Wednesday, February 19, 2014

Life - Why Snow Tires and How

And why snow shovels, blowers, boots, gloves, hats, and all the stuff you need to be out there in the cold.

I know this isn't a bike thing but if it helps one of you out there then it's worth it to post. With this winter, with all the snow everywhere, this is sort of pertinent.

The gist of this post is that, if you live in a snow area, instead of spending $1000 on a carbon wheel or powermeter you should allocate that money towards dedicated snow tires (and rims if possible, to avoid the mounting/dismounting process of switching tires on rims). If you wreck your car in the snow it's infinitely worse than not knowing your FTP.

The Golf on its first drive on snows - it was a doozy, a drive that normally takes 7 hours. The last 4 hours took us about 8 hours due to the virtually unplowed highways and roads.
The rims are the OEM rims; we have the OEM all season tires on aftermarket rims.

A lot of people get taken in by the "all season" label on tires, thinking they're good for everything. Now, granted, the best tire for a given condition won't be as good in other conditions. There's no one "best" tire.

For example in warm, dry weather the best tire tread would be to have no tread - you maximize the rubber to road contact, there's no need for any tread to get rid of water, grip ice, whatever. Bolt on those slick-tired rims and go out and have a blast.

Of course if you get hit by a sudden thundershower then those slicks will be virtually undriveable. They float easily over water, losing traction, and taking any kind of directional control away from you. If you need to go straight then it can be okay, but to lose traction in a curve… it's not good.

I, of course, experienced this first hand when I "economized" by using tires until they were near slick. This meant I had to really slow down in rain, typically to 50 mph or less in a strong downpour.

So what's the deal with winter tires?

First, a quick tire summary.

1. All seasons - these tires have a tread compound that remains flexible in colder temperatures, typically under 35-40 degrees F. They normally have more aggressive tread than "summer" tires and usually work well in a broad range of normal conditions - rain, very light snow (no accumulation so the tire can cut through to the pavement), and of course dry conditions.

The advantage is that until you're dealing with conditions where snow or ice mask the road these types of tires generally work very well.

I like buying a wider all season tire. Properly selected it won't affect rolling diameter so it won't change your speedometer, but it will give you a wider footprint in the dry. It will reduce gas mileage a bit, perhaps 1 or 2 mpg, but you can usually make up for that with slightly better driving habits. The advantage of the wider tires really show up when you need to stop in the dry - that's when tire size makes the most difference.

Here's a tip - if your anti-lock brakes kick in when you make a panic stop (i.e. you feel the brakes going on and off) then that means you're out braking the TIRES. Your brakes are fine, your vehicle is fine, but your tires do not have enough traction relative to your brakes. When one magazine tested a bunch of modded cars (all 350Zs) they found one surprising thing - all the cars with similar size front tires (245 wide front tires) stopped in similar distances, regardless of how many thousands of dollars the brake upgrades cost. The car that had the widest front tires, 270s, and bone stock, base level brakes, stopped significantly better than those massive-brake equipped competitors. Using that as a cue I fitted 285s in the front. I can tell you that it was very hard to activate the anti lock brakes after that.

2. Summer tires - these tires typically maximize performance but sacrifice cold weather traction. When I say "sacrifice" that's a huge understatement - they basically have zero cold weather traction, like you might as well be driving on a Teflon road sprayed with oil.

On a 30 degree day I pulled away from a traffic light on a car shod with summer tires. With virtually no throttle (I knew I was on summer tires and I knew it was cold), with very little input (turning left across three lanes of road so not really a true one lane left turn), I broke the tires loose and almost hit the car waiting to go straight. Luckily I didn't hit anything but the look of shock on the other driver's face probably mirrored mine.

If I buy summer tires for a car I usually try to get the widest tire that fits on my car. I know that in the wet I'll have to slow down but in the dry it'll be nice.

3. Winter tires - these tires are optimized for snow and ice conditions. The tread compound remains softer even at low temperatures, like 0 deg F, unlike a summer tire. They have many "sipes" in each tread block. Sipes look like someone got a wiggly straight cookie cutter and cut parallel squiggles across each tread block. Sipes deform in cornering, creating another edge for each sipe. If a tread block has three sipes in it then in a corner, or when under stress, that tread block will have three extra edges (so a total of four edges). This really, really helps when it's icy out, because your 20 tread blocks on the pavement suddenly becomes 80 tread blocks.

Due to the wide spacing between the tread blocks, winter tires tend to be pretty good in deeper standing water. This is because the weight of the vehicle is focused on those tread blocks, enabling the tire to cut through the water better. With a less treaded tire, like a slick, the weight of the vehicle is spread out over the whole tire's foot print and therefore there is less pressure to break through to the pavement. The tread blocks spacing also gives the water somewhere to go - without evacuating the water from under the tread the water simply can't go anywhere quick enough and it ends up staying under the tire. That's why you hydroplane at higher speeds - the tire can't excavate the water quick enough so it starts to "surf"on the water. Once you start hydroplaning you have no choice but to see where the car wants to go.

The disadvantage is that winter tires are optimized for snow and ice conditions. That means that they're not optimized for dry pavement. The sipes that help so much in icy conditions make the tire feel sort of squirmy when you turn in dry conditions. Also, as the tread wears down and the tread block gets shorter, it can't flex as much. This means you start losing the sipe advantage. Many non-studdable winter tires state that after the tread is 50% worn then you should treat the tire as an all season - the tire loses most of its winter advantages. The idea is that you would leave worn winter tires on for the summer (as all seasons), wear them out, and get new winter tires the following winter.

You normally want to use taller, narrower size winter tires, compared to normal tires for your car, so that the tire can cut through snow better. If you look at pictures of rally race cars in snow stages they have incredibly skinny tires fitted. I'll point out that rally cars normally have super aggressive studded tires for snow stages since they don't have to worry about paved performance. Such tires are great in snow but they'd rip apart pavement and reduce traction on such surfaces significantly.

Common Winter Tire Myths (That I Believed)

Some common winter tire myths that I believed include the following:

1. They are horrible in the summer/warm/non-snowy-conditions. This is true if you're racing your car, but for general use they're pretty good. Due to my financial situation at the time I drove for two years on winter tires exclusively. Although there was a bit less traction than the summer tires I bought eventually (which were also 50mm wider), it wasn't like I was limited in any way by the winter tires.

2. Put them on the front if you have front wheel drive. This is the worst thing to do. In fact, if you have a front wheel drive car and have two good and two not-so-good tires, you should put the good tires in the back.

Doesn't make sense, right? Why put the better tires in the back? They barely do anything back there. Well, yes, that's the point. Your front tires not only get you going but they do the majority of the braking and turning. If you put your good tires up front then you're going to get sucked into a situation where the front tires maintain traction while the back ones lose it. It's not good - I was in a car going backwards at 50 mph on a highway because the good tires on that car were up front.

If you have just one pair of winter tires then you should put them in the back. You may not be able to get up a hill but you won't lose control mid-turn, like, say, on a 50 mph sweeping curve (that is normally fine at 65 mph or faster).

Normal cars are designed to understeer if you go beyond its limits. "Understeer" means it doesn't steer enough, i.e. it goes straight. It encourages you to slow down to make it through turns and such. Putting the good tires in front negates all that engineering. It's great if you want to go drifting but not great if you're just trying to get your kid home.

3. All seasons are just as good as winter tires. Ask the Missus, who got stuck in our 2010 Jetta at our mailbox. It's basically a flat driveway, maybe a 2% grade, but such a little grade that for us cyclists you'd think about shifting down only after hammering up such a grade for a few minutes. Yet she got stuck in the driveway to the mailbox with all seasons. She immediately went and got snow tires put on. Now we're good in pretty deep snow, even on 8-10% grades.

All seasons lack the bigger tread openings that the winter tires have. They have no sipes. They're usually wider and lower profile, so they're optimized for sledding over the snow, not cutting into it.

4. Winter tires are noisy. Well, yes, the studded tires are noisy. The less expensive winter tires, typically meant for studs, like the Firestone Winterforce, are pretty noisy. I had a set of those and they were so noisy they almost drowned out the sound of the coffee can exhaust on the car.

However the current generation of studdless snow tires are incredibly quiet. Among these I'd count the Bridgestone Blizzaks, the Dunlop Graspics, the Continental ContiWinterContact, and the Pirelli Winter Sottozero, all of which I own or have owned and/or driven extensively. The tires I put on our Expedition, the Bridgestone Blizzaks, were significantly quieter than the OEM all season tires on it before.

The Hondas with Dunlop Graspics, less noisy than the Winterforces.
The sipes cut into the tread blocks are visible since snow has penetrated them.

5. I have 4WD/AWD, I don't need winter tires. Whoa. Yes, whoa. In snowy/icy conditions you need good traction from all your tires. 4WD/AWD is a crutch to make up for low traction tires (relatively speaking) because it puts power through all four tires. However, if you need 4WD/AWD to get going then you probably don't have the right tires on to turn or stop in an emergency, both of which use primary just one pair of tires. In other words if you need to turn quickly you need good traction from your front tires. If you want to brake hard you need good traction from your front tires. If you need to get going with a front wheel drive car then you need good traction from your front tires.

If you don't have good traction in your front tires then you probably won't be able to turn or stop when you really, really, really need to. 4WD/AWD will let you get into situations that are beyond the capability of your tires. With winter tires and 2WD (front wheel drive for most of us now) you should be able to get through pretty much everything short of snow deep enough to float your car.

Recently (Dec 2013) I drove, back to back, similar year Fords, an Explorer and our Expedition. I drove the Explorer to where we store the Expedition and drove the Expedition back - we needed the extra space in the Expedition else we would have used the Explorer. In retrospect I'm glad we did because of the tires on the respective vehicles.

The Explorer had all seasons. The Expedition had snows. In the Explorer not only did I slide down the driveway out of control but the thing also crab walked along the road due to the road's crown (the rear of the Explorer wanted to slide left, toward the gutter, because as soon as I touched the throttle a bit the rear tires would lose traction). With the 4WD I could get going but it was hard to stop and hard to turn.

I parked the Explorer and prepared for a sketchy drive back in the Expedition. Incredibly it was just the opposite. It was totally undramatic, so much so that I forgot to put it in 4WD on the way back. Just to experiment I drove down the driveway and tried to stop. In the Explorer, on all seasons, I slid into the snow bank and then into the road. With the Expedition, shod with winter tires, the vehicle stopped within a few feet in the middle of the steep downhill driveway.

Because of 4WD/AWD's seduction (because it gets you moving) I think it's even more important to get snow tires for such a vehicle. This way you can get going, of course, but you can maintain control once you get going.

The Blizzak tires when I picked them up. They're huge.

If you open the picture up you'll see what looks like faint marks on each tread block. They're actually the "sipes", resembling very fine razor type slashes in the tread block. They flex independently, like bristles on a broom, to grab ice and snow. In the summer they're not that great, in the snow and ice they are an absolute miracle.

Many winter tires (every one I've used) says the sipes only reach about halfway through the tread block. Once the tread is at 50% then you have no sipes - now you're on an all season tire. Leave them on in the spring, wear them out through the summer, and put new winter tires on in the late fall.

Tires mounted on the Expedition (obviously in warmer weather).

Tires, underneath, in action on about 4-6" of snow on the road, with 1-2' on the sides (Feb 2014).
Travel speed approximately 35 mph.
I decided to skip going to the trailer appointment that day.

As part of the ongoing work to get the Bethel Spring Series underway I headed out to get a brake controller and tow hitch installed on the Expedition. I did that in the middle of "heavy snow fall", after missing the prior appointment due to the "heavy snow fall". With the Series rapidly bearing down on us I decided to go regardless of the predicted 1-3" of snow fall within a few hours.

Knowing the difference between snow tires and all seasons, it became pretty apparent who had what tires. The drivers driving very slow, very gingerly, they probably had all seasons. The ones driving a bit faster, probably snows. Having experienced both types of tires on a 4WD vehicle I knew that 4WD wouldn't let an all-season shod vehicle go very fast.

With conditions only slightly better than the picture above I was able to drive somewhat normal speeds, 45-55 mph on the relatively unplowed I-384. The other highways, I-91 and I-291, were too congested and I drove at the speed of traffic. On I-91 one driver only felt comfortable going 15 mph, in much better conditions than I-384.

Ironically I passed three cars that had spun out within 200 meters just before merging onto I-384. The snow didn't discriminate - there was a 4WD (pick up), a FWD (Dodge Neon I think), and a RWD (Infiniti G35, unless it was the AWD version). A state trooper had just lit the first flare to protect the first vehicle. From what I could tell they all had all season tires. All seemed to have lost the rear tires first and hit the snow on the left side of the road. All seemed fine, relatively speaking.

So that's my schpiel on snow tires.

(And on snow throwers - each winter I usually hurt my back shoveling snow. I thought shoveling was good, gave me a work out, etc, but when I looked at my training log for 2013 I missed virtually all of February because I hurt my back. This year we got a snow thrower and, guess what? My back is still limping along! I said to the Missus that this was one of those "penny wise, pound foolish" things. All the powermeters in the world won't do any good if I simply cannot get on the bike.)

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