How should clip on aerobars be adjusted to the user?

Question

The context here is an endurance setup, with a fit optimised for the hoods/drops. Clip-on aerobars are being fitted to give an additional hand position especially into sustained headwinds; this very different position relieves pressure and stress on the hands and wrists. We (it's me helping a friend - I've done my own by trial and error) don't want to compromise the rest of the bike fit, which was done professionally, and which will be applicable for the majority of the time.

I've seen some advice about height (example, but that's in a TT or tri context, aero above all else, to the extent that they recommend a reduced crank length so the knees don't come up as high. Even then they don't say much about the reach on the aerobars (when that's adjustable without changing the stem). I know from my own recent adjustments putting mine out too far that it can be quite important, as my thighs contact my ribs.

For other aspects of DIY bike fitting there are plenty of more-or-less accepted approaches, but what about for aerobars, whether that's for endurance or a TT novice? I know a bit about the principles (I discuss them in an answer along with some more details on my setup) but wonder how to match those principles to a user. We don't have a turbo trainer available, but have good roads for test-riding, and I'd be interested to hear if trainers added something significant.

Answer 1

For clarity, the OP is asking about fitting clip-on aero bars to an endurance road bike. I have no personal experience with this.

I will say this: there are at least two relevant parameters. One is the bar's length. The other is the stack height, i.e. how far above your handlebars are the elbow pads. Here, it's possible that lower may not be better, based on this post by Torsten Frank where he addresses their use in ultra-distance cycliing. Basically, too low a stack height may mean you have to lower your torso angle in the aero bars, and this could strain your upper arms (supporting the body), and change the angle of your neck. I believe he advocates a slightly higher stack height for the bars.

It's true that all else equal, a higher torso should equal a higher coefficient of drag area (CdA). However, with aero bars, you are also putting your arms in a narrow position and you're shielding your forearms from the wind. And if you are thinking about long rides, comfort is a higher priority than it would be in a time trial (to be fair, comfort in an Ironman tri bike leg is also a very high priority).

One unmentioned point: many long-distance riders may stash snacks in handlebar bags. Aero bars block your access to most handlebar bags. I know that Apidura makes handlebar bags compatible with aero bars. This isn't a product recommendation, it's merely one brand I'm aware of.

Answer 2

Decent aerobars offer many degrees of adjustability. You can move the elbow cups in/out and fore/aft (peel off the padding, and the cup base should look like a colander). You can adjust the reach and in/out rotation of the extensions, rotate the whole assembly up/down in front, and use spacers to raise the elbow cups.

Make sure to order a set of spacers. I started with no spacers on my aerobars and could only hold that position for 10 minutes. When I added 30-mm spacers, I could hold the position indefinitely.

Position the elbow cups so that your arms are supported near the elbows, and so that your upper arms are close to vertical—if your upper arms are reaching forward, that means you're doing more work to support your upper body, and you want to avoid that. Position the cups far enough outboard so that you can breathe comfortably—too close and your arms constrict your chest.

Now position the extensions so that you've got a comfortable grasp near the ends. Many aerobars are available with J-bend and S-bend extensions, and I prefer the J-bends myself. I also prefer to have the ends rotated inward at the top--it puts my wrists in a more comfortable position.

I prefer having the whole assembly rotated upward maybe 10° from horizontal, and some people have them angled up much more steeply. My impression is there's no aerodynamic harm to that.

Answer 3

I'll start with a disclaimer. I have no particular knowledge about fitting aero bars and have never ridden with them myself (although have used 'puppy paws' fairly often so do have a rough idea how it feels.

Given that your friend doesn't want to compromise the rest of the bike fit, we'll assume that is the 'gold standard' and they can comfortably get into all the 'normal' positions (tops/hoods/drops/aero hoods). I'd also assume for this type of event the aerodynamic objective is to get narrow and hide the forearms rather than getting particularly low.

I'd start by getting your friend to get into both the drops and aero hoods positions and measure the position of the elbows relative to the headset top cap (most likely a little above and behind). I'd aim to get the arm rests in a position where the elbows were in roughly the same place (but narrower) as those previous 'normal' positions.

I'd then adjust the bars themselves to a position where the grips felt comfortably in reach and not too stretched. Given we have already placed the elbows in a similar position this probably places the grip area a fraction beyond the hoods.

The end result will be a position that is slightly higher and narrower than 'aero hoods' but more comfortable to hold and with a more open hip angle allowing better power production. I'd say this position has a very high chance of being comfortable because it's putting the body in a very similar position to how it normally would be.

Using that as a starting point your friend could then experiment with a slightly more stretched position if they felt it was beneficial/comfortable. I notice the position you have adopted on your own bike is a little more aggressive/stretched than my fitting approach would come to.

Answer 4

I tried aerobars for a while - they were useful when on a long straight empty road. For any riding where there is traffic or people or turns, not so useful. Main problem is you're a long way from the brakes for safety, and from the shifters for undulations in the road.

My main problem turned out to be neck pain - it wasn't obvious while riding, but after ~30 minutes in the tuck I had problems looking forward. Even with the helmet tipped way back on the forehead, forward vision suffered.

My top considerations would be comfort and safety. Aero gains and speed are third, at best.

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They do make an excellent platform for bikepacking light stuff like sleeping bags. I once carried a 1RU ethernet switch on my aerobars for a couple kilometres - why? My bag was full.