[Apex1]

How much grip do you want on your sports drive? Your car seems to be equipped to handle spirited drives though the corners where grip is king. What is the wear pattern of the tires? Outside shoulder nearly to the cord or inside showing signs of wear. The reason I ask is what suspension alignment details look like. Did the previous owner put camber into the car to prevent front outside tire shoulder roll. Can you get this info as it will provide some starting point for tire replacement.

Many brands allow tire fipping. Others do not. If the shoulders are only for one corner, not a good choice if you want to maximize the tire tread. Many track guys know this and extend their wear by using the inside shoulder on their outside wear use. The other variable is do you drive your car in the rain? As a case in point here is Bridgestone older Summer tire model RE71R when driven on the street and the tires were flipped, The rain gutters are running against evacuation so almost causing hydroplaning. Currently, my tire choice is RE71RS, but will be changing to my OEM rims with Michelin PS4S for the winter.

The new Bridgestone RE71RS are not flippable due to their asymmetric tread pattern. Never the less, as they wear, I may flip them during their final wear days. My camber is -2.9 f and -2.5 r with a little toe out in front and some toe in in the rear.

I do not skimp on my tire selection as they are the final part of rubber meets the road.

 

[Apex1]

docman- Read carefully the comparison of the Yoko A052 and Bridgestone RE71RS. Summer tires for the street, the Stones would last longer than the A052. With little milage each year, as long as you can afford the initial Tirerack and your Tirerack local install shop, then you would need to be able to use them up in say 5 years. You maybe able to get 10-12000 miles our of the RE71RS, but maybe only 6000 out of A052's. The Advan A052's are softer than the RE71RS. The other tires are not rated as Summer extreme tires by the TireRack, but certainly can give longer performance but not the grip. The question is are you going to drive your car enough to get more than 10,000 before you sell it in the future. Not likely, so spend money now, go drive it hard. Have some camber put back in to the alignment. Say -1.5f and -1.5r. camber and 0 toe f and 12 minutes of toe in in the rear. The outside front tire shoulder wear is the badge of courage as it measure how much front tire roll over you are extracting. Rippled front tire wear almost to the wear stars between the crown of the tire and the shoulder of the sidewall shows good play activity at the right tire pressure.

 

[Apex1]

docman - My size suggestion is 255/35/18 f and 275/35/18 r. Thats exactly what I am running. I am pretty sure your local shop that has a connection to the tirerack can mount this size on your 8 inch wide front rim and 9 inch wide rear. The RE71RS is a new model for the older RE71R that was discontinued a couple of years ago. Bridgestone just started importing this model in April of 2022. My size became available in August. The Tirerack can pre scrub the tires as a breakin. They will be ready to fly as soon as mounted. I did not know about this service, mine only took a couple of drives to get the rubber soft and sticky. Read the TireRack white paper on their test with the BRZ. I was especially interested in the wet application as this tire came out ahead of the softer A052. The TireRack has these in stock now.

One mod you might be interested in is the WaveTrac ATB LSD. Take a look at their web site and read about how the wave slider transfer torque from the slipping slide to the gripping side. It actually works without causing a lot of understeer. I'm talking about the application of throttle at the apex to the exit of the corner. This LSD is excellent in that it does not totallly lock up as some clutch models do. Instead it allows some rotation deviation between rear tires. so you get maximum torque without mandating wheel slip as the clutch type does on lockup. I've had mine for 3 years now without any issues. It allows me to have a pretty consistant slip angle of 8 degrees without triggering the PSM.

 

[Apex1]

docman - The limiting factor in the front tires selection is that OEM front wheel is 8 inch wide. So the 245/35/18 will be a better match. It works very well with the 275 rear. Especially with a Wavetrac LSD that does add some understeer in front. So the contact patch is larger in front and with the better traction in the rear, makes for a great combo.
If you have both the Michelin PS4S as a winter tire and the Bridgestone RE71RS summer tire, there is no comparison. I have both so in dry and wet conditions, the Stone works best. Only when the rain is enough to create a hydroplane condition, then the Michelin is better, but not until.

 

[Apex1]

docman - Send us a picture of your new HRE wheels/tires. Hopefully you chose the RE71RS to pair with the new wheels.

 

[Apex1]

I get it. Lets talk next year.

 

[Apex1]

That's what autocross taught me in that you can run these stiff walled tires with substantially less tire pressure. There were many runs with 26 PSI in my old RE71R. I always pumped them back up before leaving the track though. The instrument panel was constantly on telling me I had a flat tire. I tried to turn off the msg, but just had to deal with it. At any rate, my usual pressure was around 30 PSI on the street (just enough psi to keep the flat tire msg off). This gave me a little cushion when hitting ruts or chip seal dips in the road.
The outside temp is really what keeps the car in the garage though. Now with better wet traction from the RE71RS tires, there is less need for another tire, like the Michelin PS4S which does not have stiff side walls.

 

[Apex1]

docman- I would use a front offset of 47 for a 9 inch front wheel and a 36 offset for a 10.5 wide rear wheel. Hope that helps

 

[Apex1]

Docman - A new Everyday Driver, Season 12 TV compares a 987.1 S vs a Toyota GR 86 trying to keep a $34k entry for a gentleman's sports car on new RE71RS. Quite a test for a 16 year old Cayman. Give it a look, shows how brakes can make a big difference.

Toyota GR86 or Porsche Cayman - Which is better at the...

Everyday Driver compared the GR86 to a 2006 Cayman S (987) to see which car is better for the same price. They were torn about which one they'd give the edge to.

www.gr86.org

 

[Apex1]

Docman- the above side by side testimonial with change over drivers. I would add at least your -2.3 f camber f and -2.1 r using your Cayman R springs and swaybars. R brakes to stop the action, steel shifter cables and a GT3 short shifter, you should be all set.

 

[Apex1]

docman, good choice of a new 981. Not sure what size wheels your new Cayman has but you certainly can go back to the Rack and ask about the gentleman's sports car RE71RS tires. For those who do not track their car but want immediate turn in and very stable braking, corning and acceleration, these are the tires for you. I have both the RE71RS and PS4s and there simply is no comparison. I have not tried the newest edition Sport 5 models. but they certainly are not Summer extreme tires.

 

[Apex1]

I would like to see a competition between the RE71RS and the new PS5. "TireRack" Why not use a Cayman this time and a little longer course. We can digest the results. Mid engine and wider wheels/tires in the rear. For me, I have setup my car to utilize this running 255/35/18 f and 275/35/18 r, with a Wavetrac LSD adding more push requiring a larger tire patch in front. If TR uses a car with PVT, that would match my setup pretty closely. Both wet and dry tests as well as g loading and time trial. We will see which tire has the higher spring rate side wall giving the best turn in control, braking, acceleration and G loading.

 

[Apex1]

Greg summed the tire choice up well. What I have found over the years is what to do with heat cycled tires, that are not even close to their wear bars in all three measurement places, Well I am using these tire up on the street. Yes, when its a down pour I have to be extra cautious with speed, but in my world, I would not be using my Cayman that day. So, last year, I finished off a set of Bridgestone RE71R's and put about 10k miles on them total of which less than 5% were track miles. What this usage did for me was to appreciate the unique features of these tires have for the street. I really liked their turn in and grip,
Yes they were noisy and had some vibration but they were free. I tried to switch back to my OEM setup with Michelin PS4S's, but did not like the result, so they stayed on the wall in my garage. I used up the Bridgestone's and ordered a new set of RE71RS which are on the car now, even in the winter because I find I'm not running to the store or other errands with this car. It stays in the garage until there is limited forecast for rain and the temps are above 40 degrees. So now I can have great turn in, braking, g loading and traction every day I use the Porsche.

This video is from two guys using their Porsche Cayman 987.1S vs a Toyota GR86. What this shows is the expanse of usage of the new RE71RS, which I agree with. The bridgestone created a wide range of excellent features and benefits so that they eliminated my use of the Michelin PS4S's completely.

 

[Apex1]

The PS5 looks to capture the same market that Bridgestone did with the RE71RS. That is taking an autocross tire and making a general sportsman daily driver with track abilities. They fignured out that their tire could do this multi role better and ultimately sell more tires. So that's what was behind the test between the Cayman and Toyota GR86. That test opened my eyes and confirmed what I already discovered that the new RE71RS could be used for a daily tire very very well. The only clevit was the use when the outside temps go below 40 degrees. So off my car they went and on went the Michelin PS4's for winter use. These two sets of tires is as close as I could get them. My tire shop would not mount the Michelin PS4's 255/35/18 front tire on my 8 in oem front wheel, so I had to go down one size to 245/35/18 vs the 255/35/18 for the RE71RS wheich are mounted on Signature 9 in f wheel. So, my lineup is the 18 inch OEM wheels are 8 in wide in f and 9 inch wide in the rear fitted with Michelin PS4's 245/35/18 f and 275.35/18 r. The other street tire setup is Signature 18 9 in f and 10 in r. RE71RS 18/35/255 f and 18/35/275 r. I do get a little more understeer from the Michelin tire setup, but on the street that's OK.
I do have more specific alignment requirements that work with both sets of tires. Toe out in f, 4 minutes on each side for improved turn in. I recently had my alignment changed to this spec and the camber reduced in f to -2.7 and -2.4 r. I also changed the castor to 8.4. In the rear I called for toe in of 8 minutes each side. My car sets on Tarett Cup Race LCA's without any rubber bushings, so its locked in place. That's important to keep the alignment as close to the my spec as possible to prevent inside tire wear during street operation which is about 95%.
Comparing the new Michelin PS5 to the RE71RS will show the benefits of Bridgestone's race heritage. We do need a side by side trial done though in white paper conditions with a mid engine car,