Track Suspension Setup Considerations......

[Tom and Vipers]

I have never specifically tuned a suspension for the track.

My only experience with springs and bars was simply tuning a few Supercharged Studebakers (!) for 10/10's street driving.

However, I took a 93 Formula to Nelsons Ledges and found the car behaved amazingly weird which has led me to think about setup strategies.

Here is what the bizarre Formula did:

Heavy Heavy push. It was impossible to pin the car out! In fact when setting up to try to HP the back out, while it could be done, the HP required was so excessive, the whole car shuddered when this was achieved on a 30 mph hairpin - barely had enough HP to do it.

I would say this car PUSHES!

But guess what, when you hit the brakes, the car would immediately spin out just like a rear brakes shifter cart!

This combo had a bit of entertainment value because in the hairpin, I was going in too hot and then hitting the brakes to bring the car about and then throttling out of the corner.

What I was thinking was what about setting a car up in the opposite direction: Set the car neutral to loose and then the brakes to push. If you blow it and the rear starts to come out, you catch it with the brakes.

I don't know if this would work, however, the opposite was quite predictable/controllable in my Formula.

Any comments?

NOTE: I also don't hear a lot of talk about push and loose, over and understeer here or on the GM fbody boards. While the Viper may be much better balanced, those fbodies do push a lot. Still no discussion. Is this an area where people do not experiment?

 

[GTS Bruce]

I like neutral but a little loose under heavy throttle and neutral on brakes too while turning in.Too much push or understeer is frustrating,(and slow) Bruce

 

[Arthur R Davis]

I attended VIR this time. My back ground is oval tracks. I found the Viper GTS to be TIGHT!!! Ecept when on the brakes, then it is LOOOOOSE! We drove the viper to VIR and went to have a good time, which we had a blast. Got educated though, on the road course, nothing even like a oval. I fell in love with road courses, because it really demands driver skill and not driver trance ( no offence intended to oval racers.) I looped the car once, stayed on track and no flat spotted tires. I had the alignment changed to loosen the car up and but also within streetable limits. The set-up is a very "agressive" street setup and well within streetable limits as to not cause the wife a nervous breakdown when she drives it. The GTS is still tight by race standards but close to neutral by street standards (well outside federal mandates). Rules prohibit shock, spring and sway bar changes, so air presure is the only way to legally alter spring rates. I run fairly consistant with 2.22 beening the best lap with my son riding with me. Our car is showroom stock 2600 miles and no mod at all. I was very conservative as I only used 20-30% of my stock pads and 2.5/32nds tread wear while recording 367 track miles all weekend. My tire temps never exceeded 120 degrees so that says my tires where not even to a good operating temperature. (if I drove this easy when I raced, I would have been fired on the spot!) I feel that a 2.08 could have been obtained with a "track only alignment" and with a car that wasn't someones pride and joy (mainly MINE)! After learning what the cars really are, when Skip Thomas tells anyone that the GT-1 cars are basically stock engines, I am a believer. The GT-1 cars was consistantly around the 2.01 mark. I didn't notice much changing going on in thier group tring to find more speed though, will have to ask Skip about that.

Have a great day,
Art

 

[Henry Cone]

Art, good to see you on the message board. How about posting your alignment settings for all of us to compare to?? We can always learn more about optimizing settings for the street and track!!

 

[Tom and Vipers]

Federal mandates for suspension balance? (How would the spec even read! Has balance been quantified?)

#%&@#*$^#&

Oh!.... I see what I'm doing wrong!! I'm supposed to CARRY a tube of Vaseline .........

 

[Arthur R Davis]

Sorry it has been so long in responding. My Father passed on 6Aug01 and have been with him until.

And yes the Govrenment tells us what is safer under our cars also.

Henri, with the rules mandating that only stock springs,shocks, and sway bars be used in our class, (They really made it hard to fine tune) leaves us with the basic adjustments. The GTS are sprung too stiff for VIR!!!

What I did was:
1- set the camber to 1 degree on all 4 corners.
2- set toe-in to 1-32 inch per wheel x4
3- set caster to 4.5 degrees on front
4- set caster to 0 on rear

This loosen the car a bit. This set-up is street freindly and a MILD track set-up. Tracks like toe-out not toe-in. Also I recorded front tire temps that indicated that my camber with probly 2 degrees off yet. I really wish I had got your temps.

I would have gone more agressive if I had not been afraid of excessive road wonder and tire wear on the street. I am having a gig made so I can do my own setups with the vipers as my present gauges will not stick to the spindles.

Note also that Debbie liked it better on the street which really makes me wonder if I was too conservative!!!

 

[Henry Cone]

Art, sorry to hear of your loss. Our deepest sympathies go out to you and your family.

Thanks for posting your alignment information. It makes for an interesting comparison to our settings. I wish that we did get a chance to get tire temps on more cars as we could gather more information about how to get these cars set up as best as possible.

For comparison to Art's setting, here are ours:

Viper #1 (Was Janni's car, now mine)

Left Front............Right Front
-1.8 deg....Camber.....-1.9 deg
+6.1 deg....Caster.....+6.2 deg
-0.01 deg.....Toe......0.00 deg

Left Rear.............Right Rear
-1.6 deg....Camber.....-1.4 deg
+0.10 Deg.....Toe.....+0.15 deg


Viper #2 (Was my car, now Janni's)

Left Front............Right Front
-1.9 deg....Camber.....-1.9 deg
+5.8 deg....Caster.....+5.9 deg
0.00 deg......Toe.....-0.01 deg

Left Rear.............Right Rear
-1.4 deg....Camber.....-1.4 deg
+0.12 Deg.....Toe.....+0.14 deg


Both cars were set up with the driver sitting in the car during the alignment - we found that it made a difference in the settings.

These settings are certainly more aggressive that Art's but we find them to be perfectly fine on the street. Undoubtedly tire wear is not as good as with the stock settings but wearing them out has not been a problem so far (usually flat spots from the track are the problem). And clearly the contact patch for straight line braking is reduced in order to have a better patch when cornering.

We would love to get input from others on track settings. As Art mentioned, we run in Super Stock class at Viper days and are thus limited in how much we can change....

 

[Arthur R Davis]

Thanks Henry,

Taking out caster will cause a tweaky feeling on the street, but will help the push. Again, I wish I had taken your tire temps even more now, as your front camber settings appear to be about what I had in mind to try. On the street that much tends to wear the outer edge a little more than usual. Although the rear caster wasn't mentioned, under torque the appled angles affects weight transfer and can upset the car if they are very far out.

Every track has a "personality" so to speak, so the ACRs can fine tune to a particlar corner to possibly gain, BUT they will be giving up something somewhere else. They have the abilty to easily change wedge and thus the cross weights.

 

[Bob Woodhouse]

This thread reminds me of one we did three years back when we were developing the alignment specs for track events. Dean Word and several others were involved, people that were running up front or garnering the national championships in Viper Days and World Challenge. Please do not flame me but we are spreading a lot of mis-information here. I do not have enough keyboard time available to set it straight. Here are a few basics tho, Oh, and Henry, good job, good specs and they will drive well on the street.
1st, lots of negative camber does not wear the outside edges of your tires. Negative camber relates to the tip-in at the top of the tire allowing it to run more on the inside edge at the road surface, thus slightly more wear there but a good flat footprint when side-load is applied. 2nd, less castor will not improve turn-in, the opposite. To relate to this, sit on your Harley and turn the front wheel, you will notice the wheel wants to incline or lay into the direction of the turn. Lots of castor makes the wheel tip or lean into the corner. This is a good thing. Most sports cars will run with lots of castor.(4.5 to 7.0 degrees). Economy or regular sedans will run 2.5 to 4 degrees. 3rd, All street cars and some race cars are set up with understeer or "push". The reason is to make sure we get to see the crash as it happens. No not really, just that it is safe, it is controllable. (Otherwise you hit the tree butt first). Of course neutral is ideal for some drivers but that is rarely ever the case on any car for very long. When you attend "advanced road racing" or any of the second level driving schools you will learn that a slight "push" car is many times the fastest set-up. Stock Vipers have a small amount of push and can be driven quickly using trail braking. 4th Learning weight management is a good step to understanding all of this. 5th, Tire pressures can tune you some yes, never spread more that 3 or 4 pounds front to rear, start cold in the 27 to 30 pound area and look for a hot working pressure of 36 to 40. It can go higher, if working well what the heck. but worrying about temperatures can drive you nuts, use only as reference, watch for more than a 20 degree spread across the face of the tire. 6th There are no Vipers, none, that are sprung too hard for any road coarse in this country. Now if you turned your adj. shocks full on, look there.
7th Suspension balance, a stock Viper has within 50#s the same weight on all four corners. A good thing, and it is nice to have it checked with a shop that can do racing align and set-up. This is changeable on all Vipers. Easier on ACR's. As to weight jacking, I would venture that maybe Paul Mumford, (best street/track Viper Driver I know)when tuning for a particular nuance in a particular corner of a particular track would be qualified to do this and find 2/100th of a second. What is gained in one direction comes off in the other. Given that, remember all tracks turn 360 degreess more in one direction than in the other.

 

[Henry Cone]

Bob, thanks for the great information. You should recognize the slignment settings on our cars - Tom Sessions got them from Bill. I wanted to get a good information thread going on this as there hasn't been much on this subject lately. We have a lot of new people taking their cars to the track so we need to share this information.

I was hoping that we could get input from some of the other Viper Days participants on minor nuances or improvements to these settings. Our experience with them has been very good but I'm always willing to learn.

We still need to get the corner weights checked on our cars, though it should really be just a double check baseed upon the information that you gave. It's pretty impressive that they come so close from the factory.

Thanks for doing everything that you do to support the Viper community...

 

[Henry Cone]

Okay, I thought I would bring this thread back to the top with a question. In prepping our cars for Putnam Park we were checking the tires for their wear pattern. The cars were last run at VIR so the wear pattern reflects running there.

Anyway to my question - it appears from the wear pattern that we could add more negative camber to the rear. From one of my posts above we are running -1.4 degress of camber on both sides of the rear. Is running with -1.8 to -1.9 degrees in the rear too much??

We're not too worried about tire wear - wearing tires out from street milage is not our problem. And since this is the case, are there more aggressive settings that we use that would be better for the track??

Thanks in advance!!

 

[Frank Parise]

I think Bob's summary is excellent. This is a really fun subject and very involved. A quick and easy prescription for a good track set-up is very difficult. There are too many variables to list, but one of the critical components is the driver.

As a supplement to what Bob said, here are some of my findings:

(1)Tire temperatures will tell you two very important things...(a)whether your alignment is favorable or has latent defects for that particular track and driver; (b)whether you are getting the tires warm enough to produce their optimum traction. If you're not seeing 180 degrees in pit lane, you're not using the tires well enough to worry about anything else. This took me about 4 years to do it consistently.


(2)I've never met a driver that prefers to steer the rear end of his car instead of the front end (unless you're driving a junker in the dirt). Interestingly, most drivers like to brag about their heroic driving abilities and sliding the car around the track. This is usually a fantasy, and it's the slow way around the track anyway.

(3)Try a little toe-out up front to help your corner-entry turn-in. The tighter the track, the more toe-out. 1/16" to 1/4" total toe out, depending on the track.

(4) Once you race your Viper with an effective rear wing, you'll never want to take it off again.

(5) You can run alot more negative camber than you are running now.

(6) Different spring rates for different drivers.

(7) Small changes in tire pressure make big changes in handling characteristics. Most guys are using too little pressure because they think it increases traction..which is not always true.

 

[GTS Dean]

Just a few quick thoughts:

1) In a Stock or Super Stock car, alignment and tire pressure are critical. The more competition you have in your class, the more that little things like 1/2# of cold inflation pressure make a difference.

2) If the track has a bunch of straights connected by short corners, you can keep the tires more upright to maximize straight line acceleration and braking.

3) Corner weight - That wonderful distribution of the stock Viper goes right out the window as soon as your fanny hits the seat. Having a passenger ride along brings the balance back at the expense of added weight to haul around.