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Rob's Garage

The weighty matter of winter driving Add to ...

Hi Rob, sorry to continue this tire discussion - but seeing as how it's that time of year, I would like to ask one more tire question.

Is it beneficial to put extra weight in the trunk of a front-wheel drive vehicle for the snow?

Thank you, Debbie

No problem, Debbie. This is now more than a series of questions; we are approaching a discussion tread - I mean thread!...tires on the brain.

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And you're right; it is that time of year. Actually, when you think about it, tires are arguably the most important pieces of your car and there is an entire culture built around (no pun intended) tires. Along with the culture you will find the science behind this very complex industry.

Check out this site: Tire Rack tech info. As I was typing this reply, I did a little web surfing and came across this piece of info from The Tire Rack, and honestly, I wrote this next sentence before I looked at their web site.

If you were to park over a piece of glass and if you could get under that glass to look up, you would see that your car is resting on a tire contact patch area of about four square inches. Now you might think that combined with the three other corners that would be lots, but think of the tasks that tires are asked to do:

  • provide forward traction
  • stopping traction
  • steering
  • control water (hydroplaning)
  • maintain grip in snow
  • etc., etc.

And while all this is going on - sometimes at the same time! - your tires have to maintain proper contact with the ground.

Sorry to seem like I'm deviating Debbie, but I simply want to illustrate all the dynamics that take place at each corner of your car.

So, with that in mind, consider the weight bias of each vehicle. How did the manufacturer balance or distribute the weight of your car? This distribution of weight has a direct impact on the contact patch, which ultimately either keeps you moving or provides the means to get stuck. The more the weight, the greater the contact patch under adverse conditions. Now, of course, there is a limit and obviously too much weight is a bad thing as this condition can cause all kinds of other problems…

Back in the day, rear wheel drive was the norm and there are enough of us that remember the traction problems that came with those cars. But it also meant that those big trunks could swallow copious bags of sand or cement blocks or whatever was lying around. This of course made up for the lack of weight over the rear, drive axles. What this little piece of re-engineering did was shift the weight bias to the rear of the car (or truck). This was a good thing because typically, the weight of the vehicle was split approximately 60 per cent to the front and 40 per cent to the rear. By adding the weight to the trunk, more of a balance was created and in some cases, the bias was shifted to the rear. Not counting for overloading the car's carrying capacity, this was not altogether bad as the weight in the trunk was only there over the winter.

Now, fast forward to today's front drive cars and we have a whole different ball game. The weight bias has now increased to about 70:30 front to back - however, the drive wheels are (of course) at the end of the vehicle that already has a weight advantage. This set-up comes from the factory with its own built-in advantages when it comes to winter driving conditions as the drive wheels also steer the car, so with normal driving skills (whatever that means), a person is less likely to get into a dust-up with a snow bank. That said, there are still those that will place a little weight in the trunk - I think old habits die hard.

So Debbie, no, you do not need to put weight in your trunk when the snow flies - just install a good set of winter tires at all four corners and you'll be good to go.

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