Shredded ACR tire, look at my Alignment?

[CarbonDan]

Something that can contribute is not going fast enough, maybe?

The idea with negative camber is to make up for the suspension flex, so that it ends up being flat in turns. So the theoretical optimal amount of negative camber is dependent on the amount of grip (tires, conditions, etc). More grip, more neg camber. But if you don't use it all, the wheel doesn't get flat and you're riding on just the insides through the turn too- rather than distributing load across a flat tire. Negative 3 is a lot of negative camber for a street tire, but on the Kumhos and with all that aero, it's got tons of grip for that camber

FYI: On properly setup and driven race cars, insides wear the fastest anyway. You're always either wearing evenly (in a turn) or wearing the inside fastest (when in a straight line, especially coming out of turns and hard braking). But 2 sessions is very fast.

Maybe it's a tire pressure issue. What are temps across the tire?

Also, camber dictates what part of the tire will wear fastest. Toe is how fast it will wear. The more toe, the more the tires are "scrubbing" rather than rolling.

I thought about that too, that the aggressive negative camber will only put the contact patch flat if you're driving it hard enough, but I'm starting to think there's something about the chassis rigidity, shock stiffness, and double wishbone suspension that makes the viper not really roll over that much.
I'm not sure though, I'm still fairly new to all this!

You can judge if I'm going fast enough for this camber or not in this video from yesterday. A high level AM driver could probably quite easily extract a 1:43 out of this car at this track. Maybe down to a 1:40 if they're really haulin the milk. This was my first real track day with the car and there is much more performance left on the table. I think Turn 6 (the long left sweeper at about 70ish MPH) is what's killing the passenger front inside tire.
https://www.youtube.com/watch?v=X-8DRhVJOXY

[Pappy]

Having been down this road, I have my own theory. I was going through front Kumhos (cording the inside) early on. I moved to as much caster as I could get (7 degrees) and 2.2-2.4 degrees negative camber. The suspension is designed to have some caster gain with compression. When you turn the wheels, caster translates to negative camber gain on the outside wheel, and positive camber gain on the inside. With my current setting, at track ride height (suspension not compressed), when you turn the wheels 10 degrees you end up with -3 degrees of camber on the outside, and - 1/2 degree on the inside tire. At 20 degrees of turn (a little much for normal track cornering), you get -3.6 degrees outside, and +1/4 degree inside. The camber gain/loss will be more with the suspension compressed - like at corner entry after braking - due to the designed-in caster gain. That means you could end up with well over 4 degrees of negative camber on the outside tire during hard, compressed cornering if you start with -3 degrees static. Since the Viper suspension is well designed and there is quite a bit of roll stiffness, the inside tire actually does some work in a turn - unlike a lot of other cars. If you run too much static camber, you end up with too much negative camber on the outside tire (in a turn) and not enough translation toward positive camber on the inside tire. I noticed that my tires were tearing the rubber from inside to outside, which means that the damage was probably being done on the inside tire that was trying to help corner but with insufficient camber to be effective. If you ever saw the Viper PCOTY tires after a bunch of journalists got through with them, it was very apparent that the tires were shredded on the inside edge from the inside-out. Just my $.02 worth. BTW, I designed my track car suspension with lots of caster gain with compression, and not much static camber or camber gain with straight ahead compression. That keeps really wide tires flatter on the ground for braking and starts adding a ton of "good" camber (negative outside, positive inside) the second you start turning the wheels.

Pappy

Edit: At -1.8 degrees of static camber I was able to abuse the outside edge of the tire.

Viper Kumho 1.jpg

[Lawineer]

I thought about that too, that the aggressive negative camber will only put the contact patch flat if you're driving it hard enough, but I'm starting to think there's something about the chassis rigidity, shock stiffness, and double wishbone suspension that makes the viper not really roll over that much.
I'm not sure though, I'm still fairly new to all this!

You can judge if I'm going fast enough for this camber or not in this video from yesterday. A high level AM driver could probably quite easily extract a 1:43 out of this car at this track. Maybe down to a 1:40 if they're really haulin the milk. This was my first real track day with the car and there is much more performance left on the table. I think Turn 6 (the long left sweeper at about 70ish MPH) is what's killing the passenger front inside tire.
https://www.youtube.com/watch?v=X-8DRhVJOXY

It's super hard to tell from video, and I'm certainly no pro. 1:47 to 1:40 is a ton of of time though- especially on a short track. That's getting lapped every 25 minutes. Fast cars are easy to drive fast, but really hard to drive even close to their limit. This is why Spec Miata and Spec Boxter are so popular.

I seriously doubt -3 is too much for the car though. The car also just has a lot of power, a lot of brakes, a lot of downforce and etc. It's going to eat tires quickly.

Part of me wonders if the Kumhos just get too soft and overheat. After all, they are a street tire. I found I went through Pilot Sports way faster than R888R and NT01. They wouldn't overheat and get greasy. Kind of like street brake pads. I'll go through a set in a day, no problem provided I don't die in the process. They basically just melt all over your rotor.

[CarbonDan]

Having been down this road, I have my own theory. I was going through front Kumhos (cording the inside) early on. I moved to as much caster as I could get (7 degrees) and 2.2-2.4 degrees negative camber. The suspension is designed to have some caster gain with compression. When you turn the wheels, caster translates to negative camber gain on the outside wheel, and positive camber gain on the inside. With my current setting, at track ride height (suspension not compressed), when you turn the wheels 10 degrees you end up with -3 degrees of camber on the outside, and - 1/2 degree on the inside tire. At 20 degrees of turn (a little much for normal track cornering), you get -3.6 degrees outside, and +1/4 degree inside. The camber gain/loss will be more with the suspension compressed - like at corner entry after braking - due to the designed-in caster gain. That means you could end up with well over 4 degrees of negative camber on the outside tire during hard, compressed cornering if you start with -3 degrees static. Since the Viper suspension is well designed and there is quite a bit of roll stiffness, the inside tire actually does some work in a turn - unlike a lot of other cars. If you run too much static camber, you end up with too much negative camber on the outside tire (in a turn) and not enough translation toward positive camber on the inside tire. I noticed that my tires were tearing the rubber from inside to outside, which means that the damage was probably being done on the inside tire that was trying to help corner but with insufficient camber to be effective. If you ever saw the Viper PCOTY tires after a bunch of journalists got through with them, it was very apparent that the tires were shredded on the inside edge from the inside-out. Just my $.02 worth. BTW, I designed my track car suspension with lots of caster gain with compression, and not much static camber or camber gain with straight ahead compression. That keeps really wide tires flatter on the ground for braking and starts adding a ton of "good" camber (negative outside, positive inside) the second you start turning the wheels.

Pappy

Edit: At -1.8 degrees of static camber I was able to abuse the outside edge of the tire.

Fantastic wealth of info, greatly appreciated the education!! I'm on my first year of tracking still but have been hitting it quite hard, going to every event possible and learning as much as I can. Suspension theory is a big void in my understanding currently.
Can you suggest a solid baseline alignment spec I should ask for with Hoosier R7s? I know it's not quite that simple, but a good starting point that I should shoot for would be helpful.

This is what I've got now which has burned through both front inside tires in short order (3-4 sessions).

Attachment 47872


Maybe
Front -2.4
Caster 7
Toe 0

How about rear camber and toe?

[TKO MOTORSPORTS TEAM]

Fantastic wealth of info, greatly appreciated the education!! I'm on my first year of tracking still but have been hitting it quite hard, going to every event possible and learning as much as I can. Suspension theory is a big void in my understanding currently.
Can you suggest a solid baseline alignment spec I should ask for with Hoosier R7s? I know it's not quite that simple, but a good starting point that I should shoot for would be helpful.

This is what I've got now which has burned through both front inside tires in short order (3-4 sessions).

Attachment 47872


Maybe
Front -2.4
Caster 7
Toe 0

How about rear camber and toe?

Couple things Dan that may help

1. Laser alignment is not the way to go. Unfortunately most shops use laser because its fast and easy. If you can find a proper race shop with a setup rig, scale pads, string fixture etc.

2. Factory suspension settings are not good for track day cars

3. Vipers are notorious for not holding setup. Reason: Large tires, lots of grip, lots of load and rubber bushings all contribute not holding set up. We mfg our camber caster lock out plate kit that fixes this problem

Here is the setup we use with some explanations why. Its not the end all be all magic setup its just what we have found that works well with some minimal trade offs. We get 4 track days or 2 full test days out of front tires pro and amateur drivers. Slicks vs street tire about same life

All cars have our camber caster lock out plate kit installed and our bushing kit.
Front
Cam 2.5-2.8 deg max. You loose a little corner turn in but tire life is much better so its a trade off
Caster 6-7 deg. TKO bushings or factory rubber you dont want to run more then 7 deg you start to bind up the suspension once you go more then 7 deg. Caster split from side to side .5 deg or less is ok
Toe in .080-.125". Toe in helps with heavy front engine cars. Better tire life with a slight trade off of slower turn in. " Zero" toe will make car darty and hard to work with. " Toe out" Car will feel pretty good for 4-5 laps BUT toe out will cause excessive tire wear

Rear
Cam...... 2.0-3.0 deg. Rear tire life is usually not a problem. If you run 3.0 or more you may find on corner exit car may get a throttle loose
Caster..... hard to measure accurately even with special tools. If you can keep it as close to 1 as possible
Toe........ In .060-.125" this will keep car more predictable and stable.

[Arizona Vipers]

I thought about that too, that the aggressive negative camber will only put the contact patch flat if you're driving it hard enough, but I'm starting to think there's something about the chassis rigidity, shock stiffness, and double wishbone suspension that makes the viper not really roll over that much.
I'm not sure though, I'm still fairly new to all this!

You can judge if I'm going fast enough for this camber or not in this video from yesterday. A high level AM driver could probably quite easily extract a 1:43 out of this car at this track. Maybe down to a 1:40 if they're really haulin the milk. This was my first real track day with the car and there is much more performance left on the table. I think Turn 6 (the long left sweeper at about 70ish MPH) is what's killing the passenger front inside tire.
https://www.youtube.com/watch?v=X-8DRhVJOXY

You're going really fast dude. When I was there, there was a member there with an ACR. This guy is extremely experienced and fast, been racing for decades and he was running 1.45's... I'm sure you know who he is.

[Arizona Vipers]

Sorry to resurrect this thread, but I'm in the same situation myself, similar alignment specs (-3.0 front), murdering front v720s just like this.
I'm putting on 19" hoosier r7s on Tuesday and getting the ride height adjusted again, recorner balance and realigned. Can you chime in on what alignment specs I should start with, particularly front camber, to optimize front tire life? What was the final culprit and solution to the original problems.?

Was it your passenger side tire that corded first? Turn 6th at the Ridge was killing my front passenger tire too. As a side note, Hoosier A7's on my car the fronts lasted only 3 sessions. And I corded front Yokohama 40 compound slicks in TWO sessions at Chuckwalla. The best tire for longevity will be the R7's you are planning to run. Put the widest you can up front, when I ran Hoosier's I ran a 335 front.

[CarbonDan]

Couple things Dan that may help

1. Laser alignment is not the way to go. Unfortunately most shops use laser because its fast and easy. If you can find a proper race shop with a setup rig, scale pads, string fixture etc.

2. Factory suspension settings are not good for track day cars

3. Vipers are notorious for not holding setup. Reason: Large tires, lots of grip, lots of load and rubber bushings all contribute not holding set up. We mfg our camber caster lock out plate kit that fixes this problem

Here is the setup we use with some explanations why. Its not the end all be all magic setup its just what we have found that works well with some minimal trade offs. We get 4 track days or 2 full test days out of front tires pro and amateur drivers. Slicks vs street tire about same life

All cars have our camber caster lock out plate kit installed and our bushing kit.
Front
Cam 2.5-2.8 deg max. You loose a little corner turn in but tire life is much better so its a trade off
Caster 6-7 deg. TKO bushings or factory rubber you dont want to run more then 7 deg you start to bind up the suspension once you go more then 7 deg. Caster split from side to side .5 deg or less is ok
Toe in .080-.125". Toe in helps with heavy front engine cars. Better tire life with a slight trade off of slower turn in. " Zero" toe will make car darty and hard to work with. " Toe out" Car will feel pretty good for 4-5 laps BUT toe out will cause excessive tire wear

Rear
Cam...... 2.0-3.0 deg. Rear tire life is usually not a problem. If you run 3.0 or more you may find on corner exit car may get a throttle loose
Caster..... hard to measure accurately even with special tools. If you can keep it as close to 1 as possible
Toe........ In .060-.125" this will keep car more predictable and stable.

Thanks for the info!! I actually was just on your site yesterday looking at your camber lockout kits, looks like it's definitely in my future.
I'm going to give your settings a shot and then plan to get your kit soon. As I'm still in the rapid learning phase, I want to make sure I'm working with a stable platform, so as to eliminate as many variables as possible, and making sure my alignment doesn't wander will be a big help.
I'm also trailering my car to the track and still using through-the-wheel macs straps, which I know have to be placing excessive strain on my alignment already!

[CarbonDan]

Was it your passenger side tire that corded first? Turn 6th at the Ridge was killing my front passenger tire too. As a side note, Hoosier A7's on my car the fronts lasted only 3 sessions. And I corded front Yokohama 40 compound slicks in TWO sessions at Chuckwalla. The best tire for longevity will be the R7's you are planning to run. Put the widest you can up front, when I ran Hoosier's I ran a 335 front.

Yep passenger inside, I can feel it happening through turn 6, I can get my GT3 (with 245 fronts) to sort of dance through that section by modulating the throttle and riding that line between under/over steer, but the ACR sort of just plants itself through there and powers along. There's so much damn grip it's hard to complain, but it clearly comes at the expense of tire life!
I still can't get over your GTA video at the ridge, it's like watching Shaq dunk on your backyard basketball hoop

[Racingswh]

Couple things Dan that may help

1. Laser alignment is not the way to go. Unfortunately most shops use laser because its fast and easy. If you can find a proper race shop with a setup rig, scale pads, string fixture etc.

2. Factory suspension settings are not good for track day cars

3. Vipers are notorious for not holding setup. Reason: Large tires, lots of grip, lots of load and rubber bushings all contribute not holding set up. We mfg our camber caster lock out plate kit that fixes this problem

Here is the setup we use with some explanations why. Its not the end all be all magic setup its just what we have found that works well with some minimal trade offs. We get 4 track days or 2 full test days out of front tires pro and amateur drivers. Slicks vs street tire about same life

All cars have our camber caster lock out plate kit installed and our bushing kit.
Front
Cam 2.5-2.8 deg max. You loose a little corner turn in but tire life is much better so its a trade off
Caster 6-7 deg. TKO bushings or factory rubber you dont want to run more then 7 deg you start to bind up the suspension once you go more then 7 deg. Caster split from side to side .5 deg or less is ok
Toe in .080-.125". Toe in helps with heavy front engine cars. Better tire life with a slight trade off of slower turn in. " Zero" toe will make car darty and hard to work with. " Toe out" Car will feel pretty good for 4-5 laps BUT toe out will cause excessive tire wear

Rear
Cam...... 2.0-3.0 deg. Rear tire life is usually not a problem. If you run 3.0 or more you may find on corner exit car may get a throttle loose
Caster..... hard to measure accurately even with special tools. If you can keep it as close to 1 as possible
Toe........ In .060-.125" this will keep car more predictable and stable.

Great info here and thank you for sharing it!! Beats my guessing at what "might work". Go with something a race team has proven to be correct.

Do you know of any race shops in the East that do alignments that way instead of a laser machine? I just don't know at my level whether it would be worth it or not to be honest. I am about 4 to 5 seconds off the pace of a good pro driver depending on track length.

You get 2 track days, wait I read it again, you get 4 track days but only 2 test days of tire life out of front ACR Kumho's? That's amazing!! I am not sure what the difference is between test and track days?

[Arizona Vipers]

Yep passenger inside, I can feel it happening through turn 6, I can get my GT3 (with 245 fronts) to sort of dance through that section by modulating the throttle and riding that line between under/over steer, but the ACR sort of just plants itself through there and powers along. There's so much damn grip it's hard to complain, but it clearly comes at the expense of tire life!
I still can't get over your GTA video at the ridge, it's like watching Shaq dunk on your backyard basketball hoop

As I was starting to get fast at the Ridge, I was going into 6 with so much more speed, it understeered so badly that I thought something in my suspension was broken. But it was just the driver and that turn lol. I don't see the Kumho's lasting more than a few sessions there....

[TKO MOTORSPORTS TEAM]

Great info here and thank you for sharing it!! Beats my guessing at what "might work". Go with something a race team has proven to be correct.

Do you know of any race shops in the East that do alignments that way instead of a laser machine? I just don't know at my level whether it would be worth it or not to be honest. I am about 4 to 5 seconds off the pace of a good pro driver depending on track length.

You get 2 track days, wait I read it again, you get 4 track days but only 2 test days of tire life out of front ACR Kumho's? That's amazing!! I am not sure what the difference is between test and track days?

Hello Racingswh

Finding a good race shop or shop thats know how to properly setup a car is a rare these days. Former nascar, imsa, and pro-scca mechanics as well as some very talented amateurs are out there working in shops and home garages. Next time your at the track ask around and talk to some of the more serious outfits and drivers see who they are using. There is also the option to do it yourself; It may seem daunting and look like alot of black magic but its really not when you break it down. Although it maybe cost prohibitive or to time consuming.

4-5 seconds slower then pro driver time is VERY GOOD . One of our pro drivers is Memo Gidley; We run back to back hot seat testing with one of our very experienced amateur drivers; times are about 6-8 seconds difference depending on track. You can see your 4-5 is very good you should be proud of that. Sounds like you have some talent so it would definitely help to have your car setup properly. Couple things to think about. 1. Cost proper car setup will cost you quite a bit more then a simple alignment 2. Time. It will take a good shop a minimum of a few hours setup a car for the first time.

"Track day" is just running with groups like hooked on driving, green flag, speed sf etc. 20 minute sessions maybe 4-5 per day. "Test day" track is open run as much as you like usually from 9am-4pm 1 hour break for lunch. Vipers since they have such small fuel tanks we get about 30-40 minute max run time and have to fuel so the tires get some rest time.

There is really no "correct" setup for any car or driver. You go with what works and produces the results your looking for. If you find a setup that gives you better lap times and good tire wear then use it. Car setup is a moving target. There is always a little more on the table your trying to find.

[Arizona Vipers]

Took me years to get my alignment perfect, here's what works for me running slicks:
Front camber -3.4, rear camber -2.1,
Rear toe 2mm in each side
Front toe zero

And TKO is right, I use the guy that does all the Cup Car teams around here and he uses old school strings. I run shims as well because my alignment did indeed move as TKO stated.

[Racingswh]

Hello Racingswh

Finding a good race shop or shop thats know how to properly setup a car is a rare these days. Former nascar, imsa, and pro-scca mechanics as well as some very talented amateurs are out there working in shops and home garages. Next time your at the track ask around and talk to some of the more serious outfits and drivers see who they are using. There is also the option to do it yourself; It may seem daunting and look like alot of black magic but its really not when you break it down. Although it maybe cost prohibitive or to time consuming.

4-5 seconds slower then pro driver time is VERY GOOD . One of our pro drivers is Memo Gidley; We run back to back hot seat testing with one of our very experienced amateur drivers; times are about 6-8 seconds difference depending on track. You can see your 4-5 is very good you should be proud of that. Sounds like you have some talent so it would definitely help to have your car setup properly. Couple things to think about. 1. Cost proper car setup will cost you quite a bit more then a simple alignment 2. Time. It will take a good shop a minimum of a few hours setup a car for the first time.

"Track day" is just running with groups like hooked on driving, green flag, speed sf etc. 20 minute sessions maybe 4-5 per day. "Test day" track is open run as much as you like usually from 9am-4pm 1 hour break for lunch. Vipers since they have such small fuel tanks we get about 30-40 minute max run time and have to fuel so the tires get some rest time.

There is really no "correct" setup for any car or driver. You go with what works and produces the results your looking for. If you find a setup that gives you better lap times and good tire wear then use it. Car setup is a moving target. There is always a little more on the table your trying to find.

Yeah I would have to think I would be WAY slower than Memo Gidley!! I was 4-5 seconds slower than a Pro we hired to drive our endurance car. A 2 time SRO champ, drifting world record holder and Bronze FIA driver. I don't know if he has Memo's pace in doorslammer's or not? He was pretty amazing in what he had to work with but doubtful he would have Memo's pace.

I will find out what my race team uses for alignments. I thought they used a laser machine but I could be wrong? I just don't know. Time and cost is a factor though so it may be a laser machine. I can tell you I am not a good enough driver to be able to tell the finer differences. I just drive the thing and have fun with my buddies!!

[TKO MOTORSPORTS TEAM]

Yeah I would have to think I would be WAY slower than Memo Gidley!! I was 4-5 seconds slower than a Pro we hired to drive our endurance car. A 2 time SRO champ, drifting world record holder and Bronze FIA driver. I don't know if he has Memo's pace in doorslammer's or not? He was pretty amazing in what he had to work with but doubtful he would have Memo's pace.

I will find out what my race team uses for alignments. I thought they used a laser machine but I could be wrong? I just don't know. Time and cost is a factor though so it may be a laser machine. I can tell you I am not a good enough driver to be able to tell the finer differences. I just drive the thing and have fun with my buddies!!

Dont sell your self short. A car that has a good setup that works you will most definitely be able to tell the difference.

[Racingswh]

I will find out what my race team uses for alignments. I thought they used a laser machine but I could be wrong? I just don't know. Time and cost is a factor though so it may be a laser machine. I can tell you I am not a good enough driver to be able to tell the finer differences. I just drive the thing and have fun with my buddies!!

The team building one of my cars, Phoenix Performance, has a bunch of SCCA National Championships, 29 or 30 total I believe. John Heinricy I think has 11 driving their cars and of the two guys building my car Andrew has 10 and Kurt has 2. I was curious so I asked them and they use a Hunter machine for setup.

[TKO MOTORSPORTS TEAM]

The team building one of my cars, Phoenix Performance, has a bunch of SCCA National Championships, 29 or 30 total I believe. John Heinricy I think has 11 driving their cars and of the two guys building my car Andrew has 10 and Kurt has 2. I was curious so I asked them and they use a Hunter machine for setup.

Nothing really wrong with using a hunter machine for shop setup if you know what your looking for and it works for you. Only real problems with using a machine we find are continuity, adjustment/accuracy, speed and portability . If your running your car and having a good time with your buddies these problems arent any concern. Keep it simple, have fun and be safe.