hmmm..first winter snow and not too happy..

[Roadkill]

Originally Posted by mywidebody02

Mine is like it is on rails with my winter tires. Assuming your x drive is working it is all in the tires. Pirrelli ice and snow.

Amen. Pirellis are like glue. 19's and i have to really try to slide around.

[Boston X5 4.4]

Originally Posted by user1000

Just got a great set of winter tires, dunlop grandtrek WT M2 on original BMW 18's but the truck is not acting the way it should.

You didn't pick the wrong tire ...I have driven the Dunlops (17's) in the worst winter conditions in MA/ME/NH/VT and they have been awesome. Might be just different to what you were used to - my X does not handle in the deep snow as good as my old jeep either.

No need for any hand wringing for anyone buying winter tires. Any of the top rated winter tires will be equiv - Dunlop grandtrek, Pirelli Scorp., Hakkas, Blizzak etc. etc. - we are not entering the scandinavian ice rallying circuit

[kaptain]

Originally Posted by Helmuth

And BTW: dropping tire psi is not a good idea. Winter tires should have a little bit more pressure then summer tires (+0,2 bar).

I think it really depends on the conditions. But I noticed rally cars generally use Skinny tall tires so I think that would support the idea of a non deflated tire.

However if you are on really deep snow, I bet an under inflated set of tires would be more useful, to make the car float higher up and not get bogged down.

This link says to slightly over inflate.

Meanwhile this article claims over inflating is a myth.

[Naz24]

Originally Posted by kaptain

I think it really depends on the conditions. But I noticed rally cars generally use Skinny tall tires so I think that would support the idea of a non deflated tire.

However if you are on really deep snow, I bet an under inflated set of tires would be more useful, to make the car float higher up and not get bogged down.

This link says to slightly over inflate.

Meanwhile this article claims over inflating is a myth.

isnt the point to "dig in" to the snow to hit the pavement so you have more traction and to not float higher up?

[m5james]

Originally Posted by kaptain

I think it really depends on the conditions. But I noticed rally cars generally use Skinny tall tires so I think that would support the idea of a non deflated tire.

However if you are on really deep snow, I bet an under inflated set of tires would be more useful, to make the car float higher up and not get bogged down.

This link says to slightly over inflate.

Meanwhile this article claims over inflating is a myth.

I made the mistake of taking the M5 out in the snow and taking it to work one day...I was all over the place. Even worse was the guy in front of me in a Corvette. The problem w/ sports cars, maybe even the X5, is that the width of the tires is actually worse to have in snow vs skinny tires. Having wide tires IS just like having snow shoes on...you stay on top, but that's not beneficial for a car that needs traction to go forward vs being able to lift your foot straight up and forward for movement.

Once the snow starts hitting here in Boise, ID, the cars stay parked in the garage and I spend more time driving my 90 S10 Blazer w/ skinny little 195 tires that drives AWESOME in the snow. I've driven the X in the snow to Reno, but it is a little sketchy, and while the electronics are there to save me, they can also be a little intrusive as well.

Wide tires w/ small sidewalls are great on dry pavement, but skinny and tall sidewalled tires are the key to being able to drive around in deep snow...look at images of rally cars in the snow as they have the skinniest damn tires w/ big sidewalls.

[ardidi]

Originally Posted by m5james

Wide tires w/ small sidewalls are great on dry pavement, but skinny and tall sidewalled tires are the key to being able to drive around in deep snow...look at images of rally cars in the snow as they have the skinniest damn tires w/ big sidewalls.

That's why it's impossible to find winter tires that fit the rears on the stock 4.8is setup. It's simple physics: pressure=force/area. With wide tires, you're splitting up the same weight of the car on more surface area, which is not what you want in the snow. For greater traction, you want the same weight on less surface area, so you want skinny tires. However, I'm assuming BMW recommends the 255/55s because it's a good balance between being decently skinny, compared to the stock tires, yet wide enough so that you don't lose that much performance during dry conditions, especially because winter tires have softer rubber than all-season or summer compounds.

[JCL]

Originally Posted by ardidi

That's why it's impossible to find winter tires that fit the rears on the stock 4.8is setup. It's simple physics: pressure=force/area. With wide tires, you're splitting up the same weight of the car on more surface area, which is not what you want in the snow. For greater traction, you want the same weight on less surface area, so you want skinny tires. However, I'm assuming BMW recommends the 255/55s because it's a good balance between being decently skinny, compared to the stock tires, yet wide enough so that you don't lose that much performance during dry conditions, especially because winter tires have softer rubber than all-season or summer compounds.

There are a couple of physics problems with this. The first is that pressure on the inside and outside of the tire are the same (putting aside sidewall stiffness issues). So, if your tires have 32 psi, then that is your ground pressure. It doesn't matter how wide the tire is.

Larger tires simply don't have more rubber on the ground, that is a common misperception. A wide tire and a narrow tire have exactly the same footprint in area. They just have a different shaped footprint, either short and wide or long and narrow.

A wider tire doesn't float because it has more area. It can hydroplane easier because it is harder to squeeze the water out the side. A wider tire does have to 'climb up' the leading edge in snow, and it has a wider leading edge. A narrower tire cuts through better, and the rest of the footprint follows in the track created by the narrower leading edge.

[c4racer]

Originally Posted by m5james

I made the mistake of taking the M5 out in the snow and taking it to work one day...I was all over the place. Even worse was the guy in front of me in a Corvette. The problem w/ sports cars, maybe even the X5, is that the width of the tires is actually worse to have in snow vs skinny tires. Having wide tires IS just like having snow shoes on...you stay on top, but that's not beneficial for a car that needs traction to go forward vs being able to lift your foot straight up and forward for movement.

Once the snow starts hitting here in Boise, ID, the cars stay parked in the garage and I spend more time driving my 90 S10 Blazer w/ skinny little 195 tires that drives AWESOME in the snow. I've driven the X in the snow to Reno, but it is a little sketchy, and while the electronics are there to save me, they can also be a little intrusive as well.

Wide tires w/ small sidewalls are great on dry pavement, but skinny and tall sidewalled tires are the key to being able to drive around in deep snow...look at images of rally cars in the snow as they have the skinniest damn tires w/ big sidewalls.

I made the mistake of taking my vette up skiing the week of thanksgiving. I was only supposed to be going up to 2500 feet, but ended up in a situation where I had to go further up to 5K feet when my friends at the lower elevation house ended up delayed due to car trouble. It's good to have multiple options on a place to stay, but I was sure wishing I had just driven the X5 like my wife told me to when I pulled in to this parking lot...

You should have seen the stares I was getting from a group standing outside the bar in the evening after skiing when I drove the car out of this parking lot. At that point the tires had zero grip because they were now cold, so I could barely even move the car!! When the tires were warm they weren't too bad, on this flat surface. But no way I was going to make it up the hill where my buddy's cabin is, so he came down in the SUV to fetch me




But ya - summer sports car sized tires are really bad in the snow!!

[m5james]

Originally Posted by c4racer

I made the mistake of taking my vette up skiing the week of thanksgiving. I was only supposed to be going up to 2500 feet, but ended up in a situation where I had to go further up to 5K feet when my friends at the lower elevation house ended up delayed due to car trouble. It's good to have multiple options on a place to stay, but I was sure wishing I had just driven the X5 like my wife told me to when I pulled in to this parking lot...

You should have seen the stares I was getting from a group standing outside the bar in the evening after skiing when I drove the car out of this parking lot. At that point the tires had zero grip because they were now cold, so I could barely even move the car!! When the tires were warm they weren't too bad, on this flat surface. But no way I was going to make it up the hill where my buddy's cabin is, so he came down in the SUV to fetch me




But ya - summer sports car sized tires are really bad in the snow!!

yeah, there are times I wish I had listened to that little voice of logic, only to pay for it after the fact. Hey, at least you had the coolest car up there!

[sprocket1200]

my Pirelli's work awesome.

i suspect it is the rubber...