" I did not think I was going too fast". A common remark from people losing control of front wheel drive vehicles. What the average person and some experts are not aware of is that there can be as high as 950 pounds or more weight on the front axle of their vehicle than the back. So a car that feels like a limousine on the front holds like a golf cart on the back
A 3000lb car with a weight ratio of 65% front weight and 35% rear weight will weigh 1950lb on the front and 1050lb on the rear. After you use 10 gallon of fuel from the rear tank one of the front wheels has as much traction as both rear combined.
If you analyze single vehicle accidents you will find most of them had better tires on the front than the back or a very large weight difference. In fact the worst balanced cars have 4 times as many fatalities as cars designed with better balance. How are you going to tell how fast is too fast under these conditions when it is possible for a balanced car to handle fine on a slippery surface at 50 mph and an unbalanced car to loose control at 20 mph and both to feel the same to the drivers.
I guess your point is slow down!?
Race driver’s and driver’s who test cars for magazine reviews are well aware that FWD cars understeer and RWD cars oversteer. If you go too fast in a FWD car into a corner the front of the car pushes straight ahead even when you turn the wheels to make the car turn. That is understeer, eventually when you gain traction with the front wheels the back of the car can whip around and you’ll spin out. This doesn’t happen much on dry roads to normal drivers at reasonable speeds. It does happen to drivers in low traction conditions such as rain, snow, and ice. And it can happen when you drive the car too fast.
FWD cars get good traction for startting and stopping but really aren’t an optimal set up for cornering at high speeds or in low traction situations.
Why am I not concerned with numbers, weight distribution, if I am driving front wheel or rear wheel drive? it is because I don’t drive a half inch from being totally out of control. Drive sensibly and stay home when the weather is bad and you just may end up dying from something other than a self inflicted automobile crash(notice I did not say “accident”?)
As OP stated, in spite of evenly worn tires on both front and rear, FWD cars WILL have better traction on front due to the weight bias.
FWD is an engineering compromise is at it’s best, cruising in a straight line. Drivers would be wise to pay attention to car loading like they must with boats and planes and not take FWD for granted.
And as carefully as one thinks they drive, it goes out the window in an emergency maneuver when the “other guy” isn’t quite so careful.
I think the points brought up are excellent and some of the reasons 2012 is the year all new cars must have stability control.
Just to repeat: If you have FWD, keep the best tyres on the back, not the front!
With any car, don’t try to drive it to the limit of it’s abilities or yours. At least don’t do it near my car!
Just as an added thought; If you listed the best handling consumer on road vehicles in each class in the world, you’d be hard pressed not to include mostly RWD cars. If you listed some of the worse handling consumer on road vehicles in the world, you’d be hard pressed not to include some rwd cars and trucks. I think it says a lot for the importance of weight distribution for all other vehicles as well; including 4 wd and awd. Amazing how many people buy 4wd trucks, leave them empty and expect good over the road performance in either 2 or 4wd.
“If you analyze single vehicle accidents you will find most of them had better tires on the front than the back or a very large weight difference. In fact the worst balanced cars have 4 times as many fatalities as cars designed with better balance.” <Harvey M, OP>
Can you back that statement up with solid research or is this just a hunch of yours that you are posting as fact???
I took university studies which had the fatality rates per million registered cars and then graphed these figures against the weight ratio. I used 4 size classes in order to keep a consistent graph. As it turned out some smaller balanced fwd had fewer fatalities than larger fwd cars. In all there where 30 popular models
In my very limited racing experience (just ice racing when young) I feel confident in saying two things about those that did. In addition to all the other factors there was an equal fastidiousness about balance with the drivers. Secondly, they were keenly aware of driving balance in their family cars and any towing as well and showed a general concern for it as a safety factor in every day driving. That’s why even today, I keep 10 bags of tube sand in the garage, which I even use from in my trucks in the summer when normally empty.
I was looking for the data collected that stated the condition of the tires on the vehicles involved in crashes that resulted in at least one fatality.
I don’t agree that FWD is more accident prone.
There are plenty of SUVs and big RWD sedans careening off the road too.
The tire condition was collected by interviewing insurance claims adjusters who record condition of tires and by investigating auto wrecking yards and also rescue services. The graphing was done for fwd only. There are not enough numbers to accuratly graph suvs but for the few there are it looks like a 58/42 suv will have fewer fatalities than a61/39 suv
I hear you, but I take from it that FWD cars are not automatically immune from balance problems in handling because the weight is over the drive wheels. All poorly balanced cars regardless of their drive train are more difficult to control. We all agree that top heavy SUVs have their own problems. FWD cars can have theirs as well. I see no problem.
The tire condition was collected by interviewing insurance claims adjusters who record condition of tires and by investigating auto wrecking yards and also rescue services
Of my 30+ years as a Software Engineer and SW-Engineer Manager…I worked 10 of those years consulting to the Insurance industry. Interviewing claims adjusters is a very very inefficient way to get the data…and EXTREMELY INACCURATE. The insurance industry stores all this data in HUGE databases (one large insurance company had well over 10 terabytes of data collected on just auto crashes). The data is very very documented…They keep data on everything…Driving conditions…vehicle…Vehicle condition…even the color of the vehicle…Every accident for over 30 years is stored. One of my jobs was designing a analysis tool for the guys who wrote the actuary tables to analyze the data.
To say that a tires had anything to to with the accident…is at best statistically irresponsible. There are far far too many other factors NOT being considered to make any kind of broad based conclusions. Far too many other factors going on.
Once I started to graph weight ratios to fatalities I thought there should be a mathematical way to project when car would would tend to go out of control. A vehicle is most unstable when one front when one front wheel has more traction than both rear combined which would be 67/33
So to reach 67/33 the following forces have to be present to destabilize vehicles with the following weight ratios
- 50/50 --.95G
- 55/45 --.70G
- 60/40 --.42G
- 63/37 --.26G
- 64/36 --.19G
- 65/35 --.11G
- 66/34 --.06G
So it looked like rear traction was of the utmost importance. All together I have talked to over 1000 people about their accidents and looked at 300 or 400 vehicles all with better tires on the front.
It became apparent why race car drivers are so picky about balance
50/50 weight ratios have been the optimum for years. Pontiac Tempest in the '60’s had a motor in front and the tranmission in the rear to improve weight distribution. Yet, if you tune the suspension you can get a Porshe 911 which is heavy in the rear to out corner just about any other sport car.
So weight distribution is important and most designs shoot for good weight distribution. But other aspects of suspension tuning can improve the performance of front or rear heavy cars. The whole thing is too complicated to over simplify into a conclusion that FWD cars all handle badly or are dangerous.
Ralph Nadar did hammer the Corvair while some driver’s felt they handled great, until the point the rear axle rolled under and then the car flipped. Up until the moment it flipped it was one heck of a great handling car!
I never said all front fwd are dangerous.
Front-wheel drive with weight ratios of 60/40 and approaching 50/50 ie 59/31 have about same fatality rate as an average rwd which is about 50 per million. It is when the weight ratio is more than 64/36 that the fatality rate climbs to 200 per million.
Have worked on suspensions for 35 years and do not know which you can do to rear axle that weighs 1000 pounds when the on front axle weighs 2000 pounds
"The whole thing is too complicated to over simplify into a conclusion that FWD cars all handle badly or are dangerous. "
In agreement with UT. Consider that FWD is the engineering compromise that allows for better space utilization at the expense of optimal handling. RWDs seem to have an inconsistent legacy from the best handlers to the worse. From what I have read, the average public is better with understeer in normal driving than over steer. FWD has an abundance, so for normal, unstressed driving, commercial fwd is the compromise. Start adding loads, towing, slippery conditions, higher speed cornering, emergency maneuvering, and the naturally poorly balanced fwd looses it’s way. Stay out, as best you can, of “stressfull” situations, the fwd is a functionally safe way of transporting people, not heavy loads. Specialized cars and trucks all used for their intended purpose are always better and seldom FWD. FWD is a very difficult drive train to specialize with and are therefor more problematic when stressed. This has been well described by most of the previous posts who assert not to drive in weather that’s too slippery and towing limitations with the balance issue etc. With it’s dynamically poor weight distribution, initial traction advantage not withstanding, it will always be a second class citizen to optimal handling performance, but can be safely used within limits set by owner’s manuals.
I still see no disagreement with anyone’s point of view thus far…we just have too much time on our hands, re explaining ourselves.
Start adding loads, towing, slippery conditions, higher speed cornering, emergency maneuvering, and the naturally poorly balanced fwd looses it’s way
I COMPLETELY DISAGREE with this.
FWD becomes a problem ONLY when driven to EXTREME. You keep ANY fwd vehicle in LEGAL safe speed limits and you won’t have a problem what-so-ever.
Where fwd really shines over rwd is driving in snow. fwd is VASTLY superior to rwd when driving in snow…no question.
Here are some videos showing changes in behaviour of a fwd with different traction combinations. The stability test is mine.
http://www.youtube.com/watch?v=tGzZ85QEM3M front wheel drive stability
http://www.michelinman.com/tire-care/tire-basics/reartire-change