One of the most common questions we get asked is; ‘I see the chainset and cassette options but what do these mean / refer to?’ We can well understand the confusion! It’s easy for even experienced cyclists to feel quite overwhelmed. Especially when faced with the choice of what handlebar width, stem length and cassette ratio to specify, to name but a few.
Here then is our beginners guide to gearing explained and how to choose the right fit for you.
So, when we say gearing what specifically are we talking about?
We are referring to the size of the chainrings (how many teeth does it have) at the front and the cassette cluster (also known as cogs or sprockets just to confuse matters further) at the rear. Basically, the parts that the chain revolves around.
Now for the nitty gritty, how does selecting one option over another affect how the bike performs?
To put it as simply as possible the smaller these are then the easier it will be to spin the pedals.
Normally on most bikes there are 2 chainrings, an inner and outer. The inner is always traditionally by virtue of its small number of teeth the climbing ring. And the outer chainring is the best suited for flatter terrain and descending. They are offered in the following standard ratios;
Known as ‘compact’, both the inner and outer chainrings are quite small so this is best suited to hilly terrain and is especially popular with newer cyclists.
Known as ‘semi-compact’ this was introduced because some riders felt that the 34/50 chainring combination was a little too low. By this we mean that on the flat and particularly when descending riders tend to spin out or run out of gears. So, Shimano opted for this ratio which with the 36 inner chainring still offered assistance on the climbs. But, also in having a larger outer ring of 52t would perform better on flatter terrain or when descending.
Back in the 90’s and 2000’s before the advent of compact this was the traditional chainring combination. With both the inner and outer chainring being of a large size this only makes this suitable for amateur racers, time-triallists or someone who avoids hills like the plague!
The new kid on the block is the single ring chainset which is derived from mountain bikes . On these bikes a lack of a front derailleur is considered an advantage so it does not collect mud and debris and jam up as a result. It has seen something of a surge in popularity in road bike circles thanks to the advent of the gravel / adventure bikes. These are equipped to perform as well off-road as on they do on tarmac surfaces. Therefore, the lack of front derailleurs again can be seen as an advantage if the bike is to be used mainly off-road. These are normally offered in sizes between 38 and 42 teeth.
Contrary to the chainrings the larger the sprocket size in terms of how many teeth it has the easier it is to pedal. So, a larger biggest sprocket at the top is more advantageous for climbing. Depending upon what groupset is purchased there will normally be a collection of sprockets ranging from 8-11 in number. Cheaper / lower end groupsets will have 8 sprockets and those at the higher end will typically have 11 or 12.
You therefore need to select an appropriate cassette for the terrain you will riding over on a regular basis. Wider ranged cassettes such as 11/32 or 11/34 are the best choice for climbing.
Slightly closer ratio cassettes such as 11/25, 11/28 or 11/30 are better for riders with a good level of fitness or who prefer flatter terrain.
Combinations / Recommendations
Chainrings 34/50 and cassette 11/32 or 11/34
What we here at Ribble refer to as a climbers ratio and one we recommend to customers who regularly ride over hillier terrain or are new to cycling. (note the small chainrings, large sprockets and longer length rear derailleur in the image above).
Chainrings 36/52 and cassette between 11/25 and 11/34
For riders that have a high level of fitness or if the terrain is not generally hilly. It is therefore worth opting for slightly less extreme gearing than when compared to the climbers option. This offers the following benefits;
- The gap between gears is not as high, ideally you would keep the number of sprockets as close as possible. The reason for this is to avoid loss of pedaling rhythm when changing gear. As well as the loss of power generated through the pedals due to this loss of rhythm. Therefore, opting for smaller spaced cassettes like an 11/25 or 11/28 avoids this jump in gear change. This also has the added benefit of making the pedaling action smoother.
- When descending the gears do not spin out as fast, by this we mean that you can pedal for longer before the chain loses any traction . You then have to freewheel until you slow sufficiently enough to start pedaling once more.
- Specifying larger chainrings and / or closer cassette ratios also make the bike faster on the flat.
The size of chainring that is selected will also affect what size cassette is required. If maximum off-road capability was selected it would no doubt be a 38t chainring on the front and 11/42 on the rear. Single chainring set ups are now very popular with MTB’s, CX bikes and Gravel bikes due to their low gear ratios.
For any road bike a larger chainring and / or a more closely spaced cassette is more beneficial.
We hope this guide helps you to gain an understanding of what to choose when buying a new bike. If, however you still need assistance then please contact one of our highly experienced customer service team. They are always available at the end a phone on 01772 963400 or by email at [email protected]