Tire wear specifically on Left biased Roval?

[bob]

I have 2 questions maybe Rob will chime in too? I never thought about tire wear and what relationship that would have to tire pressures assuming we are in operational temperature of the tire carcas.

I have always used a pyrometer to determine hot target tire pressures. So my 1st question is if you have even wear accross the tire does that imply that you are indeed running the right pressures at that particular camber/toe?

I have been lazy. I take a set it and forget it approach to tuning, alignment, and tire management. I'm leaving performance on the table. So let's say I get interested in becoming something more that mid-pak backmarker. Let's take a left biased roval (autoclubspeedway). It has a few nothing right turns and the rest all hard lefts and the oval section. The LF inside tire gets the most punishment. Alignment is setup typical road course S550 Mustang GT both fronts -3.0 camber -1/16" toe out. I'm thinking I could help the wear on the LF by reducing camber. Question 2 is how much to reduce to see and maybe feel a noticible change or see a change in laptime? Some people claim to feel 0.5-1psi air pressure. I can't do that. I think I need a change of 2-3psi to feel something. I am not looking for holy grail absolutes just out to make enough change to learn something and maybe impress myself enough that this is a direction I should explore.

 

[Bill Pemberton]

For those that are very technical to those that are just somewhat astute to the nuances of various tracks you have now entered the ..........
twilight zone of serious track addicts!! Blacksheep 1 will likely pop in here for some really good data and info and the main thing you are really illustrating is the fact that after getting some experience under our belts we wake up one day and realize some tracks eat up our rubber friends quicker than others and especially on one specific side. This is where we evolve and start talking about rotation of ye olde rubber more often or playing with tire temperatures more often than when we show up at the course. No longer can we say , yes, we have air in the tires, now we have to figure on stagger , track temps, course biases , etc. This is a fine art and will not admit to being a Guru or expert , but I commend you on asking the question because that is the start , the awareness , and the commitment to go faster. The advantage you have is there are some skilled and talented guys/gals who will answer your question better than my paragraph or two of somewhat semi intelligent rambling and you will be set to dominate those vehicles with funny yellow bowties in their grills. Sit back , relax and wait for the stellar prognostications of the Guru for You 2 of Blacksheep 1 --- or maybe DaveW, or Dave_ W, or ...............


Yes , answers are forthcoming , TMO is a helpful place!!

 

[bob]

You illuminate the thing that got me thinking about this.... Tire wear tire rotation. I have my own tire machine and balancer. I flip tires sometimes but it is a lot of work and 50% of the time tire life is long enough so I just deal with it. But I'm coming from racing lighter vette to 3700lb mustang. Either hoosiers are being made thinner or this heavy girl is wearing her shoes out faster. Tire wear must be a good 30-40% faster. I'm getting to cords fast at $1600/set.

 

[67GTA]

Proper rotation makes a huge difference. I’ve been running BFG Rivals S 200tw. 29 heat cycles and some highway miles on a 305/30-19 set, which I was really happy with. Same exact tire in a 315/30-18, after proper track alignment by WR Teknica, and I corded the shoulder of RF and the inside tread of LF with 13 heat cycles. I should have rotated them after the 9th cycle, and would have been good for at least 8 more, depending on the track. For me, ACS is tough on RF, Big Willow is killer on LF and LR (stick axle, 0 camber). Buttonwillow and Chuckwalla are both much easier on tires in my experience.

You mentioned your LF gets the most abuse at ACS - I’m assuming it’s wearing on the inside edge?

 

[Dave_W]

Well, my experience is mostly autocross, but a friend of mine told me he ran Lime Rock (only one left turn, for some reason named The Left-Hander) with staggered camber settings and was faster. Also, the NASCAR guys use positive camber on the LF and negative on the RF and seem to do pretty well. I'd say start by looking at temps & wear - is the "inside" tire hotter / wearing more on the inside edge? Is that what you mean when you say the "LF inside tire gets the most punishment?"

Never looked at the ACS roval track map before. Is it on purpose that the "infield" section looks like a guitar neck and pegboard? Going with staggered camber is going to lose you some grip on the infield hairpin, but you might be able to make up for it by carrying a little more exit speed on the following chicane. Question - is the LF "punishment" from dragging the LF inside edge on the LH turns, or from overdriving the tight RH turns?

Honestly, it's a good line of reasoning, and something I might try. With your current setting of -3 degress camber, I'd try dialing out half the camber on the inside, i.e. set the LF at -1.5 degrees. Realize you'll lose some grip on the RH turns, but you're looking to more than make up for it with higher apex speeds in the LH corners. Be careful with your braking as well, since the contact patches are different and you might feel a pull to the side with less camber. Keep adjusting camber based on tire temps and handling feel.

 

[JDee]

Mosport has 3 lefts (2 of them very fast very downhill corners) and 7 rights. Back in the day I ran staggered camber on the front, about 1/2 degree less negative on the right front, we were maxed out at -3 on the left. Threw away a bit on the 3 lefts. Comparison of over 100 laps showed an average gain of about .2 of a second per lap. Running endurance races of at least 4 hours that represented a significant amount. Don't remember what wear was like. There were no new tire issues and I didn't care much about wear since they would easily last 4 hours at endurance pace and at the time I had a factory tire deal so they were just free expendables.

That was an edge case and I don't do it now, both sides are now equal at about -3.5 maxed out.

 

[blacksheep-1]

Across the face tire temps are over rated, I know in Tune To Win they talk a lot about that but they are running independent suspension formula cars, maybe 2 inches of suspension travel and a lot of aero grip. We don't have that, we have to work with they way our cars are designed, plus add on aero. Also FWIW I've never run the Roval at Charlotte (well I have in a laydown kart.. but). So I would base my numbers on Daytona or possibly Homestead or Kansas I'm familiar with all of those. I don't understand why your LF is taking the biggest beating, generally it's the RF that takes a hit and yes you can "stand up" the LF to help inside tire wear or add camber to the RF to keep from killing the outside of it. On those tracks it is well worth the effort to experiment (Kurt had to start form the rear at Kansas and in 5 laps went from 20 something to 4th, that car was a rock star on the oval, but.. had to give up some for the slow rights) AJ finished the race in 2nd, thanks to fuel mileage, but it was one of my favorite races. You may also want to take a look at that bump steer on the oval as well. I only know maybe 3 drivers that can feel the difference in a 1psi difference in pressure, AJ and Kurt are 2 of them. However, you should still try to nail the pressures because a 2psi difference is sort of cumulative, 2 psi over all is probably not too horrible, 2 psi miss on each tire can translate to 8 psi over all, which is a total loser.
Anyway here's some food for thought.

(32) nominal pressure increases | The Mustang Forum for Track Enthusiasts - TrackMustangsOnline.com

 

[Grant 302]

The LF inside tire gets the most punishment. Alignment is setup typical road course S550 Mustang GT both fronts -3.0 camber -1/16" toe out. I'm thinking I could help the wear on the LF by reducing camber.

I’d have a tendency to suggest reducing the LF camber perhaps in conjunction with higher pressure in it. Go to zero toe if the first two adjustments don’t fix the problem enough for your liking.

Good luck!

 

[blacksheep-1]

I’d have a tendency to suggest reducing the LF camber perhaps in conjunction with higher pressure in it. Go to zero toe if the first two adjustments don’t fix the problem enough for your liking.

Good luck!

You know, I was thinking about this some more, I'm wondering at what point these cars add camber, I know the magic in the foxbodies was 4 degrees of caster, that would add camber during turn in. I'm wondering if what we are seeing here is actually too much caster. You're the numbers guy, I'd have to sit the car on scale pads.
I'm going to my favorite (NOT) tire track this weekend, Homestead/Miami, so I'm going to get a dose of this soon

 

[bob]

You know, I was thinking about this some more, I'm wondering at what point these cars add camber, I know the magic in the foxbodies was 4 degrees of caster, that would add camber during turn in. I'm wondering if what we are seeing here is actually too much caster. You're the numbers guy, I'd have to sit the car on scale pads.
I'm going to my favorite (NOT) tire track this weekend, Homestead/Miami, so I'm going to get a dose of this soon

Rob,

ACS is like Homestead with moderate banking VS daytona with foot flat steep bank where it is more like motorcycle of death thing. So I would have similar wear ACS and homestead. I'm racing the heaviest car I have ever raced (2019 mustang GT in T2 min weight 3600) coming from pretty heavy T2 vettes (3400-3500lb diff restrictors). Tire wear is so rapid I'm really feeling it in the wallet! I will run 4 races + 2 qualys at ACS in these last couple months and my A7's are done even after rotating tires run square! I could get more flipping.

My LF gets punished if standard negative camber because the inside of tire is most on the tarmac then this inside section is dragged up the banking. At the same time the RF rolls over and we see outside wear which is typical. But I have enough camber where the RF outside wear is noticeably less than the LF inside wear.

***********CASTER! I have not thought of that? So you are thinking caster adds camber with steering input and I should see that as weight change on the scales as I turn my wheel? ***********

 

[Grant 302]

You know, I was thinking about this some more, I'm wondering at what point these cars add camber, I know the magic in the foxbodies was 4 degrees of caster, that would add camber during turn in. I'm wondering if what we are seeing here is actually too much caster. You're the numbers guy, I'd have to sit the car on scale pads.
I'm going to my favorite (NOT) tire track this weekend, Homestead/Miami, so I'm going to get a dose of this soon

FWIW, I think the inside of the LF would be worse off if you reduce caster. The caster also reduces camber on the ‘inside’ tire with steering input. Gotta consider the whole setup.

I’d go the other way, if possible. Less static neg camber and more caster.

 

[blacksheep-1]

FWIW, I think the inside of the LF would be worse off if you reduce caster. The caster also reduces camber on the ‘inside’ tire with steering input. Gotta consider the whole setup.

I’d go the other way, if possible. Less static neg camber and more caster.

Yes, I agree

***********CASTER! I have not thought of that? So you are thinking caster adds camber with steering input and I should see that as weight change on the scales as I turn my wheel? ***********

It should increase camber on the outside tire (RF) and you should see things move around as you turn the wheel

try to boil it all down to the essentials so you can visualize it.



And I'd take Daytona over Homestead any day, the shorter corner radius really makes tire management a huge issue for me.

 

[bob]

To update I ran ACS last weekend SCCA Majors race . I'm officially cording my LF and RF A7 hoosier in 2 15min qualys and 2 30min races. OMG my wallet! I took 1 degree of camber out of the LF and increased tire pressure to take some load off the edges and get more tread on the road. I'm way higher than the fast pressures we ran on the lighter vettes. LF -1.7 RF -2.7 My wear looks better. Next step is to get the car on the turnplates and see what the camber does as I mess with caster and turn the wheel. I did not have enough tools at the track for that this weekend. I also go to the track myself and between impound and having no friends I could not get any meaningful data from my pyrometer. Session after session I was increasing pressures and my laptimes kept falling. Best guess I was close to 37-42psi hot. Again no friends so taking pressures in the paddock after getting out of the tech scale line so really a big guess. Anyone else running hoosiers and are you seeing faster times set with higher pressures closer to the hoosier recs? All I can figure is this heavy girl needs more air pressure?

 

[Grant 302]

Again no friends

Friends don’t let friends guess their hot pressures!

But seriously, it’s hard to help with specific setup suggestions without the data. At least for me anyway. Especially since I don’t have S550 experience.

 

[bob]

Friends don’t let friends guess their hot pressures!

Yeah...but I bet I'm close. Tire usually grow 10psi for me. I have to spend some time at HPDE trackday where I have more sessions and more tracktime to do some testing. There is just not enough time on race weekends. This whole S550 development is a guessing game for me. I came later to vettes and all the work was done for me and all I had to do was follow along. I'm surprised so few race the S550 and I'm basically trying to find my a$$ with both hands.

The MCS coilover front struts with camber plates full neg camber only get me -2.7. I have to get to max for my class -3.5 and my tires probably need to be there too. When I change the camber bolt thing on the strut my skinny 295's hit the strut! So I need more spacer. Scrub radius change is a concern but I don't have a lot of choice.

 

[steveespo]

Stand that left front up, at Daytona I went to -1.9 LF, -2.9 RF and the car felt much better on the banking transitions. On the infield the camber wasn't sorely missed and my tires had more even temps than when I had equal front camber at Charlotte. It does take experimenting and I don't think there is much speed in it for a driver of my caliber but should prolong inner shoulder tire life on the left.

 

[Grant 302]

You’re using camber bolts?

JMO, but just say ‘no’ to camber bolts, if I’m understanding you correctly.

 

[Grant 302]

There is just not enough time on race weekends.

I’ve heard this argument before. And while I understand that it gets hectic enough on any track day, if you can’t make the time on a race day, you need more time and practice to dial in your base setup to your liking for the particular track. Forgive the run-on sentence.

 

[bob]

You’re using camber bolts?

JMO, but just say ‘no’ to camber bolts, if I’m understanding you correctly.

I do not have bolts per se. But there are 2 bolts on my struts and I can get more camber but I also cut the clearance of strut to tire. I do not want to go there but my camber plates are maxed out. I need 1/2 Degree more. No place else to get it but at expense of increasing scrub radius.

Raceday only has race and qualy. There just are not enough sessions like an hpde where I'm on track 4-5x a day.

 

[JDee]

Vorshlag plates and get their cutting jig to cut the tops out of the shock towers and you should be able to get at least -3.5. It is a simple cutting job.