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Wednesday, December 15, 2010

Tires and Snow

I received an interesting email from Lynn in Canada with a great question about snow tires. It seems that although the Mudzillas he runs on his Wolverine work great in the mud and muck, they don’t work well at all at pushing his snowplow down his driveway .

So what’s up with that?

Well, tires are far more complex than most folks realize. Think about how much controversy goes on surrounding tire wear, choices, air pressure and compound in NASCAR, F1, or any other racing you may follow.

While we may not be quite as ‘leading edge’ as racing, the same technology applies.

So to answer the question why certain tires work better than others, let’s first take a look at the tire’s compound. Hard rubber will wear slow, but it also doesn’t ‘grip’ the ground, especially when that ground is sand or snow. So a tire with better performance is a softer tire. Too soft though and it will wear out as you look at it. But too hard and it won’t grip at all.

The next part of the equation is the tread. Sure, big tread can move mud just like a paddle moves sand or water for that matter. But in snow (and performance on dirt) the tire’s tread needs to flex. The flexing allows the rubber of the tire to stay in contact with the ground longer, but also gives it a slight slingshot effect in moving the machine forward. Part of this ‘flex’ is helped by the small little slits in the tread called siping. These sipes also help the tread to flex, or squirm, thus allowing it to grab to the surface more. The tread also needs to trap enough of the surface to allow it to grab, but also be able to release that material so it doesn’t ‘clog’ the tread and not allow the tread to work as designed.

Now let’s look at air pressure. Air pressure has a similar but different effect on bias ply and radial tires. But basically you need to have a low enough pressure to allow the tire to flex (there’s that word again) to allow it to grip better, but not so low as to allow the tire to wallow around and roll over in cornering. Basically tire pressure is a very subjective item and the correct air pressure can only be found with a bit of experimenting on your part.

So to sum it up, snow requires a soft tire with a flexible tread with siping to make it even more flexible. That gives it the most traction. You also need to run the tire’s air pressure as low as possible without doing harm to the tire and wheel.

That sounds all well and good until you try to add that information to a specific ATV. In case you haven’t discovered this, ATVs are not all created equal. This inequality for our purpose here, can be focused mainly on the operation of the front differential.

And here’s the problem with front differentials – while lockers are pretty straight forward in their ability to apply equal traction to each front tire, the so-called ‘limited slip’ differentials are exactly that – limited!

Here’s what happens when a limited slip differential detects slip - a difference in the speed of both front tires. When one tire tends to move faster than the other, or slip, the differential tries to bind and attempt to limit the excessive speed of the faster spinning tire. To cut to the quick here, what happens when you have bigger tires with more traction is that they can overwhelm the design parameters of the limited slip differential and it can’t bind the differential enough. So, your limited slip differential doesn’t work as planned!

That means that on many machines with limited slip differentials (and those can come in many fancy names, but are basically every 4wd system that doesn’t have a lockable front differential) a tire with too much traction can actually cause you to have less traction.

Confused? You’re not alone. And if you’re not confused I could go on until you are.

But I won’t.

What did we learn? The best tire is one that has a soft compound with flexible tread and siping. You need to adjust you tire pressure to as low as you can for the conditions, and on ATVs without locking front differentials you also need to remember not to overwhelm your drive system with too much traction.

And just in case you were observant enough to notice the many pictures of the ACT and wondered – yes they are my favorite all around tire…….


  1. Great article Doug.

    A lot of folks don’t realize how important the rubber compound is when it comes to traction, in most cases I think it’s as important and in some cases more important than the tread design itself.

    If you buy tires for your vehicle and you want “snow tires” then you’ll end up buying “winter tires” that are made of a softer rubber compound that all-season tires and that’s why they grip better, because they are softer.

    I’m on my 5th set of ATV tires; the OE, Goodyear Mud Runners, Maxxis Big Horns, Carlisle Bad Lands and my current set of Carlisle ACTS.

    Without question my ACTS are hands down the best tire that I have had in the snow and by far the best all around trail tire. I have been amazed at the places I have been in the snow, even now that they are down on tread. I remember how impressed I was with them in the snow last year while riding an 800 Max that came with the ACT HDs, it was a very impressive combo.

    My 6th set of tires will be another set of ACTs.

  2. I have a 800 max xt that had ACTs they good but they are only 25" tall.I Like 27" Big Horns because the stay on top and are about 4" taller than the ACTs.

  3. Okay, let me get this straight. You say ACTs are only 25" tall, and you like 27" Bighorns because they are 4" taller than ACTs.

    1) ACTs do come in other sizes than what came on your Outty. We love the 26 inch ACTs. They also come in an XL/R model that has an even taller tread.
    2) I struggle to see how 27" Bighorns can be 4" taller than 25' ACTs. The math says 2".
    3) 27" Bighorns are way heavier than ACTs and would drastically effect the handling of the ATV in every situation.
    4) Bighorns have a very stiff tread (that's why they last a long time) and therefore have far less traction in the snow. That's why they 'stay on top!'
    5) Nice try justifying your purchase.

  4. I have used the bighorns and the ACTs in the deep snow,hears a video.

  5. Send the video or a link to the video if it's on You Tube to my email via the website..

  6. Here's a couple questions for you Doug. Don't the kingquads have an RPM limiter when you lock the differential? Does that limit its ability to really spin the tires to cut through that deep snow as compared to the Sportsman, Grizzly, and Bruteforce that don't have RPM limiters.

  7. You know, to be real honest I remember hitting the rev limiter in the snow on the Grizzly with the locker in, but not the Brute Force or the King Quad. Of those three, the last one I powered through the deep snow on was the KQ. It was awesome! No limiter.....

    Now with that said, oftentimes I've made it further with feathering the throttle and steering back and forth for traction!

  8. Well sweet, I must be wrong about the kingquad rev limiter, I believe it was All-Terrain Vehicle Magazine were I read an article and that was their gripe.

    I share your passion of cutting trails open through the deep snow. It is a blast, though cold. My tire selection has been limited to ITP 489s, kenda bearclaws, or maxxis bighorns. While I feel the bighorns have more traction in deep snow than the other two, they sure do suck at steering your atv when it is slick. They also suck power on my Sportsman 500. The bighorns seem to push strait ahead and not want to turn. I would assume that is do to not having a ridge down the center of the tire. The Sportsman still ate my friends Honda foremans for lunch in the deep stuff though, due to them not having lockers, and I believe also due to their manual trannys not being able to find that sweetspot in the RPM as easily.

    I have noticed that the ITP mudlite XTR has a similar looking tread pattern to the ACT. What are your thoughts, comparisons on those two tires?

  9. The Mudlite XTRs are very similar to the ACT XL/Rs. We haven't spent enough time on 12 inchers to be certain, but they seemed much stiffer and seemed to slide around a little more than the ACTs. And that's our favorite feature of the ACTs - how controllable they are.

  10. When I get better tires for my (soon to be) RZR, I can't decide whether to go with the Terracross r/t xd or the ACT HD. I will be spending all my riding time on the paiute trails in the summer and playing in the snow in the winter. I know you love the terracross tires as well as the ACT. Which would you choose?

    Thanks again so much for your help and for sharing your vast experience. It sure helps us younger guys save money by not having to waist it on trial and error to find the right parts. Your website is the greatest!!

  11. Thanks for the kind words Dan. Appreciation is the fuel that we run on ;-)

    Honestly, we have spent very little time with TerraCross tires on any of our RZRs but plenty of time using them on other machines. That's mainly because we just never managed to get a set to use - or take the time to arrange a set.

    But that's not to say that we don't love them. They were our tires of choice on recent Rhinos and Teryxs.

    So now with all that said, my choice would be one of those two! Either will be awesome tires. I believe the ACTs will work a bit better in the mud and snow and the TerraCross may last a bit longer.

  12. Hi Doug. I've had 5 different sets of tires on my ATV including Maxxis Big Horns and my 6th set is on its way.

    Hands down my favorite tires so far have been my Carlisle ACTs, in fact I liked them soo much I have my second set on the way.

    In my opinion the only thing the BHs did better than my ACTs was that they lasted longer and at this point I’ll take superior handling, steering response and over all traction over longevity.

    The ACTs quicker steering was the first thing I noticed and it was a welcome surprise. No more drifting around corners at higher speeds. That was the first thing I noticed and didn't like about the BHs, they don't handle the corners well at all.

    The ACTs are excellent tires in the snow too, very very impressive.

    I'll run my new ACTs through the summer and put on a set of ACT HDs for the winter. I can't wait to see just how awesome the HDs are in the snow with the 1" tread depth.

    I too thought BHs were great tires until I tried a set of ACTs. These are truly one of if not the best "all condition tire".


    Tired LOL

  13. All this talk of the ACT's has convinced me that that is the way I want to go for the RZR. I'm planning on 26" ACT HD's. Add another $500 dollars to the wants list! It keeps getting longer! I better stay off this website for a while! j/k

  14. We feel really bad about our advice costing you money so we initiated an investigation. We found out that in the long run listening (and taking) our advice on products will actually lead to a much happier life. When the cost of these products is compared to the cost (and harm) of drugs, alcohol, therapists, and depression we've found them to be an incredible deal. So good in fact that we've decided to charge an additional fee if you take our advice ;-)

  15. You've convinced me!! Where do I sign!

  16. Doug to be honest I sure think you deserve a hefty "fee". There are a lot of (not to mention any names) atv magazines and other companies charging people for piss/poor reviews and comparisons that just can't hold a candle to the good, solid, usable information that you provide.

  17. And that's exactly why I started this. I found myself sitting right beside other editors at new model introductions hearing the same information, then going out riding the same machines, and even sitting around the dinner table and bar talking about the day. And yet, when the information hit the printed pages, the findings were considerably different.

    Your bill is in the mail ;-)

  18. I didn't know were else to put this so here it is. Great to hear you are liking the STI Black Diamonds! I have a couple questions....

    Do you know how the Black Diamonds compare with similar tires as far as weight goes? With such a stiff sidewall it seems like they may be a real heavy tire.

    Have you had a chance to run (or know anyone who has) the new Pitbull Growlers or Rockers that I keep reading so much hype about on other ATV/UTV forums? The reason I bring these up is because all the reviews I read rave about them, but I'd like to hear reviews from someone I trust(Doug) before I make any decisions on them. Any input would be appreciated.


  19. We've had a bit of scale malfunction here so I don't want to quote any specific weights. With that said, the Black Diamond XTRs are probably mid-weights - not as light as the ACTs nor as heavy as the Bighorns. The carcass is thicker and the tread a harder compound. With that said we thought they'd handle closer to the Bighorn than to the ACT.

    We'll find out more as we put more miles on them. And we keep in mind that we have the taller (and heavier) tread than what we'd probably choose on our own. Maybe the next sets we'll get the ATR (I think that's what they're called ;-)

    We have not tested the Growlers or the Rockers. Many companies are a bit hesitant to send us tires as they are afraid of what we say.

    With that said, the Bighorns have proven to be a highly popular tire. Our opinion is that is junk. It is too stiff. We have always loved the ITP ATR and Terra Cross. When they came out with their Baja Cross, I was told it was to answer the Bighorn's popularity and long life. It's heavier and stiffer and I hate it! Worse than the Bighorn!

    The answer to what works is a lighter, more flexible tire with a softer rubber compound. The tread needs to be open but with a bit of lateral carryover so they run smooth on the harder-packed trails.

    My favorite is the ACT, ACT HD, Terra Cross, and ATR. We'll have to put on a few more miles to find out if the new Black Diamonds will be on that short list.

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