...according to a recent Motor Trend article.

I was surprised to learn that if you're buying just 2 tires, they should always go in the back, regardless of drive type (AWD/FWD/RWD). This is contrary to what I've always heard since I was a kid.

The article also mentioned a counter-intuitive recommendation to handle a blow out -- first step on the gas to regain control, then pull over!

Interesting article...

 

What was their reasoning for putting them on the back of a FWD?

 

The reasoning was based purely on empirical data. The article stated that no matter what wheels drive the car, the new tires belong out back. My guess is that, because the back ends of most cars are lighter and are not subject to steering input, their traction comes at a premium over the front wheels, which ARE steered and bear more of the car's mass (and initial forces like cornering and braking, whereas the rear wheels see the most action only when accelerating).

The blow-out advice is very sound. It happened to me once while on the NY State Thruway at about 80 mph, while I was accelerating to pass another car. I am thoroughly convinced that I maintained control of the car ONLY because I was accelerating.

Marty

 

"What was their reasoning for putting them on the back of a FWD?"

I think the main reason is to control oversteer. The author describes doing 2 tests on a wet tire company test track. When the best tires were mounted in the front, the car would spin out of control at a particular point on the track. In the second test, the best tires were at the rear, and he could easily traverse the same point at the same speed without losing control.

The article also mentioned the importance of tire pressure. Even a 5 pound deficit can lead to significant hydroplaning. According to the tire company, it's much better to have a slight excess pressure than a deficit.

 

Did they comment on wether or not these findings would hold up in the snow?

I would imagine in the snow you would still want the best tires up front to have the requisit traction to not get stuck.

 

>>"What was their reasoning for putting them on the back of a FWD?"
>>
>>I think the main reason is to control oversteer. The author describes doing 2 tests on a wet tire company test track. When the best tires were mounted in the front, the car would spin out of control at a particular point on the track. In the second test, the best tires were at the rear, and he could easily traverse the same point at the same speed without losing control.
>>

So, wouldn't it make sense to put new tires on the front of a MINI, which tends to understeer?

 

"Did they comment on wether or not these findings would hold up in the snow?"

No. But dynamic behavior on a snow-slicked surface is probably similar to a wet surface.

If you're stuck in the snow, oversteer is not a big concern!

 

In snow you need your best tire moving the car ,if it steers it also so be it,

 

>>...according to a recent Motor Trend article.
>>
>>I was surprised to learn that if you're buying just 2 tires, they should always go in the back, regardless of drive type (AWD/FWD/RWD). This is contrary to what I've always heard since I was a kid.
>>

>>
>>Interesting article...
>>

I was given the same advice by some people at the Tire Rack. After living with it both ways I can verify they're 100% correct.

 

I've seen this one before, and the logic went that (on FWD anyway) the fronts wear the fastest , so people are used to driving with less tread on the front. Turn that around, and people may experience 'unexpected handling characteristics'. The bit about understeer being safer than oversteer I understand, but I can't say I buy the reasoning overall.
In any case, one should rotate the tires so you don't get into the conundrum of buying only one pair.

The flaw in the logic is that it would follow that you don't rotate your tires F->B because then the least worn tire would be on the front. Then again, most people aren't logical and pay more attention to their latte' than their tires...

 

from Tire Tech on TireRack.com.

"Most vehicles are equipped with the same size tire at every wheel position. Ideally all of these tires should also be of the same type and design, have the same tread depth and be inflated to the pressures specified by the vehicle placard or owner's manual. This combination best retains the handling balance engineered into the vehicle by its manufacturer.

However due to the front tires' responsibility for transmitting acceleration, steering and most of the braking forces on front-wheel-drive vehicles, it's normal for front tires to wear faster than rear tires. If the tires aren't rotated on a regular basis, it's also common for pairs of tires to wear out rather than sets. And if the tires aren't rotated at all, it's likely that the rear tires will still have about 1/2 of their original tread depth when the front tires are completely worn out.

Intuition suggests that since the front tires wore out first and because there is still about half-tread remaining on the rear tires, the new tires should be installed on the front axle. This will provide more traction, and by the time the front tires have worn out for the second time, the rear tires will be worn out too. However in this case, intuition isn't right...and following it can be downright dangerous.

When tires are replaced in pairs in situations like these, the new tires should always be installed on the rear axle and the worn tires moved to the front. The reason is because new tires on the rear axle help the driver more easily maintain control on wet roads because new, deeper treaded tires are more capable of resisting hydroplaning.

Hydroplaning occurs when the tire cannot process enough water through its tread design to maintain effective contact with the road. In moderate to heavy rain, water can pool up in road ruts, depressions and pockets adjacent to pavement expansion joints. At higher speeds, the standing water often found in these pools challenge a tire's ability to resist hydroplaning.

Exactly when hydroplaning occurs is the result of a combination of elements including water depth, vehicle weight and speed, as well as tire size, air pressure, tread design and tread depth. A lightweight vehicle with wide, worn, underinflated tires will hydroplane at lower speeds in a heavy downpour than a heavyweight vehicle equipped with new, narrow, properly inflated tires in drizzling rain.

If the rear tires have more tread depth than the front tires, the front tires will begin to hydroplane and lose traction on wet roads before the rears. This will cause the vehicle to begin to understeer (the vehicle wants to continue driving straight ahead). Understeer is relatively easy to control because releasing the gas pedal will slow the vehicle and help the driver maintain control.

However, if the front tires have more tread depth than the rear tires, the rear tires will begin to hydroplane and lose traction on wet roads before the fronts. This will cause the vehicle to begin to oversteer in which the vehicle wants to spin. Oversteer is far more difficult to control, and in addition to the initial distress felt when the rear of the car starts sliding, quickly releasing the gas pedal in an attempt to slow down may actually make it more difficult for the driver to regain control, possibly causing a complete spinout.

Members of The Tire Rack team had the chance to experience this phenomenon at Michelin's Laurens Proving Grounds. Participants were allowed to drive around a large radius, wet curve in vehicles fitted with tires of different tread depths — one vehicle with new tires on the rear and half-worn tires on the front, and the other with the new tires in the front and half-worn tires on the rear.

It didn't take long for this hands-on experience to confirm that the "proving grounds" name for the facility was correct. The ability to sense and control predictable understeer with the new tires on the rear, and the helplessness in trying to control the surprising oversteer with the new tires on the front was emphatically proven.

And even though our drivers had the advantage of knowing we were going to be challenged to maintain car control, spinouts became common during our laps in the car with the new tires on the front. Michelin advises us that almost everyone spins out at least once!

Experiencing this phenomenon in the safe, controlled conditions of Michelin's Laurens Proving Grounds rather than in traffic on an Interstate ramp in a rainstorm is definitely preferred!

In case there is any doubt, when tires are replaced in pairs, the new tires should always be installed on the rear axle and the worn tires moved to the front."

Alex

_________________
Alex ext 294

800 522 8473

Tire & Wheel forum moderator

www.tirerack.com

alex@tirerack.com

 

Alex, I get how this explains for hydroplaning in wet conditions, however, 99.95% of my driving is done in the arid conditions of Arizona. Does this still hold true for dry weather conditions or is this only for potential hydroplaning?

 

I have known several people with FWD cars who have replaced front tires on two, even three occasions while leaving the rear tires alone "because they have a lot of tread left on them". What ends up happening in all these cases is you have old, hardened tires often with scalloped wear patterns which create a lot of noise, but 'there is still a lot of tread left'. These cars often act squirrely in turns even in dry, warm weather, and are almost nightmarish if not downright dangerous in bad weather.

Tires have not only a life based on usage, but time as well. A brand new tire, never used but kept in storage for a few years will deteriorate and is not going to have the same grip and handling characteristics as a factory fresh tire. A tire installed on a car seeing daily use and exposure to sun, air, ozone and other environmental nasties will deteriorate much faster, even if the mileage is low. Look closely at an old tire and you will see cracking and other signs of deterioration.

How many times have you used an old pencil and needed to use the eraser? The same thing happens with tires.

There is a movement to require 'best if installed by' dates on tires. I think this is a good idea, as well as 'real' dates of manufacture rather than some indecipherable code.

 

Don't be lazy..... Just rotate your tires!

_________________