Understeer - help please

[cmore]

Well I'm getting a bit frustrated by the Lotus... seems from week to week the car handles almost completely different. I know these cars are very sensitive and I'm having a difficult time deciding to changing my driving technique or change the setup. Part of me wants to leave the car alone and just deal with it, but I figure I will ask.

Here's the latest stats that I continue to adjust between events:

SCCA Super Stock
2005 Lotus Elise without LSD
BWR Front bar on 4th setting
LSS Shocks and Springs
205f/245r Hoosier A6
Cold temps: front 31, rear 33 psi
Hot temps: front 33, 36.5 psi
Front toe: +1/8"
Rear toe: -3/16"

Here's what I noticed today:

Corner entry and mid-corner understeer on slow to mid speed corners. High speed fast transitions were fine with a touch of oversteer as I like.

Many times I have to plant the nose hard and trail brake to get the car to rotate. Though today had many medium speed sweepers that didn't require any brakes thus I couldn't get any weight on the front end.

Thoughts:

I could move the rear toe to -1/16", but I don't think it is worth it.

Should I just leave this setup alone and continue to get used to the car?

Thanks,
Chris

[ZJChaser]

I backed my rear toe-in to 1/32" just a touch basically and that helped but my issue was not turn in, it was on power exiting the corners. Might check your caster as well? You tried softening the front sway bar? You also didn't note your camber.

I also hope you got you + and - signs mixed up on your toe settings. Should be + toe-in in the rear and - toe-in(toe out) on the front....at least thats how I most always see it displayed

[kestrel74]

Seems like really high tire pressures !!... I run 26 hot with my AO48's and it's perfect...

[Cinesnow]

Yes, tyre pressure is waay too high! I'm at 20 f 22.5 r
BTW, what rims are you you on? the 6.5's or 7" in the front?

[Randy Chase]

Decrease rear toe

You do have the shims pulled right?

[fishguy]

what are your pyrometer readings on the tires when hot?

[Surferjer]

All of the aBOVE and get used to some corner off understeer.

[davecarama]

WOW, your tire pressures are high.

Have you ever used Hoosiers before?

Go with stock tire pressures and adjust no more than a 1/2 pound at a time until you have them dialed in.

Typically, the reason you would overinflate a tire is to stiffen the sidewall so you get less rollover. That theory is mainly for people on street tires and for novice drivers. It helps INDUCE understeer and keeps the rookies under control.

The hoosier tires have VERY stiff sidewalls. You could ALMOST run them with no air. (don't though).

Changing the tire pressure change the shape of the footprint. Overinflating will balloon the tire so the middle will hit more, underinflating will wear the outside more because the middle kinda tucks up.

Stick with the stock pressures, and adjust verry little bits at a time.

PS, I can sell you Hoosiers WAY less than Tirerack. PM me and we will talk.

Dave

[cmore]

I'm basing my information on the A6 on this info:

https://www.hoosiertire.com/Tctips.htm

Weight Hot Cold
1800-2200 lbs. 34-37+ 26-31

"+Higher pressures will improve the performance capability but will require a more sensitive feel to take advantage of the increase."

I've pulled all of my shims and I will check castor even though it won't be 100% accurate, because I my setup platform won't accept the weight of the Lotus.

[Maypo]

All respect to Davecarama, but my experience with the A6s is that Hoosier's recommendations are basically correct. When I started competing in the Lotus on the Hoosiers, I set the pressures low (22 and 25) and worked them based on their temps. At 24 and 28 I reached temperature-spread nirvana (which I thought was interesting because those are the consensus pressures for the 048s). So, I continued at those pressures, fiddling with the suspension and trying to dial in my driving to get the 'Elise understeer' down to acceptable proportions.

Granted, each car model can demonstrate a range of behaviors but -- to put things into perspective -- I was running 1/2" toe-out in the rear to get some decent steady-state balance. Then, last September our local Hoosier expert introduced me to the Hoosier pressure recommendation... Wow, some actual improvement! Mine is an ASP car, so I have the luxury of swapping springs and adding camber, but the car's current behavior is worlds better than it was, albeit with some excess understeer I believe I will be able to lessen further.

A final note on my experience: Tire temps are basically unchanged from 8-lbs lower pressures I was using. So, the A6s seem to be untunable with a pyrometer, which is annoying.

[Icedog_16]

Might going with a tire in back that's not as wide (or wider in front, assuming there are no issues with rubbing) help? Stock difference front-to-rear is 30mm and you're at 40mm. I'd think that would tend to increase your propensity to understeer.

[cmore]

Originally Posted by Icedog_16

Might going with a tire in back that's not as wide (or wider in front, assuming there are no issues with rubbing) help? Stock difference front-to-rear is 30mm and you're at 40mm. I'd think that would tend to increase your propensity to understeer.

205F and 245R is the standard National level setup for the Elise on the A6.

I'm trying to eliminate variables so I can just concentrate on driving. I did a 6 hour long stringing of the car to check for squareness and toe adjustments. Now that I know where square is on my car replicating it is very quick.

If everyone agrees this setup is "fairly-ideal" I am going to leave it alone and only concentrate on driving techniques. I'm just looking for something that I'm doing that is completely wrong.

Changing the car and myself each event is not getting me anywhere.

Thanks!
Chris

[CosmosMpower]

Honestly you're probably entering the slow corners too fast, that's it. Your setup is pretty good.

[cmore]

Originally Posted by CosmosMpower

Honestly you're probably entering the slow corners too fast, that's it. Your setup is pretty good.

Ok, well if everyone agree my setup is good I'll just concentrate on changing my technique. Pat Salerno told me that I need to drive hard into the slow corners, and use a lot trail brake to get the car to rotate. He said the front is so light that without driving it in hard and planting, you'll get understeer.

I'll leave the car alone now and just concentrate on driving.

Thanks!
Chris

[Mr. Know]

Sorry for my ignorance...but this seems like a good spot to ask. Is the light feeling in front a precursor to understeer? In tight corners at lower speeds the car has traction forever...but at higher speeds in moderate corners the front end feels light, but still turns in well. Am I at the edge of experiencing understeer...or am I close to the limit of the car (which I doubt)?

[ZJChaser]

non power steering will get easier to turn in with increased speed.

[CosmosMpower]

Originally Posted by cmore

Ok, well if everyone agree my setup is good I'll just concentrate on changing my technique. Pat Salerno told me that I need to drive hard into the slow corners, and use a lot trail brake to get the car to rotate. He said the front is so light that without driving it in hard and planting, you'll get understeer.

I'll leave the car alone now and just concentrate on driving.

Thanks!
Chris

Everyone has their own style and I do trail brake a LOT in this car but there's still a limit of how hard you can drive into a corner. At some point you will just plow when you go in too hot.

[Randy Chase]

Or too much front slip angle

[cmore]

Originally Posted by CosmosMpower

Everyone has their own style and I do trail brake a LOT in this car but there's still a limit of how hard you can drive into a corner. At some point you will just plow when you go in too hot.

Got it!

Do people change their BWR bar to anything other than the 4th setting? From what I've read it seems for autocross you just keep it on the 4th setting and go.

One of the top national guys said he would occationally put it on the 5th setting if he had a really open slalom that he wanted to try flat out.

[Randy Chase]

Originally Posted by cmore

Got it!

Do people change their BWR bar to anything other than the 4th setting? From what I've read it seems for autocross you just keep it on the 4th setting and go.

One of the top national guys said he would occationally put it on the 5th setting if he had a really open slalom that he wanted to try flat out.

Yes. but since your toe settings are off, my bar settings would not apply.