The Ultimate Guide to Buying a Kids' Bike

Happy venturing down a gravel path, up a mountain road or on the MTB trail, the 20 in. woom OFF 4 kids' mountain bike can also hold its own on the pavement and is specifically designed for kids.
Imported.
Best Use | Mountain Biking |
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Frame | 6061 T6 aluminum with butted and hydroformed tubes |
Mountain Bike Style | Cross-country |
Bike Suspension | No Suspension |
Fork | Light carbon fork; 1 to 1-1/8 in. tapered steerer tube; 100 x 15 mm thru axle; post mount for disc brake |
Crankset | Lightweight, forged aluminum, 4.3 in. (110 mm), kid-specific cranks with narrow tread (Q-factor); narrow-wide chainring with 28 teeth in the front |
Bottom Bracket | Thun |
Shifters | SRAM X5 trigger shifter |
Rear Derailleur | SRAM X5 rear derailleur |
Rear Cogs | Sunrace 9-speed 11-32T |
Number of Gears | 9 gear(s) |
Brake Type | Hydraulic Disc Brake |
Brakes | Promax Hydraulic disc brakes |
Brake Levers | Ergonomic brake levers designed for childrens' hands |
Rims | Tubeless-compatible Alexrims wheelset |
Front Hub | Front hub for disc brake, 20h, 14 gauge, 100 x 15 mm, 2x bearings without quick release |
Rear Hub | Rear hub for disc brake, 20h, 14 gauge, 135 x 12 mm, alloy cassette body, 4x sealed bearings; without quick release |
Wheel Size | 20 inches |
Tires | Schwalbe Rocket Ron with ADDIX SPEED rubber compound 20 x 2.25 in. |
Tire Width | 2.25 inches |
Handlebar Shape | Riser Bar |
Handlebar | Aluminum; sandblasted; silver anodized; width: 570 mm rise: 20 mm |
Stem | Forged aluminum; CNC-machined; rise/drop: +/-15 deg. with flip-flop design to adjust the handlebar height; length: 50 mm |
Seat Post | Anodized aluminum; 27.2 x 250 mm; insertion marks indicate the minimum insertion depth; quick-release seatpost clamp |
Saddle | Mountain-bike specific saddle with side protection |
Pedals | Fiber-reinforced nylon; flat; 2 x 6 pins; chromoly axle |
Headset | Fully integrated 1 to 1-1/8 in. headset; sealed industrial bearings |
Chain | KMC X9 NPGY 1/2 in. x 11/128 in. |
Weight | 18 lbs. 8 oz. |
Bike Weight | Bike weight is based on median size, as sold, or the average of two median sizes. |
Gender | Kids' |
20 IN | |
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Height Range | 46 - 51 |
Effective Top Tube | 18.1 |
Head Tube Angle (degrees) | 68 |
Seat Tube Angle (degrees) | 70 |
Wheelbase | 33.5 |
All measurements are stated in inches unless otherwise indicated.
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The woom air is a fantastic first entry into mountain bike for a younger kid. This model doesn’t have suspension, so if your kid is already hucking off jumps you would probably want that model. But the amazing thing is you can always upgrade the fork! The build quality is fantastic. We had woom 1&2s and the thing we loved still holds true with this modem, it’s super lightweight which is key for a kid who is starting out with a bit of “hike a bike”. The kid wanted me to mention that the seat is comfy, and the shifting is easy, and he loves how lightweight it is. If you have a smaller child, this might not fit until they are 6+. Our son is 44” and he is on top toes as the lowest seat post, so any shorter and you’ll want to wait or look at the woom 3. Love the bike and happy it provides the ability to introduce my fomo son to MTB!!!
My son LOVES this bike. He started with riding with a guardian when he was 4, and he outgrew it very quickly. He could only go about 3-4 miles on it because of the weight and the fact that it was a single gear bike. With the Woom 4, he is able to ride 6-7 miles at least, and has a blast. The bike is extremely light weight, and having front and rear brakes, and a cassette in the rear makes a huge difference. This bike is definitely a step up. The bike is extremely well made - it looks and feels like a premium bike. It is geared towards mountain biking but it does not have a suspension. The bike came mostly assembled in the box, and the instructions to finish setting it up were extremely easy to follow. The tools needed to put it together are included with the bike. My only disappointment is that it is still too small to fit in my bike carrier. I have a Thule Apex XT 4-Bike Hitch Rack, and the bike does not fit on it.
… not for the price. For starters I needed to buy a kickstand separately. The purists will say “but it’s a mountain bike” … yeah, but it’s a kids bike! And for the price, provide the kickstand and let me decide whether to keep it on or not. Additionally, and this will vary from kid to kid … the shifters take a little getting used to, so it’s not really kid friendly from the start. And the gear ratios should include one higher gear. Otherwise solid color and good build.
This is an awesome kids bike , my 7 year old grand daughter loves it. I had the REI bike shop convert it to tubeless before it left the store. And the 18 lb. range makes it one of the lightest on the market, do a comparison and you see.