Which is faster, a road bike or recumbent?

Which is faster, a road bike or recumbent?

One of the most hotly debated topics online is how fast recumbents actually are, closely followed by various arguments on whether or not they can climb hills. I am frankly astonished by the amount of misinformation out there, when these questions can be quite easily answered by actually riding them and doing some direct comparisons for yourself. However, for the purposes of this article, I shall become that most loved of creatures inhabiting the online recumbent forums, a theoretical bicyclist. Here’s my take on it.

Hill Climbing

Let’s attack the hill climbing question first, as it feeds directly into the overall speed question.

Can recumbents climb? You hear this all the time – “recumbents can’t climb hills”. This statement makes no sense because a bike cannot do anything by itself. I understand the intention behind the statement but semantics matter, as there are a lot of factors to consider. A bike, in whatever form, is merely an enabler of cycling functionality. Therefore a better question is – can a rider climb as well on a recumbent as a standard road bike? Those looking for a binary yes / no answer are going to be disappointed, because the actual reality is much more nuanced than that. The short answer is ‘better for some hills, but not as good for others’.

The factors that need to be considered are as follows:

  • Bike weight
  • Wheel size
  • The aero drag of the bike plus rider
  • Rider strength
  • The length of the climb
  • The gradient of the climb

All these factors interplay in subtle ways that need to be considered. First of all, however, lets detail the basic principles without considering the interplay between each factor.

Bike weight – the heavier the bike, the slower you climb. If you have 2 otherwise identical bikes where one is heavier than the other, the heavier one by definition requires more energy input to climb uphill at the same speed as the lighter one. That’s just gravity in action and there’s nothing you can do about it, short of adding a motor to your bike. But we are considering human power only for this discussion. It’s also easy to state that road bikes are in general lighter than recumbents. There are very few recumbents below 10KG whereas most decent road bikes are less than 8 KG. A ‘good’ racing recumbent generally weighs between 10-12 KG, although there are exceptions such as the Challenge Fujin SL2 which has a claimed weight of 8 KG.

Wheel size – if we assume the use of exactly the same type of tyres for 2 otherwise identical bikes where one has bigger diameter wheels than the other, then all other things being equal, the smaller wheeled bike will be slower due to the higher rolling resistance of the tyres on the ground. Construction of such a bike where ‘all other things are equal’ in this case is probably impossible, but let’s stick with it for the sake of argument. If you don’t think wheel size matters, imagine what happens if you run 1 cm wheels and hit a vertical bump 1 cm high. The bike is jolted to a violent stop. The smaller your wheels get, the more you ‘fall’ into road imperfections, and the more energy you have to expend to ‘climb’ out the other side and over small bumps.

Obstacles like cattle grids are very useful for demonstrating this – on the Quetzal with twin 26 inch tyres at a lowish PSI, I can float over them, but on the Fuego or Sprint with 20 inch front wheels, your eyeballs are shaken out of their sockets and you lose significant amounts of speed by the time you get across. You can mitigate this to some extent using very supple tyres and running at lower tyre pressure, but the fact remains that a smaller diameter wheel by definition requires more energy to climb out and over any small bump / dent in the road surface than a larger wheel, which translates into lost forward speed.

Aero drag – the higher your aero drag coefficient, the more you are slowed down by air resistance. This doesn’t matter a lot for steep climbs but can be a factor on gentler gradients.

Rider strength – This is obvious, but a stronger rider would climb faster than an identical rider who wasn’t so strong. Although this has nothing to do with the bike and therefore seems redundant to the discussion, when you start interplaying all the factors together, rider strength matters – a LOT.

Climb length – if a climb is short enough that you can go anaerobic, sprint, mash or otherwise brutalize your way to the top, it has different implications for the superior climbing platform than a long climb where you must sit at or below FTP for the duration of the climb. Think a 5 minute sprint versus something that takes an hour.

Climb gradient – the gradient of the climb has a direct correlation to the speed you can ascend at. This is also important when you consider other factors.

Surely it’s not that complicated, right?

So now let’s see how these all work together.

We can all agree that, taken in isolation, a lighter bike will allow you to climb faster than a heavier one. On a 1 hour 15% torture fest, you will get to the top significantly quicker on the lighter bike, if you haven’t ended up puking all over the road half way up. However, what about a 2% gradient? What if one bike is significantly more aero than the other? On a 2% gradient, some riders will be able to ride hard enough that they could be faster on a more aero bike, even if it is significantly heavier than a less aero bike.

I can climb the 7 mile hill out of Innerleithen faster on the M5 CHR than I can on the Tarmac (3 KG lighter but much less aero). It has a long pull at 1-2%, and only gets up to 5 or 6% nearer the top. It’s close, but the CHR is faster for me for the same power. A weaker rider will not benefit so much from a more aero bike, due to the fact that the amount of energy needed to overcome air resistance goes up at the square of speed, so the benefit of superior aerodynamics lessens as speed drops off. A stronger rider would find an even bigger advantage on this climb on a recumbent.

As power drops off, eventually aerodynamics becomes negligible and you can more or less remove it from the equation – at which point a heavier bike is always going to be slower. So you can see how gradient, rider strength, drag coefficient and bike weight all interplay, and that’s just one example!

Now imagine a series of short, steep rollers. A much heavier, but supremely aero bike will be able to maintain a higher speed for longer up the climb than a slower, less aero bike, as it gathers more speed on the descent and still has an aero advantage for part of the climb up the other side. Again, depending on rider strength you may be able to maintain the extra speed long enough that you get to the top before the ligther bike catches you up again. The M5 loves this sort of terrain. The Cruzbike was the undisputed champion here though, where you could reach high speeds on the descents, and then pull high power through the pedals up the other side and really fly.

Rolling resistance plays a more significant overall factor at lower speeds than it does when going faster (for the same reason as above – the energy to overcome wind resistance is more important at higher speeds due to the fact it goes up as a square of speed). So a very aero bike such as a lowracer with a 20 inch front and 26 inch back wheel may be faster than a dual 700C wheeled bike, depending on what power you are putting in, and what the gradient is. If you are going fast enough that the aero benefit outweighs the increased rolling resistance, then you’re quids in. On steep hills, the smaller wheels become a definite disadvantage though, especially if the road surface isn’t great. If you can’t ride fast, you don’t benefit from the aero advantage and therefore the wheels will slow you down more.

On a short climb, a standard road bike rider can use the upper body to pull power through the pedals when they stand up, and they can go powerfully anaerobic to get to the top very quickly. The very strongest and most adapted recumbent riders can do similar on leg power alone, but most of us definitely have a lower maximum wattage on a recumbent due to the inability to use the upper body. Going anaerobic on a recumbent is, for most people, less powerful. MBB riders can include some upper body usage but it’s not as pronounced as a road bike. So once again, rider strength is a big factor here.

If you are well adapted to the platforms, your FTP on either will be roughly the same. This is just another way of saying you don’t get free power out of a road bike (or MBB) just because you can use the upper body – you can put yourself into the red quicker, but it has to be paid for. Your aerobic system can handle so much effort regardless of your bike. So in a sprint climb, you can mash up the hill considerably faster on a road bike, at the expense of putting yourself further into the red. On a longer climb, although you can’t go much beyond FTP you can still stand up and take some of the load onto the upper body which you can’t do on a recumbent.

There comes a point where the limitations of the aerobic system equalise the two platforms, and neither gives you any real benefit in the long term. I have noticed that over a multi hour ride, my sustainable average power is pretty much the same on a recumbent or road bike. My normalized power may be slightly higher on the road bike due to the ability to put higher power out for short periods, but there’s only so far you can go with that before your body tells you enough. So all my hard rides tend to end with an average power within 5W of each other no matter what platform I ride.

On the flat, weight doesn’t play anywhere near as big a part. Rolling resistance still applies but the the aero drag of the rider plus bike is the biggest determinant of who is faster. I can annihilate my Tarmac times on the flat when riding the M5. In fact, as long as it’s flat or a very slight downhill, I can beat the local strongest riders on TT bikes. One of my local routes happens to go down the local 25 mile TT route and I have the KOM for that section. Not bad for a 44 year old who’s only been riding hard for a couple of years – I wish it was me but it’s really just the bike πŸ™‚ For roughly similar wattage to the course record holder, I am slightly faster on the CHR, without any help from a tailwind. It’s hard to know what size the other rider is, but I’m quite big so smaller riders will find a recumbent even faster for the same power – if you don’t believe me look up Larry Oslund on YouTube. Nuff said. The Fuego is heavier and with smaller wheels, but is still faster than the Tarmac. It’s not as fast as a TT bike though, which shows how rolling resistance and weight does still affect performance on the flat.

On descents, you will destroy pretty much anything upright on a bike like the M5. The only thing that really slows you down is your own sense of mortality or tight bends. The rest is a blaze of high speed glory πŸ™‚

Just tell me which one is faster please.

I wish I could. Basically, for any particular rider (assuming full adaptation to the recumbent platform), there is a crossover point in terms of gradient below which a recumbent is faster, and above which a road bike is faster. This point is where the aerodynamic advantage drops off enough that the weight penalty of the heavier recumbent makes the climb slower. Where that point sits depends on all the factors above. You can push it higher with a lighter, more aero recumbent. Stronger riders push it higher than weaker riders. Rollers are influenced more by aerodynamics than weight. Long gentle climbs also favour aerodynamics more, but as the road turns up, the weight and rolling resistance play a bigger part and eventually your road bike becomes faster just by virtue of it being lighter.

Whether a recumbent is faster overall for you depends on all the factors above, and also on the terrain in which you ride. If you live in the Florida flatlands then yes you will be faster. I look at Strava plots of people on recumbents cruising around Florida at 23 mph without barely breaking a sweat. That is something I just can’t imagine where I live (hills in all directions, and darn steep at that – I rarely get to 20 mph average unless I stick to a few flatter main roads) and to be honest I think I would find that kind of terrain rather boring, but there’s no doubt that recumbents are super fast in these conditions. As you progress towards hillier terrain, you need to become stronger and have a lighter bike with large wheels in order to remain faster on a recumbent. Eventually however, you will be faster on a road bike regardless.

If you are not strong at all and ride a heavy recumbent, you are more or less guaranteed to be slower in any terrain other than pancake flat (if you live in Holland or Florida then this does not apply). This is a good point to take on board if you’re just starting out and have some idea about beating your favourite GC hero up the local climb on your new 17KG Fuego. Until you can average say 200 watts for a sustained period, most of the time you’re going to be faster in mixed terrain on a road bike regardless of what recumbent you ride. I have found that at my current fitness level, averaging maybe 220W around the 40 mile Innerleithen loop, I am almost exactly the same time on the Tarmac and the M5. The M5 is at the fast end of the recumbent spectrum, both in terms of weight and aerodynamics. The Tarmac is the Expert model, a decent road bike but not silly expensive or light. The M5 weighs about 11KG with all the bits I’ve added to it (pedal extenders, neck rest, tail bag etc). The Tarmac weighs about 8.5KG similarly ready to ride. This route has one steep 10 minute climb, lots of steep rollers, a 7 mile gentler climb and a 7 mile section on a very gentle descent. The rest is a combination of up and down so there is very little flat ground. A stronger rider would be faster on the recumbent (the gradient at which hills become slower is pushed higher) and a weaker rider would be faster on a road bike. You need to take all these factors into consideration to figure out which is faster.

There are other things to consider as well. Over the course of a long ride, comfort becomes a significant factor. The recumbent is easily the winner here. You can stay in a super aero position all day without trying. You may be able to hold a good aero position for a while on a road bike but sooner or later it’s going to start hurting.

Conversely, towards the end of a hard ride when the legs really start to hurt, the recumbent rider just has to grit his or her teeth and bear it. On the road bike you can continue to eke out a little bit more power using the upper body when the legs have had enough.

Conclusion – ride yer bike and enjoy it, regardless of what shape it is

In my experience, it’s a lot simpler to just get out there and ride your bloody bike. Let the armchair physicists argue it out online – go out and do your local loop hard on both platforms and find out for yourself which one is faster for you. Your experience may vary wildly compared to another rider who may be significantly stronger or weaker than you. It all depends on the terrain and the rider strength.

The most important thing is to have fun. I ride and love both platforms. It took a long time to overcome my back problems and get back on a road bike, but now that I’ve managed it I appreciate a road bike for what it is. The two platforms are a completely different ride experience and I don’t see a need to be either for one or the other – both put a smile on my face every time I go out. That’s what really matters to me!

I sincerely hope that I have now made things even more confusing for you πŸ™‚

3 Comments

laidbackbikes Posted on4:08 pm - May 29, 2019

β€œThe Fuego is heavier and with smaller wheels, but is still faster than the Tarmac.”

Have to add caveat that it is true much of the time with a rider of your fitness!
Sadly Fuego isn’t in production now so the ‘fast’ Nazca model is the Gaucho 28 (as used by McCraw on LEL).

Others might argue that a P38 is fastest for them – think the Fuego does hold it’s own and with light wheel set it did well for Peter Haan in NL.

Other factor is frame rigidity – on ‘bents the bottom bracket isn’t traingulated (unless Cruzbike) so a section of your effort goes into re-shaping the frame (ok it springs back again but even so!)

It’s a good read though and tackles the endless enigma. I think the fun element comes into it – although I remember the Guy Martin tandem event where he said he didn’t really try on a solo recumbent as he didn’t expect anything from it! In that 24 hour record the main problem was comfort of seat – getting dialled in with right seat cushion is pretty important.

β€’β€’ FTP stands for Functional Threshold Power – I had to look that up!

    recumbentcyclistuk Posted on5:53 pm - May 29, 2019

    Yes, I think the Fuego is the perfect bike to illustrate the argument – strongish riders can make it a pretty fast machine even in the hilly Borders, whereas less strong riders find it a pig on the hills and it is much slower for them comparatively. I bet Dave McCraw could eke some serious speed out of it when he’s had his spinach.

    Good to see you poking holes in my argument already – the frame flex question is a good one. I’m not convinced it has a huge impact as I was almost as fast on the Pelso Brevet up Windydoors as the CHR, and the Cruzbike which was more rigid than either was actually slower. However that could have been due to my own poor technique on MBB, perhaps I was losing power through the arms in some way. I don’t find the Fuego that much slower than the CHR either and the Fuego is very flexy.

    This all leads back to my final conclusion – it’s better to ride the darn things and see how they work for you! πŸ™‚ I bet frame flex has a different effect as well depending on whether you are a spinner or a masher.

westonfront Posted on4:43 pm - May 31, 2019

On the contrary you have cleared away the hype and (almost) summarized the facts / physics. My experience on both platforms agrees completely with your conclusions. What I did seem to find, empirically last summer was that my design of bars on a std upright made a big difference to ease of hill climbing. I could simply put in more power and do so in more comfort. Crazy bars seem crazy good

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