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Why cycling kit that FITS matters more than you think!

Whether you care about speed or not, find out why choosing the right cycling kit is one of the biggest upgrades you can make

Whether you’re a seasoned racer or just getting into cycling, the importance of cycling kit that fits right cannot be understated. The right kit will be more comfortable, faster and maybe make you enjoy cycling just that little bit more. Let’s see how much faster your cycling kit can make you.

As cycling journalists, we're often asked what the best upgrades are and how to get quicker. Now, the obvious answer is to train more, but cycling kit that fits you right can offer more benefits than increased comfort alone. 

2023 Castelli Prologo 7 jersey

Saddle sores, rubbing jerseys and jackets that are tight under the arms don't have to be the norm. These common problems are all avoidable.

Getting the right kit doesn’t just mean taking a quick look at the size guide, because most brands will have different ranges for different disciplines and types of riders, depending on your body type and personal preference.

To help explain, we've got our hands on what is basically the entire 2023 Castelli summer collection. The choice is vast, and for good reason!

Castelli has a large range of products, from more relaxed fitting clothing to aero training kit and class-leading aero products. Even products towards the lower end of the range benefit from trickle-down technology and decades of industry experience to provide mile after mile of comfort. So, how do you go about choosing what’s right for you?

Loose fit 

2023 Castelli unlimited entrata jersey and entrata bib shorts

First up, the Unlimited Entrata jersey and Entrata bib shorts are designed for both on and off-road riding, offering all of Castelli's tech but without the aggressive fit. 

The more relaxed fit suits those who wish to forgo some aero in favour of a less revealing fit. It can also be used for any type of riding, often feeling more comfortable than a race-fit jersey.

Loose-fit jerseys are longer in the torso than race-fit jerseys, so are suited to those who prefer to sit more upright on the bike than those who get tucked up nice and small on the drops.

2023 Castelli entrata bib shorts

It’s also likely to be more comfortable when sitting at the café or out for a drink after work, without worrying about whether your belly button is going to be on show.

This would be a great option for less experienced cyclists. While you could definitely find cheaper, if there’s one area that you’re going to invest your hard-earned dosh in, then surely it should be your kit. After all, there’s no other part of your cycling gear that sits directly against your skin.

If we had a pound for every time someone said my x, y, or z hurts on a bike, then we could probably buy ourselves quite a few Castelli jerseys...


As we know from our various surveys over the years, a lot of our readers and followers are seasoned cyclists. This bit's for you!

Whatever you’re buying, there seems to be a sweet spot where above it you can spend a hell of a lot more, and only get marginally more benefit. With the Castelli range, we reckon this is that spot: the Prologo 7 jersey and Endurance 3 bib shorts.

2023 Castelli Prologo 7 jersey

The jersey has aero raw cut arms but a slightly larger body than a full race fit jersey, so it'll fit more body shapes while providing more of an all-day comfort for those long endurance rides.

A mid-fit cycling jersey like this one strikes a balance between a relaxed fit and a race-orientated snug fit, providing a comfortable and non-restrictive feel without excessive fabric. This provides more freedom of movement which makes it suitable for various types of cycling such as long endurance rides, touring or commuting.

While not as form-fitting as a race-fit jersey, it still follows the contours of the body, thus improving aerodynamic efficiency compared to a loose-fitting jersey. This might have more of an effect than you think on those faster group rides.

2023 Castelli Endurance 3 bib shorts

Bib shorts are an essential part of any cyclist’s wardrobe. When they fit correctly, they will reduce discomfort and chafing, improving your riding experience.

Different chamois pads are engineered with different densities, shapes and thicknesses to cater for the style of riding you’re doing, but personal preference does play a significant role when selecting the right chamois for you.

A road cycling chamois typically has a medium thickness, providing cushioning for the sit bones. You might wonder how some people ride on such thin saddles. This is partly down to personal preference, but also choosing the right bib shorts.

2023 Castelli PROGETTO X2 AIR seat pad

The Progetto X2 Air seat pad used in these endurance bib shorts has a two-layer design, meaning that it’s the two layers of chamois rubbing against each other rather than your skin against the chamois.

It also features multi-density foam and comfort inserts, and there's also ventilation to help air flow so you don't get all sweaty and clammy. 

Race fit

Of course, there are plenty of riders out there who are looking for every marginal gain and the very best kit in the land.

2023 Castelli Aero 6.0 jersey and premio bib shorts

In most instances that means looking at what the pros are using, but quite often pro level kit is either out of bounds for us mere mortals or you’ll have to sell a kidney.

However, when it comes to clothing, you might be surprised to find that you can get the very same kit the likes of Remco and Alaphillipe are wearing for less than you think.

Castelli’s Aero Race 6.0 jersey is the same jersey that was used by Team Ineos and now Soudal Quick-Step, and as the name suggests it's engineered for racing.

2023 Soudal Quickstep Castelli kit

If you’re a competitive cyclist then a race-fit jersey is a no-brainer, as most of the wind drag is caused by your body when you're cycling. 

Race-fit jerseys will show off a little more of your body of course, but they are designed so that they won’t restrict your movement. Certain members of the team admit to doing most of their training in aero jerseys, as going fast never gets old and they can still be rather comfortable.

2023 Castelli Aero 6.0 jersey sleeve

The sleeves of a race-fit jersey are often longer and have a specific cut, which enables them to fit comfortably in an aggressive position rather than when stood up.

They are also tapered, meaning they’re narrow towards the opening and gradually widen towards the shoulder which allows for a close fit around your biceps and triceps. The style of sleeve isn’t going to be for everyone, but they are the ultimate choice for the pros and keen riders wanting to go fast.

2023 Castelli Aero 6.0 jersey and premio bib shorts

The Aero Race 6.0 jersey features a dropped tail, meaning that it’s longer at the back than it is at the front to prevent the jersey from riding up. 

Like the aero race jersey, the Free Aero RC bib shorts are also designed for racing. They have a raw cut edge at the waist and the end of the legs, so they stay put without any silicone grippers.

How important is it to have cycling kit that fits?

2023 Castelli summer kit riding shot

So, we’ve gone through some different styles of cycling kit to help you try and find the style that’s right for you. This needs to take into consideration your riding style, body type and personal preferences, but what we do know is that when your kit fits you right there are some aero gains to be had.

Kit is often considered one of the most cost-effective aero gains, so let's see how many watts are up for grabs and which items you should focus on. 

We spoke to Xavier Disley from Aerocoach, an expert in aerodynamics, to find out just how much quicker your kit can make you.

2023 Castelli Aero 6.0 jersey

"Taking care of your aerodynamics is relevant for everybody," says Disley. 

"People think sometimes that aerodynamics is only applicable if you’re going at very very high speeds... but for anyone riding a bike, if you’re travelling in still air over mid 20’s kilometres an hour so 25 kph or so, you’re going to be affected by aerodynamic drag quite considerably."

Interestingly, he added that it's not only at high speeds you can expect to see benefits: "If you’re travelling slower than that speed but you’re going into a headwind then the relative air speed over the body is very similar to what it would be like if you were travelling faster in still air.

"Even though you might not think that you’re quick enough to be concerned about aerodynamics, it really does make a difference and especially if you’re going for longer rides, you can see that the more aerodynamic gains that you can make will be exacerbated and highlighted by saving much more time over a longer ride."

2023 Castelli summer kit riding shot

If you think of a silhouette of a rider from the front, the vast majority of that is going to be the rider rather than the bike. This means the surface area and frontal area of your body is much greater than your bike.

For most people sitting on a road bike in a standard position, "your body is going to be creating somewhere between 75% and 80% of the drag of the whole system," Disley explains. Therefore, what you cover the rider in is going to be really important. 

Fabrics make a big difference both in terms of how bulky the clothing is and how close-fitting it is, as clothing that sticks out will increase your frontal area.

If we really get in to it, the exact fabrics you use at particular air speeds you're experiencing will have a big difference too. 

Do aero cycling jerseys make you faster?

2023 Castelli entrata summer kit

We can talk about this in terms of power output savings, and if you have access to a power meter, Disley says the savings you'll get in terms of power output will change the faster you go. 

For example, you could expect to save around 5-6 watts if you're swapping from a standard jersey to an aero jersey at 30kph, and up to 20 watts if you're travelling at 45kph. Remember this could be riding downhill, but can also be riding at a lower speed into a strong headwind as the relative air speed is higher. 

"It’s important to bear in mind how the importance of these wattage savings gets greater and greater the faster you go but it’s still there at the lower speeds," Disley says.

"If you’re travelling at 30 km/h and you’re saving 5 watts or so, over a longer ride that’s minutes that you’re saving."

2023 Castelli Aero 6.0 jersey and premio bib shorts

Disley says that he likes to use a watts-to-pounds ratio to see how many watts you can save for as least money as possible.

"Your tyres and inner tubes are quite a good one but clothing is absolutely right up there. Swapping to a different jersey in terms of an aerodynamic benefit will have something very similar to going to a slightly deeper set of wheels.

"Obviously, if you’re going from wheels that were heavier and there’s a weight saving involved then that’s slightly different but purely from an aero point of view you can roughly equate the two."

How many watts do aero socks save?

The question we all want answered!

"It's not as much as a jersey but you'll be saving a watt and a half, a couple of watts, at 30kph with a set of aero socks and then if we increase the speed up to 45kph so more of a high racing speed, then that becomes more like 5 watts," according to Disley. 

And since aero socks are a fraction of the price of a deep-section aero wheelset, they might be worth it after all!

Which range best suits your style of riding? Let us know in the comments section below...

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