Compact cranksets started appearing on road bikes in the mid-2000s. It’s hard to believe that 20 years have passed since their inception. Their onset revolutionized road cycling and opened the category to a much wider audience, improving rider performance and enjoyment overnight.
If you’ve been grinding gears for a while now, struggling to make it up some of the moderate to more challenging climbs in your area, you are a candidate for a compact crankset.
If you have ever watched professional road racing, you may have noticed that the chainrings on their bikes are large. Their outer rings can be in the 53T to 55T range or even bigger, combined with a 39T or a 42T inner ring. Victor Campenaerts raced on a 58T at the 2022 Dwars door Vlaanderen for him to attack the final descend!
So what is a compact crankset and how is it different from a standard crankset?
A compact crankset combines a 50T outer ring with a 34T inner ring. It provides additional lower gears to amateur cyclists to make hill climbing easier.
Benefits of a compact crankset
1. More low gears for climbs
Most of us need help on the lower end for moderate to steep climbs, and a compact crankset will do that.
The combination of a compact crankset with a larger cassette such as 28T, 30T, 32T, and 34T allows amateur cyclists to go up steep hills while still maintaining a respectable cadence.
The versatility of compact cranksets makes them a standard on road bikes since they provide the best of standard road racing doubles and touring triples. Amateur cyclists typically ride less than 30mph (48kph), but they can maintain a higher and more efficient cadence while losing a minimal amount of top speed with a compact crankset.
Think of standard cranks like a sports car. You can go super fast with them, a welcomed feature, but not imperative, and certainly not one you use very often.
Jeff Solomon has developed a visual representation of gearing differences between a compact and a standard crankset. Play around with the gearing combination to visualize them.
2. Tighter gear spacing
Besides a wider range of gears, compact cranks allow for tighter rear cassette spacing, which means less violent cadence jumps and more subtle changes in power when shifting.
When cyclists start to lose fatigue, they typically only need a small change to maintain speed. A tighter gear spacing with a minimal jump of only one or two teeth between gears on the rear cassette can make or break your cadence.
Compact gear ratios offer fewer redundant gears and less overlap. This means you have more useful gears to choose from and you’ll spend more time with your chain in a straighter line with your cassette.
3. Minimize front shifts
A 50/34T compact crankset lets you handle more hilly terrains without the need to shift to the small ring.
For example, on those days when I’m feeling spry, I can get away with the 50-25/28T to power it over smaller climbs or rolling terrains. Minimizing front shifts reduces wear on the chain, chainrings, and front derailleur and creates fewer opportunities for the chain to drop too.
More reading : How to Shift Gears on Road Bikes
3. Save some weight
If you’re running a standard crank or a triple, switching to a compact will save weight simply because it requires less material to fabricate them. Fewer teeth mean smaller diameters that require shorter chains, so you save some weight from the chain as well. The total savings can be somewhere between 50g to 100g.
Can I use compact chainrings on my current setup?
It depends on your current crankset setup.
- Five-bolt. If you’re running the older five-bolt system, you’ll have to check your BCD (Bolt Circle Diameter). The BCD is measured between the center of the chainring bolts. BCD measurements for a five-bolt system are typically 110 for compact (50/34T) or semi-compact (52/36T), and 130 for standard crankset (53/39T, or larger).
- Shimano Hollowtech 2 (4-Bolt) crankarm can be used for 50/34T, 52/36T, 53/39T, and 54/40T (12-speed) chainrings.
- SRAM AXS (12-speed) crankarm can be used with 46/33T, 48/35T, and 50/37T chainrings.
- Campagnolo 4-bolt crankarm (11 and 12-speed) can be used for 50/34T, 52/36T, and 53/39T chainrings.
Do pro cyclists use compact cranksets?
Compact cranks aren’t just reserved for recreational cyclists, the pros use them too on ultra-demanding and long-distance hilly stages in major pro events like the Tour de France, Giro d’Italia, or Vuelta.
Retired climbing sensation Alberto Contador rode with a 34T inner front chainring and 12-32T cassette. Now you know how he made his victories look so easy.
Of course, it takes more than low gears to win in the pros. Their job is to ride, ride a lot, making them much fitter than everyday cyclists. You’ve seen their legs on TV, they are rather impressive, but their superior strength and fitness can push much bigger gears at the same cadence.
Enjoy it on the tube, but best not to try it at home.
Are new bikes equipped with a compact crankset?
It depends on the value of the bike and its use. Low to mid-range road bikes usually come with a compact crankset. Mid to premium range road bikes often come with semi-compact crankset (52/36T). The popularity of standard cranksets (53/39T) is slowly declining and is only seen on the pro cyclists’ bikes these days.