Gear Ratios Explained For Triathlon | Choosing The Right Cassette, Chainrings & Shifters

The gearing you have on your bike is such an important factor when it comes to improving your performance and your enjoyment, yet it’s possibly one of the most commonly forgotten things. So, let’s take a look at the gearing you should choose for a triathlon?

In association with Shimano.

Gears really do have a huge impact on our riding. Gears that are too low, or too easy, may leave you spinning out, wishing you had a couple of harder gears. Whilst, gears that are too high, may bring you to a grinding halt on a steep climb.

Firstly you have the chainset. Simply put the lower the number of teeth on the chainrings the easier the gear. So, there are a few common options with these. There is the standard, with a 53t outer ring, and a 39t inner ring. You also have the semi-compact, that has slightly easier gears, with a 52t outer ring, and a 36t inner ring. Then you have the compact, that is even easier again, with a 50t outer ring, and 34t inner ring.

The other area you can customise your gear ratios is with your cassette. It sort of allows you to fine tune and optimise your gear selection and you’re not short of options either. Shimano cassettes come in a number of ratios including 11-25T, 11-28T, 11-30T, 11-32T, 12-25T, 14-28T! Whereas a larger number on the chainset means harder gears, on the cassette a larger number actually means easier gears. So, for example, I have quite a nice range on my bike as it goes from 11 teeth on the smallest sprocket, up to 30 teeth on the largest. So, it’s very well suited to a hilly terrain because I have a range up to 30 teeth.

There are so many options when it comes to gear ratios but we hope this video helped you to understand what is available. If you found it useful, don't forget to give it a thumbs up and share with your triathlon and cycling friends 👍

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[TiberiusPaulSavu]

What always helps my friends who aren't into bikes understand gear ratios is when I explain that we're actually talking about a ratio. For example, on a compact, 36-tooth chainring, 18-tooth cassette cog means you'll spin your legs once, while the wheel spins twice. On a superhuman 55-tooth chainring, and an 11-tooth cog, you spin your legs once, while the wheel spins 5 times. Bring cadence into it and it all makes sense as to how it translates into speed. That's just my gear ratio 101 way of explaining things to bike newbies (not that I'm not a tri newbie myself).

[xGshikamaru]

I need to confess: I use a triple chainring on all my bikes. With a 30teeth chainring I don't need to worry about any climb even if I bonk, with a 53 chainring I can go faster while descending. I chuckle when people talk about 1x drivetrains, as if having a 1x would save you 50W... Electronic gears may be nice but they are massively overpriced. 1 SRAM Red eTap or Dura-ace DI2 groupset costs as much as all my bikes combined, and I'm not even talking about Campy EPS groupsets. Just the bar-end shifters cost you an arm...

[toddholmes]

When discussing cassette and chainring sizes, you snuck in an important point: “provided they are compatible”. It might take another full video to explain what derailleurs (and chains) are compatible with the various options. Or just go to your trusty compatriots on GCN. 😀

[McStoolio]

Love watching these clips - good memories of Lanzarote.

[Motorsportsgeek]

53/39 with 11-34, best of both worlds

[elirocha]

Installation was quick and easy. It doesn't make a whole lot of noise, and it's worth every cent.

[julianengel]

Maybe it would be worth highlighting that a compact crankset would not be compatible with more teeth and that it is important to look for the bolt circle diameter (BCD) to ensure you got the right fit.

[BikeBodyMind]

Been seeing some road bikes lately with clip on aero bars and Sram Red blips on them. Seems like a good idea for people who don't (or can't) get a full on tri bike.

[johnbouttell]

In the 2014 Tour de France, Tony Martin used a 58 chainring to win the 54 km TT by 1:49; mind you, you've got to be able to turn a 58 chainring. Easier said than done.

[lindatodd]

Thanks for explaining the chainrings and gear ratios, it always been something I have never quite taken the time to fully understand and it is not that complicated is it! It is a shame the pricing of Di2 tends to add 1k to the price of a bike, I just could not justify it when I bought my TT bike. I hired a road bike in Lanzarote last year which had Di2 and I loved it.

[michaelcloherty]

I have a 39 50 with a 40 cassette with a road link have all the gears i need easy downhill easy on the flat

[michaelcloherty]

Maybe swartzenager might push a 55 crank and a 11 cog but who wants to be swartzenager

[edparry]

Better explanation than GCN! Many thanks

[phxrsx]

Compact crank with a 11-28 on the back is fine for 90% of age groupers.

[jason_woodbury]

When switching chainrings and/or cassettes, do you have to be thinking about he length of your chain needing to be adjusted as well?

[AdrienFloor]

Thank you, that was very interesting !

[Northwindbreeze]

Are you driving by a lawnmower at 4:50 mate?

[chefroadman]

Need help which is the best choice for my bike i used 53/39 chainring, 11-34 or 11-28t sprocket?

[natefdot]

What is your Opinion on 1x gearing for road bikes? IS it the future? I personally could see it sweeping through Draft legal Triathlon within the next few years. Im considering going 1x on my road bike.

[alanbayliss]

Might have been good to point out that with cassettes with 30+ teeth sprockets you will need a medium cage rear mech to cope with their size (as opposed to the short cage which most bikes seem to come with).