Decrease psi in winter? - K-Bikes.com - Excellence in Motion
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post #1 of 14 (permalink) Old Nov 23rd, 2005, 10:54 am Thread Starter
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Decrease psi in winter?

Maybe this has been answered somewhere,couldn't find it.I run 38 front,44 rear.My question is should I increase or decrease,or just run the same pressure in cold weather?

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post #2 of 14 (permalink) Old Nov 23rd, 2005, 11:13 am
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I believe you should raise your tire pressure in cold weather.

"Since air is a gas, it expands when heated and contracts when cooled. In most parts of North America, this makes fall and early winter months the most critical times to check inflation pressures...days are getting shorter...ambient temperatures are getting colder...and your tires' inflation pressure is going down!"

Check out this article: Air Pressure, Temperature Fluctuations
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post #3 of 14 (permalink) Old Nov 23rd, 2005, 1:28 pm Thread Starter
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Thanks rickd for the info and the link,very helpful.

Enjoying The Ride. Eddie Layton
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post #4 of 14 (permalink) Old Nov 24th, 2005, 11:28 am
 
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Exclamation Before you increase it ...

Consider the fact that neither the BMW owner's manual nor the tire manufacturers recommend increasing tire air pressures in cold weather (at least not that I'm aware of).

For that reason, I stay with the recommended pressures of 36/42, and leave them unchanged during cold weather.

If you were going to change your pressure, I'd think you'd want to lower it slightly to increase traction; but I'm not saying you should do that.
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post #5 of 14 (permalink) Old Nov 24th, 2005, 12:01 pm
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If you increase the air pressure in your tires, make sure you are very careful before the tire warms up.. Personally, I tend to lower the tire pressure when it's cold to make the tire to be more plyable/softer and allow more traction, at least that's similar idea as running less tire pressure when riding on the track, when traction is important.

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Last edited by cat0020; Nov 24th, 2005 at 12:13 pm.
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post #6 of 14 (permalink) Old Nov 24th, 2005, 9:33 pm Thread Starter
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Thanks guys,lower pressure to 36/42,will ride tomorrow,going to leave at 8:30 AM will be around 19 degrees for a dinner ride to Indiana didn't want to have too much air.I like traction.

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post #7 of 14 (permalink) Old Mar 5th, 2006, 1:02 am
 
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I see two guys in this thread suggest lowering tire pressure to increase traction. Do you know this to be true or are you just guessing? I agree that it seems like lower pressure would let a tire grab more but when I started racing cars I learned it to be just the opposite. In every 4 wheel situation that I've ever seen, in efforts to balance front and rear traction, more tire pressure always means more traction. And I've seen pressures all the way from 8psi to 60 psi run at the track. And Nascar adjusts pressure to 1/4 of a psi to gain this balance.

So I know motorcycle tires are different. Does someone know that they indeed pressure/traction relationship than car tires?

Second, I would answer the question slightly differently. I have a smartire and I watch temperatures and pressures change as the tires heat up. Since tires start out colder in the winter time and eventually still heat up to about 100 deg F, you get more pressure change in the winter. You get about 1 psi for every 10 degrees the tire heats up so from 40 deg to 100 deg F is about 6 psi. Based on that, you may want to lower your tire pressure a couple of psi in the winter time so that your warm pressure is the same.

Thanks,
Jerry
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post #8 of 14 (permalink) Old Mar 5th, 2006, 8:04 am
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I'll throw in my 10c on your points Jerry, and the others in the thread. I get nervous when threads start talking tire pressures as something standard everybody should adopt when temperature and riding style and load are critical.

What I agree on is that tire pressure changes with starting temperature and as the tire heats up, the pressure increases. Jerry, with your Smartire gizmo, how long do you need to ride to get the temperature up 100 deg F and is it the same on both wheels? My problem is, if I'm starting a short commute ride at 30 deg F and my tire pressure only reaches 50 deg F, 'cos I'm a pussy rider on ice, then theory suggests my tire pressure might need to start higher.

However, we might turn all this on its head for exceptional ice type roads which nobody would recommend I'm sure. Our bike tires are profiled for exceptional corner handling with surface area on the corners. Now on cold icy roads I'm not into hard cornering or speed. I just want maximum rubber area in contact with the road surface if and when that nasty slide starts. For this reason there may be some logic in setting pressures at the lowest end. BUT the danger is when weather and speed pickup, you're riding on under inflated tires.

If you ever get a rear drive cage stuck in ice, you take out pressure to get out as the last resort don't you?

Jerry, as you can post some useful info for those without the Smartire. When the weather and temperatures pick up, it would be useful feedback to know your tire pressure and temperatures for say urban and sustained high speed cruise in different ambients.



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post #9 of 14 (permalink) Old Mar 7th, 2006, 1:27 pm
 
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Vox,
You're the only guy I've communicated with lately who has used very low air pressure to deal with ice and snow. Living in California we don't have much of that and when we go to the mountains the law requres we use 4WD or chains. But back in the Midwest as a kid I spent one entire winter with about 8 psi in my rear tires slogging thru snow/ice. It works.

But on a motocycle, I think it would be best to avoid such extreme conditions.

As for my experience: My commute is 2 miles of city streets at about 50 mph with stoplight and then 22 miles of freeway at 80-90 mph (yes, that's pretty much the flow of traffic). I've noticed that the new Continental tires I just installed seem to heat up slower than the bridgestones I took off (but they seem to have excellent grip when cold). I'd say it take about 10 miles at freeway speeds to come up to temperature (usually in the 90's lately, ambient has been in the 50's most of the time).

I'd say that if you're driving carefully on city streets at 50 mph or less you'll probably never get the tires more than 10 to 20 degrees above ambient so your pressue won't change much.

When summer gets here I'll be watching to see how hot the tires get and how high the pressure gets. I bet I'll see 50 psi on a hot day.

Cheers,
Jerry.
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post #10 of 14 (permalink) Old Mar 7th, 2006, 4:23 pm
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Quote:
Originally Posted by edlk1200
Maybe this has been answered somewhere,couldn't find it.I run 38 front,44 rear.My question is should I increase or decrease,or just run the same pressure in cold weather?
Ratings on rear tires say maximum 42 psi cold.
Why would you run them at 44 cold?
I run mine at 40 cold unless I'm loaded down...then it's 42.
I've always heard to use the maximum rating only when the vehicle (cage or bike) is carrying heavy load. That's why we run 37-38 on the front....less load up there.
I've been getting great mileage on my tires so I'm curious about the theory behind the higher pressures.

'04 GT...Orient Blue...Staintune...Ohlins...Power Commander
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