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Topic Review (Newest First)
11-27-2012 02:05 PM
Joeywhat The whole "narrow vs wide" argument is mostly moot on passenger vehicles. In most cases, you can't even get tires that are significantly narrower then stock sizes anyways, so there's not a huge difference in tread width. If you're comparing a huge truck tire to something off a smart car then yes, I'm sure there are notable differences, but otherwise it's not making a huge difference.

Find wheels you like that are within budget, put quality tires on them that are of an appropriate size, and be on your way. Going down a size or two likely won't make any appreciable difference.

And remember, significantly smaller tires will have significantly different load ratings then stock options, so going to a very small/thin tire may not even be safe for your vehicle.
11-27-2012 09:36 AM
JonathanGennick I went the stock size -- 215/55R16. Just got walloped this morning with a $700+ bill on repairing the minivan. Decided that a second set of rims and TPMS chips will need to wait until next year, and that pretty much decided the question of what size tire to get.

My mechanic is putting in the order this morning. With a little shipping-luck I'll have the tires on the car for the weekend.
11-26-2012 04:53 PM
sailor Honestly, it'd be nice to have both wide & narrow tires (grin).

Narrow for the deep crud, and wide for the bare or Icy.

Now THIS theory is REALLY temperature dependent, since sliding on snow & ice results from the frozen stuff melting to make a water layer you actually slide on....

When it's stinkin' cold, you want the tread to stay planted as long as possible so it can take a grip. Closer to the melting point a bit shorter time in contact MIGHT reduce that melting.

I agree, it's probably a moot point in most cases since ice traction is minimal anyways except in very cold weather but it'd be fun to test!

cheers!
11-26-2012 04:29 PM
JonathanGennick
Quote:
Originally Posted by sailor View Post
Similar weight vehicles owned years ago, one with 155's & the other with low profile 175's (both had been avail. with the same std. size & profile tires in different model years) - BOTH worked quite well in "normal" snow & ice conditions without an obvious major difference in capability UNTIL deep slush was encountered, at which point the "hydroplane" effect on the wider tires was quite dramatic.
Hey, that's helpful to know, thanks.

I've pretty much decided on the narrower tires. The hydroplaning aspect that I read about in my earlier link, and again in your anecdote, has pretty much convinced me.

I did run the "buy a second Focus so I can test wide versus narrow" by my wife just now. That one did not fly.

Your point about "snow" encompassing so very much is well-taken. Today we have unplowed and unmelted snow to deal with. Other days it will be slushy muck. Then there the days when it's just cold, bare pavement. Then you've got the cold, hard-iced pavement. Is narrower better in all those conditions? I dunno. It'd be fun to have two cars and run some tests.
11-26-2012 04:16 PM
sailor IMHO, lack of recent experimental evidence is primarily because it's hard to justify a grant to "research" something that's generally considered as "obvious".

The use of "tall & narrow" wheels & tires to "cut through" loose or soft material to firmer material underneath both for traction & to reduce rolling resistance has been "standard" since Horse & Buggy days. You'll note that tractors had been designed in this manner until recently, when "no-till" or "low-till" farming became more common & wider &/or longer tread for flotation came into play to reduce soil compaction. A similar situation can be noted on "Jeeps", where tall & narrow was std. for general purpose & snow use while wide "flotation" tires were special purpose for flotation on soft terrain of all types.

Wide tires for automotive use originated in racing, where reducing contact time with the pavement reduced heating of the tread & subsequent loss of traction. Hydroplaning becomes more of an issue with wide tires, and is combated with wider tread grooves to allow water to escape.

Would less then 10% increase in width be noticeable in a winter tire? (20 mil is 9% of 215, the difference from 195's). I can only speak from my experience here, to whit:

Similar weight vehicles owned years ago, one with 155's & the other with low profile 175's (both had been avail. with the same std. size & profile tires in different model years) - BOTH worked quite well in "normal" snow & ice conditions without an obvious major difference in capability UNTIL deep slush was encountered, at which point the "hydroplane" effect on the wider tires was quite dramatic. The sports car that was such a "beast" in snow of all depths with 4 corner studded snows would get tossed around quite a bit when the tires couldn't cut through the deep slush. A foot of loose snow or more, drive it like a wet road! 3" of slush, look out! (at highway speeds)

Sounds kinda dramatic, but that car was GREAT fun in the winter until hitting that deep salted slush that tosses everyone around.... that combo worse than any others I've owned.

Hope that helps a bit, snow is such a different driving environment with it's own variations in handling depending on conditions - you really need an Eskimo vocabulary of 100 different words for "snow" to describe the different conditions possible!

To go on a bit..

For example, vehicles that "oversteer" or "understeer" naturally due to weight bias on pavement usually react the OPPOSITE way on snow. "Skid School" practice cars to demonstrate this years ago (sticking to RWD) were often a Mustang for nose heavy and a Corvair for tail heavy. Skid pad circle in the wet, the Mustang would plow & the Corvair would hang the tail out. Repeat on snow and the reverse would be the case as the added weight gave more traction to that end on packed snow. Given enough speed to break things loose the results would reverse again - proving the advantage of inherent balance.

On our FWD cars, that extra weight on the drives can help at low speeds. You just have to remember that the added momentum can also make it "push" as speeds & cornering loads increase. The "kicker" is to remember that if the tail gets loose you need to keep your foot in it as you countersteer, back off the gas when it's skidding already & the tail will become the front!

Luck!
11-26-2012 03:54 PM
thenorm it may not be the type of evidence your looking for, but look at off road trucks.

those driving on sand have very wide tires to "float"
wheras narrow tires would sink.
11-26-2012 07:33 AM
JonathanGennick
A plausible explanation of why narrower might be better

Hey, I found something interesting. I've been looking around for some sort of experimental evidence that narrower really is preferable in winter tires. There's an amazing lack of such evidedence, so I decided last night to look at the problem from a standpoint of hydroplaning. That took me to a Ford truck forum, which pointed me to the following research paper:

http://deepblue.lib.umich.edu/bitstr...6.0001.001.pdf

The introduction states:

Quote:
The project addressed a specific area of concern involving the control of heavy duty
trucks on wetted pavement. The concern deals with the lightly-loaded, or near-empty
condition in which truck, tractor, and semitrailer tires are less capable of providing good
wet-traction performance. The traction handicap derives from the fact that the lightlyloaded
truck tire contacts the ground with a footprint which is rather short relative to its
width such that there is risk on wet pavements of developing significant hydrodynamic
pressures over a substantial portion of the tire's contact length.

Since the tire rolls in the longitudinal direction, a very short contact length
dnnension implies a very short time interval during which water on the roadway must be
expelled from beneath the footprint. If the contact shape is short, but wide, a long escape
path is presented for water flowing laterally while the short available time implies that very
high water velocities must prevail if the fluid is to escape and thus allow the tire tread to
engage the pavement.
This idea of the narrower contact patch being longer, and thus providing a longer interval for water (and presumably for snow as well) to be expelled is an interesting one. It's the first plausible support I've found for the narrower-is-better meme that is so common (and yet unsupported) across the Internet.

There is also this abstract that I found:

http://cat.inist.fr/?aModele=afficheN&cpsidt=16250009

which states:

Quote:
Some recent studies of several tractor-trailer accidents on flooded highway surfaces, however, suggest that in addition to inflation pressure, truck tire footprint aspect ratio (tread contact area width to length) may significantly effect dynamic hydroplaning speed.
Interesting stuff, and again it supports the narrower-is-better theory.

Some direct, experimental evidence would still be welcome. I wish that I owned two Focus vehicles. Then it would be fun to buy the same brand and model winter tire in wider and narrower sizes, and compare the two against each other. Does the one-inch difference between the 195s on the S trim level and the 215s on the SE trim level really matter? It'd be fun to put two Focus's together and put that question to the test.
11-25-2012 02:15 PM
Joeywhat You should be able to find plenty of tires that are at least rated at 91, which is less then 100 pounds less load per tire (still about 1300 pounds per tire). The GVWR is only 3990 pounds.
11-25-2012 01:34 PM
JonathanGennick I have to allow for five adults on church days. My immediate household is four adults. Two and three people in the vehicle is the more common scenario, but four and five happen often enough.


Sent from my iPhone using FF Mobile. Typos and terseness are to be expected.
11-25-2012 01:10 PM
Geezer
Quote:
Originally Posted by JonathanGennick View Post
What about the load and speed ratings? The placard on my vehicle calls for 93H. Only one of the 15" options at Tire Rack meets the 93 rating. Only one meets the H rating. None meet both.

I really wouldn't worry about the speed ratings. How often are you going to be driving over 100mph? H speed rating is over 130 mph and I doubt there's very many foci that can come close to that. Common sense has to enter into the equation as well. Snow tires are simply not designed for high speeds and one needs to adjust for that.

Load ratings can be important if you are constantly at the full gross carrying capacity of the car (hauling 3 or 4 passengers all the time, load the rear with bricks, tools, etc.).
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