Chainrings are literally a vital cog in the machine that is your bike. They’re the part responsible for transmitting the energy you create by turning the cranks to the rear wheel via the chain.
Here’s all you need to know about them.
So what exactly is a chainring then, and why’s it so important?
Well, a chainring is the round, spiky bit connected to your cranks that pulls the chain round. The size of a chainring (often expressed in terms of the amount of teeth on it, e.g. a 53t ring) plays a direct role in your bike’s gearing, with bigger rings meaning a higher (harder to push) gear and smaller rings a lower (easier to push) gear.
A ‘classic’ road racing bike, for example, may use a 53t large chainring, while a bike more aimed at leisure and sportive riding may use a 50t large chainring as part of a hill-friendly ‘compact’ chainset. Most modern road bikes feature a dual ring set-up with a front mech being responsible for shifting duties.
The majority of mountain bikes have moved away from having multiple front chainrings in favour of a medium-sized single ring. The thinking behind this is that by shedding the front mech assembly a lot of weight can be saved whilst also shedding the bike of niggly moving parts. On top of this, rear cassettes with a wider spread of gear ratios has meant that there just isn’t the need for as wide a spread of cogs at the front.
As far as BMX’s are concerned then the only real change in chainring technology has been their shrinking to allow more ground clearance.
Are chainrings completely interchangeable then?
Largely speaking, yes. As long as your attempting to replace them with a chainring(s) designed to work with your chainset. Your cranks will have a specific bolt layout or fitment spec so you can’t just fit a BMX chainring to your triathlon bike. Although we’re not sure why you would…
As with other parts of the transmission, chainrings will wear over time as they are ground down by the mixture of dirt and lube which forms a sticky black paste on your chain. Keeping your chain clean and lubed will prolong their life, but in the event of their being worn – watch for the dreaded ‘hooked’ or ‘shark’s tooth’ profile forming on the ring’s teeth.
OK, so say I want a new chainring for my MTB?
The type of MTB chainring you choose will depend on the age old budgetary equation; the more you spend, the lighter and better the chainring but largely speaking, they’re not too heavy on the wallet.
The number of teeth on your chainring(s) is a deciding factor in your bike’s gear ratio, with a greater number of teeth meaning a higher (harder to push) gear, and fewer teeth meaning a lower (easier to push) gear. Your gearing comes largely down to personal preference and the type of riding you enjoy, so if you are happy with your current setup be sure to replace like with like when it comes time for new chainrings.
One of the latest developments in the rock and roll world of the mountain bike chainring has been the staggered (thick/thin or narrow/wide) chainring. Put simply, the teeth are correspondingly thick then thin resulting in a profile which grips to the chain and aids chain retention. Often to the point where many riders no longer feel the need to run a front chain guide. Ditching a triple ring setup and investing in a staggered chain ring is a great way to breathe new life into an aging drivetrain.
And what about chainrings for my road bike?
Generally, all road chainrings are made of aluminum but the five-arm spider is the norm, as opposed to the four-arm MTB standard, so that’s five bolts as opposed to four.
The most common types of road chainset are the standard double, the compact double and the triple. The standard double is the ‘traditional’ chainset type beloved by racers and anyone with the legs to push big gears over not-so-hilly topography. Typical gearing for a standard double is 53t-39t which offers big enough gears for competition usage.
Then there is the compact double which gives the same number of gears (2×10 or 2×11) but smaller chainrings meaning lower gearing options for leisure and sportive riding. A typical compact setup is 50t-34t. And finally there’s the triple which tends to feature predominantly entry-level and touring bikes via three rings with profiles around 52t-42t-32t.
The latest development in road cycling technology is actually an idea which has been around in various guises for a while. Oval chainrings seek to maximise the legs natural motion and are favoured by some of the peloton’s fastest racers.
Let’s talk about BCD
Aside from the number of teeth, you may also need to know the Bolt Circle Diameter (BCD) of your chainrings in order to replace with ones of an identical size. Now, there are ways of working this out but it’s complicated and involves decimal points… We recommend a much more straight forward/lazy method of consulting the website of the manufacturers involved. Trust us on this one!
Need to know: BMX chainrings
BMX bikes use a single chainring (also often referred to as a sprocket, chainwheel or front cog) up front which mounts directly onto the crank’s spindle and arm so there is no need for a spider. You just need to ensure that your new chainring matches your cranks.
There are two types; spline drive (where the chainring is machined to fit onto splines on the end of the spindle) and the more common bolt drive (where the chainring is bolted onto a non-splined spindle).
In the case of spline-drive cranks, you will also need to be sure the sprocket matches the number of splines on the spindle, and the diameter of the spindle, as standards can vary from manufacturer to manufacturer.