Aspect ratio and winter traction

I am confused myself, first he was arguing for skinny tires, than he posts picture of wide snow tires and posts

Which is one of the many reasons why wider, bigger tires are better [can hold more ice crystals and snow]
and at the end he writes he does not argue with idiots, when he clearly is arguing with himself
So go figure ...

 

I'll try my hand at this...

1) There is a difference between deep snow, hard pack, and ice in terms of traction. OP asked about hard pack. In snow you'll typically see on a driving surface (<6" depth) narrower is definitely better, even if you have wide street tires, it's not going to make you float like the arctic trucks. Narrow IS better in these conditions because it provides less forward resistance. To entertain the idea of flotation as seen in the arctic trucks, think about what surface area the tire is exposing. A narrow tire will focus all of its downward force in a straight line, like a pizza cutter, while a wider tire will have its force distributed across a wider face. Seeing as we're talking about hard pack I'm gonna throw the idea of cutting through snow out of this specific conversation.

2) Contact patch size. Your air pressure is the primary factor in size of contact patch. Whether you have super wide tires, or very skinny tires, at a given PSI your contact patch will be very similar (higher sidewall stiffness will lessen the size of your contact patch). The first picture and the picture TRDMountaineer posted illustrate that. If you are running 30 PSI in your tire, that air is holding up your vehicle and it requires a certain surface area to support the vehicle without resting on the wheels (see Figure 1). To gain a larger contact patch you need to increase the load pressing on the tires or decrease the air pressure in the tires (See Figure 3). The point others have made is that your contact patch doesn't change size, it simple changes shape. A wide tire has a more square contact patch, a narrow tire will have a longer contact patch (See figure 2).

3) Contact patch shape. Referencing information in the links below, a contact patch will be able to hold more force along its comparatively sized axis. A narrow/long contact patch will provide better linear traction. A wide/square contact patch will provide better lateral traction compared to a narrow tire. As brought up in the links, F1 and drag cars use wider tires for practicality and heat dissipation.

4) Traction != Friction. Due to the unique nature of tires and rubber, the standard F=μ*W equation does not accurately represent the traction you will get out of a tire. Between the tire and the driving surface there are micro-interactions that occur which means the true traction you get from a tire will be greater than the coefficient of friction, and can be greater than 1. What this means is that the greater the contact patch size and the more edges in the tire (tread/siping), the more traction you will gain.

Conclusions: A narrower tire may provide better straight line accel/decel. A wider tire may provide better lateral traction. Contact patch won't change size with tire width. It probably doesn't matter what width your tire is. What matters is tread pattern, siping, and compound. Oh, and skinny tires are better...




Figure 1: Contact Patch Size Equation





Figure 2:




Figure 3:




Figure 4:

https://www.physicsforums.com/threads/wider-tire-giving-better-traction-debate.330790/

http://www.stevemunden.com/friction.html

 

You're right, I'm full of shit, I've never driven down a snow covered road in my life and get stuck every time the angel puke flies... You can say I'm full of shit all you want, fact remains, I haven't been stuck and get where I'm going just fine on SKINNY tires. I see no need to prove to you that my truck moves just fine in the snow. Troll on bro.

 

I bet you dont even own a set of skinny tires. You own F150 there are no SKINNY tires that fit your truck.. smallest thread size is at 7 inch and that's not skinny that's normal for truck tires. Anything 6.5 -8 inches is normal.
So before we go any further,,, post the skinny tire size and model you using wso we can check on TireRack what is that skinny size you are using.

WHat club ? You making no sense, I think you completely lost your marbles.

 

This thread is like an automobile accident. I just can't help but look.

No snow or mountains here in northwest Montana...

 

Right now, my stock tires are 265/70, next set will be 245/75 (which by the way is also a stock size and, in my book qualifies as a skinny tire). And, again, you're arguing my personal experience, I'm not going any further with you, you keep going on thinking that super wide drag radials are the best tires for winter

 

Our friend must be pretty tough.

 

I just read this whole thread! Very entertaining for a Friday evening...

Thank you TW!!!!!

 

Thanks for all the help guys. I think I've narrowed my choices down to a 265-75 M+S or a 245-75 AT. Now just need to decide which one...

 

just read this thread, wow i thought i might learn something. i think new tires work best,lol. yeah what do you mt. boys and girls know about driving on bad roads in winter, its not like winter is very long out there.

 

I just got home from a 25 mile drive (my daily winter one way commute) on a combination of back roads and 2 lane highway. The roads are currently covered in 4 inches of fresh snow covering packed snow, which is covering ice in many areas. Blue has me so convinced I don't know what I'm doing that I almost thought about putting the truck in 4wd and going ridiculously slow. Then, when my tires continued to hold traction, I gained the confidence to drive as though I have a clue. You almost had me for a minute there Blue..

Edit to add that there was some mountain driving involved in those conditions.

 

Also, have we taken driving like an idiot into consideration when talking about people getting stuck with skinny tires? There's no substitute for driving with some common sense, like changing out of your ski boots before moving your car closer to the daycare to pick up your kids...

 

Right, the 74 is a ratio.

NO.
245 is a FIXED WIDTH. It absolutely CANNOT get "fat".
245 is 245 is 245 is 245.

End of discussion.

 

Yea this OP didn't make sense from the first post...

It's rough being uneducated...


245/75/16

245 is MM (tire width)
75 is a percentage of the 245 mm (tire's sidewall)
16 is inches (wheel diameter)

 

You are certainly getting some mileage out of that statement and picture eh @rcsb jon?

 

It applies

 

Yes, 245 is a fixed width. But if you compared it to a 225mm wide tire that was much shorter in diameter, then the 245 would be "skinnier" even though it had a wider measured width. Fat vs skinny has nothing to do with measured width. Measured width is fixed. Fat vs skinny is relative.

The rear tire on my old ford tractor was really wide. But it was also about 6 feet tall. It was a "skinny" tire even though it was probably nearly three times the width of the 245's on my Tacoma.

 

Let's all agree 265 mm (10.5") is the most common stock width. Anything less is skinny in my book.

 

Skinny and tall is better. My experience here is for street driving, not off road. I've read through most of this thread but not all and I know people have different experiences and environments they drive in.

I know this will probably mean nothing by this point, but I do have real world experience with the whole tire width thing for winter driving. (at least in Iowa, Nebraska, South Dakota and Illinois anyways) This was on my old 2008 Scion xB LOWERED and was about a pop can height off the road(roughly 5" off the ground at best).

My first Snow tires were General Altimax Arctics (non-studded) at the size of 225/55/16 (oem on that car). They were light years better than the Good-for-a-years all-seasons that were stock. That was my first snow tire ever and now they will go on all my cars. Then I read and heard about how skinnier tires do better for the winter. So after a few winters I got new ones.

My second set was the same General Altimax Arctics (non-studded) but this time I went for a 205/60/16. I didn't think there was going to be much of a difference. Boy was I wrong! It handled better, stopped better and got better forward traction than the wider tires. ESPECIALLY when there was packed snow, slush and icy conditions. I was even able to plow through some snow that car has no business being in, 8-12" of snow is a lot when you have a car that you have to be careful about opening your door around curbs. haha But the darn thing would go really well and handled great too.

My experience is that skinny tires while keeping outside diameter close to the same is going to be better in wintery conditions on the road than wider tires. I fully understand that if your in super deep snow that you want balloons for tires to stay on top of it. BUT for everyday people that want better winter traction for safety on the road, skinnier is better. Not to mention a dedicated snow tire that is made for these conditions. Come on guys look at the racing community, all forms of winter racing use tall skinny tires for a reason.

 

The last 3 posts in here made complete sense which does not represent the thread as a whole. We need some more complete and utter nonsense and stupidity back in here.