Word at the water cooler is that the days of the Race and Pro Compact cranksets are numbered… I’m hearing all road bikes will be fitted with a standard 50/34 crankset with the 52/36 Pro Compact and the 53/39 Race cranksets going the way of special-order only.
That leads to my question: Is there a noticeable difference between a pro compact and a standard compact crankset that the change would matter?
It just so happens I can speak from experience. I have one of each. A 52/42 I don’t ride anymore, a 52/36, and a 50/34. The 52/36 and the 50/34 both roll with the exact same cassette, also – 11-28 10sp. Now please, bear with me, this is going to get a little geeky, but the idea is to get the average cyclist to think a little deeper than average on this.
So, to get into the nuts and bolts of this. First, it’s important to look at the pluses of the bigger “pro compact”. This is simple to do because there’s one; top-end speed. While you’ll suffer a little on the low-end, the top-end of the bigger chainring will definitely make it a little easier to either keep up with the group downhill, or bury it. There’s another side to that, though; you’re probably not fast enough to need the extra two teeth. I know this because I’m pretty fast but I’m not quite fast enough to miss them. You’re going to have to be in the 25-mph (40-kmh) average crowd to need the extra available in a 52 tooth chainring. Escape velocity with a compact 50/34 crank and an 11-28 cassette is just a shade over 40-mph (64-km/h). At 120 RPM you’ll be at about 42-mph (67-km/h). Escape velocity on a 52 tooth chainring is almost 45-mph (72-km/h).
In other words, unless you’re in the upper crust of the cycling world, and I mean the top 5% in the world, you’re not going to miss the two teeth.
Normally, I’m for the coolness aspect of cycling. A 52/36 crankset is far “cooler” than a 50/34 because the big gear is bigger. Not so in this case, though if I were ignorant of the 50/34’s benefits I would side on the bigger gears. I’m not, though. Having ridden the 50/34 extensively, I’m very much in favor of it over the 52/36 for a cyclist of my caliber (22-mph average on a fairly flat open road course). The compact crankset fits the 11-28 cassette gearing better for a flaw in the gearing selection when the cassette gears start jumping three teeth per cog. Again, what I’m about to get into is for the faster crowd 20-mph average and above. If you’re in the 18-mph crowd, there’s no circumstance I can imagine where the 52/36 is better than the 50/34.
With the 52/36 combo, there’s a hole between 18.5-mph and 21-mph where the cogs skip three teeth to fit everything in to an 11-28 cassette. It’s the same for both a 10 and 11 speed cassette. For solo cruising, that’s too big a jump exactly where you’re used to cruising. The 21-mph gear is a little bit on the tough side in a cross or headwind and the 18-1/2-mph gear is a little too easy. With the 50/34 combo, the hole is between 15 and 18-mph. Both gears are going to be a little easier than you’d normally cruise at. Faster gearing after that hole jumps two teeth per cog which means a 10-rpm jump between gears. This is easily more manageable.
On the other hand, when I’m riding with my group, I’m just fast enough to not have a problem with the gearing gap with the 52-tooth crank. In our group we’re almost always cruising between 21 & 26-mph so the 18.5-mph to 21-mph hole isn’t as “in your face”. Still, cruising with the group on the Trek, with the 50/34, is a little easier to find the right gear to match the cadence and speed I want.
So how deep does the rabbit hole go?
My friends, when the Venge’s chainrings wear out in a few years I’ll probably opt for the 50/34 combination over replacing them with what’s on there now. There’s just no reason for me to stick with the bigger combination, other than vanity. As cycling and vanity goes, the vanity is only important in how one looks on the bike. When it comes to how one rides, one looks best when one rides one’s best. Being honest, for me, riding my best is done on a 50/34 compact.