How fast can a 21 speed go? (Different bikes compared)

Have you ever wondered how fast a 21-speed bike can go? Today, we will explore this answer for hybrid bikes, mountain bikes, and road bikes. We will also see how much the fitness level matters.

How fast can a 21-speed bike go?

A 21-speed bike can go as fast as 44 mph (70 km/h). But that requires a fit rider and a light bike with good gear ranges. The better question to ask would be: How fast can YOU go on YOUR 21-speed bike?

How fast can you go on a 21-speed bike?

Your speed on any bicycle depends on two things:

Your fitness level and your bike.

The determining factor is probably about 75% your fitness and 25% your bike choice.

Because the sad truth is this:

Yes, you will be faster on a top-of-the-line road bike than on a basic mountain bike. Especially over long distances and on paved roads.

But a Tour de France rider on a mountain bike will still be faster than you if you ride that pure-bred 30-speed racer. Probably in both sprints and long distances.

The rider is just the bigger factor in all of this.

So let’s take a closer look at what speeds you can expect, based on your fitness level first.

We will then look at what difference the bike choice makes and how uphill / downhill affects your speed.

What is the top speed of a 21-speed bike?

Let’s assume that we are talking about a regular (hybrid) 21-speed bike for this.

The average rider can expect to top out around 36 mph on a good bike.

A rider who is in really good shape may be able to push it past the 44 mph mark.

But keep in mind that this is not a modern road bike purpose-built for racing.

Road bikes usually come with more gears and allow you to maintain higher speeds for longer.

What is the average speed of a 21-speed bike?

Again, this is more about the rider than the bike.

Most beginners may average around 8-15 mph (12-24 km/h).

An average rider may average about 17-23 mph (27-37 km/h).

A trained (and fit!) rider may average as much as 28 mph or more (45 km/h) over a long distance.

How fast can a 21-speed mountain bike go?

An average person can expect to go as fast as 30 mph (48 km/h) over a short distance on a mountain bike. 15-20 mph (24-32 km/h) is a realistic average speed for most people.

Generally speaking, a mountain bike is always going to be slower than a comparable road bike. MTBs are heavier, have bigger tires (more resistance), and have a more upright riding position (more drag) as I explained in the article Are mountain bikes good for the road?.

Below is a list of different types of 21-speed bikes and how fast you can expect to go.

For this comparison, we will only look at the Average Rider from Table 1 above.

As you can see, upgrading your bike will make you faster.

But it will rarely ever be faster than a fitter rider.

How fast can it go downhill?

To go truly fast, it helps to go downhill.

But the bike’s downhill speed is not as dependent on the number of speeds.

Rather, it is often limited by the highest gear range.

So a single-speed bike can be just as fast as a 30-speed bike.

The bigger question is: How steep is that hill and how long can you roll for?

If you have a big enough hill, a 21-speed bike can realistically reach over 60mph (100km/h).

But that is hypothetical and often not safe to do in real life.

At these types of speeds, the average bike is not safe anymore. Most budget bikes are not made for these types of downhill speeds. The brakes, frame, and tires were not designed for these stresses and are not safe.

The only way to safely reach speeds of 60 mph or more, is on a purpose-built road bike.

How fast can it go uphill?

How fast a 21-speed bike can go uphill depends on the hill and the lowest gear ratios of the bike. And again, more than anything else it depends on the fitness level of the rider. Realistically, uphill speeds vary between 1mph and 25mph.

The steeper the climb, the slower the bike.

If it is really steep, it may even be too steep to ride uphill at all.

As a general rule of thumb, the only gears that matter, in this case, are the low gears, or even ultra-low gears.

Those are the biggest cogs on your rear wheel combined with the lowest front chainring.

The bigger the largest rear cog and the smaller the front chainring, the easier your bike will crawl up the hill.

21-speed bike gears explained

The 3x drivetrain has 3 chainrings in the front and 7 cogs in the rear. This setup is often found in budget or older 21-speed bikes.

The advantage is that it gives you 1 chainring for climbs and acceleration, 1 cog for everyday cruising, and one cog for downhill and top speeds.

The disadvantage is that it may have redundant gear ratios that don’t give you 21 unique speeds.

Some of the front-and-rear combinations can be quite similar.

Here is a great in-depth explanation by Yellow Jersey about how bike gears work if you want to learn more.

Modern bikes often use a 2x drivetrain that combines 2 chainrings in the front with up to 11 cogs in the back (effectively a 22-speed bike).

The 2x drivetrain is generally more efficient and has fewer redundant gears.

Are 21-speed bikes fast?

Now you have seen how fast 21-speed bikes can be.

But are they fast compared to other bikes?

Let’s summarize:

• For most people, 21-speed bikes are fast enough. But they are usually not the fastest bikes around.
• 21-speed bikes are great for the everyday rider. They have enough gears for acceleration and top speed, as well as trails with uphill and downhill sections. You can tour with them and use them around the city. And most importantly, they are often less expensive than “faster” bikes.
• Remember that you are limited to 21 steps to get from the slowest to the fastest gear ratio – you are not limited in speed itself.

But if you are looking for a truly fast bike, you may want to upgrade to a road bike instead.

Compared to an 18-speed bike, however, it is probably going to be faster – unless you compare it to a modern 2×9.

How about a real-life test?

If you’re interested in seeing a real-life test on bike speeds, check out my article How fast can a 7-speed bike go? (Faster than you may think).

In it, I took my humble 7-speed hybrid bike for a spin and went as fast as I could. The results truly surprised me and shows that the number of gears is less important than most people think.