This topic has been discussed before. But I think I've thought of a new reason for the bike to be slower in the extreme cold.

In previous threads, I've heard mention: air density, tire rubber (less pliable = more rolling resistance), hub grease (mentioned that one myself a few times), and the extra layers, all add up to slow you down.

but I came up with a new possiblity while riding yesterday (-10F) that I haven't heard or read before. At least it's new to me, I haven't heard or read it mentioned before

Shrinkage. yes the same thing that happens to men in cold water, can happen to your bike parts.
Have you ever adjusted your cones? just a degree or two in either direction can make the difference between loosey goosey, just right, or way too tight. What happens when your axle gets cold? it shrinks, contracts, gets shorter, trunkates, thus compressing your cones & races around your bearings, making your cones too tight and slowing you down.

Yes i know, your bearings are shrinking too, but They're probably not the same alloy, so they're shrinking at different rates.

this might also hold true for cartridge bearings, Inner rings contracting on bearings, but probably not to the same extent, since there isn't as much metal in that direction of contraction.

It's my hypothesis.
I'm sticking to it.

Slightly related, I was thinking earlier today, while trying to undo some seized bolts, if heating up or cooling down the metal would make it easier or harder to remove the bolts, or if the bolt & the surrounding metal (+threads) would expand/shrink at the same rate.

Ya, for exactly this reason I leave my wheel in the deep freezer for a few hours, right before I tension the cones...

Axle and ball(bearing) shrinkage can be an embarrassing problem which is best avoided!

A few weeks ago somebody (rumrum6 ?) said their wheel didn't spin nearly as freely in cold and I wondered it might be due to something like this.

Might have been just the grease though. I had a Nissan car from the late 80's with a manual transmission. It took some extra oomph to get that shifter to move when it was really cold. Got better as the transmission warmed up. I eventually started using a different gear oil with better winter operating characteristics and that helped a lot.

Only saying this because lubricants can really be affected by cold and it wouldn't surprise me if it made a significant impact on bikes.

A "normal" grease doubles in viscosity for every 17 C / 30 F temperature drop. There are special tricks in motor oils which make the temperature dependence less, but that also makes them expensive.

SO... could we use a grease that is synthetic.. which isnt affected by cold as much.. .

I use the synthetic oil in the snowblower.. what a difference cranking.... starts easily on the coldest days.

It's this crazy new chemical called water, gets inside bearings when it's warm and also when you ride in snow/rain, then freezes when it's colder and thus you go slower.

Hey! I think i've seen them selling this stuff at gas stations. It only comes in bottles right? And almost always more expensive then gasoline? Ya thats the stuff

I'm PAINFULLY slower in the winter.

I wonder if your muscles themselves are somewhat less capable. With all that cold air nearby, you think a lot of the body's energy would go to keeping those areas warm.

Moving is the best way of maintaining body temperature in cold weather. That's why you start to shiver when you're cold enough, muscle movement warms up your body. Being surrounded by cold air doesn't make your muscles slower or weaker per se. Elite XC skiers cover 50km of very demanding competition track in about 2 hours, in temperatures anywhere down to -15C. I know I would be hard pressed to ride the same track in summer in that time. The temperature limits in international competitions (-15C means precautions, -25C means delayed or cancelled competition) are to avoid frostbites on exposed skin (face) and effect of cold air in lungs. And those limits are for professional athletes, in a sustained exercise at the top of their performance. Their muscles seem to be doing fine.

In conditions where I ride, cold air is more of a psychological factor, if even that. In my experience, biggest slowing factors for me as a commuter and utility cyclist are rolling resistance (caused by studded tyres, lower PSI and snowy/soft surface), extra weight and layers on self. In very cold weather, drivetrain and hub lubricants, although those tend to warm up somewhat during riding.

--J

You should add that those skiers don't wear much in the way of insulation, just some thin base layers and a toque...

Yup, of course you will feel the cold, but ARE you cold? I think too many people dress like they shouldn't feel the cold and end up being cold due to overheating and sweat. You can run naked in the winter if you wanted too, the trouble comes when you stop. You will then lose the battle to generate enough heat... THEN it is time to layer up with your dry insulations. There was some mad professor around here who did this to prove a point, went out into the winter and survived the night with almost no gear... simply by moving. OF course, below -25C i don't recommend

My excuse is that, I'm just getting slower as I age and can't spin like I used to.

I think I'm slowest in Winter because I have to control my breathing to avoid excessive mucus buildup. When you breath as quickly as you can through your mouth, your body compensates by moving extra mucus.

In the summer time, I can breath more quickly and I don't have to limit myself so much.

Of course the lube would have an effect. The shrinking and enlargening of certain materials do make a difference though I doubt it's much when you are in the "normal" temp range of 35 to 80 degrees F.

Sail area. This factor IMO is a primary in the winter. This 2x polyester jacket I wear over everything greatly increases my 'shadow'.... wind/air resistant surfaces. Then the 2-3 layers on my legs.. the sorel boots.. I guestimate an 8-12% increase in sail area... at least. Then the added 12-14 lbs of clothes weight...

For me it's about the cardio workout.. slower is fine.

Be interesting.. for some math type.. to figure the horsepower it takes.. to move a bike with a certain weight.. under wind with sail area. I suggest in horsepower offhand... another unit of measure.. who knows. Some way to quantify the work done.........

I think you're really on to something here. I'm usually in one of the highest gears, but today at 5 F I was in the middle ring in front in one of the lower gears (back) and I was hurting to get some kind of speed going. Not fun. Very weird. Yesterday the same thing, in the morning it was cold at 9 F, but the afternoon was just fine with 29F, had a good speed and everything.

i have a great invention that adds about 10% to my winter speed: ski goggles.

keeping the blasting cold out of your eyes makes a huge difference and actually adds to the top speed i can go.

Oh thank god!! I thought I was just out of shape! Now I have an excuse...

In hindsight I have to say though that maybe the fact that one of my front brake pads was slight stuck at the wheel (rust, frozen) might have something to do with my slowness (duhhh!)

I don't think anyone mentioned that colder air is more dense. Also, we tend to limit our output when we know it will cause a heavy sweat inside our insulation.

Still ... I suspect that the malleability of the tires and viscosity of the grease in the components play a much bigger factor. Race car drivers will talk about the temperature of there tires affecting handling. This is the reason they swerve their cars under caution. I would suspect that tires have a "sweet spot" temperature wise with minimal rolling resistance. Above which ... they start coming apart.

Of course ... it depends on the speed you're going. I have to wear more layers for on road cycling than off road.

I've heard that it's harder for your body to absorb oxygen when the air is very cold. Anyone know if this is true?

No, i don't think that is true... in fact the air is denser when it is colder(at the same altitudes)... so there is more oxygen in your lungs, though breathing denser air may be more work. This is why turbo-charged cars have extra pep in the cold, denser air!

Actually it's more about traction for them. A warm tire grips better than a cold one.

At a certain point of low ambient temperature, it's a matter of never being able to "warm up" physiologically.