Track and street alignment for 2008-2009 Vipers . . .

[rcl4668]

I have a 2008 Viper convertible with completely stock suspension. After 3 HPDE events thus far this eason I am noticing that the left front PS2 tire on outside edge is becoming far more worn than the rest of the tire that still has significant treat remainin. In fact, the outer tread grooves have completely worn down.

Question: The car handles great on the track and the street but would my car benefit from a track alignment? As the car is driven at this point approximately 50/10/40 on track, autocross and street, what settings would I need to suggest to my Viper tech? I am assuming I shoud shoot for settings that are a good compromise between street and HPDE driving.

Can someone like Mark Jorgensen with HPDE/track experience share exactly what those settings are? I am a noob when it comes to suspension settings so please imagine you are talking to a 6th grader.

Thanks for any feedback you can provide.

/Rich

 

[ViperGeorge]

On my 06 I run -2.0 degrees front camber and around -0.5 degrees rear camber with about 1/16 toe (out I think) in front. Seems to work fine on the street and its great on the track.

 

[redtanrt10]

Mark can definately help you out w/specs as can Archer too. In the VOI magazine (2 issues back?) there is great information on setting up an ACR that is applicable to your viper. The alignment isn't going to decrease tire wear. Your LF tire is taking a pounding because your driving on a clockwise track. You need to rotate tires, and, if your going to run 3-4 events in 6 months go and get a set of track wheels and track tires. (I killed the shoulders of my PS2's after a couple of events). I first went with Toyo RA 1's that came with a set of used forgelines. I just bought a set of Kuhmo's from JonB for less than $1200 and upgraded to a 305X30X18 front. Using this type of tire you can drive to and from the track. You'll save your stock tires and DOT tires like Kuhmo or Toyo's are much better at the track then PS2's. After that you can decide to trailer or have a friend take a set of Hoosiers

 

[Viper X]

Rich,

Opinions will vary and there is no magic, perfect set up for all tracks. I'm not sure how much actual track time Mark has in his new Viper but no doubt he's been exposed to tracking Vipers for a while.

The car will feel much better on the track with a track alignment, even a mild one and tire wear on the track will improve significantly with a good track alignment, especially as your go faster. Your street tire wear will also be negatively affected if you are too aggressive with your "track" alignment.

Here's where I'd start if I were in a mostly stock car:

Front camber, -1.5 to - 2.0
Front toe out, - 1 mm
Front castor, 5 to 6 positive. L & R
Rear camber, -1.0 to -1.5
Rear toe in, -1 to -2 mm

In my 09 ACR, I run the following:

Front camber, -2.7
Front toe out, -2.5 mm
Front castor, 5.2 positive
Rear camber, -1.5
Rear toe in, -2 mm

Tire wear is pretty good, tire temps confirm the set up works pretty well on the tracks that I run and with my relatively smooth driving style.

On a "twistier", slower track, I would increase rear camber to about -2.0 and might go to -3.0 front camber.

On a higher speed track, I'd reduce front camber to about 2.2 and reduce front toe out to about -1 mm.

Glad you are tracking your car,

Dan

 

[mjorgensen Woodhouse]

On a stock car the static negative camber will not really show tire wear for the length of time the tires will last at the track. We have been using -2.0 to -2.3 in the front forever and have had no problems with wear. The caster will be different from car to car a little but you should have +6 if possible. The rear should be -.8 to -1.2 depending on how much is in the front. The rear tires are so wide that drastic camber will only limit power application and braking. The toe settings will always be toe in in the rear from .2 degrees to .4 degrees total toe in. The front can be in or out depending on how you drive. The toe out will make the car turn well but may be twitchy under braking, toe in will help with stability.

As stated there is no "perfect" answer, it all, depends on your abilities and driving style.

 

[rcl4668]

On a stock car the static negative camber will not really show tire wear for the length of time the tires will last at the track. We have been using -2.0 to -2.3 in the front forever and have had no problems with wear. The caster will be different from car to car a little but you should have +6 if possible. The rear should be -.8 to -1.2 depending on how much is in the front. The rear tires are so wide that drastic camber will only limit power application and braking. The toe settings will always be toe in in the rear from .2 degrees to .4 degrees total toe in. The front can be in or out depending on how you drive. The toe out will make the car turn well but may be twitchy under braking, toe in will help with stability.

As stated there is no "perfect" answer, it all, depends on your abilities and driving style.

Thanks Mark and welcome back from the VCA-imposed "phantom zone."

/Rich

 

[escapedan]

Oh boy, I think I messed up...I am new to Vipers and just learning about alignment settings, so I'm going to chock this up to rookie mistake or shop mistake. Here's what happened:

I took the below specs from "Viper X" to the alignment shop:

Front camber, -1.5 to - 2.0
Front toe out, - 1 mm
Front castor, 5 to 6 positive. L & R
Rear camber, -1.0 to -1.5
Rear toe in, -1 to -2 mm

Here's what I ended up with (very important to note Viper X specifically states toe "out" in the front and "in" for the rear, but the shop just read the "-" and I think I got toe out in the front and the rear):

Front camber: -1.8 (right and left)
Front toe: - 1.1 mm (right and left)
Front castor: +5.4
Rear camber: -1.5 (right and left)
Rear toe: -1.1mm (right and left)

Now my 2006 Viper Coupe seems really twitchy and wants to oversteer even at slower speeds. I'm scheduled to autocross Sunday and drive Thunderhill on 11/6. It's a bit sketchy to drive right now...

Can anyone confirm my thoughts about the rear being toe'd out based on the specs they gave me? I'm scheduled to go back to the shop on Saturday morning and really want to get it right....and not crash...

 

[JonB]

This illustrates the 'risks' that users and posters alike take when adopting well-intended advice offerings here. One NEVER KNOWS when a simple 1-digit typo may occur! Even the SRT engineers gave a wrong part # digit recently....that advice may still be 'out there'.

I think your Front Toe is off. Should be closer to Zero. But as stated, there are SOOO MANY VARIABLES: Tires-Pressures-Ride-Height-Suspension-Driver Weight, style, etc. to get it perfect.

GOOD ON YOU for recognizing the importance of a confidence-inspiring setting.... GET IT FIXED to your satisfaction. I would start with Front Toe...

 

[EXHLR8N]

I have found that tire inflation is just as important. Two weekends ago, we ran at Spring Mountain.

Dan Everts had suggested 29 front/28 rear cold tire pressure, with maximum 35 hot coming off the track for the PS2's.

When I came off the track at lunch time, my hot tire was 37 to 38. I immediately dropped them to 35 and it made a huge difference on the next run.

Any thoughts from you guys on tire pressures?

 

[Magnus_]

I took my car to a local speed shop called BlackDogRacing, they actually race many vettes, and have quite a following locally with other race car setups...

I talked with the owner for a bit about my car, my driving style, where I drive it, etc.. and they aligned it to a setup they thought would work for me. They told me that if I didn't like it, to bring it back and they'd re-adjust it.. On the first try they got it right and the car drove absolutely perfectly.

If you have a local speed shop that you can work with, that would be your best bet as you can talk to someone in person about how you're going to be driving the car, the tracks, etc...

Also, if you run two sets of tires/wheels, then you can go even more aggressive. I went with a full track alignment. The car does like to hunt on the highway, but nothing that bothers me at all. I run street tires when on the street and am not concerned with how they wear as I don't put many street miles on the car anyway. Think about it, if you put a couple thousand street miles on in a year, on a specific set of tires that may wear goofy, its not really that big of a deal if you replace them in 2 years anyway right??

The best things I've done to increase my enjoyment out of HPDE's are:
Full Aero (from JonB)
Hoosier R6's on SSR's (from JonB)
Track Alignment

My car is an absolute pleasure to drive on the track.

 

[Viper X]

Oh boy, I think I messed up...I am new to Vipers and just learning about alignment settings, so I'm going to chock this up to rookie mistake or shop mistake. Here's what happened:

I took the below specs from "Viper X" to the alignment shop:

Front camber, -1.5 to - 2.0
Front toe out, - 1 mm
Front castor, 5 to 6 positive. L & R
Rear camber, -1.0 to -1.5
Rear toe in, -1 to -2 mm

Here's what I ended up with (very important to note Viper X specifically states toe "out" in the front and "in" for the rear, but the shop just read the "-" and I think I got toe out in the front and the rear):

Front camber: -1.8 (right and left)
Front toe: - 1.1 mm (right and left)
Front castor: +5.4
Rear camber: -1.5 (right and left)
Rear toe: -1.1mm (right and left)

Now my 2006 Viper Coupe seems really twitchy and wants to oversteer even at slower speeds. I'm scheduled to autocross Sunday and drive Thunderhill on 11/6. It's a bit sketchy to drive right now...

Can anyone confirm my thoughts about the rear being toe'd out based on the specs they gave me? I'm scheduled to go back to the shop on Saturday morning and really want to get it right....and not crash...

If you got an alignment with "toe out" in the rear, you won't be happy as the car will not handle well as you describe, it will oversteer. Hard to believe any alignment shop would go with toe out at the rear of a Viper but they may not have done a Viper track alignment before.

Get it back to "toe in" at the rear, and a little bit of "toe out" up front, which is pretty simple to do, and the car will handle much better. The rest looks OK.

Good luck,

Dan

 

[Chuck 98 RT/10]

Thanks for any feedback you can provide.

/Rich

Congrats on tracking! It is time for one of these. It will really narrow down your tire alignment issues.

Longacre Racing Online -- Online Catalog

 

[Achilles99]

Congrats on tracking! It is time for one of these. It will really narrow down your tire alignment issues.

Longacre Racing Online -- Online Catalog

+1 on this suggestion. I've tried a few different alignments and tires, and they all produce different results (add different tracks and temps, different pressures, etc. and you've got a ton of variables to deal with). Looking at tire wear helps somewhat, but nothing beats temperatures for an accurate reading of what's going on. This might help give you a general sense of why:

The Tire Pyrometer, A Useful Tool. TRG / The Racer's Group

A couple of weeks ago, I had a brand new set of Hoosiers that didn't perform well. I thought it was my new alignment. Fortunately, a friend of mine ran the same alignment and did fine. Turns out the tires overheated (tires were manufactured too long ago), causing me to oversteer everywhere. Tires were overheating because they weren't gripping, and I ended up cheesegrating them.

Nothing ***** worse on the track than not knowing why your times are suffering. Randomly changing tire pressure wastes run times and accelerates tire wear if done wrong. Same with alignment changes. You'll easily get back the money invested in a pyrometer.

P.S. - Dan's alignment specs are right on. Toe in rears (I did mine 1/8") and toe out front (1/16"). I'm using -2.7 in front, and will try -2 in rear this weekend. Was using -1.3 rear before, but wanted to try a friend's setting. I was not able to get above 4.2 caster when I went to -2.7 up front. That didn't bother me or my friend's Viper on the track in terms of turn-in ability. Camber was more important to us and our tires.

 

[Achilles99]

Oh boy, I think I messed up...I am new to Vipers and just learning about alignment settings, so I'm going to chock this up to rookie mistake or shop mistake. Here's what happened:

I took the below specs from "Viper X" to the alignment shop:

Front camber, -1.5 to - 2.0
Front toe out, - 1 mm
Front castor, 5 to 6 positive. L & R
Rear camber, -1.0 to -1.5
Rear toe in, -1 to -2 mm

Here's what I ended up with (very important to note Viper X specifically states toe "out" in the front and "in" for the rear, but the shop just read the "-" and I think I got toe out in the front and the rear):

Front camber: -1.8 (right and left)
Front toe: - 1.1 mm (right and left)
Front castor: +5.4
Rear camber: -1.5 (right and left)
Rear toe: -1.1mm (right and left)

Now my 2006 Viper Coupe seems really twitchy and wants to oversteer even at slower speeds. I'm scheduled to autocross Sunday and drive Thunderhill on 11/6. It's a bit sketchy to drive right now...

Can anyone confirm my thoughts about the rear being toe'd out based on the specs they gave me? I'm scheduled to go back to the shop on Saturday morning and really want to get it right....and not crash...

Are you sure your toe measurements are in mm? I find it hard to believe that 1.1 mm will affect handling at all. In fact, how are they measuring it? 1.1 seems to be the error tolerance for most machines. It might be worth you setting up strings (you can use jack stands) to measure your toe. I only use strings now, I find it more accurate than laser alignments.

 

[Catwood]

Measure tire temps. The only reason I measure pressure is to know a starting point. I adjust based on temps. Pressures fall where they fall. Usually in 1/2 # changes

I have found that tire inflation is just as important. Two weekends ago, we ran at Spring Mountain.

Dan Everts had suggested 29 front/28 rear cold tire pressure, with maximum 35 hot coming off the track for the PS2's.

When I came off the track at lunch time, my hot tire was 37 to 38. I immediately dropped them to 35 and it made a huge difference on the next run.

Any thoughts from you guys on tire pressures?

 

[escapedan]

Thanks everybody for the replies and advice - I definitely want to get this right before hitting the track. I agree, 1mm seems like too small a measurement to make any difference at all.

I attached the alignment sheet - maybe I'm reading it wrong?? The "before" measurements, naturally, are where I started. The "actual" measurements are after the alignment was completed.

Check it out....

 

[Viper X]

Escapedan,

Not sure what you got from your alignment guy in terms of toe but have the following comments:

1 - I use Smart Strings to do my toe in / toe out work. Very accurate and repeatable but a bit time consuming. With this set up and these fine strings, you can measure toe down to .5 mm - which is about as good as my eyes can see with magnifying glasses.

At the front of the car, I've found that you can set the car up at 0 toe, or dead straight ahead when static, and you will get a little bit of toe out due to the play in the rubber bushings of our front suspension. So, for a first timer, I'd go with the 1 mm toe out up front as I suggested - your net will be more while moving under load (turning). I run 2+mm toe out up front on each side for a total toe out of 4+mm. The car does hunt a little bit on the street but really turns in well at the track and I've been running this toe out or more for the last 3 years, so I'm kinda' accustomed to it.

2 - No offense to machine alignment guys but I don't think you can get this type of accuracy on any machine unless it is constantly being calibrated. Most racers use strings.

3 - After reviewing your specs, it appears that both your front and rear toe is about -1. I don't know what this shop uses -1 to indicate, is it toe in or toe out - you should ask.

4 - At the rear, a little bit of toe in will help stabilize the car at speed, specially when braking but also when accelerating out of a turn as the rear tires tend to want to push back and out.

5 - Finally, too much toe in or out will cause the tires to scrub while running down the road and will make the car difficult to handle while wearing the tires out prematurely.

Good luck,

Dan

 

[Viper X]

Hey Achillies,

Nice to hear that you're having fun with your car. 2 degrees negative camber worked OK for me at the rear of my GTS with Hoosier R6s but could get a little squirelly under heavy braking as the tires started to lose grip, i.e. heat cycle out.

Did not work as well with my ACR - not sure why. Power difference or suspension geometry differences I suspect. Had a few minor traction issues with braking and acceleration with that much negative rear camber, so went back to 1.7 negative as I don't like oversteer, but this may work well for you.

It will be interesting to hear your results on this change.

Dan

 

[escapedan]

Dan (Viper X),

Thanks for taking a look at my specs - I'm heading back to the alignment shop tomorrow to get them to adjust the rear toe - to make it toe in a bit. I will also get those strings ASAP. Very much appreciated!!

Dan (Escapedan)

 

[Achilles99]

Update: Track conditions were cold and I couldn't get tires up to temp for half the day, but pyrometer suggested a few things.

1) New camber of -2 in the rear was too much. I had a temp difference of 40degrees between inside and outside of tire (should be 10 degrees optimally). It was squirmy under hard braking, too. I'm going back to -1.5 and see how that works. I didn't have a tire pyrometer when I was at -1.3 unfortunately.

Dan - You were right again about camber. Apparently, -2 is too much for either the ACR or regular SRT coupe.

ChrisGTS was out there on track with me (on PS2's). He was running -1.3, and his temp readings were great. I'm guessing that if I'm running R888's, I should be able to corner harder hence my next try at -1.5. Does that logic sound right?

2) For R888's, 37-38psi gave me a nice temp level reading across the inside, middle and outside of the tire. However, I could never get the tire to read more than around 140-160 degrees (optimal 180-200). Should I have dropped the pressures a little to heat the tires up? I wonder if that would have caused an underinflation (ie, middle temp reading too low)?

3) I'm undecided about camber in front, but I'm thinking that -2.7 could be too much. I was running more than 10 degrees differential inside to outside, but not as bad as the rear. I might try to bump the camber down a tad. I will say that going to 305's up front (CCW 12" wide) made a world of difference on braking. I could stop a lot faster.

Of course, all the above is dependent on temps and tracks. YMMV!

 

[Achilles99]

Dan (Viper X),

Thanks for taking a look at my specs - I'm heading back to the alignment shop tomorrow to get them to adjust the rear toe - to make it toe in a bit. I will also get those strings ASAP. Very much appreciated!!

Dan (Escapedan)

Escapedan - if you have access to a 4post lift, you can avoid buying the $400 smartstrings setup. I tie strings front to back on my lift, and measure them to be 8' apart. Then, I drive the car up, and measure the distance between hub and string. Adjust both sides equally. IE, if you measure 13" on one side and 14" on the other, put both at 13.5". Also, keep in mind that the "equalizing" number will be different for both front and back hubs depending on wheels. After adjusting, remeasure strings to make sure they are at 8' front and back. This keeps your strings parallel to each other even though your car may be a little crooked on the lift.

If you're doing caster/camber (see my other thread on how I and a few others do it), don't bother with the strings until after you are finished with caster/camber. Toe comes last, and the strings will only get in your way. Changing caster/camber changes toe, but changing toe last shouldn't change your camber/caster.

 

[escapedan]

Achilles - unfortunately I don't have regular access to a lift, I'd have to use my buddies at his garage and its not always available. I was thinking of finding some other guys that are interested in chipping in on a set of the smart strings and splitting the cost.

UPDATE - I had the car aligned again at the same place and now have 1mm TOE-IN on each side for the rear. Even being new to this car, I was able to feel a difference cornering and coming out of corners. It feels a bit more planted now.

VIPER X - it looks like you are dead on about the alignment "rack" being a poor choice. Check out the spec sheet I received yesterday compared to the one I received on 10/17. Clearly, something is way off. For instance, my first alignment (10/17) set the driver side rear toe to -0.7mm. Just a week later the "before" setting showed the driver side rear toe to be -6.0mm!! How is that even possible? It seems very strange that the driver side rear toe would actually change 5.3mm in just one week. I've literally put less then 100 miles on it since the 10/17 alignment. Anyway, I'm sure there is some good answer....

Looking forward to my first track day with a Viper (11/6) - I have a feeling I'll be getting much better lap times then in my old Datsun 240z!

 

[Achilles99]

I actually had the same thing happen to my truck (I paid someone for that alignment job). Went back the next day, turns out the jamb nut on the tie rod was loose, and the toe changed. Maybe the same thing happened to you, since you went to the same alignment shop?

 

[Achilles99]

Update: Track conditions were cold and I couldn't get tires up to temp for half the day, but pyrometer suggested a few things.

1) New camber of -2 in the rear was too much. I had a temp difference of 40degrees between inside and outside of tire (should be 10 degrees optimally). It was squirmy under hard braking, too. I'm going back to -1.5 and see how that works. I didn't have a tire pyrometer when I was at -1.3 unfortunately.

Dan - You were right again about camber. Apparently, -2 is too much for either the ACR or regular SRT coupe.

ChrisGTS was out there on track with me (on PS2's). He was running -1.3, and his temp readings were great. I'm guessing that if I'm running R888's, I should be able to corner harder hence my next try at -1.5. Does that logic sound right?

2) For R888's, 37-38psi gave me a nice temp level reading across the inside, middle and outside of the tire. However, I could never get the tire to read more than around 140-160 degrees (optimal 180-200). Should I have dropped the pressures a little to heat the tires up? I wonder if that would have caused an underinflation (ie, middle temp reading too low)?

3) I'm undecided about camber in front, but I'm thinking that -2.7 could be too much. I was running more than 10 degrees differential inside to outside, but not as bad as the rear. I might try to bump the camber down a tad. I will say that going to 305's up front (CCW 12" wide) made a world of difference on braking. I could stop a lot faster.

Of course, all the above is dependent on temps and tracks. YMMV!

I checked my alignment settings... I was actually at -3 (not -2.7) up front, and -2.4 (not -2) in rear. I guess the suspension settled a little bit after a few run sessions! I'm going to try around -2.5 up front and -1.5 in rear, will report back after next track session. Hopefully someone will be able to use the pressure data.