So, I've been reading "Bicycling Science" 3rd edition by David Gordon Wilson and there is alot of information in this book about every detail of how a bicycle does what it does. Granted this book is only a precis to the subject and contains alot of further-reading type resources for the curious. However I've come across a glaring lack of information.
We have a pretty good idea of what happens to the human body in very cold weather. But... what happens to your BIKE in super-cold weather? (I'm talking sub-freezing temperatures approaching and passing 0F).
This subject occurred to me as I was riding to work this morning when it was about 13 F and my bike had been riding on the front of a city bus for 4 miles even before I had gotten on it (in the winter I like to bus part-way in the morning so's I don't freeze to death). When I finally put foot to pedal it felt like I was biking through molasses. It was difficult to pedal, my coasting duration was almost non-existent and every bump felt like I was off-roading.
Anyone else have this experience? Suggestions for counter-attacking? Or thoughts on how this happens?
(mods: can we cross-post with bike mechanics?)
The BikeForums Team
-adv-
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Nothing horrible will happen to your bicycle in super cold conditions. Well ... I have heard of plastic parts snapping off, but other than that ...
Before it gets cold, you should wash your bicycle thoroughly ... clean off all the old summer greases, dirt, etc. etc. Then let it dry completely before going out in the cold. If you must add some grease, add something that is fairly thin and NOT WAXY. Believe it or not, WD40 seems to work quite well for me in cold temps ... and I've used a thin chainsaw lubricant too.
Although many people will disagree with me for some reason, and I'm not quite sure about the way to express this in physics terms, your tires will lose more air in the cold than in warmer temps. Try this experiment. Blow up a balloon in your nice warm living room. Fill it quite full so that it is definitely firm. Now take the balloon outside where it is cold and hang it from your mailbox or fence. Leave it there for a little while. Now go and take a look at it. You'll see that it has shrivelled so that it is not firm anymore. That's what can happen to your tires too. And when your tires are flatter, riding is more difficult.
However, if you are riding on snowy/icy conditions, you want your tires to be flatter ..... so you'll just have to live with the fact that riding the bicycle is going to be more difficult to ride.
Turboem1
Although many people will disagree with me for some reason, and I'm not quite sure about the way to express this in physics terms, your tires will lose more air in the cold than in warmer temps.
You are correct and I would hope noone would argue against the physics. That is the ideal gas law.
PV=nrT
P = Pressure
V = Volume
n = Number of moles of gas
r = Universal gas constant = 8.314472 J/mol K
T = Temperature
So as temperature drops in a set volume (bike tube/tire), the pressure must also go down.
As far as riding in the cold, it usually causes lubes to thicken and parts to become brittle and break in extreme conditions.
Portis
When I finally put foot to pedal it felt like I was biking through molasses.
That's not normal and an overstatement of the effects of cold on a bike. A typical 21 mile ride for me in 13 F weather takes about 15 mintues longer than it would take in 70 degree weather. IOW, what normally takes 1 hr 30 minutes would take approx. 1 hr and 45 minutes. That's hardly a moving in molasses effect.
Granted wind can make you feel this way but then again it always can. But temp alone is not enough for this effect, not even close.
Wowbagger
You are correct and I would hope noone would argue against the physics. That is the ideal gas law.
PV=nrT
P = Pressure
V = Volume
n = Number of moles of gas
r = Universal gas constant = 8.314472 J/mol K
T = Temperature
So as temperature drops in a set volume (bike tube/tire), the pressure must also go down.
I don't know how applicable the ideal gas law is for bike tires. In any case, according to it, a drop from room temperature (300K) to freezing point (273K) should result in a less than 10% decrease in pressure. Definitely not enough additional rolling resistance to create the effect described.
Machka
I don't know how applicable the ideal gas law is for bike tires. In any case, according to it, a drop from room temperature (300K) to freezing point (273K) should result in a less than 10% decrease in pressure. Definitely not enough additional rolling resistance to create the effect described.
Yes, but I'm not talking about a drop from room temperature to freezing point. At freezing point your bicycle should ride much the same as it does at room temperature. I'm talking about a drop from room temperature to ... say ... about -20C or -30C or -40C .... well below the freezing point.
Skillie
Were you biking through snow? I find that fresh snow and tire-mulched snow presents a significant amount of rolling resistance. It almost feels like I'm biking over sand sometimes.
I've used lithium grease in my bearings down to -25C so far without experiencing a significant extra amount of drag while pedalling or coasting over pavement (when I'm going over snow, I'm pretty sure it's the snow and not the bearings that are slowing me down). But this is my first winter doing so, so I would hold little weight to my experience with bearing lubrication in the cold. I'm happy with the grease though, and like that I don't have to worry about the bearings too much when we get temperature spikes during the winter months.
-20C temperature should make a 10-20psi difference in tire pressure, while 0C temp will make a 5-10psi difference, depending what you had the tires inflated to, if you're following the gas law above. I doubt the air is actually escaping from the tires any faster though -- it just exerts less pressure. At 13F, the decrease in pressure won't account for the magnitude of extra resistance you felt (as posters above have noted -- I'm agreeing with them, except the part about tires losing air).
ghettocruiser
Grease thickens in the cold, some worse than others. Some external-bearing bottom brackets are pretty bad this way when new. My raceface BB cups got so stiff I could barely turn them with my hand. After a summer of break-in the problem didn't reappear the next winter.
rajman
I imagine the freeze-thaw cycles will also lead to more air escaping from your valves, if that's what you were getting at Machka.
As far as deviations from ideal gas law, they should be minimal with air even with moderately low temps and moderate pressures. Water vapour will cause you trouble in these circumstances, however.
Deviation from ideal gas law will increase as temperature decreases and pressure increases </end chemistry rant>
PsySal
I had some trouble with a shifter cable being really sticky when it was very cold (-25C). I guess the lubricant froze up a bit, becuase I had just replaced the other shifter cable and lubed it really well (with a light oil) and it wasn't giving me any trouble. So light oil might be a great idea...
CdCf
Yeah, shifter cables getting "sticky" is the only problem I've experienced. On the other hand, this sets in as soon as it drops below zero. Probably some water in the shifter cable housings.
jeff-o
I really must flush my brake cable housings with some WD-40 very soon. The brakes are definitely not as smooth as they used to be!
Ernesto Schwein
it was about 20F/-5C yesterday and saturday it was almost -15F/-26C. The difference in rolling resistance is definite and I would compare to 2 or 3 cogs in the rear. When its really cold the wheels really don't spin, it feels like the brakes are on. I don't really notice a difference above 20f/-5c.
GGDub
freehubs freeze and literally become free. Not fun when you're trying to get to work on time.
Ernesto Schwein
freehubs freeze and literally become free. Not fun when you're trying to get to work on time.
I've yet to have this happen although I believe the people that say it does. I leave my bicycle locked to an outside rack all day long at temps below -15F/-26C and lower on a regular basis. I've never had any special lubricants or winterizing done to any of my wheelsets. I winter commute all winter long. About the only theory I have is that I don't freewheel very much or maybe I'm just lucky.
ghettocruiser
^^^ Tends to happen with freehubs that are either new and well-greased or old and worn out.
Portis
freehubs freeze and literally become free. Not fun when you're trying to get to work on time.
This might happen, but it is worth mentioning that it is rare. I ride daily and have for years, I've never had this happen. I'm just mentioning this, for any noob's that read this and think that their freehub body is going to freeze if they ride in winter. It isn't!
yairi
Fixed gears for the win. It just works
ghettocruiser
^^^ Because everyone know that the best time to try obscure new bicycle types is when it is -15 and snowing. :D
Seriously though, one time as an experiment I tried riding home from work without changing gears or letting myself coast. As I result I can say that it's not gonna happen anytime soon. Maybe next summer as a pilot study or something.
Can anyone jump curbs on a fixie?
Severian
^^^ Because everyone know that the best time to try obscure new bicycle types is when it is -15 and snowing. :D
//edited for length//
Can anyone jump curbs on a fixie?
Well they do say that winter is the best time to learn how to drive a manual transmission... or at least that's how one of my college room-mates learned.
and you *might* be able to bunny-hop in a fixie, I'm pretty sure you can do a roadie shuffle (front wheel up first back wheel following).
GGDub
This might happen, but it is worth mentioning that it is rare. I ride daily and have for years, I've never had this happen. I'm just mentioning this, for any noob's that read this and think that their freehub body is going to freeze if they ride in winter. It isn't!
Remember we're talking about real cold temps here, the kind not likely seen in Kansas. After having this problem, I found out three other people who went through the same thing. I've never had it happen in temps above -20c. When this was happening last week, my thermometer read -29c.
It has to do with moisture in your freehub body, causing the little spring thingy to stick which doesn't allow the latch to come back down and grab the teeth in the hub which then engage the wheel.
ghettocruiser
^^^ If -30C is a frequent reading on your thermometer, I would think it would be worth packing a set of wheels with low-temperature grease for the the winter. With all the extra things slowing us down in the winter, molasses bearing grease and touch-and-go freehubs are the last things I would want. But they rarely come into play in Toronto, obviously.
Severian
This brings up an interesting point. Right now I've just got Park's basic synthetic grease. Are there other greases I could look into or should I just go out and get some decent lithium grease?
Portis
Remember we're talking about real cold temps here, the kind not likely seen in Kansas. After having this problem, I found out three other people who went through the same thing. I've never had it happen in temps above -20c. When this was happening last week, my thermometer read -29c.
It has to do with moisture in your freehub body, causing the little spring thingy to stick which doesn't allow the latch to come back down and grab the teeth in the hub which then engage the wheel.
I understand that. I just want to make sure that everybody else does. "super cold" is a relative term, depending on where you live.
Ernesto Schwein
This brings up an interesting point. Right now I've just got Park's basic synthetic grease. Are there other greases I could look into or should I just go out and get some decent lithium grease?
for Madison? Well, unless the climate in Wisconsin changes substantially I highly recommend this stuff:
Valvoline #614, you can get about a 5 years supply at NAPA for less than $4.
MikeR
Try this experiment. Blow up a balloon in your nice warm living room. Fill it quite full so that it is definitely firm. Now take the balloon outside where it is cold and hang it from your mailbox or fence. Leave it there for a little while. Now go and take a look at it. You'll see that it has shrivelled so that it is not firm anymore. That's what can happen to your tires too. That's true as far as it goes, but you have made assumptions that are not accurate. If you take that balloon back into the room it will expand again – not because it got more air but because air expands as it warms and contracts as it cools, so cold air takes up less room than warm air.
So when the temps drop you don’t lose air but you do lose air pressure. Yea, I know – I’m splitting hairs again! :rolleyes:
dobber
Although many people will disagree with me for some reason, and I'm not quite sure about the way to express this in physics terms, your tires will lose more air in the cold than in warmer temps. Try this experiment. Blow up a balloon in your nice warm living room. Fill it quite full so that it is definitely firm. Now take the balloon outside where it is cold and hang it from your mailbox or fence. Leave it there for a little while. Now go and take a look at it. You'll see that it has shrivelled so that it is not firm anymore. That's what can happen to your tires too. And when your tires are flatter, riding is more difficult.
Maybe I'm missing something, but why aren't you inflating the tire back to the correct pressure?
Severian
Maybe I'm missing something, but why aren't you inflating the tire back to the correct pressure?
mostly because if you inflate a tire at 32 F at 120 PSI when you take it indoors to a room that's, say, 64 F, double the temperature, the pressure will double because the volume stays the same. Boom goes your tire.
Machka
mostly because if you inflate a tire at 32 F at 120 PSI when you take it indoors to a room that's, say, 64 F, double the temperature, the pressure will double because the volume stays the same. Boom goes your tire.
That ... and also riding on slippery/snowy conditions is easier with somewhat flatter tires ... increased traction. I run my mtn bike tires around 50 psi in the summer and around 30 psi in the winter.
The busses on Fraser Island (a completely sand island off the east coast of Australia) do the same thing when they take tourists around the island.
ghettocruiser
mostly because if you inflate a tire at 32 F at 120 PSI when you take it indoors to a room that's, say, 64 F, double the temperature, the pressure will double because the volume stays the same. Boom goes your tire.
Nope. PV=NrT where T is the temperature in Kelvins, not F.
If you're doubling the temperature in Kelvin by bringing it in the house then you'd have to be inflating the tire on Neptune. :D
Converter at http://www.ilpi.com/msds/ref/tempunits.html
Severian
Nope. PV=NrT where T is the temperature in Kelvins, not F.
If you're doubling the temperature in Kelvin by bringing it in the house then you'd have to be inflating the tire on Neptune. :D
Converter at http://www.ilpi.com/msds/ref/tempunits.html
Woops! Well it looks like I'm moving to sunny-sunny neptune for winter this year. Chewie, hook up the generator and stand on it to 400 watts! We've got to make the Neptune run in less than 3 parsecs!
Cosmoline
The only problem I've had has been slightly sticky gears. I made a point of cleaning the bike of any excess grease or oil and I keep it outside as much as possible. In my experience what kills metal and causes rust most is the condensation of temp. changes when you bring the bike inside.