What is a Groupset on a Bike?

Heard the word ‘groupset’ in cycling conversation? Nodded along sagely whilst thinking, “What in the world does THAT mean?!”? Well, don’t worry. You’re not alone. Groupset is actually the collective name for a series of bicycle components. I’m going to run through exactly what this word means and what each of the bike parts are that are included within it.

To paraphrase a little from Pulp Fiction, it feels like the path of the righteous cyclist is beset on all sides by the inequities of not being able to afford all the bikes you really want and the tyranny of bike snobs who try and confuse and confound with technical terms.

I may not be blessed but, in the name of good will and charity to fellow cyclists, I will attempt to shepherd you through the valley of jargon darkness to understanding what this term is all about.

So, what does the phrase ‘groupset’ mean on a bike?

In simple terms, it’s all the components that are involved in moving and stopping the bike.

This includes three broad categories:

• Power transmission
• Gear shifting
• Braking

It doesn’t include:

• The bike frame
• Wheels
• Saddle
• Handlebars
• Pedals (though this is sometimes up for debate)

We’ll go through the three categories of Groupset components now and look at each of them in more detail.

Understanding the components in a bike’s groupset

So, we know that a bike’s groupset is the collection of components that make it go…and make it stop. To recap, these are: the power transmission, the gears and the brakes.

Within each of these umbrella categories are a number of different components. Some of which you may already be familiar with, so you may never even have seen (Bottom bracket, I’m looking at you).

Let’s see what they are.

Power transmission

‘Power transmission’ is a large category that includes the most components, so it’s a good place to start.

The purpose of these components is to take the rotational energy that you generate from pedalling and turn this into rotational energy in the wheels (specifically into the back wheel as the front wheel just gets pushed along by the rest of the bike).

There are three elements to the power transmission:

• Crankset
• Chain
• Rear cassette

Crankset

The pedals are attached to the crank arms, which is part of the crankset.

The crankset comprises the crank arms, the crank spider, the chain rings and the bottom bracket.

The crank spider is a star or spider shape and attaches the chain rings to the base of the crank arm.

There will be between one and three chain rings of varying sizes on a bike’s crankset and these hold the chain at the front end.

The bottom bracket holds all the other parts of the crankset onto the bike inside a hollow tube at the bottom of the bike frame. Its job is to allow the crankset to turn freely as you pedal.

Chain

The chain connects the chain rings to the rear cassette, transferring the pedal power to the rear wheel.

When you shift gears, the derailleurs will move the chain from one side to another (literally ‘de-rail’ it). This will allow it to move from one chain ring to another, or one cog in the rear cassette to another.

It’s important to keep the chain clean and well lubricated. It has a circuitous route to follow around the cogs and derailleurs and will tend to skip teeth on the cogs, or fall off altogether, if it isn’t well maintained.

Rear cassette

The rear cassette, or cogset, is made up of a number of different toothed sprockets.

It is attached to the hub of the rear wheel and the chain will pass around it (and through the rear derailleur underneath).

Moving the chain from one sprocket to another is the job of the rear derailleur.

Gear shifting

Not all bike have gears, of course, but those that do will generally have the following:

• Gear shifters
• Front and rear derailleurs

The purpose of gears is to move the chain from one combination of chain ring / rear sprocket to another.

Changing ‘up’ a gear will enable faster speeds on flat roads or downhills.

Changing ‘down’ a gear will allow more easier climbing of steep slopes.

Gear shifters

The gear shifters are attached to the bike handlebars (although, for those who are old enough to remember, back in the day they were attached to the down tube).

The right gear shifter controls the rear derailleur at the back wheel.

The left gear shifter (if you have one) controls the front derailleur near the pedals.

On most ebikes, mountain bikes, and hybrid bikes, the gear shifters tend to be a separate pair of levers next to the brake levers – within easy reach of your fingers.

Most modern road bikes, by comparison, tend to have the gear shifters and brake levers integrated into a single unit – one on each side of the handlebars. The levers are pulled towards you to brake, with a combination of side pushing and button/levers handling the gear shifting.

Front and rear derailleurs

The front derailleur is located above and slightly behind the front chain rings.

The rear derailleur is located below the rear cassette.

Their job is to push the chain to one side or the other to enable gear changes.

On modern bikes these feel like an oddly archaic device but, with no better alternative, these are what most bikes use. They’re fairly complicated and fiddly and can be prone to failure and the best way to combat this is to keep them clean/lightly lubed and check for damage regularly.

Braking

Sadly, there comes a time when you and your bike need to stop or at least slow down. That’s when the brakes come in to play.

There are a number of different components involved in braking, the key ones being:

• Brake levers
• Brakes
• Disc brake rotors

Brake levers

We’ve already seen that brake levers can be standalone units on the handlebars (as they are on electric bikes, MTBs, hybrids, and fitness bikes). Or they can be integrated with the gear shifters, as on modern road bikes.

Brake levers pull towards you to slow you down. That’s obvious. What’s less obvious is the means by which that pulling force gets translated into braking force at the wheels to slow you down.

There are two methods for this: via cable or using hydraulic brake fluid.

Brakes which press against the wheel rims will use metal cables. Brakes which use a metal rotor disc at the wheel hub instead (known as ‘disc brakes’) might use either cable or hydraulic fluid. More expensive bikes and brake systems will tend to use hydraulic fluid as this can give more confident stopping power and the brakes will also self-adjust as the pads wear down.

On the downside, hydraulic disc brakes are difficult (and costly) to maintain – they’re a job for the experts. Whereas metal brake cables can generally be adjusted easily and cheaply at home.

Brakes and disc brake rotors

There are different types of brakes on bikes, which can normally be put into two broad categories: rim brakes and disc brakes.

Both have their pros and cons. On e-bikes, which tend to travel at higher speeds, it’s worth investing in better quality brakes, such as disc brakes, for confident stopping.

Compatibility issues

It’s tempting to think that, in terms of the components of a groupset, you can cherry-pick the ones you want – like a bike buffet.

Spend a little more to get better quality derailleurs, spend a little less on brakes to compensate.

This is sound in theory but sadly, in practice, mixed groupsets is likely to cause major compatibility issues.

In many cases, there can even be forwards and backwards compatibility problems within the same brand.

My advice is that, unless you really, really know what you’re doing, then it’s best to replace like with like and keep within the same component brand and model when you’re changing out parts of your groupset.

Conclusion

So, there you have it! The answer is that the groupset on a bike is the collection of components that transfer power from the pedals to the wheels, shift gears and brake.

No longer will you need to hope for a change in topic when this comes up in bike conversation.

Now, you can nod wisely, say, “ah, yes, groupsets…just be careful about compatibility issues if you’re planning to upgrade your brake levers”.

Then you’ll be able to go on to say, “hey, do you know what they call a Quarter Pounder with Cheese in Paris…?”