Why are recumbents so slow uphill?

I've ridden a recumbent a few times and noticed that going uphill is very, very slow. Given that recumbents are supposed to be more efficient than diamond frame bicycles, why are they so darn slow uphill?

Related: does "efficiency" mean something different when applied to recumbents?

• Often times, when you're going uphill, you use part of your weight / stand up on a bicycle. You can't do that on a recumbent. Also, you may have lower gears on a recumbent which makes climbing slower but easier on you. – Batman Sep 8 '17 at 1:13
• Yes, I understand that but It's commonly argued that recumbents should be more powerful as you are pushing against a backrest and not against gravity. – RoboKaren Sep 8 '17 at 1:16
• It's possible the body position and gripping on an upright allow the use of upper body muscles for leverage that the recumbent does not. Also, how many hours have you put into a recumbent vs traditional? If it's a small fraction then it makes sense. – ebrohman Sep 8 '17 at 2:17
• I wonder if a Diamond Frame bike would go faster if the rider was somehow strapped down to the saddle. – Criggie Sep 8 '17 at 3:13
• I think this question is ill-formed. An econocar get better mileage and thus is more efficient than a race car but it will climb Pike's Peak more slowly. Just because one vehicle is more efficient than another doesn't necessarily say anything about its speed (it may, but it needn't). I think this question needs revision. – R. Chung Sep 8 '17 at 18:36

"Efficiency" seems like it should be easy to measure. Power out ÷ Power in. Obviously nothing in life is so easy.

Here's a blog post by a randonneur who has compared power output on his recumbent to that on his diamond-frame bike (there are some related posts at the end that are also interesting).

He's found that his peak power output is higher on his DF bike, but his calories per mile and his watts per mph are lower on his recumbent. So those are a couple of non-obvious ways to define efficiency that show the recumbent being more efficient.

The author also writes about feeling "muscle-limited" on recumbents due to his inability to recruit as many different muscle groups, and "lung-limited" on DF bikes. And there's some interesting discussion in the comments.

Bike geometry and bio-mechanical topics have been discussed by others already, but I wonder if a large part of what you're observing is a relative difference between speeds on the two types of terrain?

Think of it this way:

You ride a "regular" bike on the flat. Your ultimate top speed is essentially governed by aerodynamics. You reach a speed where the force of the air you're pushing against equals the force you put in.

When you ride a recumbent under the same conditions, it's more aerodynamically efficient, so your top speed is higher.

Makes sense.

Going uphill it's a little different.

A larger part of your input energy goes in to overcoming gravity. Which is why your top speed will be lower.

Riding a recumbent uphill, you're still overcoming exactly the same amount of gravity, so aside from other mechanical advantages a recumbent may or may not give you in this situation, your top speed will be roughly similar to riding any other type of bike. The aerodynamics play a much smaller part in the equation..

Summary : the relative difference in the two top speeds is going to be greater (and more noticeable) on a more aerodynamically efficient machine.

Caveat: I'm neither a scienctist, nor a recumbent rider :P

• Good point - a 20 kilo bike is slower up a hill than a 10 kilo bike for the same rider. And recumbents tend to have a bit more frame and structure to them. – Criggie Sep 8 '17 at 21:58

Not sure why it hasn't been mentioned in the other answers but recumbents are generally much heavier than traditional frames and on steep gradients weight makes a big difference.

Looks like a 2000\$ recumbent is around 30lbs and a 2000\$ road bike should be around 18lbs or so.

Efficiency i.e., not wasting energy, is not the same as allowing high power output.

I thought recumbents were efficient because of low aero drag compared to a conventional bike.

With respect to power output, my guess would be that when riding a conventional bike out of the saddle, the arms pull against the bars as the feet push against the pedals, allowing the musculature of the whole body to contribute to power output. When riding a recumbent only the legs can contribute, hence the higher potential power output of a rider on a conventional bike.

Recumbents are generally heavier than a non-recumbent bike designed for the same kind of riding and sold at the same price.

With a few exceptions (mainly FWD MBB ‘bents), a rider of a ‘bent cannot use upper-body strength to apply additional power to the cranks.

Most riders who have “ridden a recumbent a few times” are not appropriately conditioned to drive the recumbent as efficiently as they are to drive a non-recumbent bike. Becoming properly conditioned and learning the proper pedaling/riding technique is often referred to as “getting your ‘bent legs” which gradually occurs over a period of a few weeks to a few months. If I spend a lot of time riding one of my ‘bents with a low bottom bracket and then go back to riding one of my ‘bents with a high bottom bracket it takes me a week or so to acclimatize again because even that hits my leg muscles differently; it’s a bigger change to go from any non-‘bent to any ‘bent. Until you get your ‘bent legs, you notice the difference mostly when going up steep hills.

The primary advantage of a ‘bent as far as efficiency goes is the superior aerodynamics. First, not all ‘bents actually have superior aerodynamics: My Sun EZ-1 Lite shopping and utility bike is less aero than my old Schwinn. Second, aerodynamics have almost no effect at the slow speeds at which hill climbing occurs: Below about 15mph (combined forward travel speed and wind speed) the aero profile is essentially meaningless and if you’re going faster than that you’re either a serious athlete or not climbing a real hill.

On any bike, the legs are almost straight when the pedals are at the farthest point away. Now, think of the reverse, when the pedal is closest, on a bent your upper legs are at about 90 degrees from your abdomen whereas on a DF your upper leg is almost parallel to your abdomen. Therefore on a bent your big glute muscles are already half extended as you start the power stroke, whereas on a DF you have full use of those muscles at the start of the power stroke.

I am fairly new to bent riding and have come to accept snail speed on hills, on group rides I keep up otherwise, and everyone seems to accept that, for me, the price of still biking in my senior years is slow on uphills! I do love being pain free!

• Welcome to the site. Likely you will speed up when you body adjust to the bike, and you adjust your riding to the needs of this bike on those hills. I am now using my fourth 'bent and keep improving even after 10 years of previous 'bents. – Willeke Jul 14 '18 at 19:33

I've done a decent uphill ride last weekend on my recumbent, and have two realisations:

1) Its hard to ride for long when your feet are above your heart - I was getting numb toes until the grade levelled out.

2) There's a minimum speed required to keep your balance, and if you can't do 5 km/h then you're going to be too wobbly and all over the road.

I have a 22 tooth grannie chainring and its too small to be useful. So I sit in the 32 tooth middle ring and a 32 tooth rear gear and grind away at that.

I've done this climb in 35 minutes on a road bike. and 42 minutes on a bad day. This recumbent ride took 59 minutes, and admittedly my heart rate was below 150, whereas it was in the 170s on the road bike.

Upshot - recumbents ARE significantly slower up hills.

Aside - doesn't help that my steel recumbent weighs 20 kg. My 11 kg aluminium road bike feels like a feather by comparison. And fancy race bikes feel like nothing-at-all. So that added weight doesn't help one's uphill speed at all.

• This begs the question why your heart rate on the recumbent is lower. It's not the first time I've read about this (I don't own one), but never found a good explanation. – StefanS Jul 14 '18 at 14:38
• Maybe when @Criggie gets more experience on his recumbent, 'gets his 'bent legs' the heart rate and the speed will go up some. I see improvement every time I take a certain hill on a new bike till I am fully adjusted to the bike and from there is not much difference anymore. (My hills are short/low, so I can not get numbers for them.) – Willeke Jul 14 '18 at 19:31
• @StefanS I'm suspecting that there's less vertical movement (ie pressure) required in the blood circulatory system. My personal limiting factor seems to be oxygen - I'm breathing hard and with the chin close to the chest its hard to get more air. On a road bike your airway is a lot more linear and free to flow. – Criggie Jul 14 '18 at 23:22
• @Willeke try an uphill start from the middle of the steepest part of the hill - that's an interesting experiment – Criggie Jul 17 '18 at 9:48
• @Criggie, I usually walk across the road crossing till I get to the highest point. On real hills I have been able to start uphill but I hate it. Our short hills do allow you not to do it. – Willeke Jul 17 '18 at 9:50

One thing to consider is that on a Diamond frame bike you can stand on the pedals when going uphill to use your mass as an advantage. Some people may even do this unconsciously. That sort of thing is not really possible on a recumbent bike.

• I'd have to disagree there - a DF bike rider can put all their body weight on a pedal, and can add some more by pulling on the bars. By comparison a recumbent rider can push their back into the seat, essentially duplicating the power of a leg-press machine in a gym. Your leg muscles can generate far more than your own body weight (but I'm having problems finding decent comparable numbers.) – Criggie Jul 17 '18 at 9:46