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      12-12-2012, 09:48 PM   #1
Yobyot
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Summer tires and temperatures

"Consumer Reports" recently wrote that "summer tires" noticeably lose traction in weather below 40 degrees F. That's a pretty definitive magazine, so I accept that as a fact. It got me interested so I called Goodyear customer service, who refused to say that temperature affects the tires on my car at all.

OK, so a trusted consumer organization says summer tires lose traction and the manufacturer says nothing on the subject.

Fortunately, I coded my car to show the actual pressure and temperature of the tires in iDrive. (I think this is insanely useful and cannot understand why BMW didn't ship the car with this enabled).

Here in Boston, it was cold today (about 38 degrees F). After driving about 10 miles on the highway at about 70mph, iDrive showed temperatures in the tires to be in the mid-60s F.

Does anyone know what the optimum temperature of the tires should be? If I remember correctly, in the fall when the weather was warmer, these tires reached temperatures in the 90s F. I wonder if there really is a big loss of traction if the temperatures can't get above 65 F or so.
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      12-13-2012, 04:21 AM   #2
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Quote:
Originally Posted by Yobyot View Post
Here in Boston, it was cold today (about 38 degrees F). After driving about 10 miles on the highway at about 70mph, iDrive showed temperatures in the tires to be in the mid-60s F.

Does anyone know what the optimum temperature of the tires should be? If I remember correctly, in the fall when the weather was warmer, these tires reached temperatures in the 90s F. I wonder if there really is a big loss of traction if the temperatures can't get above 65 F or so.
There is a lot written by the tire companies and motor industry on summer/winter tire performance.

From Continental, here is just one example with comment and advice.

http://www.conti-online.com/generato...ter-tyres.html

It is clear, if you run two cars (one on summer, one on winter rubber) at low temperature and just feel the rubber, you can detect the summer tire has hardened, whereas the winter tire is very grippy in feel.

As to running temperatures, I've actually used an infra-red thermometer around the tires on a cold damp day and you find there is not much heat in the tread area. It can be just a couple of degrees above ambient. Wet roads and the tread is cooled quite quickly, so the rubber compound is not at the high temperatures we would expect, even after running decent mileage.

Winter driving doesn't typically heat the tires like we'd see in summer driving. Hence why in winter, besides tires with softer rubber compounds, it can be necessary to have a little more setting presssure, as the tires don't heat up to the working pressure we'd ideally be running on. I run 2 - 3psi more in winter, just to get the ideal working pressure.

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      12-13-2012, 10:13 AM   #3
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Quote:
Originally Posted by HighlandPete View Post
There is a lot written by the tire companies and motor industry on summer/winter tire performance.

From Continental, here is just one example with comment and advice.

http://www.conti-online.com/generato...ter-tyres.html

It is clear, if you run two cars (one on summer, one on winter rubber) at low temperature and just feel the rubber, you can detect the summer tire has hardened, whereas the winter tire is very grippy in feel.

As to running temperatures, I've actually used an infra-red thermometer around the tires on a cold damp day and you find there is not much heat in the tread area. It can be just a couple of degrees above ambient. Wet roads and the tread is cooled quite quickly, so the rubber compound is not at the high temperatures we would expect, even after running decent mileage.

Winter driving doesn't typically heat the tires like we'd see in summer driving. Hence why in winter, besides tires with softer rubber compounds, it can be necessary to have a little more setting presssure, as the tires don't heat up to the working pressure we'd ideally be running on. I run 2 - 3psi more in winter, just to get the ideal working pressure.

HighlandPete
Thanks.

The link you posted reads to me like a mix of marketing and fact. Still, it was useful. The page seems to lament the fact that you don't have a winter tire rule in the UK like many other EU countries do. That's what's called "a marketing opportunity." :-)

As to the facts, it's unusual to see a recommendation to run winter tires year round if you don't switch.

My experience was with Goodyear US customer service; in this country most companies try to say nothing at all when contacted about the technical details of a product for fear of liability litigation. That's probably also why you wouldn't see a page like the one you linked on the US website of a tire company.

In my particular case, I don't intend to drive my ZSL F30 with summer tires in any kind of inclement weather. I have what we here in Boston call a "wintah beetah," a bad-weather car.

I started the thread to try and understand what risks, if any, I am taking when I take the car out with summer tires on a cold, dry day for my 40 mile round trip commute to work in stop-and-go and highway traffic. IOW, if I lose 10% of grip, I might never notice it since I am driving the car so gently.

OTOH, if going out on a cold, dry winter day when the temperatures in the tires don't reach an optimal temperature (whatever that is, I have no way of knowing), it's the equivalent of racing slicks, I might be driving the beetah more this winter.

My hope was a tire "expert" could detail what optimum tire temperatures are when the are "warm".
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      12-13-2012, 10:34 AM   #4
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Thats silly.

It's been widely accepted that summer tires are not to be used below a certain temp.

I switch to snows when the regular day time high is below 50. This usually happens at the end of October.
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      12-13-2012, 10:54 AM   #5
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If you go on Tirerack they have plenty of stories and videos comparing the performance of summer tires to winter tires.

I have a few friends who are engineers at good year, and I know what you're asking for is "At 55 degrees you still have 85% of your grip" but it's not that simple.

Rubber is a dynamic compound - the temperature, tire pressure, compound of the rubber, and age of the rubber all play a factor in deciding how much grip you have.

A Goodyear F1 summer may not have the same grip as a Contactisport @ 65 degrees, etc.

The generalization is this:

Summer tires have their grip fall off drastically in the cold. At the same time, they are designed to have a ton of grip to begin with, so are you going to endanger yourself driving if you're not pushing the limit of the tire? No. Are you increasing your risk if you have to make a sudden lane change or abrupt stop? Yes. The summer compounds on a cold day are not ideal, and that's precisely where you run into issues.

I am in the same boat as you, and a few weeks ago after hurricane Sandy we got hit with a snow storm. I still had my summer (Goodyear Eagle F1's) on the car and I commute 30 miles a day to work. So I drove my car 30 miles in a good 3" of snow on summer tires with temps below freezing and it was surprisingly confident...much more so than my old Kuhmo MX's which were so bad in the cold I literally couldn't pull my car out of a parking spot in 1/2" of snow.

If it's a dry day, you're probably fine as long as you take it easy. But again, it's the emergencies that are going to be where you run into a potential problem. If your car used to stop in 140 feet and now it stops in 180 feet, that small delta could be the difference between safely stopping and hitting the back of a truck.
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      12-13-2012, 11:13 AM   #6
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Got to get some heat into those tyres!!

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