Tune your Transmission

Choosing the right groupset for you will maximise your exertions and, hopefully, not break the bank. Pete Bonfield shows you what to look for

Groupset is a term often bandied about by those tech heads that love to talk bike kit. But just what is a ‘groupset’ and what do you need to know about them? Does your bike have the right groupset for your biking needs or should you be looking to upgrade? As you’ve probably guessed, this feature aims to demystify groupsets.


What is a groupset? 

A groupset comprises the majority of the components required to turn your frame into a bike you can ride. Bike-component manufacturers introduced the term several decades ago to describe the assembly of components they sold, and it allowed them to simplify the marketing of their products by offering different levels of performance and quality under common labels. In general, groupsets include the components cited in the ‘Meet the family’ section below.

Bizarrely, a groupset doesn’t cover all the components you need to build your frame into a complete bike; the handlebars, stem, tri-bars, wheels, tyres, inner tubes, tape and saddle aren’t included. These are usually sold separately or as ‘finishing kits’ by enterprising bike shops that want to sell complete bikes to their customers.

The reason for this anomaly is that the original groupset maker, Campagnolo (or Campag) from Italy, didn’t make these particular components and therefore didn’t include them in their groupsets. Shimano from Japan, the other main contemporary manufacturer, did the same when they introduced their groupsets in the Seventies.

These days, both supply the majority of groupset components used on bikes around the world, and are utilised by mainstream manufacturers like Specialized, Trek and Giant on the complete, ‘off-the-peg’ bikes they offer. They’re also used on the majority of bespoke bikes built from the frame up, either by specialist frame manufacturers or triathletes looking for custom-build bikes.

Although Shimano and Campag dominate the groupset marketplace, they’ve always faced competition from smaller manufacturers. French outfit Mavic have experimented with their own groupsets at various points in time while, more recently, American producer SRAM has entered the road market, offering a couple of new alternatives.

How to choose

Understanding the differences between the various groupsets on offer can be a bewildering process if you don’t keep up-to-date with the latest models. The main players, Campagnolo and Shimano, offer a range of levels of groupset, which allow you to select the option that best suits your pocket and performance needs.

So which should you choose? Well, clearly the starting point should be your budget. It’s no use deciding you need a top-of-the-range groupset if you can’t afford it. In actual fact, you probably don’t need to buy a top-end version at all. All Campagnolooo, Shimano and SRM groupsets perform well. Gear changes and braking action may feel a little smoother on the higher-end groupsets, but all will perform as required, providing reliable and durable performance.

But if they’re all pretty similar in function, why is one more expensive than the other? Firstly, weight. As you travel up the respective ranges, the different materials are used to produce a lighter final product. The extra cost goes towards maximised design features and higher-quality materials such as carbon-fibre composites, top-quality aluminium and/or titanium alloys. However, you can end up paying quite a lot for a relatively modest reduction in weight.

The weight difference from the budget options to peak-price versions is less than 2kg. When you think about it, that’s really not much – especially when many of us are probably carrying more than that in excess fat around our bellies!

It’s far better to save money by losing weight yourself, rather than spending more to compensate with a high-level groupset. You’ll run faster, too! The modest extra weight in lower-specification options is also not that much of a penalty unless you’re riding on really hilly courses. Improved fitness and aerodynamics will be much more significant in reducing bike split times on flatter courses.

It’s important to balance the pros and cons of groupset quality versus frame, wheels, tyres and aerobars, as well as your ability and ambitions, when deciding what you should buy. More aerodynamic and lighter wheels with a good set of tyres will give you a more considerable advantage than the next level of groupset.

Alternatively, a slightly more expensive frame may save weight and be stiffer, resulting in more efficient power transfer and greater comfort than a lower-cost model. In short, it could be better to invest more in the frame than a higher-specification groupset.

Mix ’n’ match

It’s generally not a good idea to mix and match your groupset. There are exceptions, but try to use the same level of component throughout. You can use, say, Shimano 105 for most of the components, but upgrade the derailleurs to Ultegra for a little weight reduction. This may make you feel a bit better psychologically, but will make almost no practical difference to your performance.

It’s particularly advisable not to mix different manufacturers’ groupsets for the drivetrain and control elements – for example, chainset, chain, derailleurs, rear cassette and gear/brake levers. While they might be roughly compatible, they’re unlikely to mesh smoothly.

If you’re aiming for real top-end performance, you may wish to substitute high-level bits of kit made by specialist manufacturers for the components offered in your groupset. Carbon-fibre brake calipers and carbon-fibre cranks are good examples.

A word of warning: make sure you upgrade your chain at the same time as your cassette or chainrings to ensure smooth running of your new drivetrain. A worn chain on a new cassette or a new chain on an old cassette may cause your chain to jump.

Make it specific

Having decided which level of groupset meets your needs for performance and budget, there are a few other factors to tailor your groupset components to your requirements. These include:

Crank length The standard length sold is usually 170mm but, if you have longer legs, you may wish to go for 172.5, 175, 177.5 or, if you’re very tall, 180mm. Conversely, if you have shorter legs, 165mm cranks may suit you better. Either way, the aim is to maximize your pedalling action.

Chainrings/chainset What sort of riding are you planning and what level do you perform at? Standard chainsets have a 53-tooth (53t) outer chainring and a 39t inner ring, which is fine for general riding and racing. But if you’re new to the sport, less strong, prefer spinning or plan to ride over particularly hilly terrains, maybe go for a compact chainset, which usually has a 48-50t outer ring and a 32-36t inner ring. This provides a lower range of gears for climbing up long hills.

If you aim to use your bike over a wide range of hilly and flat routes, you’d be better off buying a triple chainset, which may have a combination of 53t, 48t and 32t chainrings. With a triple you can ride pretty well anywhere. If you go for this option you’ll also need to specify the corresponding front and rear derailleur, and gear/brake lever options, to allow you to change between the chainrings

Cassette These are almost always nine- or 10-speed (nine or 10 sprockets), where the first sprockets are sequential (12t, 13t, 14t, 15t, 16t, 17t) before moving up in two-tooth jumps (19t, 21t, 23t and 25t). This sprocket range is fine for most riding. Alternatively, you may wish to specify a wider-ratio cassette (say 12-27t) if you’re planning to attack the gradients and have a double chainset.
If you pick a compact chainset and envisage fast descents, go for an 11-up cassette (a cassette starting with an 11t sprocket) or you’ll risk ‘spinning out’.

Brake calipers If you ride a bike with mudguard clearances – for example, a commuting, winter or touring bike – you could require long-reach calipers so your brake blocks can reach the wheel rim (rather than to the side walls of the tyres). Only a few groupsets offer this option.

Seatpost dimensions Different frames may require different diameter seatposts. Most frames use 27.2mm diameter but some require 26.8mm. It’s also wise to check if you need a longer seatpost to compensate for compact-frame geometry (sloping top tubes). Check before you buy.

Bottom-bracket threads These come in two types – European threads and UK/US threads. Check what your frame requires before buying your bottom bracket (BB). You’ll also need to find out the length of the BB axle you need. A triple chainset, for example, needs a longer BB axle.

Headset These are available in different sizes and types (threaded and threadless). Once again, check before you buy.

Drivetrain decisions

Pick the groupset that suits your budget and needs. Don’t overspend to the detriment of your frame and wheels, which will give you greater benefit. Remember: the differences between low and top-end groupsets are small and become more expensive the higher you go. But, whatever groupset you buy, make sure the crank length, chainrings and cassette range suit you.

Enjoy choosing your components and be pleased with the outcome. You needn’t be driven by functionality alone – all groupsets are functional. Let your desires influence your choice a little, so that you get a lift from being proud to own and ride your bike.


Pete Bonfield has coached triathletes of all abilities for the last 18 years, specifically on the bike



The centre part of the wheel, consisting of axle, quick-release levers (for clamping the wheel in and out of the frame), bearings and location holes for the spokes. Note: Shimano and Campag offer full-wheel options that include hubs, spokes and rims. 


The axle and bearings that are threaded into the frame onto which the cranks are secured. 


The cluster of 8, 9 or 10 sprockets attached to the rear-wheel hub. 


The component that applies the brake blocks to the rim of the wheel to control your speed and bring you to a stop.


The levers fixed to your handlebars, and enable braking to take place – by pulling the lever towards the handlebars – and gear changing – through pushing the parts of the lever sideways or pulling the inside trigger down. Connected to the brake calipers and front and rear derailleurs by cables.


Consisting of the crank arms – one end of which is secured to the bottom bracket, the other to the pedals – and chainrings (either two or

three, for road/tri bikes).


The changer (or mech) that moves the chain between the inner and outer chainrings.


The changer (or mech) that shifts the chain across the cassette of sprockets on the rear-wheel hub.


Connects your chainset to the rear cassette to transfer the power from your pedalling legs to the back wheel. 


The assembly of cups and bearings that secure the front forks to the frame, to allow steering. 

Also, occasionally the seatpost is included – the aluminium-alloy or carbon-fibre post that supports the saddle.