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Home / Reviews / Profile Design Sonic Ergo 39A review

Profile Design Sonic Ergo 39A review

In the market for some clip-on aerobars to help transform your bike leg? We test the Profile Design Sonic Ergo 39A to see if it's fit for purpose...

Profile Design Sonic Ergo 39a
Credit: Jack Sexty

Promising ‘100 distinct position options’ via the armrests and 1,500 configurations with the additional riser kit, Profile Design’s Sonic Ergo 39A is a versatile offering for those looking to dial in a great fit and elevate their tri bar set-up to the next level on a sensible budget.

The aluminium 39A is one of many different bar shapes and sizes you can pair with the Sonic bracket and Ergo armrests, and this one has a 39° upwards tilt.

There are markings to accurately set the fore/aft position, and if you want to use them on a triathlon bike there are cable guides to accommodate shifters.

How we tested

When reviewing the best clip-on aerobars, we set up the bars ourselves using our own bikes. Each set of bars then gets put through multiple test rides of varying distances. While doing so, we analyse performance based on criteria including how easy the bars are to set up, how adjustable they are, comfort, value for money and weight.

Ease of setup

Profile Design Sonic Ergo 39a setup
Credit: Jack Sexty

Fitting was simple on my road bike, and I’m a big fan of how many different bolt holes you get on the armrests to achieve the best fit.

Having your elbows and forearms squeezed too narrow or spread too wide because your set-up won’t allow for the necessary adjustments is irritating, so the number of options increases the chances you can find the perfect set-up and ride through your bike leg comfortably.

The total weight for the bracket, armrests and bars is 564g.

The extensions are lengthy, so if you have a short reach you may want to cut them down to size to avoid your legs knocking against them.

Ride feel

In terms of how they feel on the bike, I had no issues and really got on with the 39A shape. The subtle upward curve allows you to grip the bar nicely, and for short races I wouldn’t feel the need to add bar tape.

As an example of how Profile’s modular aerobar system can be upgraded, I was also sent the Race Plus Armrest Kit (£54.99) and the 43ASC 340 Carbon aerobar extensions (£299.99) to play with.

The armrest kit offers a larger, deeper contact patch, and is more comfortable in my opinion, so if you’re struggling to get on with the standard armrests and/or are targeting longer races, it’s well worth considering.

I was already familiar with the carbon extensions, as they were included on the excellent Cube C:68X I reviewed recently.

Profile Design Sonic Ergo 39a

As the price suggests they are indeed an upgrade on Profile’s alloy extensions, with a flattened section in the middle to add more forearm support, slightly wider bar ends for improved grip and guides for routing cables.

In my opinion, I think this is one upgrade too many for road bikes and they’re much more at home on a dedicated triathlon rig.

A more cost-effective upgrade is Profile’s Riser Kit (£39.99) to adjust the stack of your clip-ons for the ideal position. Risers are included in the aerobars sets from Vision and Deda that we also reviewed recently, though the Sonic Ergo is more affordable.

The bottom line

In summary, the Sonic Ergo clip-on set as it comes is functional, highly adjustable and good value, with plenty of scope to upgrade.

It’s an ideal in-between if you want more than simple bar extensions and want to dial in a better fit, or if you’re starting your triathlon journey and anticipate taking it up a level in future.

For more choice, see our list of the best clip-on aerobars.

220 Triathlon verdict

Profile Design’s Sonic Ergo 39A are versatile, good-value clip-on aerobars that are ripe for upgrading. Score: 86%


  • Decent value
  • Exemplary adjustability


  • Extensions may be too long for some
  • Upgrades can be costly

Profile Design Sonic Ergo 39A specs

Available from:Freewheel
Extensions length:400mm
Extension angle:39°
Profile image of Jack Sexty Jack Sexty Editor at road.cc


Former 220 staff writer Jack Sexty is now editor at Road.cc. Jack has raced everything up to Ironman distance, is a sub-2hr Olympic-distance athlete and has represented GB at the ITU World AG Champs on several occasions. He's also a regular kit tester on the pages of 220 and holds two world records for pogo jumping – Longest distance pogo stick jumping in 24 hours and Most consecutive jumps on a pogo stick.