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This is not a literal question so I'm not looking at / for specific models, but more a theoretical one. Let's assume I could choose between two bikes for commuting, one with a modern 22 speed drivetrain setup and another with a single speed. The geared bike weighs 30 lbs, and the single speed bike weighs 20 lbs. They cost around the same (not that it makes any difference in this particular scenario). My commute would be about 8 miles each way, so 16 miles round trip, in a major U.S. city with normal traffic and not too much elevation gain (say around 150-200 ft or so, also round trip). Let's assume the city has 4 seasons and I would commute every day. Let's say I weigh around 140 lbs. I've tried to outline both the pro's and con's below, but I'd like to figure out if I'm missing something.

Geared Bike

  1. Gears may allow for a faster overall speed if there are long uphill or downhill sections, or long open flat stretches with no traffic

Single Speed Bike

  1. There is a weight reduction vs the geared bike (in this scenario about 6%) which may result in an increase in acceleration, especially when accelerating from frequent stops in traffic or going uphill

  2. There is a slight increase in drivetrain efficiency due to a lack of derailleurs and a "perfect" chainline

If the rider regularly encounters traffic or does not ride over any substantial hills, I believe the single speed may actually be the better choice in most urban commuting scenarios. Given all of the following information, which one do you think would be faster and why? Any real world experiences and results would be welcome as well. Please disregard any other benefits not related to speed, such as the single speed having less parts = less maintenance and more reliability, generally more quality for the same amount of money spent on a single speed, etc.

Edit: I feel like everyone is missing the point of this question, so I thought I'd clarify. I own a modern 22 speed bike, a fixed gear, a single speed, a single speed mountain bike, and a relatively light 3 speed IGH. As I mentioned before, I do not want to hear about the pro's and con's of actually using each one for commuting in terms of cost, maintenance, etc.: I know about these already having owned them. I just want to know, given my particular scenario, which one you think would be faster and the technical reasons why you came to that decision. I'm not interested in discussing anything other than implications on commuting speed for this particular question.

closed as primarily opinion-based by mattnz, Criggie, Gary.Ray Mar 16 '17 at 23:51

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the question.

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    If you have access to both types of bike, consider borrowing and test-riding. Use some kind of tracking device like strava, or even a simple stopwatch to measure yourself. – Criggie Mar 15 '17 at 3:31
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    It needs to be said that weight is not a significant issue unless there are hills or you do a lot of starting and stopping. And keep in mind that your weight is added to the bike, and is by far the most significant part of overall weight. Except for fairly steep hills, +/-10 pounds is hardly noticeable. – Daniel R Hicks Mar 15 '17 at 11:36
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    I don't understand your question. You say you already have both the bikes you're asking about. If you want to know which one is faster for your commute, just get on your bikes and time yourself. Why ask us to speculate when you can just measure? – David Richerby Mar 15 '17 at 16:13
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    If you have specific data it will supersede any general analysis. Data is not bias. You are not providing a specific scenario other than 22 speed, SS, and weights. A 10 lb difference does not imply apples to apples as gearing does not weigh 10 lbs. – paparazzo Mar 15 '17 at 17:29
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    @BonJonJovi You're seeing what you're seeing because the bike that you're fastest on is the one that's best suited to carrying you on your specific journey. – David Richerby Mar 15 '17 at 18:29
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To answer this question you have to factor in all the specifics of your commute. In particular those are (including yours for completeness):

  1. Length of your commute (in time - distance is less relevant).
  2. Steepness of ascends (and descents if you accelerate down-hill).
  3. Overall 'windiness' of your city.
  4. Number of full stops and slow-downs you have to do (due to corners, crossings and traffic lights).
  5. Your physical strength and general fitness.
  6. Amount of time you are willing and able to spend maintaining your bike.

Number (1)2-5 need to be considered when choosing your gearing. If the ascends are steep (or you have expect strong headwinds often) you'd need to run a smaller gearing. That would enable you to power through the ascends and accelerate quickly - but it would also limit your top-speed. Also your long-time endurance would be worse on a high-cadence gear-setup.

Meaning: in such conditions it would probably be better to ride a couple of gears. 200%-300% difference should suffice - a range that you cat get out of a small road-race cassette.

If in turn your commute consists of shallow ascends and descends, and you pack enough strength to decently accelerate the gear-ratio you'd want to be running during your average commuting speed - then you can do just fine on a single-speed bike. I rode a commute of 27km (~17mi) on a single-speed bike for years without trouble.

If you're still undecided you might want to consider my point 6. Maintenance can be a hassle, costing time and money. But it is not necessarily much more expensive on a geared bike. On a single-speed bike you have much higher wear on your chain ring and the sprocket, due to the higher torque you put into your drive-train. On a geared bike that wear is considerably lower, since you can down-shift to accelerate, and it is spread over a number of sprockets instead of just one.

My personal choice for commuting: Internaly geared hubs

You can combine both of those upsides by running an internally geared hub. Something like the Shimano Alfine 8 should be more than enough for all commutes, and doesn’t cost more than most other geared drive-trains. It’s insanely durable and needs very little maintenance. I rode one for approximately 25-30000 km (including a technical trans-Alps tour with 20000 vertical meters) and it’s still going strong in my daily-driver commuting MTB. Of course those upsides are bought with a little lower transmission efficiency and a higher weight. But that shouldn’t be to bad for a commuter. Plus you get instant-shifting capabilities – even without pedaling! This is something I grew quite fond of, because it enables me to brake and shift later – makes it easier to keep the speed high.

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    Not getting the torque wear argument. What wears down teeth is friction. I get more miles out of $25 sprocket than an $60 cassette. And more miles from the less expensive SS chain. – paparazzo Mar 15 '17 at 17:55
  • Wear is due to friction, yes thats right. But the friction also increases with the amount of pressure on the surface. And that is extremely high when you accelerate a SS bike as compared to a geared bike. My SS chains were run down at least twice as fast as the ones on my shifted bikes. Also the chainring wears much quicker (mine was worn after one year) and costs as much as an entry- to mid-level cassette. – Marlon Mar 15 '17 at 20:08
  • OK you have much different experience than me. – paparazzo Mar 15 '17 at 20:14
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    @Marlon - Single speed chains also use fewer links so the each link will undergo a flexion cycle more frequently than a multi-speed bike chain which needs to be much longer. Plus for higher multi-speed bikes the chains are built to higher tolerances, which increases the longevity. Both probably contribute to your observed differences in chain longevity, which will also impact wear on other drive train components. – Rider_X Mar 15 '17 at 22:25
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    My experience with IGH have been the polar opposite, higher internal friction made them noticeably more slower on long commutes. Also your comment about shifting an IGH while standing makes it sound like you can shift while pedaling out of the saddle, where you probably intended to indicate that you can still shift even when stopped. – Rider_X Mar 15 '17 at 22:29
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This will heavily depend on your maximum cadence, and to a lesser extent on what your knees can handle. Specifically the maximum cadence at which you can deliver reasonable power as for many of us there's quite a drop-off in efficiency as we get close to spinning out. Your knees probably don't want a single gear that's too hard if you're going to be stopping/starting a lot (again, if you're training for track riding that might be different, but this is a commuting question).

Example case: I considered a single-speed for the short, flat leg of my (bike/train/bike) commute, but ended up getting an old cheap bike as anything better is likely to get stolen (that 30lb bike but older and more basic). In an almost completely flat ride I don't use all the gears but I do use quite a lot. It's a triple and I use the whole middle ring plus and shift into the big ring when I run out of cogs. The range of gears I get through is around 2.8--7 metres development, a factor of 2.5. On a decent sprint I reach 100 rpm in top, still accelerating, before having to slow down, on one of the longer uninterrupted stretches (400 m or 1/4 mi). To look at it another way that top gear is around 90 gear inches, higher than the 60--75 I typically see recommended for commuter SS, which feels too high for good pulling away in traffic when I stop unexpectedly in that type of gear.

In a way this disagrees with the long in

Gears may allow for a faster overall speed if there are long uphill or downhill sections, or long open flat stretches with no traffic

as I say that even a few hundred metres is enough to achieve this.

  • I felt this needed an answer from the geared side, to help people make up their own minds. – Chris H Mar 15 '17 at 10:07
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A geared bike main advantage over single/fixed gear bikes is to keep you at an efficient cadence over a wide range of speeds. This is particularly important when riding up hills. I find that on flat courses, and in the absence of strong headwinds, that advantage become quite small if you choose the correct gearing on your single speed.

A single/fixed gear bike is simpler, lighter and more efficient than a similarly priced geared bike. This is particularly true of a fixed gear bike which greatly reduce energy loss in the drive train.

So for a repeatable commute without steep climbs, you can select the gearing on your single speed to help you reach your optimal speed, based on your fitness.

If you know your functional threshold power (FTP) this can be done quite easily. Use the bike calculator to calculate the speed you can theoretically achieve on your bike and course. Then use the other bike calc to work out what gearing will keep you at your preferred cadence for that speed.

As an example if my FTP is 250W and I want to ride at around 80% effort, I'll enter a 200 Watt effort, my body weight, bike weight, riding position into the the first calculator, which gives me a speed around 31km/h.

Calculating my theoretical speed

I can use the second calculator, to select the best sprocket to pair with my 48 chain ring in order to get around my preferred 90RPM cadence for that speed (in that case 48x17).

enter image description here

As anecdotal evidence, on my commutes, I find I am consistently 10% faster on my fixie, compared to my geared hybrid. I put this down to the noticeably better power transfer, and also to a lower riding position using bullhorn bars instead of flat bars.

  • Upvoted, this is the right answer/approach to actually answering the question. – Nathan Knutson Mar 16 '17 at 16:13
1

The bike that produces the best results will be the one that optimizes these criteria:

  1. Optimal gearing for the course. This may be a single gear, if flat enough and wind is not a factor, or it may be multiple gears. It needs to be noted that a single-speed can only be "optimal" if it's the right gear ratio (or "close enough").
  2. Best aerodynamics, given the conditions. This isn't necessarily the best tuck possible, as that may be too uncomfortable to maintain, or it may make your pedaling too difficult/inefficient. It also must take into account the possible need to have a more erect posture in traffic, etc.
  3. Best bike fit. The bike should be "sized" properly and allow for the efficient operation of the pedals while still being comfortable and controllable.

Likely no single bike will optimize all of these.

(Note that I didn't mention weight. Obviously, an unnecessary 50 pounds should be avoided, but, unless significant amounts of climbing are involved, 5 or 10 pounds, plus or minus, will have relatively little effect.)

(I'll also add that the difference in efficiency between a single-speed bike and either a geared hub or a derailleur setup is minuscule. The only efficiency factor to be concerned with is the tires -- avoid low-pressure, heavily lugged tires.)

  • For an average rider, I think in most circumstances the size/fit will be the decider. – ebrohman Mar 16 '17 at 2:11
  • What about get 10 lbs from a stop to speed to 20 - 40 times? It is 8 miles in a major US city. – paparazzo Mar 16 '17 at 20:57
  • @Paparazzi - You're talking about accelerating a mass of 10 pounds to a speed of 29 feet per second. About 181 joules or 43 calories. By one account a cyclist on the flat at 20 mph produces about 185 calories/hour or 3.1 calories per minute. So this would suggest that it's equivalent to about 13.9 minutes at 20 mph. Which is clearly not right (one start of the 150 pound cyclist would be equivalent to 3 hours at speed), so there's an error there somewhere. – Daniel R Hicks Mar 16 '17 at 21:37
  • Ah, calories vs Calories (KCal)!! So divide the numbers by 1000. One start is equivalent to about 0.8 seconds at 20mph. – Daniel R Hicks Mar 16 '17 at 21:40
  • Not going to arguing with you. At 5 kg 30 km / hr - 1/2 m * v * v - I get 2250 joules. At 200 watts 11 seconds. A bit more than zero. – paparazzo Mar 16 '17 at 21:59
0

I am currently commuting around 5 to 8 km (3 to 5 miles) each way, with about 70 meters (200 ft) elevation with a basic geared bike in a city with ~2m (80 in) of snow across winter and temperatures down to -25C (-13F), and wind on top of that.

I notice that I use only one bracket, and only 3 sprockets. 1 to start because it is easier, and then the 2 next to go a little faster, especially on the way down.

In winter, the derailleur's springs get stuck, the pulley wheels accumulate dirty snow, and the derailleur's cable gets harder to pull, and doesn't pull back as well.

That results in speed loss, and also cases where I can't get the last gear, and end up using only 2, or even get stuck with the last gear I used.

Overall, as soon as winter is over (which, by looking out the window right now, is not any time soon...), I'll get a single speed for commuting.

The only question left is the gear ratio, which also depends on the shape and weight of the bike.

-1

The geared bike weighs 30 lbs, and the single speed bike weighs 20 lbs. They cost around the same (not that it makes any difference in this particular scenario).

But cost does matter. For the same cost the SS is going to be a higher quality bike. 10 lbs is big difference. Weight in the wheels more important. In this scenario I would favor the SS.

I have a geared and a single speed that weigh almost the same and I commute on my single speed. My city is very flat. About the same speed. No long stretches nor drafting in a group to need bigger gears.

SS drive train is like 1/2 the price to maintain, more reliable, and more efficient.

You may end up with a different snow / winter gearing.

A good commuter is a SS cyclocross with touring tires and you can typically find them used for some great prices.

In cyclocross racing the SS will often get combined with men 35+ years just for count and the SS kids dominate.

If you are kicking out 200 watts you are doing about 30 km/hr (no start / stop)
No start or stop you use up about 1234 k joules
Adding 10 lb the elevation adds about 11 k joules = 0.9%
20 starts with 10 more lb adds about 90 k joules = 7.3%
In a big city 8 miles you could have 40 - 100 starts
SS drive train efficiency is going to add about 1% (might be as high as 2%)
Total gain SS with 10 less lbs = 9%
I don't see how a gear is going to make up for 9% efficiency
Going from 12T to 11T is only 8% - it is more than 1 free gear
If you run a SS 32 x 12 you can do 30 km / hr with 90 rpm

  • I was using m * v * v. not 1/2 m * v * v. So just use 40 starts. I don't want to update the answer and move it to active. – paparazzo Mar 16 '17 at 22:10

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