7-speed vs 8-speed bike – Differences explained

The difference between a 7-speed vs 8-speed bike is small. They often share similar parts and only differ in the extra gear of the 8-speed bicycle. But does that mean that they are essentially the same bike? Let’s find out.

What is the difference between a 7-speed vs 8-speed bike?

7-speed vs. 8-speed bikes are very similar. They often share the same parts except for the cassette (or freewheel) and the shifter. The chain and rear derailleur are often the same part, but there are exceptions to this.

So let’s dive into the main differences between 7- and 8-speed bikes.

The Difference in gear ranges

Obviously, there is one additional gear on an 8-speed bike compared to a 7-speed bike.

That means that there are more steps within the gear range on an 8-speed bike.

But does that mean that an 8-speed bike also has a wider range of gears itself?

So is the lowest gear lower and the highest gear higher on an 8-speed bike?

How to measure the gear range

The easiest way to measure the gear range is to count the teeth on the smallest and largest cogs (or gears).

• The fewer teeth the smallest cog has, the higher the highest gear.
• The more teeth the biggest cogs gas, the lower the lowest gear.

So, a cog with 12 teeth will be a higher gear than one with 14 teeth, for instance.

While all bikes are different, the gear ranges of a 7-speed vs 8-speed bike are very similar.

Most 7 and 8-speed cassettes are in the 12T-34T range. That means the smallest cog has 12 teeth and the largest cog has 32 teeth.

Now, you can upgrade your cassette on either bike to an 11T-42T for instance. That increases your gear range without changing the number of speeds.

You will just end up with bigger steps between speeds.

Therefore, it is very conceivable to have a 7-speed bike that has a wider gear range than an 8-speed bike. And to be therefore faster.

There are, however, usually more wide-range 8-speed cassettes and freewheels available.

So the 8-speed may have a bit of an edge here.

But you may not notice the difference in real life.

Are 7-speed and 8-speed bike parts interchangeable?

Cassettes

Cassettes compatible with Shimano and SRAM use different spacing on a 7-speed vs 8-speed bike.

Seven-speed cassettes usually have a 5 mm distance between cogs, and eight-speed cassettes have a 4.8 mm distance.

That means you may be able to put a 7-speed cassette on an 8-speed bike.

But you will have to increase the shifting distance of the derailleur to allow for smooth gear changes and likely add a spacer onto the hub.

Unfortunately, an 8-speed cassette does not fit on a 7-speed bike without swapping in a new derailleur and shifters.

You will also usually not be able to add an 8th cog to a 7-speed cassette. The width of those 8 gears would be too great on most bikes.

Be cautious of cassettes vs freewheels

Keep in mind that many 7 and 8-speed bikes use freewheels instead of cassettes.

A freewheel is a self-contained unit that has all cogs pinned together and mounted onto a central hub.

They are especially common in 7-speed (budget) bikes.

If your bike uses a 7-speed freewheel instead of a traditional cassette, converting your bike to an 8-speed bike requires you to add a new 8-speed freewheel, derailleur, and shifters.

Cassettes will not fit onto these bikes without replacing the entire rear wheel or adding a different hub to your existing wheel.

Chains

Chains are mostly interchangeable between a 7-speed and an 8-speed bike.

As we saw before, the difference in distance between cogs is only 0.2 mm.

That means that most modern chains fit onto both bikes without issues.

Shifters

For obvious reasons, 7-speed shifters are not compatible with 8-speed bikes.

Or it would otherwise make it a 7-speed bicycle.

But 8-speed shifters can be made to work on a 7-speed bike if you are okay with having an “empty” 8th gear.

However, switching to this empty 8th gear will pop the chain off the cassette unless you are able to adjust your derailleur and shifter just right.

Both scenarios are not great.

So converting the number of speeds on a bike should always be followed by upgrading shifters as well.

They are cheap enough to be a no-brainer.

Derailleurs

A rear derailleur is a small arm that physically moves the chain onto the next cog when shifting up or down.

Thin wires connect the derailleur to the shifter. By changing the wire tension, the shifter makes the derailleur derail the chain to jump into another gear.

Generally speaking, derailleurs are designed for a specific number of speeds.

So most 7-speed derailleurs are incompatible with 8-speed bikes and vice versa.

Some derailleurs like this one from Shimano work on both 7-speed and 8-speed bikes, however.

7-speed vs 8-speed bike – Which is better?

7-speed and 8-speed bikes are too similar to say which one is better.

It is more important to pick the right bike for a particular situation (city, trails, racing, etc.) than to obsess over speeds and gear ranges.

That being said, an 8-speed bike is usually a little more versatile across the board.

That extra speed often translates to slightly better acceleration and higher speeds.

As I said in a previous post, an 8-speed bike is the perfect all-around bike for most people.

It has a very usable gear range for everyday life, low maintenance requirements (no front derailleur), and is often inexpensive.

But a 7-speed bike is no slouch either.

In fact, I am quite happy with my 7-speed city bike and wouldn’t change a thing about it.