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What gearing do you need to ride in the mountains?

  • Writer: Jamie
    Jamie
  • Jul 14, 2019
  • 3 min read

Updated: Jan 28


Rotor 11-30 cassette, bike drivetrain, chain, gears, gearing, mountains, road cycling
Your gearing can make or break your cycling holiday in the mountains

If it's your first visit and you live in a less mountainous country, it can be hard to know what gearing you need for a road cycling holiday in the Pyrenees. When your rides tend to feature short climbs of 5-10 minutes, you can afford to let your heart rate climb because you'll soon be over the top and able to recover. In the mountains, you have to settle into a rhythm that you can sustain for well over an hour.


The simple answer is to go low - it's way better to have gearing that’s a little too low than too high. And if you're less fit, or perhaps not quite as skinny as the pros, then of course you need to go lower still.


How to test your gearing before going to the mountains

A good way to test is to find the longest hill near to where you live, 10 minutes and around 8% ideally, and to ride repeats of it until you have totalled around 30 minutes of climbing. Keep the pace steady, as if you're on a big day in the mountains. The aim is to have a gear that allows you to maintain a manageable effort and a comfortable cadence even on the last ascent.


If the effort and your heart rate creep up in order to maintain a reasonable cadence (pedalling rate), or if your speed slows and your cadence drops to an uncomfortable grind, then your gearing is too high. And if you're thinking that you could maybe tough it out, imagine climbing like that for two hours up the Col du Tourmalet!


I'd say that, even if you’re really fit, 34x28 is the minimum. And if you're less confident in your fitness, then 34x32 is a good bet. There are some really steep sections on many of the climbs and you will appreciate being able to tackle them without resorting to a lung-searing effort or knee-bursting low cadence. This is no place for a 53/39 chainset!


Lac de Cap-de-Long, Pyrenees, mountains, cycling, climbing, what gearing, cassette size, long climb
Huge climbs such as Lac de Cap-de-Long (above) can take over two hours so you can't afford to be over-geared

If your rear derailleur has the capacity, a cassette that goes up to 32t, 34t or 36t will make a significant difference and is the most affordable way to lower your gearing. Remember that if you fit a larger cassette you will likely need to extend or replace your chain, or be very diligent about avoiding cross-chaining into big-big.


Shimano v Campagnolo v SRAM lowest gearing options

The latest Shimano 12-speed groupsets all offer an 11-34 cassette, creating a 1.0 gear ratio with a 50/34 chainset. The 105 groupset has an 11-36 cassette for a super-low ratio of 0.94.


Campagnolo offers a 1:1 bottom gear at all levels, plus ultra-low options of 45/29 x 11-32 (0.91) in Super Record and 48/32 x 11-34 (0.94) in Chorus.


SRAM continues to lead the way with ever lower gearing. The entry-level Rival eTap AXS groupset goes down to a winch-like 0.83 with 43/30 chainset and 10-36 cassette. The top-tier Red and mid-level Force eTap AXS groupsets offer a sub-compact 46/33 chainset and 10-36 cassette, giving a 0.92 ratio.


On the road, a 1:1 gear or lower makes almost any climb possible for almost any rider, but you have to remember that you will be travelling more slowly and a major climb, such as Luz Ardiden at 14km, could take well over two hours. The likes of the Col du Tourmalet, 19km on the Luz side, could represent an endeavour beyond three hours. Something to keep in mind when planning your days.


3T Strada, SRAM Force 1x, road race bicycle, drivetrain, gearing, cassette size
A 1x (single-chainring) drivetrain shows its compromise most in the mountains

SRAM also offers single-chainring (1x, pronounced 'one by') groupsets that can reach down to a 0.91 ratio with a 40t chainring and 10-44t cassette. A 1x drivetrain will be at its most limiting in the mountains where you will experience a greater breadth of speeds than anywhere else. Yes, you can achieve a low ratio with a 40t x 10-44, but the jumps between gears will be unpleasantly large and you will run out of gears by around 45kph/28mph, leaving you unable to pedal downhill even on the gentle valley descents. In short, 1x is heavily compromised in the mountains.


Pyrenees, road cycling, climbing, mountains, pipe cleaner limbs, skinny cyclist, Hautacam
Get your gearing right, and you can savour every climb

12 Comments


Red and Force eTap AXS offers a sub-compact 46/33 chainset offers 10-36 & 10-39 cassettes - which one would provide lowest gear to assist me climbing hills?


Would it be the 10-39 cassette provide maximum torque?


Also , would 12 gear using this setup be much slower than an 11 gear using 50:34  & 11:34 cassette?


this may be of interest

https://www.omnicalculator.com/physics/gear-ratio

Edited
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George Lyons
George Lyons
Mar 10, 2023

WHT crankshaft do I need to change a genesis 9000 mtb to make it a hybrid bike cranksetdo I need

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Jamie
Jamie
Mar 10, 2023
Replying to

Hi. There will definitely be options available, but I can't tell you exactly what without seeing the bike as it depends on a few things, including front derailleur capacity; bottom bracket type and options; groupset; the cause of that slipping; and also what you want to achieve. I strongly recommend that you visit your local bike shop, with your bike, where they will be able to advise you. If you simply want to use your MTB on the road, it would probably be enough to change the tyres for some narrower and faster road tyres. I hope that helps.

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Daniel Coote
Daniel Coote
May 09, 2022

Jamie - not sure you will pick this up almost 3 years later, but I have SRAM Rival eTap AXS Groupset with a 46/33t chainset, with 12 speed 10-30t cassette. Would this be considered a good option for really steep hill climbs e.g. the Fred Whitton in the Lake District & alike? Regards Daniel

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Jamie
Jamie
May 24, 2022
Replying to

That would be a super-low bottom gear that should winch you up almost anything. It will definitely feel like a big difference.

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Jamie
Jamie
Jul 17, 2019

Hey Beccy. Yes, this is just aimed at road riding (I'll make that a bit clearer!). For gravel I'd suggest that a 1:1 gear (eg 34x34, 42x42) is essential, and maybe even a little lower. The gravel is steep and rough here. I'll do a separate post about prepping your gravel bike to ride in the Pyrenees. Thanks for the good question :-)

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stewkingjr
Aug 27, 2021
Replying to

Hi, i still ride a triple, 48/36/24 x 11-34. While admittedly it's set up for touring, which i do most summers, i couldn't imagine attacking any of the major climbs with a 1:1 gear ratio as my bottom gear. I know that's just me, but two hours of continuous uphill cranking is a long time. There is no opportunity to rest by coasting. When i rode Mt Washington, i was happily in the 30 tooth cassette gear with an occasional shift to the next cog (which might have been 27 teeth?). Only on the occasional "flat" (as in "less steep") section was i able to shift one further to the 24 (?) tooth cog. I would take your advice and…

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beccy_waters
Jul 17, 2019

Hey Jay, just checking this advice is primarily for road-riding? How would gearing change if we choose to do gravel riding? I'm 5ft 5 tall and wide and definitely not race-fit!

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