[NG329]

So I've had the chance to run A7 for the first time and I was left underwhelmed. While these tires are definitely proven to be fastest in many applications, they didn't seem to work for me on my stock ZLE.

First, I downloaded the Hoosier guide and it had hot psi recommendations based on the weight of your car. For cars over 3,000lbs the recommendation was 38-40psi hot if I recall correctly. Personally, I think that is absurd. Nevertheless let me continue.

My fastest time at NJMP Lightning is 1:12.2 on Pirelli scrubs. I expected to be running 1:10s with the A7. Instead, the car struggled to hold a tight line pretty much everywhere. It also exhibited a nasty vibration anytime I would brake from 150mph (I was later told that they tend to rotate on rims). Overall they just weren't very confidence inspiring. Surely it must be driver error, right? This was my assumption. I figured that maybe I am the problem. On the A7 The best I could manage at NJMP Lightning was a 1:14.x which was about 1.5 seconds off of my PB. In frustration I threw on SC3R with 200 track miles already in them plus 400 street miles, and immediately ran a 1:13.6.

So, A couple of weeks later I finally had a chance to look at the Cosworth data. Apparently, I was cooking the tires. The tires jumped up 10psi and heated up all the way to 225*F. A7 ideal operating range is 140*F. I'll post the pic in this thread.

My conclusion is that A7 are not ideal for HPDE. By the time I had clear track I was past the midpoint of the session and the tires were practically overheated. On out laps you spend most of your time trying to get around guys getting their tires warm. I think A7 are best used for Open Track events and maybe short races. Additionally, cars approaching 4,000lbs should steer clear. The heat from the oversized ZL1 front brakes, and the heat from the engine, really do a number on the front tire's temps which you can deduce from the data.

Another tidbit of data is that it was 93*F that day. So ambient temps really played a crucial part no doubt. I have about 10 sessions on them now and I'm tempted to give them another go on a 40*F-*60F day before the season ends to see if the temps stay a little closer to their optimal operating range.

I didn't really have a great experience with them. I think of all the tire options out there, if I were racing I'd probably go with brand new Pirelli Slicks or Hankook F200 slicks in 305/680/18 + 325/680/18 sizes. (Hankooks use slightly different measurements).

I wouldn't run the Hoosier R7 either as I personally feel that the SC3R are faster and can be had on the cheap if you buy Goodyear direct with the SCCA discount. I would only run the R7 if I was instructing and just needed 30 heat cycles with consistent performance, albeit not faster-end of the A group fast.

In any event, have a look at the attached screenshot of the Cosworth data and do with it as you will.

[Christian1LE]

So A7's are basically time trial/qualifying tires. You can get 1 good lap out of them, maybe 2. After that they heat up and get slow.

Also Hoosier recommends those tire pressures to cover their own ass if they were to explode. If you ask anyone competitive they will tell you they are running those things at like 30 PSI hot.

I run R7's and I start at 24 PSI cold and aim for 29 hot for time trials. From what i've seen at the track SC3R's are very similar in lap times to a Hoosier R7. Pirelli has a big advantage too that those tires are much lighter than hoosiers so you're actually getting less HP loss at the wheels with Pirellis

But you're right that A7's are definitely not the right tires for HPDE, R7's would have been a better choice.

[khcoaching]

A7s are an excellent tire and when used properly, will smash a 3R. Your pressures were also way too high, 30-31 is more in the ballpark. In my experience, A7s can be used successfully with heavy HP cars in these type of conditions:

- Full sessions under 65degrees
- Time attack for 1-2 laps with the first flying lap the best, in any temp, and a slow out lap 3/4 of the way through it.

That's pretty much it, otherwise go to an R7.

The 3R is a very solid tire, but the A7/R7 is faster, used correctly. I am also a huge fan of the Hankook Z214. It is like a solid R7 at a fraction of the price and it was quite a bit quicker than the 3R.

Ken

[NG329]

Thanks guys.


Ken,

You’re right about the TP. Apparently, I need to change my tire pressure gauge for a more accurate one. Either way, even if I had lowered the pressure by another 2-3psi before that session, the temps would have been even higher. The heat was the main issue and they understeered virtually everywhere once they got hot. My use case was likely an incorrect one. It’s that I’ve seen Corvettes running A7 for full sessions up to 3 days or 15 heat cycles and turning good laps. In retrospect, those cars were tracked out weigh around 3,100lbs. Actually, now that I think about it, it’s definitely the weight. My buddy in a Phoenix Corvette runs 1:10-1:12 in his C5 race car on A7 but in his C7 Grand Sport with A7 ran 1:14-1:16.


My experience with the R7 is that they are the same speed as the 3R. But I rank the 3Rs better because the 3Rs do not fall off in laptimes as badly as the R7. You get 5 good 20min sessions on an R7 before it becomes a 70-75% tire. Then you can run at 70% up until you come up on 30 heat cycles. The 3Rs don’t fall off nearly as much over the course of 10+ sessions. If I were to make an educated guess/assessment, I think the Hoosiers work best on lighter cars.

[khcoaching]

Originally Posted by NG329

Thanks guys.


Ken,

You’re right about the TP. Apparently, I need to change my tire pressure gauge for a more accurate one. Either way, even if I had lowered the pressure by another 2-3psi before that session, the temps would have been even higher. The heat was the main issue and they understeered virtually everywhere once they got hot. My use case was likely an incorrect one. It’s that I’ve seen Corvettes running A7 for full sessions up to 3 days or 15 heat cycles and turning good laps. In retrospect, those cars were tracked out weigh around 3,100lbs. Actually, now that I think about it, it’s definitely the weight. My buddy in a Phoenix Corvette runs 1:10-1:12 in his C5 race car on A7 but in his C7 Grand Sport with A7 ran 1:14-1:16.


My experience with the R7 is that they are the same speed as the 3R. But I rank the 3Rs better because the 3Rs do not fall off in laptimes as badly as the R7. You get 5 good 20min sessions on an R7 before it becomes a 70-75% tire. Then you can run at 70% up until you come up on 30 heat cycles. The 3Rs don’t fall off nearly as much over the course of 10+ sessions. If I were to make an educated guess/assessment, I think the Hoosiers work best on lighter cars.

Yep, extra weight = extra heat.

[Vtor_ZL1]

Not same tire, but I went through same tire pressure learning curve at NJMP lightning few weeks ago.


Towards the end of the day, I got handle of TP rise from heat and settled on 27psi COLD, 30-32 HOT felt great - not same tire as A7 but suspect it would benefit from lower TP.

37-39 psi was kinda scary how little traction the car had!

[ICTsccaCamaro]

Yeah I'm pretty sure A7's are your autocross option, for a trackday I would defiantly want to be on R7's

[NG329]

Originally Posted by Vtor_ZL1

Not same tire, but I went through same tire pressure learning curve at NJMP lightning few weeks ago.


Towards the end of the day, I got handle of TP rise from heat and settled on 27psi COLD, 30-32 HOT felt great - not same tire as A7 but suspect it would benefit from lower TP.

37-39 psi was kinda scary how little traction the car had!

SC3R are ideal at 32psi hot which is what I run. When I ran the A7, I was setting them at 26psi cold and they would heat all the way up to 35-37psi. This particular session I did not check and they were 28psi cold. Either way, they were cooking. What times are you running at Lightning?

*Update: I just flipped the tires the other day because I plan to run them in cooler temps and when we let the air out it smelled terrible. ....indicative of burned rubber.

The R7s gripped for the first 5 sessions but they did not have the lateral stability as the SC3R. The car seemed to "Roll" a bit more in high G corners. If you're used to the SC3R you need to learn to trust the R7.

I personally prefer the SC3R over the R7. I think going forward I'll stick to my original plan of running SC3R on the OEM rims and Pirelli scrubs or Hankook F200s on the Apex 18" rims.

[Christian1LE]

My R7s are holding up well. I'm at 17 heat cycles and the grip still feels great. Fastest lap on them this weekend at watkins glen was lap 3 or 4 then they dropped off by about 4 tenths. Started 23 cold and finished the session at 31, fast lap they were around 29.

[NG329]

Originally Posted by Christian1LE

My R7s are holding up well. I'm at 17 heat cycles and the grip still feels great. Fastest lap on them this weekend at watkins glen was lap 3 or 4 then they dropped off by about 4 tenths. Started 23 cold and finished the session at 31, fast lap they were around 29.

That's really good data. Thanks for sharing. I may run them again at the beginning of the season next year since I won't be so focused on lap times. They're good for at least 4 days on my end. I got 18 sessions out of my previous set before I removed them. They had more life in them but I was definitely not running at or near my PR.

[Lewisracing]

Been running R7s for a few years on my car personally. 3600lbs. 315/30F 335/30R - 21-24psi cold depending on conditions

If I follow Hoosiers recommended initial cyclying of the tire, I can get 10-14 "raceable" heat cycles out of the tire. But only 4-5 will be at absolute peak pace. The next 5-10 will be a few tenths off but still great and last sprint race lengths with no issues. After about 15 HC they lose a lot of pace, 2+ seconds depending on the track. But can still be a DE tire if someone wanted them.
Without following Hoosiers initial HC recommendations then I only get 5-8 HCs from the tire before the 2+ second dropoff.

As others have said, the A7 is best for that TT/hero lap. A mostly gentle outlap and 2 maybe 3 flyers before they are scorching hot, all track and condition dependent of course.

[wakespeak]

Originally Posted by NG329

SC3R are ideal at 32psi hot which is what I run. When I ran the A7, I was setting them at 26psi cold and they would heat all the way up to 35-37psi. This particular session I did not check and they were 28psi cold. Either way, they were cooking. What times are you running at Lightning?

*Update: I just flipped the tires the other day because I plan to run them in cooler temps and when we let the air out it smelled terrible. ....indicative of burned rubber.

The R7s gripped for the first 5 sessions but they did not have the lateral stability as the SC3R. The car seemed to "Roll" a bit more in high G corners. If you're used to the SC3R you need to learn to trust the R7.

I personally prefer the SC3R over the R7. I think going forward I'll stick to my original plan of running SC3R on the OEM rims and Pirelli scrubs or Hankook F200s on the Apex 18" rims.

That's interesting. I ran with the tires getting to 35-37psi hot on a hot day (track ambient at 109F per Cosworth) and they wore well. I was about 2s slower than my best times but so was everyone else it seemed. Had fun trying different braking zones and lines. I will try lower pressures again but I get more inside/outside wear in my experience. Trying to get 4 days/16 sessions out of the tires at COTA. Perfectly even wear this last round with -3.0 camber and 0 toe.

Talked to a good GT3RS driver and he had a full year on his R7s. Lighter car sure.

Love the GY 3rs but listening in on the R7s.

i am watching a replay of the NASCAR event at COTA this year and they are complaining that at 22 laps (I get 8-10 laps a session) that the tires are coming apart.

[Stephen12ZL1]

Hoosiers construction tolerance is terrible and take a lot of weight to get them balanced. The carcass isn't very true on the R7s I have personally balanced. A Goodyear 3R balances very well and generally takes no more than 1.5oz total and some of them .5oz or less. I ran R7s once and they vibrated like crazy above 150mph. Comparatively the Pirelli Scrubs and other tires haven't vibrated at all. My new technique (with a crappy tire) is to balance the wheel prior to mounting the tire. It seems to work more consistently especially with scrubs which have a lot of rubber nuggets melted on the edges. My next tire to try is a Toyo RR.

[NG329]

Originally Posted by Stephen12ZL1

Hoosiers construction tolerance is terrible and take a lot of weight to get them balanced. The carcass isn't very true on the R7s I have personally balanced. A Goodyear 3R balances very well and generally takes no more than 1.5oz total and some of them .5oz or less. I ran R7s once and they vibrated like crazy above 150mph. Comparatively the Pirelli Scrubs and other tires haven't vibrated at all. My new technique (with a crappy tire) is to balance the wheel prior to mounting the tire. It seems to work more consistently especially with scrubs which have a lot of rubber nuggets melted on the edges. My next tire to try is a Toyo RR.

THANK YOU!

I honestly thought something was wrong with my car, like a control arm with excessive play or something to that effect. I'm not a fan. I think if I was in a much smaller car like a Supra, BRZ/86, 3 series, I'd be all over these.

For the Camaro, of all the tires I've tried, I'm really fond of the Hankook Slicks. Those F200s were awesome and the front tires had legendary grip. I was getting them for $1,850/set last year until they raised their prices over the winter.

I think the Goodyear and Michelin Slicks are the best options available but there's just no really good way to get them unless you have connections with a race team supplier.