Hi, I am relatively new to autocrossing and I am wondering what I can do to get rid of some of the understeer problems I have been having. Ok, first of all, my car and set up:

2000 GSR Sedan
Tokico Illumina 5 way adjustables
Eibach Sport Springs
Kumho SPT tires on stock GSR blades, in the factory 195/55/15 size.

Its a daily driver.

At the last event I did (it was the most open and fastest that I have done) I noticed more understeer then I have before. I had it set to full stiffness in the back (5 out of 5 clicks) and medium in the front (3 out of 5 clicks). Tire pressures were 35psi in the front and 33 psi in the rear.

When entering turns I would get a little off throttle oversteer, but as soon as I would go back to the gas, the car would really push, especially in turns that were a complete circle. In the slalom's the car felt really good.

I am open to any suggestions, but I am hoping that there is something that I can do without spending money.

Thanks

 

Slow down more on entry, pick up throttle more smoothly.

You're dealing with a less then ideal setup. If you can teach yourself to be smooth and patient with it and get to be quick while doing it, when you move to a better suspension and better tires you'll be able to get a LOT more out of the combination then if you were to do that right now.

 

agreed with what solox said... also, you said 35/33psi, what is the max pressure for the Kumho SPTs? most of the time on a not so grippy street tire you want to have them near max pressure.

just don't give it too much throttle through the corners because it'll just spin and push like crazy, be smooth.

 

slow dow to go faster

that basically what i have learn from the first time i went
not sure how your club does it but. at some point we get to be out on the track rounding up cones. and you really get to listen how much or how little throttle the more advance drivers use

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by verticle &raquo;</TD></TR><TR><TD CLASS="quote">agreed with what solox said... also, you said 35/33psi, what is the max pressure for the Kumho SPTs? most of the time on a not so grippy street tire you want to have them near max pressure.

just don't give it too much throttle through the corners because it'll just spin and push like crazy, be smooth. </TD></TR></TABLE>

Actually, with tires you don't want them at max pressure for best grip. There are two reasons for this. One, when a tire is inflated beyond where max grip occurs, the center of the tread is crowned, which reduces the amount of tire edge in contact with the ground. This is why when you take tire temps the center section of an overinflated tire is hotter. Remember, tire grip is a combination of mechanical grip (where the tire fills in the space around the asperities in the road surface) and adhesion which is a sort of molecular bonding between road and tire. So you really want the tire's contact patch to have almost constant normal pressure between the road and tire. And I said "almost". You actually will get optimized grip from having a slight amount of dynamic negative camber due to something called "camber thrust". Camber thrust is the net lateral force at the contact patch and is present even when there isn't any slip angle in the tire. And camber thrust acts (in a slightly diminishing manner) all the way util the tire starts to slide at the higher slip angles.

The other reason is that tire stiffness is like adding another spring to the overall suspension system. So when analyzing understeer/oversteer balance, a higher spring rate (or overall higher wheel rate) will generally diminish the cornering force at the end of the car with the highest spring rate.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Johnny Mac &raquo;</TD></TR><TR><TD CLASS="quote">

Actually, with tires you don't want them at max pressure for best grip. There are two reasons for this. One, when a tire is inflated beyond where max grip occurs, the center of the tread is crowned, which reduces the amount of tire edge in contact with the ground. This is why when you take tire temps the center section of an overinflated tire is hotter. Remember, tire grip is a combination of mechanical grip (where the tire fills in the space around the asperities in the road surface) and adhesion which is a sort of molecular bonding between road and tire. So you really want the tire's contact patch to have almost constant normal pressure between the road and tire. And I said "almost". You actually will get optimized grip from having a slight amount of dynamic negative camber due to something called "camber thrust". Camber thrust is the net lateral force at the contact patch and is present even when there isn't any slip angle in the tire. And camber thrust acts (in a slightly diminishing manner) all the way util the tire starts to slide at the higher slip angles.

The other reason is that tire stiffness is like adding another spring to the overall suspension system. So when analyzing understeer/oversteer balance, a higher spring rate (or overall higher wheel rate) will generally diminish the cornering force at the end of the car with the highest spring rate. </TD></TR></TABLE>

i wasnt necessarily meaning inflate them to full pressure, i just thought 33 sounded a bit low. a lof of street tires max is all the way up in the mid 40's. before i got 615s i usually ran my street tires at about 39-40 while their max was 45, just a suggestion.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Johnny Mac &raquo;</TD></TR><TR><TD CLASS="quote">
The other reason is that tire stiffness is like adding another spring to the overall suspension system. So when analyzing understeer/oversteer balance, a higher spring rate (or overall higher wheel rate) will generally diminish the cornering force at the end of the car with the highest spring rate. </TD></TR></TABLE>

One of the reasons those autocrossing on less that ideal suspensions will jack up their rear tire pressures, it promotes rotation at the expense of total rear grip.

Stock GSR on RT-615 Azenis, I ran 33/52 psi to get my pig of a car to rotate.
Added a Comptech rear swaybar, reduced rear pressure to a more reasonable 45 psi.
Upped spring rates to 400/400, dropped rear pressure to 38 psi.
Learned how to slow down more and stop flying into the turn too hot, dropped rear to 34 psi.

Before anyone else comments that my front pressure is too low, I'm only running 205/40-16s, and with such short and stiff sidewalls, thats all the pressure I need to not roll the tire over onto the sidewall. I was up around 38 psi hot with 205/50-15 RT-615s to avoid rolling them over. My excessive camber might also play a role in not needing as much pressure (-4.0* in the front).

(Just sharing some here. Not sure exactly what my point was. Darn holiday tomorrow has my head all a mess.)

 

ok thanks for all the help, i will try a lower entry speed and pick up the throttle more slowly/smoothly.

 

You could also soften the front suspension setting and set the rear to max. Along with what everyone else has said about tire pressure. Chalk you tires if your not rolling over the fronts keep letting air out.

 

don't soften the front too much cause then it'll just roll too.

i'd up the tire pressure to say 36 front, 40 rear. but you are probably over-driving the car anyways too.

 

I adjust tire pressure by wear, not by rotation/suspension theory. Is this wrong?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by The Destroyer &raquo;</TD></TR><TR><TD CLASS="quote">I adjust tire pressure by wear, not by rotation/suspension theory. Is this wrong?</TD></TR></TABLE>

No, you're doing it correctly.

However, if you can't adjust handling through suspension, setting deliberately incorrect pressure can be used as a form of band-aid adjustment.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by solo-x &raquo;</TD></TR><TR><TD CLASS="quote">Slow down more on entry, pick up throttle more smoothly.

You're dealing with a less then ideal setup. If you can teach yourself to be smooth and patient with it and get to be quick while doing it, when you move to a better suspension and better tires you'll be able to get a LOT more out of the combination then if you were to do that right now.</TD></TR></TABLE>
x10.

The number one cause of understeer is entering a corner too fast, and the number two cause is opening the throttle too much too soon.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by verticle &raquo;</TD></TR><TR><TD CLASS="quote">i wasnt necessarily meaning inflate them to full pressure, i just thought 33 sounded a bit low. a lof of street tires max is all the way up in the mid 40's. before i got 615s i usually ran my street tires at about 39-40 while their max was 45, just a suggestion.</TD></TR></TABLE>
I still can't figure out what you're "suggesting." The maximum recommended pressure molded on the sidewall has almost nothing to do with anything.

 

Understeer in the middle of a corner when getting decent balance going in is basically caused by two things in a front drive car.

1. Trying to get on the power too soon or too much. There is just so much traction available and if 90% or more is being used to corner, there is very little left over to accelerate with until the cornering loads are reduced.

2. Front suspension starting to bottom. I have no idea how much travel those springs allow, what ride height they put the car at, what kind of spring rate they have, or how long the bump stops are. I have seen lots of front drive cars show up that could be seen bottoming the front end in the turns and plowing like pigs. My 3dr GSR needed 800lb front springs when combined with good R tires and I've seen lots of them end up in that range. I also had shortened Koni's there that gave me some more bump travel to work with.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Targa250R &raquo;</TD></TR><TR><TD CLASS="quote">
x10.

The number one cause of understeer is entering a corner too fast, and the number two cause is opening the throttle too much too soon.
</TD></TR></TABLE>

Its a Honda how can you be going too fast.

Just install the world's biggest rear sway bar, come into a corner and lift off the gas. Your understeer problems will quickly disappear.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 94accordsedan &raquo;</TD></TR><TR><TD CLASS="quote">Its a Honda how can you be going too fast.

Just install the world's biggest rear sway bar, come into a corner and lift off the gas. Your understeer problems will quickly disappear. </TD></TR></TABLE>
At that point, a whole new set of handling problems will crop up. If you live long enough for them to become a problem

 

yeah this is a daily driver so i really dont want huge amounts of lift throttle oversteer.