Setup ideas- went from understeer to oversteer

[Zombie killer]

Originally Posted by Rob@WretchedMS

Just found another one of yours on your youtube page, with the camera on the right rear, and it looks like the yellow painted lines are what got you on that run

What were the surface temps that day?

1) The other videos are back on the old OEM tires and understeeer conditions from last year. I do have another video from this past weekend with the oversteer and the Go Pro mounted over the rear tires so you can see the front tire and hear the exhaust sound so you can tell when I am on throttle. Its is on my iphone so I will have to upload it when I get home and on wi-fi tonight.

2) I did not get surface temps on the concrete surface that day, but ambient temps were mid 60s. My front tire temps were running approx these temps on the 3rd run in a heat. The rears would run 5-10 degrees cooler depending on how I abused them.
(outside) 110
(middle) 110
(inside) 115

3) and yes, when I walk the course you have to be watchful of the wide striping on the runway. The striping can be slippery in places. Another thing that is a little slippery is the dark patches on the concrete surface where the cars have not worn away the mildew (or that is what I think it is).

I have a few different regions that I will run in and each has its own unique surface. Some gravel like and some are sealcoated which are like "ice skating" at times. This course is by far the most gripier of any I go to so this course is my testing ground.

[JDP Sales]

Man, I wish we had wide-open lots like that around here..

I agree with Rob on that particular run, it looks like lift-off oversteer. If you would have tapped the brakes just a little before the cone at :53 (while you were still traveling straight), and then gotten back on the throttle to maintain some throttle through that turn, you may have been alright.

Best regards,

Tyler
888-308-6007

[Zombie killer]

Originally Posted by JDP Tyler

Man, I wish we had wide-open lots like that around here..

I agree with Rob on that particular run, it looks like lift-off oversteer. If you would have tapped the brakes just a little before the cone at :53 (while you were still traveling straight), and then gotten back on the throttle to maintain some throttle through that turn, you may have been alright.

Best regards,

Tyler
888-308-6007

I will post a better video of my run tonight and you may be able to see the corners and hear the throttle response thru the exhaust note and tell more. Maybe yall see something I didnt realize. I will note that I used to run -1.2 camber in the rear when I was pushing bad upfront and I went back to -.50. Is it worth the time/expense to get the rear adjusted back to -1.5? I was debating whether to go back to the alignment shop for a tweak adjustment this weekend.

Yes, this old Army landing airstrip is the "bomb". It has great grip, very wide open, and fast fast fast. I think SCCA Solo has those guidelines about keeping autox speeds below 60 mph, but I have been running in 2nd gear (automatic) before and bouncing off the rev limiter 3/4 way thru the slalom and refused to shift. Thats when you know its a fast course. I usually judge my speed by how many times the ABS chirps after I cross the finish line. 3 chirps ok, 4 chirps good. LOL

[Rob@WretchedMS]

i'll wait to see the other video before i give you advice on that.

[Zombie killer]

Originally Posted by Rob@WretchedMS

i'll wait to see the other video before i give you advice on that.

Only one I took with side view. This was an earlier run where I was running about a full second slower until the tires warmed up.

Video link: http://youtu.be/CpCegqs94Kc

[Rob@WretchedMS]

well, what i'm going to say may go against everything you think, and i could be completely wrong.

I don't think you have an oversteer issue.
I would stiffen the rear swaybar, and add a bit of camber, maybe -1.2 in the rear.

I would try to avoid engine braking at high RPM in the center of a fast sweeper. Either stay in the gas just a bit, or change your line a bit to compensate.

Maybe you can find a large open area, like i dunno.... an air strip, maybe, where you can do a skidpad test, keep the car in a steady turn as wide as you can up to about 200 feet, and bring the speed up slowly and steadily until the car starts to loose traction with either the front or rear, this will help determine if it is in fact over/understeering due to the suspension/setup, or if it's induced by the engine/throttle/track factors.

just make sure there are not things to hit if everything goes wrong.

[Zombie killer]

Originally Posted by Rob@WretchedMS

well, what i'm going to say may go against everything you think, and i could be completely wrong.

I don't think you have an oversteer issue.
I would stiffen the rear swaybar, and add a bit of camber, maybe -1.2 in the rear.

I would try to avoid engine braking at high RPM in the center of a fast sweeper. Either stay in the gas just a bit, or change your line a bit to compensate.

Maybe you can find a large open area, like i dunno.... an air strip, maybe, where you can do a skidpad test, keep the car in a steady turn as wide as you can up to about 200 feet, and bring the speed up slowly and steadily until the car starts to loose traction with either the front or rear, this will help determine if it is in fact over/understeering due to the suspension/setup, or if it's induced by the engine/throttle/track factors.

just make sure there are not things to hit if everything goes wrong.

I was thinking of going back to my -1.2 rear camber. And you have a valid point about setting up a skid pad. When the local SCCA has a test and tune day the skid pad is where we find out most what is happening with varying setups. I have access to a secure asphalt area and the cones to set up a skid pad. Might be the best way to check sway bar setups and tire temps.

I have heard the term engine braking used a few times in this thread. Are we talking about the abrupt lifting of the throttle during higher rpms range ?

[Rob@WretchedMS]

Yes. Doesn't have to be abruptly either. But that is when it has the biggest effect

Long range setup help is difficult. You are in the drivers seat. Be sure to keep yourself safe.

[Nor Cal ZL1]

Tire temp spread, and temps front vs rear?

[Zombie killer]

Originally Posted by Nor Cal ZL1

Tire temp spread, and temps front vs rear?

Fronts 110/110/115
Rears 100-105

[Nor Cal ZL1]

Originally Posted by Zombie killer

Fronts 110/110/115
Rears 100-105

Is this fresh off course? If so they are way too cold. What tires are you running? I would start with dropping the rear pressure and read them again.

[Zombie killer]

Originally Posted by Nor Cal ZL1

Is this fresh off course? If so they are way too cold. What tires are you running? I would start with dropping the rear pressure and read them again.

I am running Michelin PSS in a 285/35/20 setup on all 4 corners. I started at 36 and dropped to 34 PSI on air by second set. There were 71 cars competing so we were running 25 cars a heat. The course was a fast 34 second course and I really never ever generated any heat in the tires at all. I would make a run, wait 25 cars, make another ruin, wait another 25 cars, and then make my last run. It wasnt even until the 3rd run did I ever get the front tires above 110 degrees and the rears slightly above 100. Just no heat could be made.

[Nor Cal ZL1]

Originally Posted by Zombie killer

I am running Michelin PSS in a 285/35/20 setup on all 4 corners. I started at 36 and dropped to 34 PSI on air by second set. There were 71 cars competing so we were running 25 cars a heat. The course was a fast 34 second course and I really never ever generated any heat in the tires at all. I would make a run, wait 25 cars, make another ruin, wait another 25 cars, and then make my last run. It wasnt even until the 3rd run did I ever get the front tires above 110 degrees and the rears slightly above 100. Just no heat could be made.

Ah I see. Its going to be tough to dial in until the tires get some heat built up. You may need to go to tires dedicated to auto x. How does the car do otherwise? Good to see your keeping track of the tire temps. This will help you solve almost all of your issues. Also keep in mind those tuning guides are usefull, but can also be wrong depending on what the tires tell you from a temperature stand point.

A car can understeer/oversteer from either too little weight transfer, or too much weight transfer overloading and overheating the tires. The guides are mostly written from a too little transfer perspective, and can take you in the wrong direction if you are experiencing too much transfer.

[Zombie killer]

Originally Posted by Nor Cal ZL1

Ah I see. Its going to be tough to dial in until the tires get some heat built up. You may need to go to tires dedicated to auto x. How does the car do otherwise? Good to see your keeping track of the tire temps. This will help you solve almost all of your issues. Also keep in mind those tuning guides are usefull, but can also be wrong depending on what the tires tell you from a temperature stand point.

A car can understeer/oversteer from either too little weight transfer, or too much weight transfer overloading and overheating the tires. The guides are mostly written from a too little transfer perspective, and can take you in the wrong direction if you are experiencing too much transfer.

I tried to purchase some Hankook rs3s for months and couldn't locate any in my tire size desired in the new 200 TW rating. Found some 140s but they are no longer allowed in many events. So I went with the PSS as a daily performance tire instead. They do hook 10x better than the Pzeros that were on there from GM.
I am going to find me a place to run a skid Pad and see what I can find out. Will play with rear weight (half tank vs full tank of gas) and sway bars and see if I can get a neutral handle when tire temps get up. You know its so hard to be able to tune the setup much at a autoX event and "test and tune" events are so far and few. That's why I was seeing what other auto'xrs were doing. At alignment shop right now. Dialing in more negative camber in the rear end.