Help - Search - Members - Calendar
Full Version: Autocross
ElantraClub - For Elantra Owners and Enthusiasts > Automotive > The Racing Zone > Elantra Racing


View New Posts
ElMurcielago
So Sunday I had my first experience at SCCA and it was a blast for me. My fastest time was 62 seconds which I find pretty good being my first time. The thing about it though was my car liked to oversteer some which didn't really make sense to me (or those I went there with). Suspension mods are tien lowering springs and KYB struts and front and rear strut bars. If anyone might know a thing or 2 about why I'd like to know.

Anyone else try autocross and like to share experience?
Bobzilla
There's a few of us auto-x'er's here. I started this crazy sport in 2007 with my 02 Elantra. Ran that for several years, bought and run a Swift GT, sold that and played with a C4 corvette, sold that and bought hte 2010 Forte SX I currently have. Been to Lincoln for solo nats the last 3 years and all that.

As for set up..... What spring rates are those coilovers? What tires? Tire pressures? Surface? Driving style etc. Lift throttle oversteer is common in FWD cars. When you brake or "lift" it transfers the weight to the front end, losing grip in the rear. Do this mid corner and the back will come around. Knowing more about the car would be helpful and a video of your driving style would as well. What tire pressures were you running? What tires etc.
RPW00Mirage
all day son. i posted up some runs yesterday.
slowgls
Me too man.
bhorste
I'm a 2-time regional autocross champ from way back (1996 and 1998), and that was in a '91 Ford Festiva. If the back end's coming around a little bit, that means you're going just about fast enough. biggrin.gif

Chances are you need to bump up the rear tire pressures just a bit if it's coming around like that. An easy way to check the next time you run is to get some white shoe polish (in the bottle with the sponge applicator) and mark several spots on the sidewall right up where it transitions from the tread. If the polish is rubbed off after your run, you're rolling over onto the sidewall a bit and might want to up your tire pressure. If it's still there and you were comfortable with the way the car felt, you're good. If it felt like it was still understeering, you can drop your tire pressure a little bit.
ElMurcielago
QUOTE (Bobzilla @ May 22 2015, 07:02 AM) *
There's a few of us auto-x'er's here. I started this crazy sport in 2007 with my 02 Elantra. Ran that for several years, bought and run a Swift GT, sold that and played with a C4 corvette, sold that and bought hte 2010 Forte SX I currently have. Been to Lincoln for solo nats the last 3 years and all that.

As for set up..... What spring rates are those coilovers? What tires? Tire pressures? Surface? Driving style etc. Lift throttle oversteer is common in FWD cars. When you brake or "lift" it transfers the weight to the front end, losing grip in the rear. Do this mid corner and the back will come around. Knowing more about the car would be helpful and a video of your driving style would as well. What tire pressures were you running? What tires etc.


Not 100% sure on spring rates, I'm running valera sports 205/45/15, after my first few runs I had to up the tire pressure to get good contact on the corners to 40 psi and on tarmac. I don't have any videos outside the car but I do have one inside, try to post that up when I get a chance.


QUOTE (bhorste @ May 22 2015, 07:47 AM) *
I'm a 2-time regional autocross champ from way back (1996 and 1998), and that was in a '91 Ford Festiva. If the back end's coming around a little bit, that means you're going just about fast enough. biggrin.gif

Chances are you need to bump up the rear tire pressures just a bit if it's coming around like that. An easy way to check the next time you run is to get some white shoe polish (in the bottle with the sponge applicator) and mark several spots on the sidewall right up where it transitions from the tread. If the polish is rubbed off after your run, you're rolling over onto the sidewall a bit and might want to up your tire pressure. If it's still there and you were comfortable with the way the car felt, you're good. If it felt like it was still understeering, you can drop your tire pressure a little bit.

Sounds good, I'll do that when I go to another event and check pressure more frequently.
RPW00Mirage
He's got the pressures backward.

To thwart oversteer you lower the rear pressure a bit.
ElMurcielago
QUOTE (RPW00Mirage @ May 22 2015, 11:22 AM) *
He's got the pressures backward.

To thwart oversteer you lower the rear pressure a bit.

Will that increase understeer though?
2000J25SP
QUOTE (ElMurcielago @ May 22 2015, 01:38 PM) *
Will that increase understeer though?

should make it more neutral.

Want more oversteer? raise front psi
Want less oversteer? lower front psi
Want more oversteer? Raise rear psi
Want less oversteer? Lower rear psi

My J2 is on lowering springs + Tiburon rear bar. And it will only oversteer a bit if you let off midcorner.
bhorste
QUOTE (RPW00Mirage @ May 22 2015, 12:22 PM) *
He's got the pressures backward.

To thwart oversteer you lower the rear pressure a bit.


Negative. By upping the rear pressure, you in essence add some stiffness to the sidewall, preventing rollover and keeping the contact patch on the tread.
2000J25SP
QUOTE (bhorste @ May 22 2015, 03:22 PM) *
Negative. By upping the rear pressure, you in essence add some stiffness to the sidewall, preventing rollover and keeping the contact patch on the tread.

Raising psi adds stiffness but it does reduce the contact patch. I think It feels better, but it loses traction at a lower threshold. Same goes for understeer.
Bobzilla
QUOTE (bhorste @ May 22 2015, 03:22 PM) *
Negative. By upping the rear pressure, you in essence add some stiffness to the sidewall, preventing rollover and keeping the contact patch on the tread.



QUOTE (J2Elantra @ May 22 2015, 03:58 PM) *
Raising psi adds stiffness but it does reduce the contact patch. I think It feels better, but it loses traction at a lower threshold. Same goes for understeer.


You're both sort of right. It all depends on the tires, the starting pressures etc. I know National auto-x'ers that run low rear pressures, allowing the sidewalls to roll over to get the car to rotate. I know National Auot-x'ers that run high rear pressures to reduce the contact patch to make the car more nuetral. Again, it depends on the tires and where you start. If you're starting in the 40psi range, lowering the rear tire pressure will reduce oversteer and make it a little more pushy. If you're starting in the 20-25psi range, lowering it will do the same. Tire pressures are a bit of a bell curve. Lower pressures on the left, higher on the right with the "sweet spot in the middle.You can achieve the same effect at both ends of the spectrum.

The tires themselves make a heck of a difference in tire pressures needed/wanted. I ran the BFG Rivals when they came out. 225/45/17 on 7.5" wheels. That tire was happiest at 34psi front, 37 rear on the Forte with the spring rates and rear sway bar I am running. When I made the switch to RS-3 V2 Hankooks I've fought the tire pressure for a dozen events (including Nationals) because that particular tire, on the same wheel and same car likes 40/38 to get the same feel and keep it off the sidewalls (with -3.25* of front camber).

RFEgardless.... If you're getting a little oversteer, that is preferable for an auto-x car over push. I fought push with my 02 and with the Swift GT. NEver got either of them to be as good as the Forte is now.


Here's some videos of my last event in Bowling Green, KY.
https://www.facebook.com/bob.miller.1804109...91/?pnref=story
RPW00Mirage
Cool. Do you think the difference is paramount due to me being on slicks ?
Bobzilla
Purple crack are another category completely unrelated to this entire conversation. IIRC, they run a lot lower pressures than the standard street tire. plus, what other tire can you stuff a 245 onto a 6" wheel and it work just fine?
ElMurcielago
This is good stuff for me. I'm sure there's a learning curve in autox, but that about the tire pressure in different tires causing a bigger difference in handling than what I thought is surprising to me. I knew tires had an impact on curves, just didn't think it was that big that tire pressure was a differentiating factor. Glad you guys helped shed some light for me.
bhorste
QUOTE (ElMurcielago @ May 25 2015, 03:15 PM) *
This is good stuff for me. I'm sure there's a learning curve in autox, but that about the tire pressure in different tires causing a bigger difference in handling than what I thought is surprising to me. I knew tires had an impact on curves, just didn't think it was that big that tire pressure was a differentiating factor. Glad you guys helped shed some light for me.


And it's amazing what just 1psi can do. Some of it is butt-dyno type stuff, but if it's close that one last tweak can really get it there for you.

That being said (and I'm a bit ashamed we didn't mention it before), if/when you start making adjustments... only do one end of the car at a time. Don't bump up the fronts and drop the rears at the same time. Much more likely to overcorrect that way. Same thing with any setup changes you make. Only do one end, and only do small increments (unless you're REALLY sure you missed the setup by a lot).
Bobzilla
Also the #1 adjustment is to the loose nut behind wheel. Seat time, seat time, seat time are what get you faster. Burn through a set of tires, then worry abotut making car adjustments.

Also, in Auto-X, tires are the second most important item on the car. Motons, 500hp, bg sway bars etc mean nothing if you can't get the tires to grip the surface worth a crap. If it was me in a J2, I'd search for some light 15x7.5" wheels and some 225/45/15 RS-3 or Rivals. You're stuck in a crap class (STC) so you will get destroyed by the 89 Civic Si's because they're stupid. It is what it is..... just go have a good time and get yourself as fast as you can.
slowgls
QUOTE (Bobzilla @ May 26 2015, 06:47 AM) *
Also the #1 adjustment is to the loose nut behind wheel. Seat time, seat time, seat time are what get you faster. Burn through a set of tires, then worry abotut making car adjustments.


Seat is very important. Also having someone ride with you and let you doing wrong will also help.
Bobzilla
Yep. don't be afraid to ask questions. Many "old timers" are more than willing to help you get started and offer helpful tips. There's not much "Secret" in auto-x.

This is a "lo-fi" version of our main content. To view the full version with more information, formatting and images, please click here.
Invision Power Board © 2001-2019 Invision Power Services, Inc.