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

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. (whooshing)
(upbeat music) Now, when I first started cycling, people would often ask me questions like– – What gear ratios are those? What size chain ring is that? – I’ll be honest, I
didn’t have the foggiest. It didn’t occur to me to check, let alone consider changing them, but they really do have a
huge impact on our riding. Gears that are too low may
leave you spinning out, wishing you had a couple
of extra harder gears. Whilst gears that are
too high may bring you to a grinding halt on a steep climb. (upbeat music) The chainset. Simply put, the lower the number of teeth on the chain rings, the easier the gear. So, there are a few
common options with these. You have the standard, which I have in my hands here right now. It has a 53 tooth outer ring
and a 39 tooth inner ring. And then you have a semi-compact, which I actually have on
my bike here right now. It has a 52 tooth outer ring
and a 36 tooth inner ring. And then you have the compact,
which is even easier again. It has a 50 tooth outer ring
and a 34 tooth inner ring. So, should you be looking to do a relatively flat triathlon
course where you’re going to be carrying a lot of
speed as I am right now, you may want to opt for a
slightly higher chain ring setup. Something with more teeth, so that you can keep the power
down without spinning out. Something like a 53/39, perhaps. So, there are a couple of
ways you can go about this. You can completely change the chainset for a new one as I have here, which is relatively straightforward. Alternatively, and possibly
a slightly cheaper option, is to just replace the chain rings, providing that they’re compatible. On the flip side of this, if you’re planning on doing
a hilly triathlon course, then you may want to opt for a slightly easier chain ring setup so you can get up punchy hills like this. So to help, you might want to go for a semi-compact like
I’ve got on my bike, 52/36 tooth chain ring setup, or even a compact 50/34. There are also other options
that you’ll particularly see in time trialling or with
advanced triathletes, where you see them riding
a 54 tooth, a 55 tooth, or even a 56 tooth. And actually, they do go bigger again, but they are pretty few and far between. (gentle bells chiming) 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, for example, come in 11-25, 11-28,
11-30, 11-32, 12-25, 14-28, I mean, it goes on. And, whereas a larger number on your chainset means a harder gear, a larger on your cassette
actually means an easier gear. So for example, on my bike right now, I’ve got 11 teeth on my smallest cog, and then my largest cog has 30 teeth. So, I’ve got quite a
nice range for any hills. There in my hand I have an 11-25 cassette, so if I was to do a flat triathlon, which is relatively fast, it’s unlikely I’m going to
need a 30 tooth sprocket. Instead, I’ll go for something with a slightly smaller range so I get a finer adjustment
between each gear. And, the beauty of cassettes is that you can simply swap them
out with the right tools, so you can change them from race to race or course to course. (upbeat music) Whilst the gears you choose
for a triathlon are important, the way you shift between
the gears is equally so. And, it does vary between bikes. So if you’re riding a road bike like me, you may have dual control
shifters on the handlebars. So, this allows you to
shift through the gears and brake all within one unit. But, if you’re riding
with clip-on aero bars, that actually still
means you have to shift through the gears with the same method, but then we have the
emergence of electronic gears. They shift smoothly and precisely. They shift quickly and sharply. They even shift through
multiple gears under load. They really have taken
cycling to another level, and whilst you may argue that you have to charge them from time to time, one plus, and it really is a big plus, is that they don’t
deteriorate in bad weather. And in fact, you can
actually place the shifters wherever you like on the bike. So, you can have them on the drops, or perhaps even start putting them on the end of your clip-on aero bars. We’re onto TT bikes and
things get quite interesting. See, with mechanical group sets, you’ll find the brake
levers on the base bar, and then gear shifters on
the end of the aero bars, which is fine, but you don’t
always sit in your aero bars. Say you are cycling upright
and you want to shift gear, you have to lean forward to do so. Not a problem with that, but with the introduction
of electronic gears, such as DI2 from Shimano, you now have gear
shifters on the aero bars and the base bar. And from my experience this
has been a huge benefit, especially for technical or hilly courses, where you’re spending a
considerable amount of time out of the aero bars and you still need to shift gear from your base bar. And then to take things a step further, Shimano have brought us Synchro Shift, both for road bikes and TT bikes. So, what does this mean? Well, for their electronic gears, as you are to shift through your cassette, it would adjust the front mech
accordingly, or on its own. So, to give you an example of this, say you’re about to hit a
climb, you’re in your big ring, and you shift through your gears on your cassette to an easier gear, it might drop your chain
into the small ring, but that’d be quite a sudden jump, right? So, it actually adjusts
the gears on your cassette to reflect this in a Synchro. And it works vice versa, and
in so many different ways. Clever stuff, eh? Gearing can seem like
such a complicated area, but it’s really not as
bad as it first seems. So, make sure you give it some thought before your next triathlon, do some research on the course profile, and make sure you’ve got the
right gear ratios for that. If you like this video,
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24 comments on “Gear Ratios Explained For Triathlon | Choosing The Right Cassette, Chainrings & Shifters

  1. 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.

  2. 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).

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

  4. The difference between 53t and 50t is only 6%. Imo you should choose rings and cassette based on what low gear is needed. 39/25 is about 56% higher than 34/34.

  5. 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.

  6. 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).

  7. 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…

  8. 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.

  9. 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. 😀

  10. 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.

  11. heard this same speech before.. how many triathletes switch chainsets or cassettes depending on the race? honestly i'm not in that category..

  12. My overlly competetive friend doesnt understand gear ratios,he was using a bigger gear at the cassete and the smallest chainring on my 3×7 mtb with 20t or less teeth and is fuming mad at me after losing at a kid using a bmx

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