Ridgeback Dimension 20 Review

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The Ridgeback range has recently had a complete overhaul, and the Dimension 20 is the premium option in their first geared kids' bike line-up.

Aimed at children aged 5.5 to 8.5 years old (roughly 112 to 130cm tall), the Ridgeback Dimension 20 is designed for young riders making the step up from a single speed bike to gears, and from shorter rides to bigger adventures.

At £349.99, it's not the cheapest 20 inch geared bike on the market, but our first impressions suggest the extra spec justifies the price tag.

This first impressions review gives our take on the bike fresh out of the box, with a full rider review to follow.

One of the first things we noticed was the frame's low standover height, which makes it easier and safer for a child to get on and off, especially if they're still building confidence.

The seatpost also drops lower than some other 20” wheel bikes we’ve tested, which gives us confidence that the bike should comfortably suit children at the bottom of the height range.

Setup of the bike was simple, and the gears worked well from the first turn of the pedals, shifting quickly and smoothly.

The bike has 7 gears, with a single ring at the front, which we always like to see on a children's 20 inch wheel bike. It means they only have to learn to use one gear lever, which makes things so much easier than a bike with too many gears that require changing with both hands.

There's a protective cage around the rear gear mechanism, which should help it survive the inevitable bumps and knocks of being a child's bike, and a graphic on the top tube that looks like it may help protect from scuffs as little legs swing over the frame.

We were pleased to see mounting points for a bottle cage, rack and mudguards so parents can kit the bike out as needed.

The wheels ran smoothly straight away, with no play or roughness in the hubs, and the Shimano rear hub, derailleur and cassette all point to genuinely good quality components for this price point, not just budget parts with a premium badge.

The saddle is Madison branded, with a reinforced plastic moulding at the base to protect it from scuffs, and a tougher covering on the outer faces to help it survive being propped against walls and fences, which anyone with a young cyclist will know happens a lot.

Ridgeback Dimension 20 Specification

If you like to know more about the technical specification of your child's bike, the Dimension 20 comes with:

- A lightweight aluminium frame and forks

- Shimano 7-speed gearing, with a 34t chainring and 12-32 tooth cassette (a wide range of gears, giving an easier option for climbing hills)

- Shimano SL-M315 trigger shifter

- Aluminium V-brakes with adjustable, reach-friendly levers

- Vee Nutrak Speedster tyres in a 20 x 2.0 inch size, with a puncture-resistant belt and reflective sidewall strip

- Sealed CrMo bottom bracket with bearings from German manufacturer Thun

- A steering limiter, which stops the handlebars turning too far and helps prevent falls while a child is still learning to coordinate pedalling and steering at the same time

- A lifetime frame and fork warranty, plus a 2-year parts warranty, both of which are transferable if the bike is sold on

At 9.1kg, it's a lightweight bike for a child to manage, which makes a real difference when they're getting on and off, or pushing it up a kerb (or you’re lifting onto a car roof or up and down steps).

How does the Ridgeback Dimension 20 compare to the Ridgeback MX20?

The Ridgeback kids bike range has two models in each wheel size - the Dimension and the MX.

The Dimension 20 sits £60 above Ridgeback's MX20 in the range, so is the extra worth it?

In short, yes, if you can stretch to it, though the MX20 remains a good choice if your budget is tighter.

Both bikes are built around the same frame and fork design, so sizing wise they are identical. However the Dimension fork is lightweight alloy whilst the MX fork is steel, which results in a slightly heavier bike.

The Dimension has a wider spread of gears (12-32 teeth versus the MX20's 14-28), which in combination with 500g in weight savings compared to the MX20 will make those dreaded climbs that bit easier. The 12 tooth highest gear will also help on downhills compared to the MX20, and so for those Sprogs who are wanting to adventure just a little more, the Dimension is likely to be a more suitable bike.

Elsewhere, the Dimension has aluminium brake levers rather than resin, a lighter aluminium front hub instead of steel, and wheels built with more spokes for extra strength.

The tyres are wider too, with a puncture-resistant belt and reflective strip that the MX20 doesn't have.

The two bikes also come in different colourways: brighter primary shades on the MX20, versus a more muted deep blue, sand and plum on the Dimension. Colour choice is entirely down to taste, but the Dimension's tones do feel a little more grown up.

Both bikes come with a lifetime frame and fork warranty and a 2-year parts warranty, which are transferable if you sell the bike on, giving good peace of mind and helping protect its resale value.

Buying an old-model Dimension 20? What to check first

Ridgeback updated the Dimension 20 during spring 2026, and the two versions are different enough that it's worth knowing which one you're looking at, whether you've spotted a secondhand bike, or you're buying new from a shop that still has old stock.

At the time of writing, the previous model is still available from some local bike shops and via the Freewheel website, at an RRP of £419.99, £70 more than the new Dimension 20's £349.99, despite being the outgoing model.

The key things to check:

Age and height fit: The old Dimension 20 is designed for riders aged 6 to 9, roughly 120 to 135cm tall. The new version is pitched lower, at 5.5 to 8.5 years and 112 to 130cm.

If you're buying secondhand and going by the "Dimension 20" name alone, you could end up with a bike that doesn't suit your child's height as well as you'd expect having read this review, so always check against your child's actual height rather than the model name or the age on the box.

Frame geometry: The frame shape has changed noticeably between the two versions, with the new model's frame lowered for easier mounting and dismounting, so don't assume the two bikes will feel the same to ride.

Gearing range: The old model's cassette runs 34t 12-28T; the new one is 34t 12-32T, giving a slightly easier bottom gear for hills. Worth knowing if you live in a hilly area.

Colours: The old Dimension came in red and teal. The new one comes in a more muted deep blue, sand and plum.

Price: If you're choosing between old stock and the new model at a shop, the new Dimension 20 has a lower RRP (£349.99 vs £419.99)

Should I buy an old model Dimension 20?

On paper, the new bike has the better spec: wider gear range, lower frame, and features specifically aimed at younger riders. We can't see an obvious reason to pay more for the outgoing model unless the fit or colour suits your child better.

Obviously if you find an older model significantly reduced in your local bike shop or a well maintained secondhand bike, it’s definitely worth considering, so long as you’re comfortable with the specification differences, particularly the sizing.