Mountain bike onesies combine a waterproof jacket and waterproof trousers into a single garment.

There are no silver bullets to making winter mountain biking more enjoyable, though mountain bike onesies seem to come very close.

When riding in wet, muddy conditions rear wheel spray can creep under the gap between your jacket and trousers leaving you with a wet back and soggy bottoms. A one-piece garment doesn’t have a gap between your jacket and trouser for water and mud to ingress, keeping you drier in the process.

This gap can also mean cold air gets between your layers, which is another problem mountain bike onesies avoid, keeping you warmer in the process.

Holding true to the mantra of “united we stand, divided we fall”, onesies solve the problem of water and mud weighing trousers down and gradually pulling them down. This is because the top of the suit suspend the lower.

Being a dynamic sport, mountain biking requires a lot of mobility. You don’t want to feel restricted by your clothing, especially when you’re hurtling between trees at high speeds. The best onesies feature stretchy fabrics that allow for movement where the natural gap between jacket and trousers would meet.

Mountain bike onesies are designed to be voluminous so you can fit protection such as knee pads, elbow pads, and body armour underneath.

The mountain bike onesie is aimed toward the gravity disciplines of enduro and downhill, where pedalling is at a minimum. However, if you are serious about staying warm and dry during winter (or spring, summer, autumn in wetter places like Wales) then you will likely find a one-piece suit useful whatever your mountain bike discipline.

As with all waterproofs, mountain bike onesies have the potential to make you feel like a grain of Uncle Ben’s rice – boiled in a bag. In winter this warmth is desired, though being unable to escape this layer on warmer days may pose its own issues.

Some mountain bike onesies, such as Endura’s MT500 Waterproof One Piece II, take the form of a traditional jacket and trouser combo, with the two parts only connecting at the rear sharing similarities to a ski jacket skirt or some cycling skins suits.

While the fashion jury is still out on whether mountain bike onesies are cool, there’s no denying their practicality and winter performance.

What are mountain bike onesies made from?

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Mountain bike onesies are usually made from the same waterproof materials used in waterproof jackets and trousers.

High-end onesies will feature waterproof fabrics that are more water-resistant and breathable than cheaper suits. These pricier onesies will do a better job of keeping water out while letting perspiration escape.

While most suits don’t feature a lining, soft materials are often used where contact with your skin may cause irritation such as your neck and chin.

Velcro cuffs on the ankles and wrists allow for a more fitted feel while keeping rain and spray from making their way up your arms and legs.

Mountain bike onesie features

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Mountain bike onesies incorporate many weather-stopping features, such as hoods, vents, waterproof zips and sealed seams.

Most onesies will feature a hood large enough to pull over a helmet, stopping water from entering through helmet vents.

Waterproof zips make sure that water won’t seep through and will also make any pockets a lot more water resistant, keeping your valuables dry.

Vents will allow you to dump heat fast and allow air to flow through the suit to remove any perspiration.

Sealed seams offer similar protection, making sure water doesn’t enter through connecting panels.

How should a mountain bike onesie fit?

Alex Evans / Our Media

Mountain bike onesies should be relatively loose fitting, without feeling like you’re riding in a bin bag.

If there is any tension on your shoulders (like you’re wearing a backpack) then it is a good indication that the onesie is too small.

Extra room around the knees, elbows and back help to accommodate many forms of protection, meaning you can keep them dry and clear of mud.

People come in all shapes and sizes, making any one-piece garment difficult to size. While getting the right size for other pieces of waterproof clothing can be a relatively simple process, trying on a onesie or paying good attention to a brand’s size guide before you buy is a wise idea.

Mountain bike onesies vs waterproof jackets and trousers

The main benefit of the one-piece waterproof suit is its all-encompassing nature, offering full protection and leaving no gaps for water and mud to ruin your ride.

This level of protection comes at a high price, with most suits on sale costing north of £300. For those who value the warm and dry then this is very reasonable, especially when you start to add up the cost of a waterproof jacket and trousers, which may end up in a similar ball park to one of the best mountain bike onesies.

However, there is no denying the versatility of owning two pieces of clothing over one. Layering will always be an important part of riding in challenging conditions and the ability to pair a waterproof jacket with mountain bike shorts or trousers with just a mountain bike jersey will make for a more adaptable cycling wardrobe.

However, the onesie’s appeal is its simplicity and ease of use – which can be all it takes to get you out on your bike.

The best mountain bike onesies in 2023

Leatt MTB HydraDri 3.0 Mono Suit

4.5 out of 5 star rating

Andy Lloyd / OurMedia

• £279.99 / $299.99 / €346.49 / AU$501.20 as tested
• Excellent fit
• Good performance from the material

Leatt’s HydraDri 3.0 mono suit is the brand’s entry-level onesie, which still offers premium features and finishing touches. The 10k waterproofing and breathability offer good weather protection in all but the most torrential rain.

An integrated hood is attached to your helmet with magnets, making sure it’s kept in place and not flapping around in the wind.

Waterproof zips and sealed seams make sure the HydraDri Mono Suit stays true to its name, while also protecting your valuables in its pockets.

Zipped vents allow you to dump heat when needed, but we did find the zip pullers to be on the small side.

• Read our full Leatt MTB HydraDri 3.0 Mono Suit review