Tire Pressure and Snow - Page 4

Brandon002 · #31 02-01-2014, 06:03 PM

Quote:

Originally Posted by JCL

Brandon:

You continue to confuse the various types of friction.

Older snow tires, and snowmobile belts for that matter (since you mention them) work in a particular way. They work by having a deep lug around the shoulder of the tire that digs in. As long as the lug can dig in (whether it is on the edge of an old-tech snow tire) or across the belt of a snowmobile, it will provide traction. This is where the old maxim about using narrower tires in snow comes from. Raising the inflation pressure on this design of tire will provide a cleaner should edge that grips better.

Modern winter tires have sipes all across the tread. They don't dig in in the same manner, rather all of the sipes provide traction. This is also the concept behind ice tires. These tires are not designed to sink in, but rather stay on top. And they work very well. Years back, there was no effective 20" automotive winter tire, they simply didn't exist. Today, we have performance winter tires in sizes such as the X5 sport package uses, and they in fact work better than the old tech snow tires. Overinflating these tires will reduce their winter performance.

If you are so convinced that narrower is better, without considering tread compounds and tread patterns, put an old narrow snow tire up against a modern performance winter tire and see which works better. You may be surprised.

You didn't have to go into all of that. I'm comparing my current tires at 32psi to MY CURRENT TIRES at 36psi. Same tire, same tread compound, same size, different PSI.

I added 4psi and noticed an instant improvement in snow driving. It was night and day.

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bcredliner · #32 02-01-2014, 07:10 PM

Quote:

Originally Posted by Brandon002

and when is the last time ANYTHING made friction when placed against snow?

If there is no friction between the tire and the snow or ice there is no movement.

The extra inflation does not result in the tires cutting down to the pavement. The tires utilize the snow to increase traction. You "might" get to the pavement faster if it was a spin the tires contest to do so but that doesn't happen driving down the road.

The greater the increase in tire pressure the less the tread patch. As pressure is increased the tire becomes less in contact from the outside edges in. That's the reason to increase the tire pressure if mileage is the goal. There is less friction generated so it takes less fuel to get from point A to point B.

I am not suggesting your results are false. I am saying they are an extremely unusual exception. So much that my guess your results were for some other reason.

I would not recommend or even suggest to increase the tire pressure over recommended air pressure to get around better.

Brandon002 · #33 02-01-2014, 07:45 PM

What other reason could there be? I did nothing aside from changing the tire pressure.

I drove to my brothers, increased tire pressure at his house and drove home. Road conditions were the same both ways. The only varied factor was tire pressure. Steering was better, braking was better, acceleration was better and understeer was greatly reduced. So what other factor could there be?

Brandon002 · #34 02-01-2014, 07:46 PM

I've done research on this today as well. It seems that every reliable source I've come across from auto magazines to tire manufacturers recommend a slightly higher pressure in the snow/winter etc..

JCL · #35 02-01-2014, 08:23 PM

Haven't seen many automakers recommending higher pressures for winter tires. Nor the tire distributors.

However, I understand the logic of having softer compound winter tires and people interpreting that as feeling like an underinflated tire. In those cases overinflating them will make them feel more like summer tires. It just won't improve traction.

bcredliner · #36 02-02-2014, 02:55 PM

Quote:

Originally Posted by Brandon002

What other reason could there be? I did nothing aside from changing the tire pressure.

I drove to my brothers, increased tire pressure at his house and drove home. Road conditions were the same both ways. The only varied factor was tire pressure. Steering was better, braking was better, acceleration was better and understeer was greatly reduced. So what other factor could there be?

I haven't read that anyone has said your results are false.

What I am saying is your results are not the norm and should not be interpreted as a truism but as a rare happenstance.

Adjusting the tire pressure will change responsiveness, stability and traction.
Increasing tire pressure of a given tire beyond recommended PSI will reduce traction and improve responsiveness and stability. Lowering tire pressure of a given tire under the recommended inflation will improve traction and reduce responsiveness and stability. Excessive over or under inflation will result in unsafe handling characteristics and/or tire failure.

The +/- range of results from inflation changes will vary by tire. The results of an inflation change of a given tire will not be the same if the conditions are not the same. How much the results change in different conditions varies by tire and by vehicle.

It is reasonable to try inflation changes in an attempt improve responsiveness, stability or traction for the winter. My suggestion would do so a pound or two at a time and expect that 5 pounds or more will result in an unacceptable tradeoff--such as a traction increase that results in unacceptable stability or responsiveness.

It is also reasonable to use a narrower winter tire. A narrower tire will result in more weight over the width of the tire. More weight=shorter width more friction=better traction. Just as with adjustments in tire pressure at some point of decrease in the width of the tire the results will be unacceptable or dangerous.

If I was unhappy with responsiveness, stability or traction of winter tires I purchased I would call the mfg. tech sources and explain the problem and get their recommendation of tire pressure ranges that would help and whether I have the correct tire. I don't see this issue as one to pioneer.

Brandon002 · #37 02-02-2014, 03:00 PM

Fair enough.

I guess my original post should have suggested giving it a shot, but not guaranteeing it will work for everyone.

JCL · #38 02-02-2014, 03:01 PM

Quote:

Originally Posted by Brandon002

What other reason could there be? I did nothing aside from changing the tire pressure.

The most obvious one is temperature, both of the road surface and your tires.

Brandon002 · #39 02-02-2014, 03:11 PM

Also, I don't run winter tires. I have all season Yoko's on my X5.

I do plan on getting snow tires before next winter, but after buying this X (with known problems before purchase) and taking care of all the issues it had when I bought it, very little money was left over to put towards dedicated winter tires. So I tried something to make my all seasons perform better in the snow and it worked. Just threw it out there to suggest to others that this might help them as well if they were running all seasons and having trouble with all the snow.

giodog2000 · #40 02-02-2014, 03:51 PM

Brandon , I have winter's all around (scorpions) and the X5 is nothing compared to a real 4x4 like my x-terra. The X5 is just heavy and understeers and there is not much to be done. Still very fun to drive if you know what you are doing. Snow driving with DSC off is fun also ....try it next time.

NOTE: For those of you who will flame me saying to turn DSC off to have fun , I've been a Zamboni driver for the past 25 years so I just love driving on ice with no assists and I'm not recommending this in anyway or implying it will improve your driving especially if you are not use to ice and snow and/or you do not have the skills to do so.

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