How does power differ on standard vs compact cranks? If FTP is about 225 and average cadence is about 85 which is better? Will either crank make a difference beyond obvious changes due to chainring sizes/speed. What kind of impact does it make on the athlete?
Shouldn’t effect anything. Watts are watts. You should be able to spend a bit more time in the center of your cassette which is a positive. But it won’t feel easier.
I’ve just swapped from compact to standard as I picked up a cheap ultegra group that came with 53/39. Was a bit worried I’d struggle on the hills but I think I’m going to be ok bar the few 24% climbs near home.
My ftp is somewhere near 250w for reference. I’m going to enjoy not being in the 11 cog as much as my front derailleur always rubbed/needed trimming. No other noticeable differences so far.
As long as you have all the gears you need, you’ll be fine. However, if you were to buy something new, I don’t recommend standard cranks. Given your power output, go for a compact crank next time. People fret over spinning out, but unless you are racing, this is not really a concern. There are very few roads where I spin out my compact crankset (because there is a thing called traffic). Even in races a compact crank is fine. In fact, even a 50:12 ≈ 46:11 should be plenty for most.
Making sure you have a sufficiently low gear, including a bail-out gear, is of much, much, much higher practical significance.
I have always run compact cranks, and prefer to spin at a higher cadence (95+).
when the roads pick up, i’d rather not be in my easiest gear doing a wattage way above my threshold. Even on the downhills, I have never been dropped because I didn’t have a 53 big ring.
As said above, having a bail-out gear is much more beneficial!
It doesn’t make any difference to power. Power is simply your bodies output, so isn’t affected by external factors.
Having lower gears simply means you have the option to go slower at the same power, or steeper at the same cadence
Semi-compact is where it’s at.
Gear inches are gear inches so if you’re in a 53:17 at 85rpm you’re going to go as fast as 50:16 at 85rpm.
However, bigger gears are more efficient. So watts required to maintain the same cadence/speed in the 53:17 gear combo is a little less than watts required in the 50:16 gear combo. But we’re talking really small differences. Like, 500mW.
I swapped to compact R8000 from standard cranks and could not be happier with it. I spent a bit of time looking at the ratios/speed with the compact and they suited me really well.
Where you ride is a massive part of this question. If you have large/steep hills, then you may need the compact. If you live in the flatlands, go for the standard hands-down.
Here’s my take on the whole chainring gearing debate (this goes for mountain bikes as well)
I live in NEARLY flat michigan, I’m talking 200ft elevation gain over 60 miles flat, and I run a compact 50/34 chainring setup with a 11-28 cassette on the road. When I’m racing, I know that I can basically spin out at around 39 mph, in the 50/11. On the mountain bike, I run a 34 single ring with a 10-42 cassette. Michigan is pretty well known for it’s singletrack races being super fast, I’m talking an average of 15mph over the course of some 2+ hour events. I still run the 34, even though many racers will run a 36 or 38.
I would much rather ride and race my bikes near the bottom of the cassette where gear jumps aren’t so wide, and it keeps my chain line straighter than if I was running larger chainrings, thus riding further up on the cassette.
Petar Sagan rides a standard crankset (or maybe he rides something larger!?), I most certainly don’t need to ride with pro gearing.