Types of Aero Bars Explained: Ski Bend vs J-Bend vs S-Bend

If you've worked through our Aero Bars Guide, you already know how much of a difference the right extensions can make to speed and comfort on a TT or triathlon bike. But "aero bars" isn't one single product, it's a category, and the types of aero bars on the market differ a lot in shape, feel, and how they interact with your position. Before you spend money on a new set, it helps to understand the main shapes available and what each one is good at.

What Are the Different Types of Aero Bars?

When riders talk about types of aero bars, they're usually talking about the shape of the extensions, which is the part where your forearms rest and your hands grip. The three most common extension shapes are:

• Straight extensions
• Ski bend (J-bend) extensions
• S-bend extensions

Aero bars also come in two formats: clip-on units that bolt onto a standard handlebar, and integrated systems built into a dedicated TT cockpit. Either format can use any of the extension shapes above, so the type of aero bar that suits you best usually comes down to hand position and comfort rather than the bike underneath.

Straight Aero Bar Extensions

Straight extensions have little or no curve along their length. They were common on early time trial bikes and are still found on some UCI legal setups, where handlebar shape rules limit how much extensions can bend. For triathlon, where these rules don't apply, straight bars have mostly been replaced by shaped extensions that offer better wrist comfort on long rides.

Ski Bend (J-Bend) Aero Bars

Ski bend extensions, often called J-bend aero bars, curve gently upward toward the grip section. This upward angle lets your wrists sit in a more neutral position rather than bending downward, which is a big part of why this is one of the most popular types of aero bars for long course triathlon.

Why Riders Choose J-Bend Extensions

The neutral wrist angle of J-bend extensions makes them comfortable to hold for hours, which matters when you're riding for several hours in a high hands position or any other aggressive aero setup. Many long course triathletes find that this comfort outweighs small differences in raw aerodynamics over the course of an Ironman distance bike leg.

Where J-Bend Extensions Fall Short

Because the grip area points upward, J-bend extensions give you less leverage when you want to push hard out of a corner or surge on a climb. Some riders also find that, compared with flatter shapes, J-bend extensions feel slightly less aggressive in the aero position, although the difference is often small in practice.

S-Bend Aero Bars

S-bend extensions have a more pronounced curve, with a grip section that sits closer to parallel with the ground. This shape gives you a different relationship between your hands and the rest of the cockpit compared with ski bend designs.

Pros of S-Bend Extensions

The parallel grip area on S-bend extensions makes it easier to get leverage, which is useful for shorter time trials or efforts where power output matters more than all day comfort. Riders who prioritize a low, aggressive position sometimes prefer how S-bend extensions let them apply force through the bars. Also another pro for S-bend extensions is that the relative shape of them allows you to bring the "gripping" area closer to the arm rests, which is very useful for UCI races.

Cons of S-Bend Extensions

The flatter wrist angle on S-bend extensions can feel uncomfortable over long distances, and many riders need an adjustment period before the position feels natural. For long course triathlon, this is one of the main reasons riders move toward ski bend or other wrist relief extension shapes instead.

How Aero Bar Shape Affects Your Position

The type of aero bar extension you choose doesn't exist in isolation, it interacts directly with the rest of your setup. Pad height, reach, and stack all change how a given extension shape feels, which is why we cover these adjustments in detail in our guide to optimizing your aero bar position. A J-bend extension paired with the wrong pad height can feel just as uncomfortable as an S-bend with poor reach, so it's worth thinking about extension shape and position together rather than as separate decisions.

Aerodynamic testing has found that the way you hold your hands and forearms on the extensions affects airflow attachment around the wrist, which is one of the reasons extension shape and hand position can matter as much as which bend you choose.

Common Mistakes When Choosing Aero Bar Extensions

Copying a pro's setup without testing it. What works for a professional triathlete's flexibility and riding style won't necessarily suit yours.

Ignoring race distance. A shape that feels fine for a 40km time trial may become uncomfortable over a 180km Ironman bike leg.

Overlooking compatibility. Not all extension shapes fit every base bar or clip-on system, so it's worth checking compatibility before buying.

Skipping a test ride. Small differences in wrist angle are hard to judge from a photo or spec sheet, they're much easier to feel on the road.

How to Choose the Right Type of Aero Bars for You

There's no single best option among the types of aero bars available, the right choice depends on your race distance, flexibility, and how the rest of your bike is set up. As a general starting point:

• Long course triathletes often do best with ski bend (J-bend) extensions for their wrist comfort.
• Shorter time trials and riders prioritizing leverage may prefer S-bend extensions.
• Riders racing under UCI rules may be limited to straighter shapes depending on their category.

Riders discussing extension shape on long running cycling forums like Slowtwitch consistently point out that comfort and personal wrist angle matter more than chasing small aerodynamic gains on paper, since a position you can't hold for the full race distance won't be fast in practice.

Conclusion

The types of aero bars you choose, straight, ski bend (J-bend), or S-bend, shape everything from wrist comfort to how much leverage you have on the bike. Getting this decision right makes the rest of your setup easier, including the position adjustments covered in our aero bar position guide.

If you're not sure which type of aero bar extension fits your riding style, get in touch with our team, or check out our other upgrades for your bike. We can help you match the right shape to your position, flexibility, and race goals.