Handling - AutoX setup question

[Daffy]

I did my 5th autox Sunday, still lovin it big time, still running about a sec behind the trailered - serious vettes. I'm stock except for whats in my sig. My question is, I fully expected to get oversteer, & I've had my share of 360's (woohoo), but when I'm driving hard in a sweeper or a loop to a sweeping exit - I feel the front end push out , like the front tires can't grip (understeer) & I have to play with the throttle - not to keep the rear in line, but to get the front to turn. On what could have been my best run Sunday this happened and then correcting for caused my to lose the rear for a sec & I had to correct that, etc.

Is this normal, any setup tips, tire pressure, is it my stock tires can't handle it, any ideas are appreciated. FYI, I run 44 psi in the front & 41 in the rear (running temp).

Thanks,

Dave

 

[lleone]

I found lower tire pressures work better for me. Even as low as 34F/32R I don't get any rollunder with the stock Pilots. Don't worry much about trailer Vettes, there was a WRX 2 seconds faster than me last weekend. At least it wasn't my wife.

 

[Alan Patterson]

You may want to try pulling the "sport shims" in the front to increase the camber. (You also need a tow-in adjustment if you do this) There are several threads on this in the archives that give details.

 

[MichaelP]

I thought sanctioned autox required a set air pressure to compete???

 

[Daffy]

FYI in general:

I'm running SS (super stock)class, reclassed from ASP (A street prepared) last year, in SCCA Solo II, and I'm running in Autocrossers Unlimited events which are pretty much a mirror of the SCCA stuff. Allowable mods include better autocross tires, like Hoosier, etc that are also DOT legal, catback on the viper is OK as are the K&N air filters, but I have to put my stock air tubes back on to run - as the smooth tubes aren't legal (that's a little pain in the ****). There are other changes you can make, like shocks, but not springs, yada, yada. My competition is essentially Z06's. I ran head to head with 4 last year in my second autox and finished in between the 4, but they were all trailered, on racing tires and were spnsored an tweaked - and I am obviously a novice, so the viper competes dog-gone well IMHO.

I am still running novice (SS-N) which means I also get my times compared to other novices on a benchmark to rate how we're competing with each other.

That's about all I know about autox'ing

Also, FYI, this Sunday there was another viper at the event, first time I've seen another one. A blue GTS, the guy had been to viper days, but I don't know if he's on this board. He was running about 3 secs behind my times.

Dave.

 

[Alan Patterson]

While we are on the subject, I will vent a bit about the
class SCCA (Solo 2 autocross) makes me run... in 2002, they
put all GTS and RT-10's into the "superstock" class. However,
all GT-2's and ACR's are required to run in the A-Street Prepared class. Apparently the only reason for this is the factory supplied smoothe tubes on these cars vs the corrogated version on stock GTS and RT-10's. (The K&N filters ar OK) From what I understand, I don't even have the option of installing the corrogated tubes to run in superstock! Only good news here is that there are very few A street prepared competitors here in the Sacramento area. Last time out I beat them all except for an older prepared Lotus Elan, which is like a large "go-cart" on the track. He beat me by only .4 second, so I'm at least competitive with him. NSX's, and the older Porches have not been a problem for the Viper so far. Oh, I guess it's only fair to point out that the 2-3 fastest superstock Vets (Z06/C5's) tend to run about a second faster than me. Guess they are better drivers, but ABS certainly helps a whole lot!!

 

[Mark Young]

If you can go to a wider tire in front, you'll be amazed at how it improves the understeer problem. I went to 285s and could tell the difference noticeably over the 275s. Some ViperDays drivers go all the way to 315s in front.

Otherwise, you just have to play with the tire pressures, and the difference between front/rear.

 

[Bill Pemberton Woodhouse]

Give me a call if you want any info. I have been autocrossing for 22 years,so even if I am not any good, I have been around long enought to pick up a few pointers. I am impressed you are doing so well, as street tires ( Michelins ) are a minimum of 2 seconds slower than Hoosiers on an Autocross course. You are stating that is all the farther you are behind some trailered cars, so Autocross Hoosiers and you iz da Man. Get tight with someone else who does trailer their car,have them load your extra set in their truck/suv, and do the time honored ritual of changing your tires at the event. Your times will vault ahead if you get Hoosiers, and before you take the shims out of the front, check the current Solo II rules, as this has been illegal in the past. Tire pressures do go up for street tires, but I would work on cold pressures as an easier barometer to get started with.


Be happy to help, but you are doing great and obviously having alot of fun.

Snaking through the slaloms,
Bill Pemberton
1-800-889-1893

 

[Fred(DrivingSchool)Kinder]

First, good job staying close to the trailered Vette's. As suggested earlier take out the sport shims. Tire pressure's will vary with track surface and temperature. The range of temperatures that seem to work are 34-40.

Push is normal and smooth reduction of throttle will get the front to turn-in. A quick lift may unweight the rear and put more weight to the front. Result oversteer or spin depending on conditions.

Always look ahead one turn and be smoooooooth with all controls.

Good luck with your next event!

 

[Tom F&L GoR]

Do the shoe polish - put a dab of white sponge applicator shoe polish on the tread edge and see (after a run) how much gets worn off. Then you'll know exactly how far the sidewall rolls under and particularly important, be able to balance front and rear. I start around 38 front, 34 rear.

 

[Daffy]

Thanks All.

Looks like I'm definitely a bit up on psi, I'll follow the recommendations and drop to about 38 front with the polish mark (and 35 in rear). I'll hit the archives for "sport shims", but it sounds like that may be too invasive for me - I'll check it out.

Thanks!

Dave.

 

[MichaelP]

I am trying to learn so please bare with me.

Are you refering to SCCA races?

Is Solo II Novice different?

Here is what I found in the rules:

Legal Tires: In Stock and Street Prepared categories, the tires must have measurable tread, and must be in good condition. Excessive weather checks or visible cord/plies will fail inspection. Tire pressures should be higher than used for the street, usually 45psi-Front/35psi-Rear for a front-wheel-drive car, or 40psi all around for a rear-wheel-drive car.

 

[lleone]

MichaelP - I've only ever done Solo II Autoxing. The tire pressures are reccomendations only (as long as you keep them within the safe limits). You can run DOT legal street tires which include certain Hoosiers.