Auburn Gear Releases Performance Limited-Slip Differential For Ram Pickups
15 hours ago
By Bruce W. Smith
(Photos by the author and Larry D. Walton)
Deep snowdrifts, a white dust blowing sideways across a silvery sheen of pavement, plow-shod pickups, and a single-digit temperature readout on the dash inches from my gloved hands left little doubt we were definitely in the right place when it came to testing snow tires.
Steamboat Springs, Colorado, is a snow-lover’s paradise in the middle of the winter; snow-laden winter storms are plentiful, the scenery breathtaking, and hospitality first-class.
Those attributes make it an ideal location to see first-hand how factory all-season pickup tires stack up against dedicated snow treads when subjected to some serious testing on the Center for Driving Sciences’ .9-mile road course at the 77-acre Bridgestone Winter Driving School (winterdrive.com; 800.WHY.SKID) just outside of town.
We point the nose of our 2011 GMC Sierra 2500HD Crew Cab off the paved country road and make our way up a narrow plowed lane.
At the crest of the hill, we are greeted by Gordon Speck, one of the school’s gatekeepers who motions us to park at a large tent that makes up the core of this seasonal test facility.
Just beyond the makeshift office/classroom lies a trio of road courses carefully carved out of deep snow, covering what would be a beautiful, sprawling hillside farm pasture during the summer.
Let the fun begin.
Bridgestone’s Winter Driving School is renowned for educating and honing drivers of all skill levels faced with piloting vehicles over roads blanketed with white and ice.
The school’s instructors are some of the best driver’s in the world. In fact, a number of them compete on the professional rally and road-racing circuits when they aren’t teaching students how to maintain vehicle control on slick surfaces.
Students get a heavy dose of classroom tutelage, then plenty of seat time behind the wheel of Toyota Camrys and 4Runners to put theory to track under the watchful eyes of the instructors.
Bridgestone’s driving school offers winter driving classes to corporations and special groups, and a special trailer-towing course for those who face hauling equipment over slippery roads.
It’s the best driving school of its type in the country – and at prices those on a ski holiday can afford. But we aren’t here to learn winter driving techniques or vacation.
We are here to test snow tires – and to do so using the new diesel 4×4 we’d just rolled up in.
Tire comparisons are usually done using cars or SUVs, not 7,000-pound diesel pickups. And tire tests are never done on “E”-rated tires as we planned to do.
Our gracious host, Mark Cox, the school’s director and a seasoned rally driver himself, says our request to compare snow tires on a heavy-duty 4×4 diesel pickup was a “first” for them.
That made our snow tire shootout that much more fun for everyone involved – except maybe the poor guys who drew the short straw to be the official tire changers.
As for the test itself, we invited nine of the big-name snow tire manufacturers to participate, and encouraged them to send a tire engineer along to participate in the actual tests and offer insight related to their entry.
Michelin, Hankook, Cooper, Toyo, Continental, BFGoodrich, Bridgestone, Nokian and Goodyear received multiple invites.
Only three stepped up to our tread-to-tread challenge: Bridgestone, Nokian and Goodyear.
Goodyear’s SR-A all-season light-truck tires came on our 2011 GMC Sierra HD Crew Cab and served as our “control tire.” (A control tire is run at the start of a test, mid-way through, and at the end so any changes in the track surface condition can be factored into the numbers.)
We had the tires shipped to our Alabama office, where we put them on a 3/4-ton GM 4×4 diesel crew cab and ran each set over the same 100-mile section of interstate. This dry run rid the tires of release compound and opened up the sipes.
Release compound is like a lubricant and would have definitely affected our performance numbers if we tested the tires right off the rack. Sipes, those tiny cuts in the tread blocks that grip snow, also require pavement scuffing to open them before hitting the snow.
After break-in, two sets of tires were re-mounted on 17×7.5 Accuride OEM steel wheels to fit GM heavy-duty pickup’s new 8-on-180mm bolt pattern.
We used one set of ProComp 6032 alloys for the third set. The mounted tires were then shipped off to Colorado.
Our tire shootout is very straightforward: Each set of tires is tested and scored both objectively (computer data) and subjectively (personal observations) in three areas: acceleration, braking, and handling.
Driving Sciences’ test driver Kurt Spitzner, who is also an instructor at BWDS, is our designated wheelman.
Mark “Mr. Charts & Graphs” Kuykendall, Bridgestone’s light-truck engineering manager mans the brace of Vericoms.
Spitzner accelerates the 7,200-pound Sierra Crew Cab diesel in 4Hi as quickly as possible to 30mph without triggering traction control and then stops it as fast as ABS allows.
The VC2000s log G-force, time and distance every moment of the tests, which are done six times in succession for each set of tires.
Spitzner first runs the stock Goodyear SR-A “control” tires to establish a baseline for the surface conditions. The test team allows a two-minute cool-down between each of the six runs to prevent heat-induced brake fade from creeping into the picture.
“We want to make sure we know exactly what the surface under the control tire will be,” explains Kuykendall, who has been gathering tire data like this for decades. “We’ll keep these results handy, and as we go through the day, we’ll rerun that control [tire] to see how the track surface has changed.
“Unlike a paved surface that is consistent,” says Kuykendall, “we are dealing with a surface that gets modified every single time a tire rolls over it.
“Whether that tire is rolling or sliding over the surface, it changes the ice. So Kurt has to adapt to those changing conditions to get the best numbers. It’s very similar what we teach at the school – a driver has to adapt to the constantly changing conditions that the ice presents.”
After the acceleration/braking session, Spitzner and Kuykendall make their notes giving a 5-minute cool-down window for the brakes before beginning the final test – the road course.
Spitzner makes three back-to-back laps around the winding, undulating .9-mile track while the computer records more data.
He follows a very specific line to get the fastest and most consistent laps, much like a veteran dirt-track driver does.
LATE FOR WORK
“When I first got here this morning, I burned in a prescribed route that brushed all the snow off the course, so I was down to an ice [packed snow] surface before I took the control tire out,” says Spitzner who has spent years testing winter tires at the school.
“Then I make my laps with the control tire to get a feel for how the GMC handled.
“My goal here is consistency,” says Sptzner.
Spitzner equates his driving style to the contractor who is running late for work, but not going to get in trouble if he’s five minutes late.
“I’m definitely trying not to invoke crash control, invoke ABS, or employ any advanced driving techniques to get the GMC around the course faster. My goal is to drive the vehicle based on the merit and essence of each tire; to be as quick and consistent as the tire will allow. Basically, I’m running laps at 8/10’s speed instead of 10/10’s lapping situation.”
The testing session started at 10:30 in the morning (after the snow stopped and the track was clean) and concluded at 4 p.m. The ambient temperature varied between 17 and 26 degrees with the coldest being in the afternoon.
Our control tires were run at the start of the morning session, just before the mid-day break, at the start of the afternoon session and again at the end.
Kuykendall factored in the control tire’s test deviations accordingly so the data for each set of tires was adjusted for minor changes in track conditions – much like drag racers do when correcting times for changes in temperature and humidity.
Our conclusion at the end of a full day of snow tire testing boils down to one simple precept: The test data speaks volumes about vehicle control and safety.
The lower the acceleration times, stopping distances and lap times, and the higher the G-force numbers, the better the tire. The better the tire, the more control you have behind the wheel. The more control you have behind the wheel, well, the safer you are.
While Goodyear SR-A control tires that came on our new Sierra are good performers three seasons out of four, they definitely don’t inspire a feeling of confidence to the driver when subjected to packed snow, ice and the accompanying cold temperatures.
“The control tire [SR-A] was typical of what we find in a lot of all-season/M&S type tires, in that they seem to have one characteristic that they do relatively well, and other characteristics which fall by the wayside,” says Spitzner after the tests concluded.
“In this situation, the control tire felt pretty good in terms of straight-line acceleration and how it handled in fresh, unpacked snow. To the typical driver it would feel quite good as soon as the light turned green or you were driving on powder.
“But if the snow is packed, the moment you approach that first corner and turn the wheel, nothing happens. The truck just slides straight ahead. These tires definitely don’t like ice.”
The consensus of our group was Goodyear SR-A delivers a reasonable amount of grip when it’s in fresh powder. But the reality is we’re usually not driving on fresh snow in wintry conditions – we are driving on ice.
Kuykendall says, from a tire design perspective, the type of performance exhibited by the SR-A is to be expected.
“Snow traction is more pattern-oriented; whereas, ice traction is more tread-compound-oriented,” he explains. “The typical all-season/M&S-type tire design uses a harder tread compound to give more mileage [better tread wear] and fuel economy. From a compound standpoint, that is the wrong direction for ice.”
“The key factor to a good snow/ice tire is finding a rubber compound that adapts to the road surface and retains that flexibility overall going into lower, colder conditions,” says Kuykendall.
That’s why purpose-built snow tires, which are designed to maximize grip in sub-freezing conditions on frozen surfaces, have such a huge performance and safety advantage over their warm weather counterparts.
The real test of how well tire engineers have done their homework is compiling notes and data at the end of the day-long test session. Some of the results were expected, other’s not.
For example, our test drivers gave the Nokian Hakkapeliitta LT’s mixed reviews.
“It delivered quite good acceleration and braking,” says Spitzner of the straight-line performance. “But they were a little disappointing on the road course.
“What I was least comfortable with in the lapping session,” Spitzner continues, “is while I could generate a surprisingly decent lap time with it, in order to do so, I had to take it out of its comfort zone. I had to really drive it hard. And, it was hairy on the edge.
Still, the Nokian’s lap times were close to the best times laid down by the WRTs.”
Our test engineer had similar observations, noting “Having done some things with Nokian’s Hakkapeliitta tires in the past, I was a little disappointed. They hook up well. They stop pretty well,” says Kuykendall, “But the Hakkas didn’t throw out the big numbers – or this case the small numbers – on the braking side, that I expected.”
What surprised everyone was Goodyear’s WRT snow tires out-accelerated and out-stopped the Nokians and consistently put down slightly quicker lap times on the road course.
“The Goodyears accelerate surprisingly well, and of all three of the test tires, the Ultra Grip Ice WRTs were the most linear,” Spitzner says.
Kuykendall shares the praise on the Ultra Grip Ice WRTs adding, “The Ultra Grip is probably the number two tire in the group, in terms of numbers, braking numbers particularly. Pretty solid; one of the better LT [snow] tires I’ve been on.”
The WRTs averaged about 10 seconds quicker laps around the nearly mile-long track than the stock tires. Goodyear’s snow tire out-accelerated the SR-As by nearly 20 feet and out-braked them by half-a truck length.
The difference between the WRTS and the Hakkas was much closer, with the Goodyears nipping the Nokians by less than 6 feet in the braking and acceleration runs and only 3 seconds on lap times.
Both our subjective and objective evaluations shows the Nokian Hakkapeliitta LT and Goodyear Ultra Grip Ice WRT are a big step above the performance of the Goodyear SR-A in winter conditions.
KINGS OF COLD
While the Hakkapeliittas and Ultra Grip Ice WRTs were locked in frosty competition, Bridgestone’s W965s powdered their treads.
The W965s had far better acceleration and braking numbers than either of the competitors, and worked noticeably better on the heavy GMC Sierra Crew Cab diesel around the road course.
The Blizzaks laps 10 seconds quicker than the Nokians, 7 seconds faster than the Goodyear WRT, and 23 seconds better than the SR-As.
“This is the first time I’ve tested a W965,” says Spitzner. “We use them on our school’s bus and on our F-250 we use for plowing the road courses here. But, no one has ever done hot laps in the bus or the Ford. So this test was an eye-opener for me.
“Short of flooring it and side-stepping the brake pedal to break traction, I could go at the acceleration runs absolutely full throttle, foot to the floor, and never invoke traction control. That’s pretty amazing, considering the torque the Duramax diesel delivers.”
That performance didn’t stop on the straight. Spitzner points out the Bridgestone was easier to drive on than the other two dedicated snow tires.
“The transitional response to the tire is very benign,” Spitzner explains of his lapping sessions. “In other words, I can transition from accelerating to braking, from acceleration to cornering, from corning to braking, from corning to acceleration super easily and it doesn’t upset the tire and it doesn’t upset the truck.
“The W965 is a confidence-inspiring tire on this pickup.”
Before we packed up gear and tires, ProPickup’s contributing editor, Larry Walton, and I took one last turn behind the wheel on the road course doing four laps apiece with the stock tires and four on the W965s.
That seat time confirmed what we’d seen all day: If your were a contractor running late for work driving over snow-packed roads, you’d definitely want dedicated snow tires at each corner.
The Blizzaks would no doubt get you there on time and in one piece without raising one’s stress levels. The stock M&S tires? Not happening. White knuckles all the way.
Our test data clearly shows the nonprofessional driver/professional contractor would feel the performance difference between an OEM tire like the SR-A and these purpose-built snow tires in cornering, feedback, steering response, braking and acceleration – all critical aspects for the contractor who might be plowing roads or towing a trailer during the winter.
Keep that in mind as you prep your pickups this season. Driving safety begins with having the right treads.
GOODYEAR ULTRA GRIP ICE WRT
Goodyear sent a set of Ultra Grip Ice WRTs, the company’s first dedicated winter tire for pickups and SUVs, in an “E”-rated LT265R70/17 to match the OEM tires. The “E”-rating is important for those who find themselves towing heavy fifth wheels and goosenecks.
The Ultra Grip Ice WRT (Winter Reactive Technology), a directional tire designed for light trucks that retails in the $250 range, features one pattern of tread blocks in the center region and a much different design in the shoulder/intermediate region.
The polymer blends used in the tire’s rubber compound helps it remain soft and flexible at low temperatures so they perform much better on cold road surfaces.
“The 2D blades provide sharp biting edges that help deliver excellent straight-ahead traction on ice and snow,” explains Goodyear’s Jim Davis.
“Our patented 3D ‘Waffle Blades’ in the shoulder and intermediate zones of the tire help improve shoulder block stiffness, maximizing the sipe density while optimizing steering and handling on dry and wet winter roads, as well as dry braking performance.”
“The Ultra Grip ice WRT tread pattern is designed to provide excellent grip on slush, snow and ice by dispersing slush and water as quickly and efficiently as possible.”
Nokian Tyre’s “E”-rated Hakkapeliitta LT line is designed specifically for pickups and SUVs, and they come in as our betting favorite as the Finnish snow tires have always been highly touted for their winter performance.
The tires retail for the same price as its competitors ($250) and feature self-cleaning, directional “Arrowhead Tread Pattern” and an independent-block tread design to remove snow, slush and water between the tire and the road.
The individual tread blocks also provide added lateral traction.
Nokian says the Hakka’s “large number of sipes and the innovative rubber blend guarantee good grip on slippery surfaces.”
Of interest, but not used for our tests, these Hakkas incorporate Nokian’s “Eco Stud System,” which is an advanced system of prepared stud holes with padding at the bottom to prevent the studs from working loose and keeps them in the tire for longer.