AWD vs. RWD Handling- A Partial Answer
#1
12-15-2004, 03:32 AM
AWD vs. RWD Handling- A Partial Answer
I had an opportunity one afternoon to drive and compare the handling of the Dodge Magnum AWD (All Wheel Drive) and RWD (Rear Wheel Drive) RTs. People that are considering AWD probably have already learned that there are not yet any in-depth reviews published on the AWD and how it compares to the RWD. Until such reviews are available, here are some objective and subjective observations about the handling of these cars.
To help understand my comments, I should let the reader know that the primary source of my driving knowledge and ability is road racing, not cars, but motorcycles. While I have owned and driven sporty cars, driving on the street does not provide the skill development that occurs with repeated laps on a track. I’m not equal to the professional reviewers with there car racing experience and their knowledge of 4 wheel chassis dynamics. But I did develop many driving skills transferable to the 4 wheeled world.
An objective assessment of a car’s road holding ability is a real-world skid pad: 270 degree on-ramps. I like this test because these are actual fun sections of road that enthusiasts enjoy. They are fast, 40-70 mph, and if you pick the right ramps, the test is not menacing to the public if you goof up. 270 degree ramps allow quick determination of performance, because the vehicle speed can slowly be adjusted, and the length of the observation is long compared to a 90 degree turn. I have been driving the same ramps for 25 years, know every bump and crack, and have tested the speed and the behavior of numerous cars and motorcycles. I know the results are only accurate for a given year due to things like road wear and crack filling. For instance, during one year, I tested a Saab 900 at 55 mph, a Z/28 at 62 mph, and my sport bike at …73 mph.
How is the road holding ability of the RWD compare to the AWD with its greater ground clearance, weight, different front suspension and weight distribution, and additional powered wheels? The test drive reveals all.
Finally, it was time to set the tire pressure on both cars to 40 psi and hit the road. The AWD had the vehicle leveling rear suspension, the RWD didn’t. I previous drove a RWD with leveling and I will comment on that car also.
On the 270 degree ramps, tire vibration, the initial sign of slippage, occurred at 45 mph for both the AWD and RWD. Pushed beyond that, by increasing the entrance speed into the corner or accelerating mid-corner, both cars reached 50 mph before starting to drift, that is, they were unable to hold to the inside line of the corner.
This limit of traction can be located by most drivers on 270 degree ramps, because of the time available to adjust speed mid-corner. Most drivers undershoot or overshoot the limit of traction on 90 degree corners because they don’t have a road-racer’s time-speed-spatial senses to judge the maximum possible cornering speed for an approaching turn, unless they take corner repeatedly. At the limit, the RWD was wonderfully stable, controlled, forgiving of errors throttle control -- encouraging one to push even harder, possibly reaching 1 mph greater cornering speed at about 50 mph (I couldn’t take my eyes off the road to confirm). It’s forgiving cornering behavior reminded me of the Saab 900.
Only at the limit, about 50 mph in this corner, did the AWD behave differently. It was less stable, being a bit squirrelly, nothing dramatic, but the driver is clearly aware that the limit was reached. Letting off on the gas the car immediately returned to feeling of complete stability.
The difference between vibration and drift was 5 mph. This is the warning range or safety factor, meaning, if you intend to take a corner aggressively, and you encounter tire vibration, you can be off by up to 5 mph and still make the corner. I have since noticed similar warning on wet roads. I judge this to be a good characteristic of the Continentals, because it reduces the chance for loss of control when misjudgment occurs. Many performance tires have a narrower range between vibration and drift, say 2-3 mph. It is very easy to misjudge the maximum possible speed of an approaching corner by 2-3 mph.
A week earlier I drove an RWD RT with leveling rear suspension. Unfortunately, it was on different roads and I didn’t push it to the edge, so I can’t make an exacting comparison. With those caveats, my impression was that the leveling suspension was very close in handling and bump absorption to the non-leveling.
I also drove other ramps, s-shaped and others, but didn’t learn anything to add to my comments above.
Steering. Of interest is that the lower portion of the front suspension differs between the AWD and RWD. The RWD front suspension is claimed to be “no compromise” and its lower portion is said to improve stability by reducing the effect road irregularities felt at the steering wheel. Another difference is the power steering adjusted (read boasted) for AWD. What is the net effect of these differences on steering?
The difference in the steering is immediately noticeable in the parking lot pulling out of the dealership. While the specs indication the same number of turns lock to lock and same vehicle turning radius, smaller movements in steering wheel of the AWD have greater effect. On the highway, lane changes seem to require less steering movement. Differences in stability at highway speeds are subtle, with the edge going to the slower steering RWD.
The RWD feels lighter than the 200 lb difference in weight would suggest. I couldn’t determine that it actually made any difference in cornering ability, but the RWD felt more at ease darting into the next lane. I suspect the one inch lower height contributed to this perception, but that is just a guess.
I don’t know if the suspension is the same between the 300 and Magnum, with that in mind, there is brief review of the 300C AWD and RWD by Autoweek, which probably has some relevance to the Magnum. The author makes comparative observations:
“Side-by-side testing with awd and rwd 5.7-liter Hemi-powered 300Cs on a short, low-speed autocross, with ESP off, revealed the awd version to be tighter and easier to drive in dramatic situations, such as the skidpad and the three-turn slalom. Also, there was less oversteer in the autoÂ*cross quick-lane-change simulation.”
Here is the link: http://www.autoweek.com/article.cms?articleId=101219
Performance on wet roads. With the AWD, I expected to give up a small amount of dry pavement performance for a large improvement on wet roads. I under estimated how helpful AWD really is. My first time out in the rain was amazing. I didn’t realize how much of that hemi power could be put on wet pavement with AWD. The acceleration seems almost the same on wet roads as dry ones. When I get a chance, I will do a 0-60 wet dry comparo. I couldn’t help laughing at other cars spinning their tires at wet oily intersections. Hammer the throttle mid-turn on a wet road, and fly out of a corner with no loss of control. AWD extends spirited driving into the wet season.
The Continental tires provide plenty of warning of slippage in the rain. When accelerating in a turn and you begin to feel the vibration of the tires slipping, just lighten your pressure on the accelerator ever so slightly, and moments later you will need to brake to merge with traffic that is going 70 mph.
I would like to comment about many AWD vs. RWD messages on Magnum forums -- assertions were made based on theories that were unchecked by actual driving experience. AWD has been getting a raw deal on the forums. However, I want to acknowledge that the test drive disproved some of my theories too.
I hope the foregoing is helpful to anyone trying to make decision between AWD and RWD. I wanted to learn the trade-offs myself for my own purchase. Since I probably had a better opportunity than most folks to test drive and compare a demo RWD and the AWD which I eventually bought, I decided to make at least of partial list of my observations known.
I love my Magnum because it does so many things so well.
To help understand my comments, I should let the reader know that the primary source of my driving knowledge and ability is road racing, not cars, but motorcycles. While I have owned and driven sporty cars, driving on the street does not provide the skill development that occurs with repeated laps on a track. I’m not equal to the professional reviewers with there car racing experience and their knowledge of 4 wheel chassis dynamics. But I did develop many driving skills transferable to the 4 wheeled world.
An objective assessment of a car’s road holding ability is a real-world skid pad: 270 degree on-ramps. I like this test because these are actual fun sections of road that enthusiasts enjoy. They are fast, 40-70 mph, and if you pick the right ramps, the test is not menacing to the public if you goof up. 270 degree ramps allow quick determination of performance, because the vehicle speed can slowly be adjusted, and the length of the observation is long compared to a 90 degree turn. I have been driving the same ramps for 25 years, know every bump and crack, and have tested the speed and the behavior of numerous cars and motorcycles. I know the results are only accurate for a given year due to things like road wear and crack filling. For instance, during one year, I tested a Saab 900 at 55 mph, a Z/28 at 62 mph, and my sport bike at …73 mph.
How is the road holding ability of the RWD compare to the AWD with its greater ground clearance, weight, different front suspension and weight distribution, and additional powered wheels? The test drive reveals all.
Finally, it was time to set the tire pressure on both cars to 40 psi and hit the road. The AWD had the vehicle leveling rear suspension, the RWD didn’t. I previous drove a RWD with leveling and I will comment on that car also.
On the 270 degree ramps, tire vibration, the initial sign of slippage, occurred at 45 mph for both the AWD and RWD. Pushed beyond that, by increasing the entrance speed into the corner or accelerating mid-corner, both cars reached 50 mph before starting to drift, that is, they were unable to hold to the inside line of the corner.
This limit of traction can be located by most drivers on 270 degree ramps, because of the time available to adjust speed mid-corner. Most drivers undershoot or overshoot the limit of traction on 90 degree corners because they don’t have a road-racer’s time-speed-spatial senses to judge the maximum possible cornering speed for an approaching turn, unless they take corner repeatedly. At the limit, the RWD was wonderfully stable, controlled, forgiving of errors throttle control -- encouraging one to push even harder, possibly reaching 1 mph greater cornering speed at about 50 mph (I couldn’t take my eyes off the road to confirm). It’s forgiving cornering behavior reminded me of the Saab 900.
Only at the limit, about 50 mph in this corner, did the AWD behave differently. It was less stable, being a bit squirrelly, nothing dramatic, but the driver is clearly aware that the limit was reached. Letting off on the gas the car immediately returned to feeling of complete stability.
The difference between vibration and drift was 5 mph. This is the warning range or safety factor, meaning, if you intend to take a corner aggressively, and you encounter tire vibration, you can be off by up to 5 mph and still make the corner. I have since noticed similar warning on wet roads. I judge this to be a good characteristic of the Continentals, because it reduces the chance for loss of control when misjudgment occurs. Many performance tires have a narrower range between vibration and drift, say 2-3 mph. It is very easy to misjudge the maximum possible speed of an approaching corner by 2-3 mph.
A week earlier I drove an RWD RT with leveling rear suspension. Unfortunately, it was on different roads and I didn’t push it to the edge, so I can’t make an exacting comparison. With those caveats, my impression was that the leveling suspension was very close in handling and bump absorption to the non-leveling.
I also drove other ramps, s-shaped and others, but didn’t learn anything to add to my comments above.
Steering. Of interest is that the lower portion of the front suspension differs between the AWD and RWD. The RWD front suspension is claimed to be “no compromise” and its lower portion is said to improve stability by reducing the effect road irregularities felt at the steering wheel. Another difference is the power steering adjusted (read boasted) for AWD. What is the net effect of these differences on steering?
The difference in the steering is immediately noticeable in the parking lot pulling out of the dealership. While the specs indication the same number of turns lock to lock and same vehicle turning radius, smaller movements in steering wheel of the AWD have greater effect. On the highway, lane changes seem to require less steering movement. Differences in stability at highway speeds are subtle, with the edge going to the slower steering RWD.
The RWD feels lighter than the 200 lb difference in weight would suggest. I couldn’t determine that it actually made any difference in cornering ability, but the RWD felt more at ease darting into the next lane. I suspect the one inch lower height contributed to this perception, but that is just a guess.
I don’t know if the suspension is the same between the 300 and Magnum, with that in mind, there is brief review of the 300C AWD and RWD by Autoweek, which probably has some relevance to the Magnum. The author makes comparative observations:
“Side-by-side testing with awd and rwd 5.7-liter Hemi-powered 300Cs on a short, low-speed autocross, with ESP off, revealed the awd version to be tighter and easier to drive in dramatic situations, such as the skidpad and the three-turn slalom. Also, there was less oversteer in the autoÂ*cross quick-lane-change simulation.”
Here is the link: http://www.autoweek.com/article.cms?articleId=101219
Performance on wet roads. With the AWD, I expected to give up a small amount of dry pavement performance for a large improvement on wet roads. I under estimated how helpful AWD really is. My first time out in the rain was amazing. I didn’t realize how much of that hemi power could be put on wet pavement with AWD. The acceleration seems almost the same on wet roads as dry ones. When I get a chance, I will do a 0-60 wet dry comparo. I couldn’t help laughing at other cars spinning their tires at wet oily intersections. Hammer the throttle mid-turn on a wet road, and fly out of a corner with no loss of control. AWD extends spirited driving into the wet season.
The Continental tires provide plenty of warning of slippage in the rain. When accelerating in a turn and you begin to feel the vibration of the tires slipping, just lighten your pressure on the accelerator ever so slightly, and moments later you will need to brake to merge with traffic that is going 70 mph.
I would like to comment about many AWD vs. RWD messages on Magnum forums -- assertions were made based on theories that were unchecked by actual driving experience. AWD has been getting a raw deal on the forums. However, I want to acknowledge that the test drive disproved some of my theories too.
I hope the foregoing is helpful to anyone trying to make decision between AWD and RWD. I wanted to learn the trade-offs myself for my own purchase. Since I probably had a better opportunity than most folks to test drive and compare a demo RWD and the AWD which I eventually bought, I decided to make at least of partial list of my observations known.
I love my Magnum because it does so many things so well.
#2
12-15-2004, 02:10 PM
RE: AWD vs. RWD Handling- A Partial Answer
Thank you Scott for the review, very helpful. I live in Vancouver, Canada. We dont' get much snow here but we do get rain all winter. That, and the fact that I make trips into the mountains to go skiing means that I'm 90% sure I'll get an AWD. I would love a RWD for the fun, but considering the climate I live in and the things I like to do the AWD makes way more sense. Good to hear that the AWD works great on wet roads, I'll have plenty of opportunity to test that out!
Mike
Mike
#3
12-17-2004, 08:30 PM
RE: AWD vs. RWD Handling- A Partial Answer
Scott,
It was a pleasure to read your review. I have a RWD RT but have driven AWD cars and I think that AWD does get dissmissed too quickly. Reason for me not getting the AWD was they were not out yet and I wanted my car now. I am very happy with mine and I don't think it would be a mistake for anyone to buy either of these cars.
It was a pleasure to read your review. I have a RWD RT but have driven AWD cars and I think that AWD does get dissmissed too quickly. Reason for me not getting the AWD was they were not out yet and I wanted my car now. I am very happy with mine and I don't think it would be a mistake for anyone to buy either of these cars.