wth? oversteer?
09-11-2003, 11:08 PM
#1
wth? oversteer?
I'm really puzzled. Here's my suspension setup:
18 x 7.5 Rota Subzero ~17lb
235/40-18 Kumho 712, 36psi cold
that's all I have. I've noticed that I oversteer when powering through turns. How's that possible on a fwd w/o rsb or any "real" suspension mods? I know I can throttle lift oversteer but I hate those cuz they've always seem "terminal" for me (end up perpendicular to line of travel).
During oversteer, I have the option of counter-steering and keeping throttle constant. Or I can throttle lift slightly and hope the fronts grip and I can correct. Either way, I've lost my neutral handling since installing the Kumhos last week. Why's that? How do I correct it? Lower the rear psi to 34?
Jae
18 x 7.5 Rota Subzero ~17lb
235/40-18 Kumho 712, 36psi cold
that's all I have. I've noticed that I oversteer when powering through turns. How's that possible on a fwd w/o rsb or any "real" suspension mods? I know I can throttle lift oversteer but I hate those cuz they've always seem "terminal" for me (end up perpendicular to line of travel).
During oversteer, I have the option of counter-steering and keeping throttle constant. Or I can throttle lift slightly and hope the fronts grip and I can correct. Either way, I've lost my neutral handling since installing the Kumhos last week. Why's that? How do I correct it? Lower the rear psi to 34?
Jae
09-12-2003, 05:16 AM
#3
If you are oversteering, lifting off the throttle will make it worse. That will tranfer weight to the front of the car, making the rears slide even more.
Your best course of action is to stay steady and ride it out or give a little more throttle to get some weight on the rear wheels to stop the slide.
Your best course of action is to stay steady and ride it out or give a little more throttle to get some weight on the rear wheels to stop the slide.
09-12-2003, 05:27 AM
#5
Originally Posted by njmaxseltd
Drop the rear tire pressure a bit so you have a bigger tread footprint on the ground.
You'll notice that most people run slightly higher pressure in the front to reduce understeer (increase oversteer).
At maximum lateral acceleration, the tires deform quite a bit due to side loads. Increasing tire pressure reduces the deformation. This keeps the contact patch as flat on the road as possible. (This is why autocrossers run upwards of 40psi in all 4 tires.)
Instead of reducing your rear pressure, which might increase understeer, reduce the front pressure. This will take away a bit of grip from the front, hopefully leading to more neutral handling.
09-12-2003, 06:41 AM
#6
Senior Member
Join Date: Jul 2003
Posts: 251
Originally Posted by mzmtg
That's not quite right.
You'll notice that most people run slightly higher pressure in the front to reduce understeer (increase oversteer).
At maximum lateral acceleration, the tires deform quite a bit due to side loads. Increasing tire pressure reduces the deformation. This keeps the contact patch as flat on the road as possible. (This is why autocrossers run upwards of 40psi in all 4 tires.)
Instead of reducing your rear pressure, which might increase understeer, reduce the front pressure. This will take away a bit of grip from the front, hopefully leading to more neutral handling.
You'll notice that most people run slightly higher pressure in the front to reduce understeer (increase oversteer).
At maximum lateral acceleration, the tires deform quite a bit due to side loads. Increasing tire pressure reduces the deformation. This keeps the contact patch as flat on the road as possible. (This is why autocrossers run upwards of 40psi in all 4 tires.)
Instead of reducing your rear pressure, which might increase understeer, reduce the front pressure. This will take away a bit of grip from the front, hopefully leading to more neutral handling.
I may have read the original post wrong but doesn't he want less oversteer and more understeer?
09-12-2003, 02:23 PM
#8
Alright, a lil more info. The turns I take are moderately sharp. They're roughly 40mph, on-camber sweepers, level ground (not uphill/downhill). Before entering the turn, I lift ever so slightly on gas to transfer weight forward, initiate turn, and stay constant on gas till I know I got grip. Just before apex, I'm slowly getting on the gas again, and as I pass the apex, that's when my rear starts going the wrong way. For instance, if it's a left sweeper, my rear goes right...I steer into the turn (right) to "drift" and hold the gas constant or increase slightly...or I can let up slightly on the gas and hope the fronts stick, but this's likely to make things worse.
Yes, I get too much oversteer. Tires are 500+ miles new, heat cycled for 80miles 2x. I've had 3 sets of rims/tires before and all of them either understeered or neutrally slid outwords (4wheel slide, for a lack of better description)
1) steelies/hubbies 205/65-15 29psi (performance all season)
2) 3rd gen SE rims 215/60-15 29psi (high performance all season)
3) 18 x 7.5 subzero 225/40-18 36psi (ultra high performance all season)
Jae
Yes, I get too much oversteer. Tires are 500+ miles new, heat cycled for 80miles 2x. I've had 3 sets of rims/tires before and all of them either understeered or neutrally slid outwords (4wheel slide, for a lack of better description)
1) steelies/hubbies 205/65-15 29psi (performance all season)
2) 3rd gen SE rims 215/60-15 29psi (high performance all season)
3) 18 x 7.5 subzero 225/40-18 36psi (ultra high performance all season)
Jae
09-12-2003, 03:13 PM
#9
And you've got oversteer with stock suspension? How the hell did you manage that on 18x7.5" wheels? You'll have to lower the front pressure a bit until you find the sweet spot...or maybe throttle adjust...
Your car is doing the exact polar oppisite of what mine did (stock). Now I need new tires due to lowering...
EDIT-- What offset are the wheels you purchased (as compared to stock)?
Your car is doing the exact polar oppisite of what mine did (stock). Now I need new tires due to lowering...
EDIT-- What offset are the wheels you purchased (as compared to stock)?
09-12-2003, 04:13 PM
#10
I don't understand why the fronts need to be lowered? Is it cuz they're deforming under the lateral forces (and cuz I'm not lowered?) I will increase the fronts tonight (after tires cool) and see how they do tomorrow.
18 x 7.5, 45mm offset. I got the bbk template from stillen and found out I need at least another 10mm to clear them. However, I'm not having any rubbing issues (front or rear, inside or out) with 235wide tires.
What about weight distribution? Car is nearly empty...only 10lb of stuff spread out in the trunk floor, so nothing's moving at least. I weight 125lb.
Jae
18 x 7.5, 45mm offset. I got the bbk template from stillen and found out I need at least another 10mm to clear them. However, I'm not having any rubbing issues (front or rear, inside or out) with 235wide tires.
What about weight distribution? Car is nearly empty...only 10lb of stuff spread out in the trunk floor, so nothing's moving at least. I weight 125lb.
Jae
09-12-2003, 05:59 PM
#11
the only thing i can think of is you're turning too sharply...to let the rear loose.
it would be better to turn more gradually instead of turning sharply at one moment. also, if you keep your foot on the gas, it'll keep more weight in the rear...so it'll be more planted than no throttle.
also...maybe get some springs? turning at 40mph must be giving you some embarrassing body roll...lol
i remember how bad it was when i was stock
now im on ground controls...and there is very very little body roll
it would be better to turn more gradually instead of turning sharply at one moment. also, if you keep your foot on the gas, it'll keep more weight in the rear...so it'll be more planted than no throttle.
also...maybe get some springs? turning at 40mph must be giving you some embarrassing body roll...lol
i remember how bad it was when i was stock
now im on ground controls...and there is very very little body roll
09-12-2003, 08:19 PM
#12
I don't think it's the sharpness. I get on the throttle after I've established traction just before 1/2 way into the turn. And it's only when I'm accellerating that my rear gets loose. If my entering speed's too fast, then I'd plow/understeer, which would be terminal. My line is gentle as the road allows. I'm not jerking and am smooth w/the steering, brakes, and throttle.
Springs...are a luxury @ the moment. Can't afford gc's yet, esp since i've just spent $1000 on rims/tires and another $300 on rotors and pads. I will be getting a fstb soon, before I head to the road course next month. That will help in transitions, but will do nothing for my oversteer problem.
Jae
Springs...are a luxury @ the moment. Can't afford gc's yet, esp since i've just spent $1000 on rims/tires and another $300 on rotors and pads. I will be getting a fstb soon, before I head to the road course next month. That will help in transitions, but will do nothing for my oversteer problem.
Jae
09-12-2003, 08:58 PM
#13
Senior Member
Join Date: Oct 2001
Posts: 866
I don't know why you are getting so much oversteer out of a stock suspension. Most people have the exact opposite problem. I did, and pretty much cured it with a RSB. I think a RSB would definitely exaggerate your problem.
Play with the tire pressures. I run 35 psi in mine (225/55/16 on stock '97 SE rims). Gives me good handling (about as neutral as I can get), and good wear. I have a FSTB, RSTB, RSB, and front sway bar ES bushings on stock struts/springs.
Have you checked your front sway bar end links? If they're snapped, wouldn't that increase oversteer? Don't some people remove their fronts on the track to increase oversteer? Something that may be worth checking.
Dave
Play with the tire pressures. I run 35 psi in mine (225/55/16 on stock '97 SE rims). Gives me good handling (about as neutral as I can get), and good wear. I have a FSTB, RSTB, RSB, and front sway bar ES bushings on stock struts/springs.
Have you checked your front sway bar end links? If they're snapped, wouldn't that increase oversteer? Don't some people remove their fronts on the track to increase oversteer? Something that may be worth checking.
Dave
09-13-2003, 09:51 AM
#14
I checked the links and they look good. Feel tight.
Last week I was under the car and checked torque settings on as many nuts/bolts as I could. Did that for the rear too.
Ok, heading out to play with tire pressures. If any local SoCal people want to take my car out and see what I'm talking about, just send me pm.
Jae
Last week I was under the car and checked torque settings on as many nuts/bolts as I could. Did that for the rear too.
Ok, heading out to play with tire pressures. If any local SoCal people want to take my car out and see what I'm talking about, just send me pm.
Jae
09-13-2003, 06:05 PM
#15
I checked my psi this morn and all were still at 36psi. However, the front treads have a wider "dirty" area, so I inflated the fronts to 37psi. I'll take the car out tomorrow and see if it made a diff.
Jae
Jae
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