I commute to work everyday. For the same effort I feel I am putting out (sometime with a PowerTap to measure so I know I am pretty close to my normal average), I am definitely slower in winter than summer, like about .5-1 mph slower. What's going on?

Yes. I don't have a power tap, but I'm almost certain I'm not putting out as much power, or putting as much effort into it.

Yes.

No matter how hard I ride, my spin bike doesn't go anywhere.

get a better spin bike

Yes. My FTP has dropped 10% since September. I'm hoping that some of that loss is due to the most recent test being done indoors (versus the prior being conducted outside), and after a 2 week lafoff including a light head cold.

No. We are all faster all the time.

Yes. I'm pretty sure it has something to do with the 10lbs I gained over the holidays.

https://www.icebike.org/Articles/SlowerWinter.htm

It's the drag of extra clothing layers.

I go faster, I use it to warm up my freezing body.

the air density being that large of a deterrent is very interesting.

either way i feel much slower commuting during the winter months.

My century rides take longer so I spread them over several days. It still counts, right?

Ha!

If I was any slower than I am in the summer, I would fall over

Wrong thread.

Definitely slower. A lot of it is just the cold, I think, but the studded winter tires don't help.

Cold, dry air is denser and can easily drop 1kph from your speed at a given power. Also fenders, mudflaps and bulky clothes don't help.

I haven't ridden a road bike for enough years to really tell.

Oh wait, this is BF? Yes, I am slower, definitely, by 0.75-1.25 mph.

I am much slower. My average in summer is 18 mph, in winter 15-16 mph. I guess because I get older every winter

Slower here, too. I adhere to the "denser air" theory. Seriously, I go a lot faster in hot weather; noticeably slower (1-2 mph on average) in winter.

My winter beater bike is about 10 lbs heavier then the unsalted roads warmer weather bike. Plus the winter winds seem to be a lot harder to push against and the slush at the side of the road is difficult to pedal through, etc.. Yes.

I'm not slower on warm days.

Compared to ?

This is a cool read... as at least it validates that I didn't suck more in winter.

There's also the wind chill thing - the faster you go, the colder it feels. Makes you think twice when you feel the urge to drope the hamer.