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I would like to ask some questions about aerobars, also known as tribars.

I've seen them used on bicycles meant for very different purposes. In theory, the very low, horizontal, position is ideal for aerodynamics. I've seen them used on timetrial bikes and on triathlon bicycles.

However, as a matter of intuition (I personally have never used aerobars), it seems to me they might offer a lot of comfort when you're out on your bicycle for many hours. I mean I have leaned on my (flat, mtb) handlebars when tired. Well, that intuition seems justified considering I have seen some touring vloggers use aerobars. The world famous Mark Beaumont who has gone around the world on bicycles TWICE and the second time he used aerobars.

I like to use visual aides with my question/explanations so: vlogger with aerobars:

. Mark Beaumont's world touring bicycle, the newer model:
.

Timetrial and triathlon bikes respectively: https://freerider.ro/noutati/pinarello-isi-arata-clasa-bolide-noul-armament-de-contratimp-52164 And triathlon: http://www.magazinuldebiciclete.ro/userfiles/b81e6ae7-410b-47f7-8144-c2900c09a8f7/products/11333345_big.jpg

My question - the core question - is this: How do you set-up aerobars for comfort and how do you set up aerobars for speed? What are the geometric differences between the 2 setups?

Extra questions: What are the other geometric differences between those touring bikes and a timetrial/triathlon bike? I mean in addition to geometric differences between aerobar set-up, what other geometric differences are there? What about frame geometry? Are the TT/tri bikes comfortable? I've heard TT bikes are awfully uncomfortable, but triathlons can be hundreds of kilometers long so i would assume a triathlon bike has to be comfortable... and fast.... Is a triathlon bike a bicycle ideal for BOTH speed and comfort? What are the geometric differences between a TT and triathlon bike? They look incredibly similar yet one is supposed to be for sprints, the other for cycling for hundreds of kilometers... So I dont understand how they can be so different.

And most important question: If you wanted to make a compromise between comfort and speed, how would you set-up your aerobars? And what properties would you seek regarding the geometry of your frame? As i said above triathlons can be very long... maybe look for a bicycle whose frame most closely matched a triathlon bicycle?

......................................................................................... Background:

I am actually thinking of buying a new XC bike.

I dont want to just google "ideal measurements to look for when buying a new mtb".

I've seen many times on the internet MTB geometry being characterized as "very slack". I've never really understood what that means 100%. I do know that in general the ideal geometry of an mtb and of a road bike/tt bike /tri bike are at odds with each other. I dont want an mtb whose geometry is too much at odds with speed geometry.

What I want is to creat a chimaera between an mtb, touring bike and a speed demon (a place-holder term for either road bike/tt/tri bike). Actually my original idea was just "mix mtb and road bicycle into one ideal bicycle". There's such a wide variety of bike out there, including of bikes meant for high speed, that "speed demon" seems more appropriate. I've actually posted on this forum before asking about mtb tyres at road tyre pressure. 2 inch thick, 7-10 bars. The idea was to use 7-10 bars on the road and deflate the tyres on off road. That was sci-fi. I've analyzed tyres until ive become an expert on them. I've now moved in my "project" to other issues.

While the original idea of mixing mtb and road into one ideal bike seemed daunting if not impossible, putting aerobars on mtbs is something some people actually do. Adapting mtbs for touring is something people actually do. Makes sense that you can do both: mtb adapted for touring but also set-up with aerobars. So this seems to be the right direction for my "project". I should mention the idea is for it to still be usable as an mtb, so it would still be set-up with thick tyres (or at least thicker than a road bicycle), flat handlebars and suspensions (maybe front or full, not sure yet). I could then go many kilometers in relative comfort on road and then just use it as a classic XC bike when deciding to go off-road.

But my current mtb sucks. I'm not going to set this one up like this. I definitely need a new mtb, so I should buy one whose geometry is already best suited for such compromises.

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  • Would you consider a gravel bike as well? This does depend on what sorts of terrain you're dealing with, but in general, if your rides mix road and off-road terrain a lot, chances are the off-road bits are relatively tame and you may not need an XC bike.
    – Weiwen Ng
    May 18 at 16:24
  • @WeiwenNg Gravel bikes are too similar to road bikes. Ive watched lots of comparisons on the internet between mtbs and gravel bikes and mtbs are much more versatile. In particular a flat handlebar is amazing. It gives you more and more control the wider it is. May 18 at 17:00
  • @WeiwenNg I want such a bike to do MORE than i currently do. Yes right now the off road bits are tame... with the bike i described in my post i intend to search for increasingly challenging terrain. Right now i go into small patches of forrest around my hometown which is in the flat part of my country. With the setup above i will go the mountains up north. May 18 at 17:02
  • Rather than adding yet more topics to my answer, you can make a do-it-all bike, but it will never be as quick as a dedicated fast road bike, or as capable on rough terrain as a dedicated MTB. But you might start with a cyclocross frame; people do fit suspension forks to them sometimes but if you want speed on road you don;t want to be lugging around heavy forks - they're also not very aero!
    – Chris H
    May 18 at 21:01
  • But I'm thinking of a few days mixed surface bikepacking and would actually be choosing between the MTB and the tourer. They'd probably be the same overall speed on that trip, with the tourer needing some pushing and the MTB being slower on the road sections. My last tour on the tourer had a fair bit of off-road, some rather rough.
    – Chris H
    May 18 at 21:02

2 Answers 2

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A general geometry difference between the two distinctions is a bicycle set up for speed (an aerodynamic triathlon or time trial bike frame) typically has a steeper seat tube angle (more upright) this moves the seat (the cyclist’s pelvis forward, essentially rotating their whole body forward when they are using the aero bars. This maintains the legs to torso angle similar to an open road bike position.

Whereas on a traditional road/touring/MTB with a more relaxed seat tube angle (~73° relative to the ground), using aero bars closes up the legs to torso angle (think “more bent at the hips/pelvis) which can somewhat inhibit breathing, comfort, and power generation.

There are ways to circumvent this on a road/touring bike, but with some compromises. First, a seatpost with a more forward seat position could be used. This mimics the steeper seat tube of a dedicated time trial frame. However, that position has its compromises as the body is now more forward over the BB/pedals which is not as conducive to a good climbing position (where some riders actually slide back on their saddle to be more efficient while climbing). A second way to circumvent the limitations of a touring bike geometry with aero bars is to raise up the aero bars a bit to open up the legs to torso angle. The rider will be a little higher and may catch a little more wind on their torso, but the narrower front profile of the rider will still be present offering some aerodynamic benefits.

Since every rider has a different flexibility, these adjustments may not need to be employed, and realize that there will always be compromises made when adding aero bars to a touring/MTB frame. Sometimes the compromises are minor; other times they pose real choices needing to be made as to which path is preferable.

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  • Thank you. That is very to the point and absolutely fascinating! it will take me some time to digest all that information. I too thought about adjusting the saddle back and forward by A LOT. Depending of i want to go fast or to do proper mtbing. I m thinking of gadgets such as this: sjscycles.co.uk/saddles/vk-saddle-adjuster/?geoc=RO May 18 at 19:01
  • No wait, this is actually what i had in mind: shop.bikeshore.com/product/switch-aero-system/… It s very expensive though... I dont k ow if cheaper alternatives exist though. May 18 at 19:03
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    @Biketouringfan glad I could help! Those devices you linked to could do the trick. Just make sure they are robust/not flimsy. Also, visiting a bike fitter when making adjustments like this can be a huge help (and they may have the parts you need too!). They deal with comfort and with performance/efficiency. Check around for one at your local bike shops. Usually money well spent. Also, if you think the answer has merit, give it a vote up. If you think it is the best answer also accept it (green check mark). If a better answer is posted later you can change it then. Ride on!
    – Ted Hohl
    May 18 at 19:14
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    If I understand correctly, the more backwards the seat tube and thus the saddle, the more "squished" the rider (more bent at the hips/pelvis)? (side note, how do you type enter on this to make paragraphs?) You're saying the solution to this, and more generally the way to be more comfortable with aerobars, is to make them higher? I recall in other parts of the internet that tt bike use aerobars much closer together than tri bikes. So... The compromise between speed and comfort lies i the height of the aerobars and the space between them? May 19 at 11:15
  • @Biketouringfan think of a road bike frame as a normal start point. The seat tube angle on a road bike puts the rider in a good position for power and comfort when using a normal set of handlebars (not squished). Now, when you lean over to get more aerodynamic without any other changes, the legs to torso angle will close some (bending more at the hips). The lower you get, the more closed the angle, and eventually you get to a point where it is just uncomfortable and not worth the aerodynamic benefits, especially for extended lengths of time. This affects everyone differently, of course.
    – Ted Hohl
    May 19 at 17:04
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The usage of aerobars is slightly different between competition and long distance:

  • in a TT or tri setup, you're using the aerobars to maximise speed, and will set up the rest of the bike for a very tucked position - aerodynamics are most important, so long as the ergonomics don't limit your power
  • in an endurance setup, the use is more for a comfortable, efficient position, especially when dragging into a headwind. Otherwise you'd be in the drops for hours straight, and that's not a great position. Ergonomics are more important.
  • of course it all depends on the rider - a fit that to me feels super-tucked and only bearable for a 10-mile TT could feel quite easy to a more flexible rider.

I ride for many hours at a time, not very quickly, and do use aerobars, fitted to a tourer. My wrists like them; they may help against pressure on my ulnar nerve, if I can use them for enough of the ride, but they don't help my back (which only suffers from too much climbing). I don't use them in a group, except occasionally on the front, so on my recent 420km/24 hour team event they were close to deadweight. Note that I optimise my saddle position for drops/hoods, and have aerobars that aren't all that low. The saddle type or position isn't perfect for long hours on the aerobars (too much pressure on the nose) but I don't tend to have suitbal stretches for more than a few tens of minutes at a time. I have them quite a long way forwards but have long arms - stretched out even further I might have a thighs vs. ribs issue (see Ted Holt's answer) but I might have to try it .

Laden and labelled This picture is one I uploaded recently for something else - that's my light camping setup on the tourer, but you can see the aerobars there.

When used for endurance, the main handlebar (often referred to as the base bar in the context of aerobars) is set higher than in a really aggressive race/TT position. So as soon as you clamp the bars to an endurance geometry bike, you have a different position to the same bars on a bike built for pure speed.

Many aerobars can also have adjustable height (e.g. with spacers), and when fitted for endurance use, setting them higher can be helpful. This is partly because low aerobars can prevent you using the bar tops, especially with narrow base bars or with lights fitted.

Using aerobars on flat bars is perfectly reasonable. Note that flat bars tend to start higher than drop bars for the same rider, so your legs are unlikely to come up too high. I planned to do this on Saturday because of a 210km ride on my hardtail, 150km was paved and much of that suitable for aerobars (so was some of the gravel). I would have liked the extra hand position compared to ergo grips with tiny bar-ends. But the screws were so stuck I snapped them and had to do without. BTW I ran my tyres at the max stated 4.5 bar (2.1" WTB Nano) and the ride was nice on road, OK on gravel, but I should have let them down for the proper rough bits.

The longest common triathlon is the ironman, with a 180km ride - but that has to be done pretty quickly, and it's not really a very long ride. Where things get really interesting is things like 12 or even 24 hour time trials. Once you get to ultraracing, the setups I've seen are approaching what I'd think of as an endurance fit - comfort then efficiency. An issue to be aware of is Shermer's Neck - a condition where ultra-racers quite suddenly can't hold their heads up after riding very tucked for days on end.

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  • "When used for endurance, the main handlebar (often referred to as the base bar in the context of aerobars) is set higher than in a really aggressive race/TT position." -> that s the key sentence. Fits with what Hohl said. "but I should have let them down for the proper rough bits."-> Had a similar experience. I use Schwalbe marathon mondial. I use as close as i can get to 5 bars on road. I tried once leaving them like in the forrest and the bicycles transformed into a jackhammer. You are doing well using an actual mtv tyre. SMM is so tough it's hard as a road tye even at 2.5 bars. May 19 at 11:22
  • I had to drop it to 1.9 to soften it. It will probably NOT last as much as the manufacturer intended. Still, surprisingly, despite the manufacturer saying it should never have less than 2.5 bars, it was VERY STURDY at 1.9. "not really a very long ride" - Sorry, but 180 km sounds like a very long ride indeed to me. "Once you get to ultraracing, " - you mean stuff like this: watch?v=ZEImemPWBnU ? In depth: ZIsuG8agZDI -> that guy uses a clearly touring set-up. At least it seems like that to my eyes and limited expertise. May 19 at 11:26
  • @Biketouringfan I've got Marathon Mondials - they came with my tourer and I put them back on in winter as they handle dirty wet roads better than my slicks, plus they make it almost a gravel bike. The Nanos I used at the weekend are big gravel tyres, and roll far faster than true knobblies
    – Chris H
    May 19 at 11:27
  • "Shermer's Neck" -> well, cycling should be healthy. If you get stuff like that, whatever watts you save are not worth it. "roll far faster than true knobblies"-> almost everything does. MTB tyres are awful. Well, perhaps i am exagerating, but I use to have soft compounds tyres from maxxis and kenda and I absolutely love SMM compared to those. REcently I managed to unstuck and fix my front suspension and now I can deal with the hardness of the SMM tyre just fine. Still I will probably have to circle back around to mtb tyres... But i;m going to use bicyclerollingresistence.com to find May 19 at 11:30
  • the mtb tyres with absolutely lowest rolling resistance at 5 bar or 4.5 bar. Thanks for the tip regarding gravel tyres. Perhaps WTB nano will be better for me too. May 19 at 11:31

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