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Author Topic: Strange set up?
Franckg Verified Driver
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I am a SM newbie and am just starting to dabble with suspension setting. The person that sold me the car (also offers track support etc...) included a "professional set up" in the deal with corner weighting etc.. he told me that he had set up the car to be forgiving (or slow). Before I call him up and question the set up and handling I wanted to run these numbers by the list.

These are approx measurements since I don't have my Camber/ Caster gauge yet.

Ride height - from the pinch welds
Rear 4.35" (!?)
Front 4.5"

Front Toe out 5/32" (total)
Rear Toe 3/32" (total)

Rear Camber 3.6 degrees
Front 3 degrees

No Caster or Cross measurement available

Front Sway - hardest
Rear Sway - middle

The car understeered big time and would bounce off the suspension bump.

I have a DE event this Friday and don't have the time to dramatically change the set up (which I plan using the SM guide after this week-end), what can I do in the interim in terms of simple changes... Toe, ride height?

Also, is the setup way out there that would justify a redo. I am trying to maintain a positive relationship with this guy as he still owes some parts but I am starting to wonder if he actually did anything or just eyeballed it...
TIA
Franck

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Personally I've always found that a balanced racecar is easiest to drive. This is what I would do if I was just trying to get thru the weekend without proper setup equipment:

I'm not surprised you're hitting the stops at 4.35". So raise the ride height to a good 5.25" (unless you're running the 99 shock hats). That will necessitate resetting the toe anyway, so you might as well zero it out. IIRC, raising ride height actually causes some toe in, so with any luck you'll be well on your way to zero toe already just by raising RH.

It'll probably still be understeering with more rear camber than the front. If you don't want to mess with the camber adjustments yet, at least soften up the front sway bar (use the holes that make the bar longer) and/or tighten up the rear (use the holes that make the bar shorter). If you're still understeering with the bars at the extremes, and still don't want to mess with camber, you can fiddle with tire pressures within the range of 35-40 psi HOT.

How did you get these numbers though. Are these from him? The guy who sets you up with those numbers probably shouldn't be trusted with the actual numbers anyway. Get your parts and bolt.

If you don't have the gear to accurately check the setup, I know that Just Tires offers a free alignment check so at least you'll have an idea where to start. Also, if you need help setting it up, a strategic $20 or $40 does wonders with getting those alignment guys to make a few basic adjustments.

Your profile just says you're in the "Southwest". Where are you actually located? I'm in SoCal if you need any help.

[ 02-26-2008, 12:35 PM: Message edited by: Gibscreen ]

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Rob Gibson
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Casey Z Verified Driver Made Donation to Website
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If your car is a 99 as your profile says, the ride height isn't as jacked as you might think. I know some people run them as low as 4.5" or so. Try going up to 4.75" or so for starters. One other thing to note is that unless you are on leveled scales, the RH will be off and that might explain the difference between front and rear. Also, pinch welds tend to get bent over time and that can effect your measurement as well. Between those two things you can probably assume you have some error in your measurement.

Your toe will decrease when you raise the car as Rob said. If it were me and I didn't have the proper gear I would just raise the car equal turns all four corners and see if that helps. I wouldn't assume the setup is really messed up.

One last thing. You mentioned you are new to SM. If you don't have a ton of track experience it would be a good idea to find a guy that does and ask him to drive your car. A lot of times new guys think the car is under steering when they are really just getting in too hot.

Raise the car a couple of turns and see what you think.

Good luck and have fun.

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Jim Daniels
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Rear lower than front is bad, push push push (especially on stock SM shocks [Wink] )

If you follow the setup guide you will greatly help the experience. You may want a bit of toe in for the rear and a soft rear bar to start but MUCH better that currently. It will be a new car, have fun!

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quote:
Originally posted by Casey Z:
If your car is a 99 as your profile says

Oops. I suppose I could have looked at that too.

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Rob Gibson
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Franckg Verified Driver
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Thank you all for the feedback, the car is a 99 with stock hats. I will give the suspension a couple of spins to see how the car feels.

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Listen to the car, not the so called experts inthe paddock or on the internet.

You said the car pushes and is on the bump stops. My guess is it's pushing BECAUSE it is on the bump stops. When the suspension bottoms, the spring rate goes up which causes a push.

99+ does not have an adjustable front bar. You are stuck there. But stiffening one side of the rear may increase oversteer.

I have found that most drivers will like a little toe out in front and toe in in the rear. It is more predictable for beginners.

Also the most common mistake is driving into the corner too hard, causing the push. These cars do not like to be stood on their noses. Try braking a little earlier and softer.

I go over most of this in the book.

Dave

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Franckg Verified Driver
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Dave:

I will re-read that section, I know that I have a lot to learn and the more seat time I get the better. I am committed to understanding what makes the car work and how to affect the handling before going racing, spending a lot of money and being frustrated!

kneedragger302
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Not to jack your thread, But I am also new to SM coming from years of motorcycle road racing. Dave Wheeler along with JD, talk alot about "Driving in to the corner too hard". Coming from 2 wheels, Momentum was a big thing as well as being smooth but you could also scrub off speed with a push if you got in to hot. Can one of you masters, explain what you mean and how to correct that issue. Braking early, and getting on the gas earlier????

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Nic Piekarski
Sheboygan Falls WI
Newbie to SCCA/MC and SM

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(+1) on the Setup Guide.

kneedragger, Slow in, fast out, right?

(+1) on the slight rear toe-in.

Yea, if it's hitting the front bump stops the car will initially turn in, then wash out. Shocks could be toast. I'd test their compression.

Rear camber also seems a little high to me.

Of course, the first place to look on understeer on entry, slow down.

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How does the car feel under straight line acceleration?

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"Driving is a serious business" - John Milner, 'American Graffiti'

MPR22
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quote:
Originally posted by kneedragger302:
Not to jack your thread, But I am also new to SM coming from years of motorcycle road racing. Dave Wheeler along with JD, talk alot about "Driving in to the corner too hard". Coming from 2 wheels, Momentum was a big thing as well as being smooth but you could also scrub off speed with a push if you got in to hot. Can one of you masters, explain what you mean and how to correct that issue. Braking early, and getting on the gas earlier????

I am still a novice but my experience has been rewarded with a slow in fast out approach. He who is on the gas first wins the race to the next braking zone. Also, the N/A 1.6 car turns in better under power. I don't know about 1.8 N/A or 99s.

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Michael Ross

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I disagree on slow in fast out...
My thoughts are... In as fast as you can with out sacrificing fast out.

[ 04-06-2010, 01:45 PM: Message edited by: Drago ]

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Jim Drago
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Franckg, Oh also look at how much pressure your tires build. That will tell you which tires are working and which aren't.

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kneedragger302
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Thanks Drago, that was the answer I was looking for!!!!

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Nic Piekarski
Sheboygan Falls WI
Newbie to SCCA/MC and SM

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Drago, kneedragger, Yes, all other things being equal, as fast as possible ... . Our brains are designed to solve problems.

I meant no disrespect.

Edit: Oh, and give me time. Soon I'll have a Miata for an avatar instead of my Vette.

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chrisp993 Verified Driver
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quote:
Originally posted by Drago:
I disagree on slow in fast out...
My thoughts are... In as fast as you can with out sacrificing fast out.

[yep]

Which reminds me of a friend who told me to "Late Apex as Early as Possible"

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quote:
Originally posted by Drago:
I disagree on slow in fast out...
My thoughts are... In as fast as you can with out sacrificing fast out.

ya think ...or ya do??
[duck]

most beginners start with;
slow in and slow out,
they then progress to
fast in and slow out,
then they 'get it and progress to
medium in and medium out,
then progress to
medium in and fast out,
and finally to fast in and fast out.
thoughts;
It may take 2-3 years for a true beginner with no prior racing experience to go from the first to final stage. No way around it without lots of seat time. And, without learning how to feel, read and set up the car, you will never get to "fast in and fast out".
At the pointy end of the field it is always "fast in" or you will be passed by the two or three cats on your tail.
"Who needs exit speed when you have horsepower" applies to all at the front while going door to door racing ...
[burst]

MPR22
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Interesting racing/physics article describing what Mr. Drago said.

http://phors.locost7.info/phors09.htm

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Michael Ross

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quote:
Originally posted by MPR22:
Interesting racing/physics article describing what Mr. Drago said.

http://phors.locost7.info/phors09.htm

... and the fun begins. What are you willing to trade off to be fast somewhere else? Talking chassis, suspension, drive ratios ...

Although admittedly still a noob, this is a part I enjoy. I'm sure you more experienced guys know where to focus your time in tuning.

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The 1st 1/3 of the corner separates the guys at the pointy end from the guys at the fat end of the field. I have endless data that shows this. fast in and fast out as Jim says. The middle pedal just slows you down [Smile]

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volante Verified Driver
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Jim I think it might be easier if you posted that video from Sams car when you all were at Memphis one year.
It clearly shows what Jim is trying to explain about "fast in,fast out and then the Oh crap moment" [Smile]

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volante

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Not to completely hijack his thread.

I would say bottoming out on your front bumpers is more than likely the cause of your understeer grief. I would look to fix that first. Try stiffening the front roll resistance. Insufficient shock compression force? Insufficient front droop travel?

Try slowing your entry and see if you are back on the throttle sooner (higher rpm's for a given point at exit).

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"Driving is a serious business" - John Milner, 'American Graffiti'

   

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