What are some good ideas for getting the understeer out of a front wheel drive car if you already have maximum weight transfer from the front axle to the rear.
I'd prefer to avoid shenanigans like extreme toe settings, positive camber and weird tire pressures.
If you have max weight transfer off of the front wheels, how do it turn?
What kind of corners? Track, autocross or street? What car/tires/sizes/shocks/struts/spring rates/sway bars/bushings? What alignment it on the car now?
As a general rule, what's going to make it stick is more negative camber, lower ride height and/or roll center. I was all FWD for like 25 years but have forgotten all that post Sprite/e36M3/Miata/Radical.
I do recall my 2002 Honda Civic ep3 hatch understeered like a pig. Koni yellows, Ingalls camber bolts, Progress springs and F swaybar, and an SiR rear swaybar in conjunction w/ more negative camber, no toe, and some wider 17" wheels w/ tires with fairly stiff sidewalls fixed the problem.
BTW - toe eats tires much more than camber. Flipping tires periodically will at least divide the wear side-to-side.
I was surprised at how little the rather extreme camber on my E30 affected my tire wear. Don't be afraid to camber a little extra depending on how much body roll you have. But, expect some potentially funky wet handling. The extra camber relies on grip to deform the tire so that the tread is flat on the pavement. Extra camber can negatively affect wet handling because it slips before there is enough grip to deform the tire and get to the full contact patch.
You can try stiffening up the rear. Try a swaybar first. Its kinda a band aid fix since you are potentially crippling the rear to match the front, but sometimes its highly effective.
motomoron wrote: If you have max weight transfer off of the front wheels, how do it turn?
It has good turn in and high levels of grip. It's just not very adjustable. In sweepers or on the throttle it understeers a little. On maintenance throttle it understeers a little. On trail throttle it's neutral. If I flick or otherwise provoke it I can get a little oversteer.
What kind of corners? Track, autocross or street? What car/tires/sizes/shocks/struts/spring rates/sway bars/bushings? What alignment it on the car now?
Two hairpins taken at about 45 mph, a decreasing radius sweeper (entry about 75, exit perhaps 65 mph) and a big, fast open sweeper that I take at about 85 mph. The car is a Daewoo Nubira one Hankook Ventus Evo V12s in size 205/50/15. It's a four wheel strut car with a motion ratio of 1.15 in the rear and 1.2 in the front. The bushings are all poly. There are no swaybars front or rear. The springs are 500lb/inch. I only have about 2.5 degrees of body roll at max g. I think this is because my roll centers are pretty high. I calculated about 5 inches in the front and about 8 inches in the rear. I have not noticed very much camber sensitivity. I've run the car at .8 degrees negative on the street and -2 at the track. I frankly didn't notice a difference and the tire wear wasn't that different either. I run zero toe in the front and negative 2 mm in the rear.
As a general rule, what's going to make it stick is more negative camber, lower ride height and/or roll center. I was all FWD for like 25 years but have forgotten all that post Sprite/e36M3/Miata/Radical. I do recall my 2002 Honda Civic ep3 hatch understeered like a pig. Koni yellows, Ingalls camber bolts, Progress springs and F swaybar, and an SiR rear swaybar in conjunction w/ more negative camber, no toe, and some wider 17" wheels w/ tires with fairly stiff sidewalls fixed the problem. BTW - toe eats tires much more than camber. Flipping tires periodically will at least divide the wear side-to-side.
This isn't something you asked about, but I think the roll center might be too tall in the rear. I sometimes get a weird jacking sensation in rapid transitions. I'm going to fix this by lowering the rear, but that is going to make my understeer worse, in theory.
The car handles very nicely and the grip is very good. I feel like I'm down to fine adjustments and getting better adjustability at this point.
curtis73 wrote: I was surprised at how little the rather extreme camber on my E30 affected my tire wear. Don't be afraid to camber a little extra depending on how much body roll you have. But, expect some potentially funky wet handling. The extra camber relies on grip to deform the tire so that the tread is flat on the pavement. Extra camber can negatively affect wet handling because it slips before there is enough grip to deform the tire and get to the full contact patch. You can try stiffening up the rear. Try a swaybar first. Its kinda a band aid fix since you are potentially crippling the rear to match the front, but sometimes its highly effective.
This is where I'm kind of stumped. I lift a rear tire under max G. Doesn't this mean more rear stiffness or less front stiffness is pointless?
Tire pressure tuning works real well, and it's free. If you haven't exploited this, your missing a good tool.
Many a car is inherently designed to be mildly understeering. It's deemed safer for the masses because it's stable and predictable. To overcome this requires some suspension redesigning, which you probably don't want to get into.
The driver is frequently a big cause of chronic understeering. Especially one who comes into turns too hot and simply trying to force the car through.
Yes, by generic definitions if you're already lifting the inside rear tire, the rear is already too stiff in comparison to the front. And while that same generic definition would tell you that increasing front roll stiffness will make the car understeer even more, it may not by simply reducing the quantity of body roll and the suspension movement.
It may look dumb but have you considered a bit more contact patch in the front? If you go with a bit wider (or even taller) wheel and tire combo you may be able to generate a bit more front end grip.
If it works for rear engine, rear drive cars it should work for front engine, front drive cars right?
275 front, 225 rear. function punches form in the mouth.
^^Your success is in the tires
Stiffen the rear ala: springs, swaybar, tire pressure. 2-3 neg. camber on the front plus as much caster as you can get. I found that 5 psi plus in the rear helps .
foxtrapper wrote: Tire pressure tuning works real well, and it's free. If you haven't exploited this, your missing a good tool. Many a car is inherently designed to be mildly understeering. It's deemed safer for the masses because it's stable and predictable. To overcome this requires some suspension redesigning, which you probably don't want to get into. The driver is frequently a big cause of chronic understeering. Especially one who comes into turns too hot and simply trying to force the car through. Yes, by generic definitions if you're already lifting the inside rear tire, the rear is already too stiff in comparison to the front. And while that same generic definition would tell you that increasing front roll stiffness will make the car understeer even more, it may not by simply reducing the quantity of body roll and the suspension movement.
I slept on this problem and came up with a thought. Once the tire lifts, the rear suspension is no longer resisting roll as much as before. In theory, I could cut roll by lowering the rear roll center, no?
And yah, I need to play with tire pressures, but I'm really not sure how to do so with a decent tire. These Hankooks are the first tires I've ever had that don't completely suck. By that I mean previously I could improve any tire by jacking the pressure WAY up and helping it to not fall over. I ran the previous all seasons at like 45 psi to keep them from falling over. The Hankooks don't fall over at 30 psi.
How do driver's cause understeer except by being jerky? I think I usually err on the side of being too smooth. Feel free to criticize my technique, I promise I won't get offended.
http://www.youtube.com/watch?v=vLzX7_ntl-4&feature=related
The_Jed wrote: It may look dumb but have you considered a bit more contact patch in the front? If you go with a bit wider (or even taller) wheel and tire combo you may be able to generate a bit more front end grip. If it works for rear engine, rear drive cars it should work for front engine, front drive cars right?
Thought of it but I'm out of fender space without cutting.
AngryCorvair wrote:
I actually think that looks cool ...
MrBenjamonkey wrote:The_Jed wrote: It may look dumb but have you considered a bit more contact patch in the front? If you go with a bit wider (or even taller) wheel and tire combo you may be able to generate a bit more front end grip. If it works for rear engine, rear drive cars it should work for front engine, front drive cars right?Thought of it but I'm out of fender space without cutting.
then go smaller in the rear
mad_machine wrote:MrBenjamonkey wrote:then go smaller in the rearThe_Jed wrote: It may look dumb but have you considered a bit more contact patch in the front? If you go with a bit wider (or even taller) wheel and tire combo you may be able to generate a bit more front end grip. If it works for rear engine, rear drive cars it should work for front engine, front drive cars right?Thought of it but I'm out of fender space without cutting.
Or be a man and bring out the Sawz-All!
"275 front, 225 rear. Function punches form in the mouth."
Was anybody looking for a magazine-worthy quote...?
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