Interesting tire degradation with BFG R1 S

[Pat]

[renfield90]

That band looks slightly off color to me, anyone else agree?

There is minor evidence of graining in the first and second pic, especially inside the outer of the two grooves (small bits of rolled up rubber getting in there). A thick band like that on the inside though seems a little too big for graining, especially since grained off rubber likes to collect in grooves. I'll try to dig up a pic of my tire graining to show what it looks like.

My vote is very solid in the OPR camp.

[renfield90]

See attached file, this is the first heat cycle on my tires (I don't bother with heat cycling before competitive use). This was at a local event where few people are using A7s or true slicks, so OPR practically nonexistant. You can see a small amount of rubber rolled up near one of the grooves.

[renfield90]

Here are the same tires two weeks later after a big national event, with tons of A7s/proper slicks being run so OPR was a major concern. My codriver was last to drive, he went offline in several spots and underdrove the car so it stuck on pretty good.

I really think you have OPR. You can pick it up on the racing line if there's just a ton laid down on the racing surface via sliding tires. Graining tends to be more uniform and in lower volume.

Just my 2 cents.

[e1_griego]

Yeah that's OPR.

And agreed on too much pressure. And in my experience with too much pressure the car more or less just shudders through corners. Plus add OPR on top of that and it makes it not fun.

[jbailey8748]

I thought I read somewhere that age of the rubber is a thing

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[Pat]

You guys are the best. Thank you!
Yes, after looking at the picture of the inner shoulder I started to think 35.5 psi was a bit high. I'll see if I can get a little more camber in front and run the tires at 28 psi.
Wow...28? Really? That seems low, but if you say so I'll try it. Fortunately air doesn't cost that much if I have to adjust later.
If I run the fronts at 28 hot, would you expect me to do the same with the rears? Remember, they don't have as much camber and I don't want the car to oversteer TOO much.
Again, thanks for all the help. I have never had to contend with OPR, but it makes much more sense to me now.

[stugray]

First question:

What are you times at HPR on the long track.
That way we can tell right away if you are driving hard or not.


And your tire pressures seem high, but it is hard to tell.
We are told to increase pressure on "street tires" to keep them off the sidewalls, but I run ~22.5 PSI on my hoosiers, but that is also a lighter car.

[Pat]

2:10.3 was my best that day. It was my first time out with race tires on this car, and clearly with some adjustment there is more time to be gained.
It was SO much fun!

[DarkSunrise]

Originally Posted by Pat

You guys are the best. Thank you!
Yes, after looking at the picture of the inner shoulder I started to think 35.5 psi was a bit high. I'll see if I can get a little more camber in front and run the tires at 28 psi.
Wow...28? Really? That seems low, but if you say so I'll try it. Fortunately air doesn't cost that much if I have to adjust later.
If I run the fronts at 28 hot, would you expect me to do the same with the rears? Remember, they don't have as much camber and I don't want the car to oversteer TOO much.
Again, thanks for all the help. I have never had to contend with OPR, but it makes much more sense to me now.

Agreed, this thread has been really informative. Thanks everyone who participated, and Pat for getting the ball rolling!

[stugray]

Originally Posted by Pat

2:10.3 was my best that day. It was my first time out with race tires on this car, and clearly with some adjustment there is more time to be gained.
It was SO much fun!

So you are racing hard, that is a respectable time.


You should check out the Precision run group in Rocky Mountain Vintage Racing (RMVR.com).
They would allow you to run your car in the precision group and you would get driver's school and a couple of race weekends over the year.


You would learn a lot, and get to pick some really good drivers' brains.


There were at least two other FRS/BRZs in the school last year.


And just to humble you some - My brother can tie that time in his 62 Triumph TR4, and the fastest "small bore" car (a porsche 914) would beat 2:10 fairly consistently.


I race a 71 Porsche 914 but my best time so far is 2:24.
I have had my BRZ out there once, but on the stock Primacy's and I never even got comfortable enough to disable traction control.

[Robbie]

You should be shooting for higher pressures according to BFG.
https://philstireservice.com/wp-cont...R1-S-Guide.pdf

You may not have enough front camber given the soft spring rates and the big grip from these tires. My spec 944 runs -4 degrees of camber up front with 400 lb/in and a big front bar on RR's. My BRZ needs -3 for even wear on RS3's with Tarmac 2's.

You may be out of camber adjustment, maybe some higher starting pressures to keep tire temps down. Also, the OPR on the inner shoulder is pretty typical with R compounds. The RR's I've pulled off my Spec 944 look exactly the same.

[Pat]

Hey Robbie, good to see you on here. I was hoping you might show up.
Yeah, I saw the BFG manual about proper tire pressures. That's why I was hesitant to go as low as vroom4 recommended. But hey, it's not going to hurt to try it, right?
Also, I could tell the tires were better the lower I went. I could tell they were better at 35.5 than they were at 36, but never tried anything less than 35.5. I did try 37ish and was not happy with it. I guess the plan is to dial in some more camber if I can and experiment with a wider range of pressures. Unfortunately this probably won't happen until the spring. I'll follow up with results in this thread then.
Thanks for everyone's input!

[Pat]

Originally Posted by stugray

So you are racing hard, that is a respectable time.

You should check out the Precision run group in Rocky Mountain Vintage Racing (RMVR.com).
They would allow you to run your car in the precision group and you would get driver's school and a couple of race weekends over the year.

You would learn a lot, and get to pick some really good drivers' brains.

There were at least two other FRS/BRZs in the school last year.

And just to humble you some - My brother can tie that time in his 62 Triumph TR4, and the fastest "small bore" car (a porsche 914) would beat 2:10 fairly consistently.

I race a 71 Porsche 914 but my best time so far is 2:24.
I have had my BRZ out there once, but on the stock Primacy's and I never even got comfortable enough to disable traction control.

Stugray, I'm not actually racing. I'm just out there driving around. A much as I'd like to race, I just have other priorities. Too many hobbies!
I have instructed with RMVR before. I spent a few years on ski patrol with Rome, which is how I learned about RMVR. Love that guy!
If RMVR asks me to work with them again I probably would. But I get enough free track time as it is working with other clubs that I don't really feel the need to add more to the mix right now.