Bike culture, and Western culture in general, can have a real fixation with speed. How fast can you get from A to B? What's the fastest you can ride? How low can you get your time? And so on and so forth.
But when designing our bikes, we focused on something different — how slow can you go?
Why? Because you can raise your top speed through training and exercise, but your minimum speed is determined by the design of your bicycle. And your minimum speed, not your top speed, is what actually limits where you can bike.
If the minimum speed for your bicycle is too high, you just won't be able to tackle certain hills, bridges and climbs. This is why you don't generally see fixies used to climb mountains.
If you've ever stalled out while biking uphill, this is why.
Here's how it works:
Depending on how strong you are and what kind of shape you're in, you can generate a certain amount of power by pedaling.
Based on how steep a hill is, the amount of power you generate will translate into a certain speed in miles per hour.
Depending on the gear ratio of the gear you're in, that speed will mean you're turning your pedals a certain number of times per minute. This is called your cadence, and is measured in revolutions per minute (RPM)..
And here's the important part — if your cadence is too low while going uphill, you'll either stall out or tire out, or even hurt your knees from having to mash on the pedals. If you've ever stalled out while biking uphill, this is why. The gear you were in, combined with your power output, resulted in such a low cadence that your pedals basically stopped moving at all and you got stuck.
The general rule is that you want to maintain a cadence of over 60 RPM while climbing. And if you get under 40 RPM on a hill, it's bad news bears — you'll be coming to a stop very soon. So the minimum speed of your bicycle when you're climbing a hill, then, is the speed you'll go if you turn your pedals at 40 RPM in the lowest gear.
Let's try an example. Say you have a fairly standard single-speed or fixie with a gear ratio of 70 gear inches. At a cadence of 40 RPM with that gear ratio, you travel at 8.2 MPH, and that's going to be your minimum hill-climbing speed.
Now let's say you want to climb a long hill that has a fairly steep 8% grade:
We'll say that you're a fairly fit commuter who can generate a continuous 200 watts of power for an hour.
On a 8% grade hill, that's going to result in a speed of 6.2 MPH.
That speed of 6.2 MPH is a fair amount lower than your minimum speed of 8.2 MPH, so you're going to be in a world of pain after a few minutes of this. Your cadence at 6.2 MPH is going to be about 30 RPM, which is just too low.
If you're wondering what climbing a hill at 30 RPM looks like, here's a guy on a fixie who's happy to demonstrate:
Sure, you can do a short sprint at a higher power output than 200 watts, but if this is a long incline, you're screwed.
For comparison, on our bikes we have the 3-speed drive setup so that if you're in the lowest gear, your minimum hill-climbing speed is 5.8 MPH. If you were climbing that same long 8% grade hill with the same average speed of 6.2 MPH, you'd be able to keep on trucking for at least an hour.
If you want to play around with the numbers yourself, here's a fun calculator that lets you try different hill grades and power inputs. Give it a whirl:
- Select hands on the tops and enter your weight and a bike weight of 25 lbs.
- Enter a slope of road of 8% or whatever grade you'd like.
- Enter a power output of 200 watts or so, and hit Calculate.
You'll get out a speed in MPH. If that MPH is lower than your bike's minimum hill-climbing speed, you'll have trouble with the hill. For reference, here's some minimum speeds for various bikes:
- Fixed gear @ 70 gear inches: 8.2 MPH
- SHIFTY CYCLES bike in 1st gear: 6.2 MPH
- Road racing bike in 1st gear: ~4 MPH
- Mountain bike: ~1.5 MPH
I hope this post helped you understand how your bicycle's gears determine what kind of terrain you can tackle. If you enjoyed it, please share it on Facebook and sign up to the be the first to hear when we launch!