Winter is here in the northern hemisphere, and for many people, that means snow. You’ll naturally want to have your daily prepped for the weather with a solid set of winter tires, that much goes without saying. But what should you do about tire pressures?
Here to answer that question is Jonathan Benson, the professional test driver behind Tire Reviews on YouTube. He set out for the Pirelli proving grounds, armed with a Mk 7 Volkswagen Golf wearing Pirelli Cinturato Winter 2 tires. That gave him a beautifully prepared, evenly-graded snowy surface upon which to execute his testing.
This holiday season, you could set your tire pressures based on the advice of any number of uncles, grandmothers, or scary cousins. Alternatively, you could watch the video below, understand what’s going on, and decide for yourself.
The test regime was simple. Benson set about timing acceleration runs from 5 km/h to 35 km/h (3-21 mph). For braking, the test involved measuring the distance taken to brake from 40 km/h (25 mph) down to 5 km/h (3 mph).
The results will be familiar to anyone who has done a lot of driving on soft surfaces. For example, it’s well-known that driving on sand is easier at lower tire pressures. This is because a tire at lower pressure has a larger contact patch, reducing ground pressure and allowing the car to “float” more on top of the surface rather than digging in.
“The lower the pressure, the better the grip is,” says Benson. “That’s something I’m very happy to tell you.” The clearest gains were found in the acceleration tests. The Golf accelerated to 35 km/h (21 mph) almost a full second quicker at 10 psi than at 50 psi. Meanwhile, braking distances from 40 km/h (25 mph) were 3.2 feet shorter than at 50 psi, though the improvement dropped off below 20 psi.
The video also includes a handling test. Benson times how long it takes him to complete a simple course on a snowy track. He completed runs at 50 psi, 35 psi, 20 psi, and 10 psi, noting how the car’s behavior changed at each level.
As you might imagine, 50 psi is simply too much. “I started at 50 psi, what did I notice? The car felt pretty uncomfortable,” says Benson. “Turn in felt pretty positive and quick, but then it very quickly break into understeer.” Dropping pressures down instantly improved the feel, however. “At 35 psi… the car now feels much more compliant over the bumps… brakes feel more positive,” he says.
There are yet more gains to be had, though. “20 psi feels awesome!” Benson exclaims, as he heads out on the snow circuit once more. The changes are instantly obvious to feel through the steering wheel. “Everything does happen a little bit slower, the steering definitely doesn’t want to react how it did before, but when you’re turning and when you’re braking, and the traction out of the corners in particular is just outstanding.” Lap times were seconds faster with the tires at lower pressures, too.
At 10 psi? “As for the handling, coming out of corners you can really get on the throttle…” says Benson. “There is a bit of slip, but you can feel that extra traction.” He notes the biggest benefit is when accelerating in a striaght line. “When you’re turning, I don’t know if I’m rolling onto the sidewall… but you do seem to lose a little bit [of grip] laterally.” Still, the lap time was another 0.7 seconds faster than running the tires at 20 psi. Not bad!
All these tests were done on snow, which raises an obvious question—what about ice?
Accelerating on ice showed that it’s possible to go too low with your tire pressures, even negating concerns about rolling a partially-deflated tire off the rim. The tires did still perform better at lower pressures down to 20 psi, but going one step further to 10 psi was less helpful. At 10 psi, the test car took a full 5.23 seconds to reach the test speed of 30 km/h (18.6 mph), versus 4.67 seconds at 20 psi and 4.96 seconds at 50 psi. Results were less conclusive when it came to braking, however. The car performed best at 10 psi, and worst at 30 psi.
Overall, though, Benson advises against going too low with your tire pressures. “I think we’ve pretty much solidly proven that the lower pressure is the better pressure,” “However, don’t go down to 10 psi, it’s not worth the small advantage.” He notes that at this point, you risk rolling a tire off a rim and getting stranded. The important thing to remember is that you need to reinflate your tires back up when the snow conditions are over. “Make sure you reinflate your tires [because otherwise] you’re going to get pretty serious uneven wear on the outer shoulders at such a low pressure,” he explains.
Benson’s conclusions concur with others in the field. Notably, the rally experts at Team O’Neil did a similar test some years ago. Their assessment was the same—lower pressures create a larger contact patch which aids grip in the snow.
What should you take away from all this? Basically, if you’re having trouble with grip in the snow, start with winter tires, and consider dropping your pressures lower than usual. Just know that once you start getting below 20 psi or so, your chances of causing damage or pulling the tire off the bead increase, which could cause you a lot of hassle. In any case, drive to the conditions and look after your car this winter season to minimize your chances of having an accident in the snow.
Image credits: via YouTube screenshot
when i had my ranger, i never got stuck. when i shoveled the driveway i tossed all the snow in the bed. super traction. yes there was a tendency for oversteer but i adjusted. best, it melted when it wasn’t needed any longer. oh yes i did have a bedliner.
Don’t forget to switch out your summer air with winter air
I might just have to try it this if I’m able to make my car club’s ice gymkhana on Georgetown Lake (Georgetown, CO). Typically, the course is on windswept ice with some drifts. Aim for the drifts if you need to change direction.
Keep the pressure as the door sticker says. You’ll destroy the tires with potholes.
The best way to maximize performance in snow and ice? slow the f down.
Yeah a well groomed snow covered track is a lot different than a salty/icey/maybe snowy/shitty pothole having road that is typical in the northeast.
Yeah well the article’s title is “snowy driving,” not “snowy driving on a track.”
Low pressure might be good for traction but its terrible for mileage. Maybe sidewall wear too.
To add to your point, the speed at which hydroplaning occurs on standing water (during those interim close to freezing temperatures) decreases with tire pressure.
Keep your tire pressures when you’re driving regularly.
Handy to lower pressure temporarily in a pinch while in certain situations though.
I have a Ryobi 18v inflator that I keep in the camper van. Works way better than a 12v inflator plugged into the cig lighter. 75 psi in the rears for little 16 in tires.
I was in Iceland at the beginning of this year and our group took a “super Jeep” as they’re known there – custom built vans/trucks for Iceland terrain. They have tire pressure management systems on their huge tires (34″ maybe even bigger) and will go all the way down to 3psi which will let them go over 2m deep snow. Won’t try going that low on my Ford Maverick however…
Oh! So when the TPMS says tire pressure is too low when it gets cold out, that just means that I’m ready! Nice.
Since where I live snow is a temporary thing lasting maybe a week. I’ll just leave the tire pressure alone. Good to know, but until I spend several days in Tahoe in the winter, I won’t make any changes.
10psi!?!
I drive an Audi Q7 with 275/45/20 Blizzaks at ~50psi for the winter here in Canada. If you go much below the recommended pressure for the tires with a heavy vehicle you risk having way too much sway. You lose control. I passed at least 5 vehicles sitting in deep ditches all along the highway 2 (aka Dundas Street) corridor this morning after over a foot of snow fell last night. I had no issues after cleaning the huge pile of snow off of my vehicle & just driving through the snow bank that the plow left behind my parking spot. Quite a few vehicles could barely get out of their side streets. People seem to like to try & floor it to jump in front of someone although all they do is sit there & spin!
No spinning of my tires nor fishtailing even when I pulled out of a parking lot with almost 2 feet of snow this afternoon.
South West Ontario is pathetic when it comes to dealing with snow & driving.
This is a good video, but there’s a lot of variation in snow. IME and the handling I like, I wouldn’t go as low as 20 psi unless the snow is consistently deep enough for the tires to not break through to the pavement, including frozen snow under fresh. I stick to around 30 as it’s a good general pressure for the typical variable conditions I run into. Or at least did—we haven’t gotten much snow in the last few years.
Would be interesting to know what is the variation in the results. And what happens with the different pressures when you hit thick slush… Although it would be difficult to test.
I’m also interested in that, slush is my least favorite of driving conditions.
I test mine by doing the WalMart parking lot test.
And yes obviously I can feel a 1.5 lb difference in pressure.
And using shoppers, and their carts, as my imaginary pylon cones…YMMV
Another way low pressure seems to help is that the extra flexing of the tread cleans out the areas between tread blocks. I say seems because this is simply my anecdotal observation from the first time I aired down some WinterForce tires on my old Subarus’ 13” wheels. I couldn’t get up a hairpin to the site of Audie Murphy’s plane crash as earlier snow had melted, then refrozen, and there was fresh snow on top. My tires were smooth surfaces with pretty patterns. Let them down to low 20s, and the snow & ice chunks were ejected from the low points on the backside of rotation allowing some bite and therefor progress.
I will say that 185/70/13s get a >bit< squishy for hard cornering on pavement at low pressures, though. I carry a small compressor now—but of course we haven’t had snow in a couple years. Fingers crossed!
I run my Blizzaks at the pressure on the door sticker. I mostly drive on dry pavement at home and ice, slush or hard pack in the mountains. I rarely encounter fresh snow so messing with pressure seems like overkill.
The correct solution to all winter conditions is to apply more throttle.
This is, of course, assuming you’re driving RWD as God intended.
-Resident Canadian
I do the same with my FWD. Never had a problem. Winter driving it fun. Canadian too.
Instructions unclear, bought another RWD.
As a person who drove an e36 M3 to work today in the snow, I agree.
As a person who, back in the day, drove an Elise in the snow fitted with a Pirelli SnowSport (front) / SottoZero (rear) combo setup, I agree as well. Don’t underestimate winter tires, RWD, and having all the weight of the engine and gearbox over the rear wheels. It was supremely well behaved. Just had to get used to the sound of snow against the flat bottom of the car due to the very low ground clearance.
Me too!
Elises are fantastic in snow, until the ground clearance becomes a problem.
God I miss that car.
I watched this video this weekend, ah the algorithm. As someone who airs down for off roading, it did not seem like he had ever done that for off roading. Good video. Lucky guy to have an winter track for himself for a day.