Ethos 14 to their max, which increased their height from the ground by 1 inch.

Side by side comparison of 4 year old on Guardian 14 inch and Guardian 20 small. Sizing comparison.

While having an intermediary bike between these two would be ideal, you could absolutely skip the 16 inch if can’t (or don’t want to) afford an additional bike.

While our little tester hadn’t been on a 14″ bike in quite some time, she hopped on and sped through the neighborhood with ease. With the smaller wheels and shorter crank arms, she was “spinning her wheels” a little bit, but if you’re on a budget and not trying to set any speed or distance records, this is a great solution.

Guardian Bikes Virtual Bike Sizer

Still confused about which size is best? Guardian has an avatar-based sizing guide to help you visualize and confidently determine which size bike frame is best for your child.

Their RideSizer technology will allow you to see how your child will grow on the bike and predicts how long before they outgrow the bike. It takes into account your child’s riding experience, as well as growth rates for kids at specific ages.

The recommended bike size comes displayed right away, and you can see an avatar of how your child will fit on the bike now, and when they have grown to its maximum seat height.

Based on our experience, it works great, but if you have a child with a long torso and shorter legs, be sure to check their inseams against the bike’s minimum seat height to ensure a great fit.  It’s a super cool tool – be sure to give it a try!

Other Features of the Guardian Ethos 16 and Airos 16

While the SureStop braking system is the big selling point of all Guardian Bikes, here are a few additional important points to consider about Guardian’s 16 inch models.

Guardian 16 Geometry – Body Position & Handlebars

Guardian Bikes 16 inch models are designed for beginning riders who often prefer an upright body position.  Sitting upright centers a child’s weight over their hips, just like they’re accustomed to when standing and walking. As a result, beginning riders are usually able to master balancing a bike faster when sitting upright.

Experienced riders, however, may prefer a bike with lower handlebars that place the rider in a more aggressive position.  A more aggressive position better allows the rider to shift their body weight during turns and while on hills.

Body Position on Guardian Bikes 16 vs. More Aggressive Bike

Side by side comparison of Guardian 16 and Prevelo Alpha two showing the Guardian keeps a child more upright

Compared to other higher-end bikes, the Guardian 16″ is upright like the woom 3, or Priority Start 16 neighborhood bikes. More aggressive bikes like the Prevelo Alpha Two have lower handlebars and are better suited for confident riders who like to lean in for super speed or who will be attacking ramps at skate parks and dirt trails.

Above you can see the difference in body positioning of our tall 4-year-old 43″ tester on the Guardian Airos 16 vs. the Prevelo Alpha Two. Notice both the angle of her back as well as the height of the handlebars.

All that said, an aggressive rider certainly could happily ride the Guardian 16. This super confident 4-year-old had a blast on her test rides through our local paved and wide dirt trail system. Even with the standard street-tread tires, the Guardian was able to rock those packed dirt trails.

How much do the 16 inch Guardian Bikes weigh?

The aluminum-framed 16″ Airos weighs 17.1 pounds with pedals. The steel-framed Ethos weighs about 1.5 pounds more. Compared to similarly priced bikes, the Guardian models are slightly heavier, but not by much.

Much of their difference in weight is due to the rims and tires on the Guardian bikes.  To keep the tires properly aligned through years of abuse and adventures, Guardian’s bikes come with a beefier rim than most 16″ bikes.

The Airos also has more spokes to make that wheel even more durable. The additional spokes help keep the tire properly true, even when repeatedly going down jumps or curbs. (Or just being thrown on the ground… because why not throw your bike on the ground?)

Side by side comparison of wheels of the Guardian Ethos 16 vs Airos 16, showing higher spoke count of Airos bike

For the Airos, a bit more additional weight also comes with the 1.75″ wide tires. They are slightly wider and therefore heavier than most 16″ bikes.  The Ethos’ tires, however, are the standard 1.5″ width found on most 16″ bikes.

In addition to providing slightly more cushioning and traction, Guardian has found that kids prefer the look of the Airos’ wider tires.  Based on our experience, however, for the average everyday rider (not all-terrain riders), the width of a child’s tires makes very little difference in the bike’s performance.

Gain Ratio (How easy are they to pedal?)

The gain ratio on a single-speed bike is a number that represents that single gear, or how hard or easy it is to get started pedaling and maintain fast speeds.

The gain ratio on both 16″ Guardian bikes is mid-range at 3.55.  This makes the bike geared perfectly for cruising around the neighborhood.  As a comparison, the Cleary Hedgehog is designed for aggressive riding around hills and is geared at a low 2.88 while the woom 3 is geared a bit higher at 3.8, which will allow a child to ride slightly faster on flat surfaces.

Insanely Easy Assembly

Over the last 12 years, we’ve assembled hundreds of bikes. While high-end bikes are generally much easier to assemble than cheap bikes, Guardian Bikes wins the gold medal for easiest bike assembly.

Guardian 16 inch bikes come almost entirely assembled. Even the front wheel is already on the bike! The only things you have to do are attach the handlebars, the pedals, and the seat.

Because parents often get confused when attaching handlebars and pedals, Guardian made a tiny but genius addition to their bikes. Removable stickers take all of the guesswork out of the minimal assembly required.

Removable stickers are Guardian 16 help parents line up and tighten components correctly

To line up the handlebars and the stem correctly, just line up the stickers! To make sure you’re tightening the pedals in the direction of the threads, simply follow the direction on the sticker on the crank arm. Simple genius.

Guardian Ethos 16 and Airos 16 Bottom Line

Guardian’s combination of SureStop brakes, lightweight frames, and upright positioning make their 16″ line of bikes one of our top choices for 4 to 6-year-olds riding around the neighborhood and paved bike trails.  The Airos line is an exceptional bike offering upgraded graphics, sleek aluminum tubing, and a lightweight build, while the Ethos line is a little heavier, but provides top-notch performance for its price.

Both bike lines are a best fit for kids with at least an 18″ inseam (for those riding a pedal bike for the first time).

FTC Disclosure: Affiliate links are included in this review.  No monetary compensation was provided for this review, however, the reviewed product was supplied by the manufacturer or distributor to help facilitate this review. All opinions and images are that of Two Wheeling Tots LLC.  All content and images are copyrighted and should not be used or replicated in any way. View our Terms of Use.

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