Digger Franson said:
I don't mean off-roading. I just mean driving in general. Are AT's better on ice than MT's?
It is best not to make generalizations, except that nothing is good on pure ice. If you are talking black ice, say like a quarter inch of perfectly smooth freezing drizzle, then you need a pure snow tire (or stay at home), no AT's, no MT's, no all season. These tires have millions of micropores that suck water off the ice layer like a sponge to give traction. Tire pressure on ice creates a film of water, which makes ice far more slick, and these tires deal with that to the extent it can be dealt with (Bridgestone pioneered this technology with the Blizzak, but virtually everybody else has it now). These tires also wear very poorly in warm temperatures, but those compounds do not freeze even in sub-zero temps, so they retain performance even in artic conditions. They are often called studless snow tires...studded tires are better on pure ice, but they stink on dry payment and I wouldn't run them over a studless unless I lived with a snowpack 6 months out of the year.
Now if you are talking about hardpack snow with frozen icy spots, that is a different question (although the studdless snows are still the best you can get for these conditions). Some AT's are a lot better than some MT's, and some MT's will surprise you. I disagree on the comment that tread compound is most important, and tread design less so (take a look at the most "late model" studless snow tire designs and see if you can pick out the arrowhead design of the center tread that is becoming common across these tires, as well as other similar aspects of unidirectional tread design). They are both very important.
In a 4x4 tire, I believe the most important aspects are excellent lateral and braking traction, since most open lug tire designs will provide very good forward traction in combination with 4x4. This is, in my opinion, why you see the roads littered with wrecked and stranded 4x4's in snowstorms - people get over confident with the forward traction but their OEM "all-season" tires provide poor lateral and braking traction (and once they are off the road in deep stuff, poor forward traction). It is a lack of lateral traction that frightens me the most, because I think it is the least predictable characteristic of most all season or AT tires in the snow, and the most difficult to correct once traction is lost (research studless tires and you will see a strong focus on lateral traction). This is especially true in off camber situations offroad with lockers...you want a tire that will hold a straight line to the greatest degree possible. AT's do a very poor job of this as their lateral traction is more predicated on siping than lug design (I think interlocking tread designs like the BFG AT offer poor lateral traction...just my experience).
For a number of years, I only ran skinnier tires, up to 33x10.5 BFG AT ko's. I thought they were good in the snow with 4wd, certainly as good as the all season tires I had previously. But they were always a bit squirrely around corners and it was pretty easy to kick out the rear even in full time 4wd (AWD) with front and rear limited slips. I live on the Front Range in Colorado, and we get powder that quickly packs down into an icy hardpack. I recently realized that I have never run a good snow tire.
I now run 34x12.5 Interco trxus (on 7" rims that keep the tire somewhat narrower), which is an MT tire that is siped on the inner lugs and has an inner lug design that, in my opinion, is all about lateral traction like many other Inteco tires. These tires are so good on icy snowpack that they made me realize that the OEM Bridgestone all seasons on my Subaru wagon were severely underperforming, and I put dedicated snows on the Sube (Nokian WR). Yes, I was more comfortable in hardpack snow/ice conditions in my 8" lifted XJ than in my AWD Sube. Of course, the Sube was unstoppable with the Nokians, and an awful lot of fun.
Despite being an MT, and a wider tire at that, the trxus have displayed excellent, and more importantly predictable, lateral traction and very good braking traction. They don't surprise (or at least haven't yet in two winters), which is what you want in the snow/ice pack. It is difficult to adapt to suprises in low traction conditions, but comfortable to drive something that eases gently into its limits. The forward traction is so good that I can't get the back to swing out unless I really mash on it, and even then, I really need to be in 2wd. Of course, I do have full time 4wd with a rear Detroit and front Tru Trac, which is an awesome snow setup, but not materially different than my setup with the skinnier BFG's.
I have dedicated winter tires (Nokian Q's) on my minivan (sold the Sube), and they are very good. The lateral and braking traction of these tires is simply outstanding, you hardly know you are driving on snow, and the dry road behavior is also excellent. I'd take these tires on FWD over all seasons with AWD any day of the week. If you have the coin, a set of this type tire (Nokian Q, Bridgestone Winter Dueler, etc) will be excellent for road use but they will not handle deep stuff anywhere near as well as an MT.
The trxus is the only true all terrain tire I have ever run. Not the very best at anything, but very good in every type of condition I've put it through from rain and snow to rock crawling. Kinda like the XJ. I will never run an AT again, and I don't think a 35" studdless snow tires is in the cards even if somebody makes one someday.
Nay
