I have notice that as it gets colder here in MN my average speed is slowly decreasing. Is this normal? I should add that I have been cycling for only 5mos and average anywhere from 17.5mph-18.5mph on my 8mi commute but now it seems like I'm barely breaking 17mph avs.

Physics.. science shows cold air is denser than hot air,
you push the air to go thru it, it pushes back.

also colder days tend to be windier

Tire pressure? If you're filling up your tires indoors, they'll be a lot lower out in the cold. (Topping them off outside makes for a faster ride, but do bleed some off before bringing it back indoors.)

It also takes longer for the body to warm up and there are extra clothings.

My fastest rides have always been when the temps are in the range of 65F to 80F.
Above or below that, I'm slower.

For me, it's always been the wind blowing in my face. Lately, it's been going SW, so it takes me twice as long to get to work as it does to get home.

The added bulk of more clothes slows me down a little.

If the wind isn't shifty, shouldn't a tail wind help in the winter?

Given that my route is somewhat circular, any wind will be a tailwind, headwind and side wind at some point and I've gotten my best times when there is no wind.

I've been slowing down during these last few days because of my cool/cold weather clothing. I dress in such a way that during the first 10 minutes or so, when my body hasn't generated much heat, the clothing will keep me warm and when I have warmed up, I take it easier so that I don't arrive at work drenched with sweat and soak my shorts, tights, fleece top and balaclava.

At this point in the season, my commuting is less about trying to achieve best fitness but instead about keeping my fitness or at least, slowing its decline, so just by cycling the 32km each day, I am happy.

I'm slower in cold even after accounting for bulky or loose clothes (with or without), denser air, lower humidity, wind, and the time it takes to warm up. All of these are factors, but even eliminating them I'm still slower. I think that means there must be physiological reasons. You see on the web (so it must be true ) that thermal stress impacts performance by about 10% but that seems a little glib to me.

I think it's due to a combination of several reasons. I'm sure I'm oversimplifying, but:

1. Body temperature is normally related to our circadian rhythm, so if the cold lowers our body temperature it will make us sluggish until we get warmed up.

2. I think that glycogen conversion is slower at lower temperatures and we instead rely relatively more on fatty acid oxidation, so it feels like we have less energy available. I could be way off base on that though.

OP don't worry about it, this is the start of real muscle mass building. your avrg will come back up next spring and you'll be so strong and your thighs will be so thick. do not falter, do not quit.

For all or most of the reasons already stated above and perhaps a few more, it is normal. I'm in MN too and it happens every year. Just expect it and know that it's going to take a bit longer and plan accordingly.

i find that studded tires slow me down A LOT more than the cold weather of winter.


but seriously, this topic comes up every winter and i think a majority of us daily 4-season bike commuters in cold weather climates find that cycling in 30 degrees is just slower than cycling in 70 degrees, for a variety of reasons.

Everyone rides slower in winter. Air is about 10% denser at freezing than in warm summer temps. You're wearing more clothes, that increases drag and decreases your mobility. You may be running fatter tires or studs, possibly at lower pressures. Around here it tends to also be windier, and the wind is almost always from the west which is a headwind on the way home (there's usually little wind in the morning, so I don't get a tailwind then as a bonus)

In summer my times are about 35 minutes if I'm pushing it, 39 or so if I'm just noodling along. In the winter on the same route, 43 minutes at best, as much as an hour if it's really bad (20-30 MPH headwind into driving snow).

It's a wash...

The denser air also provides more oxygen to your lungs to allow you to breath and pedal easier. It's too bad the air is so thick that it slows you down!

You've also got the change in viscosity inside your hubs to think about. The grease or oil (probably grease) is much more viscous in cold weather, making internal drag within the hubs greater. Same thing with your bottom bracket bearings, the grease will become more viscous. Between the hubs and the bottom bracket you get a pretty substantial increase in mechanical drag. Then, if you're using a heavy oil or wax on your chain, the lube becomes more viscous which means the chain doesn't flex as easily which means it takes more effort to get it to conform to chainring and cog. This is to say nothing of biological factors that work against you. As your body inhales cold air, and throat becomes cold, your body's natural reaction is to increase mucus production; which can restrict breathing. Then, as mentioned already, you have to propel yourself through denser air. And, your tires become stiffer and don't conform as easily to bumps in the terrain, which means a loss of efficiency. The list of factors working against you during cold weather just goes on and on.

Well it also depends on which way it is blowing..

you talking Air speed, or Ground speed?

heads or tails? it flips, here , seasonally.

Laden, or unladen?

African, or European?

Thanks for all the replies guys, I'll keep riding and use this weather as a training session to help me get better when spring come.

I notice the same thing. I blame part of it on heavier clothing due to both weight and wind resistance. I also think that the grease in your wheel and BB bearings gets stiffer. Last winter I switched to SuperLube silicone grease on one bike and it helped.

Maybe 10% of the forum will get that, youse guys. The rest will need a youtube clip or something...

Not our fault if the whippersnappers aren't educated in classic culture.