How Much Does Air Temp. Affect Street Riding Traction?

[Ken H.]

As it gets colder in this part of the world, thoughts turn to a question I've wondered:

 

As air temperature and thus tire temp. falls, especially when just starting out on your ride, and especially below freezing, how much is our traction actually compromised?

 

As you continue to ride in the cold, does the tire "recover" i.e. warm up enough when moving through very cold air and on cold pavement to regain traction lost to changes in the rubber due to it being cold?

 

In this question I'm ignoring issues such as frozen moisture on the pavement that of course also impacts the total situation.

 

Bottom line question is - If we ride our "normal" way/pace/style in cold weather, are we much closer to the edge of the "available traction envelope" that we think we are?

 

Anyone know, or want to take a stab at estimating?

[ShovelStrokeEd]

Based on my experience on the first day of ownership of my Blackbird, I'd say there is quite a difference. I lost the front end 1 mile from my hotel on a turn I would have had no problems with in warmer weather. It was 35 degrees as I pulled out of the hotel and got down the road a bit coming to a small roundabout used for traffic control instead of stop signs. I had to jog right then a hard left and the front just let go as I got to about 40% lean. I managed to yank it back up before hard parts other than my peg hit the ground. Now I could have made that turn at a good 5 or 10mph faster on a warm day with warm tires.

 

I am now pretty cautions about these things and prefer to get 20 or so miles in before doing any apex strafing. Tires were MEz6 and well scuffed in.

[David]

As you ponder this, Ken, keep in mind that different tire compounds react very differently to temperature. Street tires are designed to be far less dependent on higher temperatures to provide the necessary traction. This is why it's very dangerous to use a more sport-oriented tire when you dont' really need it--you'll actually get less traction on the street because you aren't riding hard enough to enter the tire's performance envelope.

 

A tire gets traction by comforming to the irregular surface of the road surface, and that process is dependent more on the temperature of the tire (and the compound) than the temperature of the road surface. A cold road surface cools the tire somewhat, but the ambient temperature of the air probably does more cooling than the road's surface.

 

I have a durometer that I've been doing a lot of testing with on the track, combined with an accurate pressure gauge and IR thermometer. It's interesting to observe the trends and the impact of various variables. Like a shining sun, for instance. It warms black tires up very quickly and keeps them there.

 

All this to say that the answer to your questions won't be universal because they'll be very tire-dependent. And influenced by tire pressures.

[Albert]

Funny you should ask that. I left work the day before yesterday on a chilly (high 30's F) afternoon. I have about a 12 mile commute and when I got home I was curious about just this subject. After parking in the garage I walked up and put my hand on the front tire. The tire surface was warm. Not excessively so but noticable nonetheless. As I said with only 12 miles of not too spirited, stop and go commuting (no freeways), I'd say tire warm up is fairly quick once you're rolling.

[Rusty1945]

I'd say tire warm up is fairly quick once you're rolling.

Isn't it the internal friction caused by the deformation of the tire as it rolls that causes heat buildup? Moreso than friction with the road surface. If true, then I don't see how air temp can have much effect other than a slight cooling from the air blast itself. Then again, I could be way off.

 

Personally, I take it easy until I've ridden a few miles whether it's cold or warm out.

[Joe Frickin' Friday]

I'd say tire warm up is fairly quick once you're rolling.

Isn't it the internal friction caused by the deformation of the tire as it rolls that causes heat buildup? Moreso than friction with the road surface. If true, then I don't see how air temp can have much effect other than a slight cooling from the air blast itself.

 

You're largely right about the source of the heating, i.e. viscous dissipation within the tire carcass. But since air cooling is the primary way to dump heat from the tire/rim assembly, a 40-degree drop in air temp means you can expect about a 40-degree drop in steady-state tire temps.

 

Heat also gets dumped during during contact with the road, but at any given time, about 1 percent of the tire/rim assembly's surface area is in contact with the road surface. And FWIW, if the air is 40 degrees colder, the road is going to be, too.

[ShovelStrokeEd]

You can also expect a roughly 3lb drop in tire pressure when going from say 80 deg F to 40 deg F. Assuming a starting pressure of around 38 PSI. This will somewhat allow the tire to heat faster due to carcass flex being greater.

 

The really important thing in all this is the tread temperature which is more or less related to the internal temperature of the tire. I rarely see, in normal riding, tread temperture much above slightly warm to the touch. Probably no more than 110 degrees or so. When riding hard on twisty roads, I might see as high as 120.

[Alan D]

At the Lima rally in 2005, a Michlin rep said the "pilot roads" used a compound that made operating temperature less critical that other tires. FWIW

[russell_bynum]

I have a durometer that I've been doing a lot of testing with on the track, combined with an accurate pressure gauge and IR thermometer. It's interesting to observe the trends and the impact of various variables. Like a shining sun, for instance. It warms black tires up very quickly and keeps them there.

 

I don't know about carcass temp, but having the tires in direct sunlight will definitely make a big difference in the surface temp. We were seeing surface temps (with an IR Thermometer) in excess of 150F with air temp in the mid 70's, but only on the tire that was in the sun. If we had one tire in the sun and one in the shade, we'd often see differences of 40-50 degrees between the two.

 

In one session, Lisa's front tire was actually COOLER when it came off the track after a full session than it was when it went out on the track after sitting in the sun for 40 minutes. I had some fun with that one.

[philbytx]

It does...tire pressure drop approx 1lb per 10 degrees F, so check your tires!

 

When riding in IL during the winter, I always waited for the sun to warm up the roads before venturing out, especially on Black tarmac, as it absorbs solar radiation heat a lot better (and much quicker) than concrete! DAMHIK :eek

 

Friction plus road heat helps a lot on tarmac but I learned a long time ago to treat cold roads like riding in the rain!

[Huzband]

Funny thing. This thread has caused me to back off on my corner entry on the street, now that temps have cooled even here in Fl.

Am I being carefull, or just paranoid?

 

No wisecracks from from you clowns in Diamond Springs, either !

[russell_bynum]

Am I being carefull, or just paranoid?

 

Backing off your entry speed is always a good idea.

 

Better to get into the turn and say "Shit...I could have gone faster" and roll on the throttle, than to get into the turn and say "Shit."

[Huzband]

AGREED!!!

[Paul Mihalka]

Better to get into the turn and say "Shit...I could have gone faster" and roll on the throttle, than to get into the turn and say "Shit."

How true!

[ShovelStrokeEd]

 

Better to get into the turn and say "Shit...I could have gone faster" and roll on the throttle, than to get into the turn and say "Shit."

 

Ask anyone who has ever followed Dick Franz up a twisting mountain road, or down for that matter. A slightly slower entry speed has very little to do with your progress down the road, in fact, it can impede same if you misjudge a corner. I really like to be on the gas at the point of turn-in, at minumum to neutral throttle and slowly transitioning into acceleration. The bike just feels so much happier when I do this right. Is it the fastest way to get through a corner? No, but I have yet to see a trophy or track queen at the end of a section. What it does do is allow me to arrive safely at the other side of the corner or section with both my dignity and my hide intact.

[russell_bynum]

Ask anyone who has ever followed Dick Franz up a twisting mountain road, or down for that matter. A slightly slower entry speed has very little to do with your progress down the road, in fact, it can impede same if you misjudge a corner. I really like to be on the gas at the point of turn-in, at minumum to neutral throttle and slowly transitioning into acceleration. The bike just feels so much happier when I do this right. Is it the fastest way to get through a corner? No, but I have yet to see a trophy or track queen at the end of a section. What it does do is allow me to arrive safely at the other side of the corner or section with both my dignity and my hide intact.

 

The first time I rode with Dick I damn near ran over him at the corner entry.

 

By corner exit, he had pulled 4-5 bike-lengths on me. He did that on every single corner, and if he wasn't sitting up and coasting on all of the straights, there's no way I would have ever been able to keep him in sight.

[Bill_Walker]

Am I being carefull, or just paranoid?

 

Backing off your entry speed is always a good idea.

 

Better to get into the turn and say "Shit...I could have gone faster" and roll on the throttle, than to get into the turn and say "Shit."

 

Or, as racing driver Sir Stirling Moss put it, "It's better to go in slow and come out fast than to go in fast and come out dead." Much as I like Russell's version, Stirling's can be repeated no matter who you're with.

[stewm_21]

"You can also expect a roughly 3lb drop in tire pressure when going from say 80 deg F to 40 deg F."

 

I was discussing this with the service rep at the BMW dealer where I bought my bike. The other point that he made was that with changing temperatures and therefore changes in pressure you can greatly effect tire wear and/or cause cracking in the rubber.

[1NOTRED]

So, which is the major factor for traction; tire or road temp?

Turns out its tire temp, as a warmed up tire will stick well even on a cold road(track). Cold tires on a cold road can spell trouble.

But, be careful, as moisture is more likely to be found condensed on cold roads.

[ncsonderman]

So, which is the major factor for traction; tire or road temp?

Turns out its tire temp, as a warmed up tire will stick well even on a cold road(track). Cold tires on a cold road can spell trouble.

But, be careful, as moisture is more likely to be found condensed on cold roads.

 

What he said +1