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!
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.
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.
