ski35off

As I was writing this up to answer some questions on a PM from an individual, I realized that I've done this at least several times now, so instead I'm making this a post that I can point people to. This applies to both the 981 and 982 GT4s as we've owned both. I hope it's helpful

Disclaimer: The GT4 is my wife's track car (she's experienced and fast, 30-40 track days/year, and she instructs at a number of local clubs, PCA National certified instructor, MSF-II certified instructor). I drive a 981 GT4 Clubsport at HPDEs, but I do try to drive her car every so often. Our experiences with tires may differ from yours due to experience level, driving style, track surface, temperature, etc. - so take with a grain of salt. YMMV.

Tires: we use Bridgestone RE71Rs on our GT4, 265/35-19 front, 285/35-19 rear. They seem to last anywhere from 25-35 sessions/heat cycles, depending track temperature and how abrasive the track surface is. The thing I like about these tires is that they are consistent throughout a session (I typically get my best times at the end of a session) as well as throughout their life. We run them until we cord them – they don’t tend to heat cycle out (but it does happen). We run them at 33 PSI front, 34-35 PSI rear hot.

Why not Hoosier R7s? In my experience, R7s are great for about 8 heat cycles, then "OK" for about 8 heat cycles, then they fall off a cliff. I'd say the RE71R's grip level is typically above the middle 8 heat cycles, so on average they're way better.

You'd be better off going with "real" racing slicks, like Pirelli take-offs, which you can typically find for about $125/ea. Yes, sometimes you'll end up with a set that isn't very good, but most of the time you're way ahead on the performance/price curve. On the Clubsport I run Pirelli DH and Yokohama ADVAN A005 (medium A60 front, hard A80 rear) take-offs for slicks, Continental EC-WET for rains (but these are no longer available).

That said, you need to be aware that running slicks means more wear and tear on the car. The "Driving on the race circuit" booklet you get with your manual set specifically says "Do not use slick tires" on page 3. There is evidence that this is a real warning; the service lives and maintenance intervals listed in the technical manual for the Clubsport lists the following:

• Drive shafts: change every 5000 km
• Crossbeam and braces: change every 7000 km (this is essentially the cast aluminum subframe under the transaxle)
• Wheel hubs: change every 10,000 km
• Rear hub carriers: change every 10,000 km

Wheels: we have two sets of the Forgeline GS1R wheels in satin gunmetal powder coat.

• Front: 19x9”, 5x130 bolt pattern, +54 offset, 71.5 mm wheel bore
• Rear: 19x10.5, 5x130 bolt pattern, +43 offset, 71.5 mm wheel bore

Also have a set of Apex Wheels on the way (we took advantage of the recent group buy). The Apex wheels are excellent bang/buck. The thing I like about the Forgelines is that they're very light and very strong, and are used by many professional race teams. In fact, my Clubsport came with 4 sets of them. I've found that the Forgelines will bend but not crack, and they're easy to repair. You can order them directly from Forgeline but you can get them significantly cheaper through a reseller. PM me if you want to know who I used.

Note, with the amount of camber we ended up running up front, if I had to do it all over again I would probably change the offset on the front wheels to +45 to push them out 9 mm. I would also tuck the rear in a few mm, say go to +46 offset to provide more rear fender clearance. That said, the specs I outlined above are tried and proven.

Suspension: all of these tires like a lot of camber to wear properly. We run the following nominal suspension:

• Front: -3.9 degrees camber, 10.0 degrees caster (factory spec), 0 to 0.1 degrees toe out each side
• Rear: -2.7 degrees camber, 0.1 degrees toe in each side
• Ride height: as low as you can go without causing a major headache for driving it on the street or loading on a trailer. Because the front splitter on the 982 extends much farther than the 981, the ride height is about 10 mm higher than before.
• The car is corner balanced but because of all the aero on the new GT4, we prioritized making sure that we kept the rake of the OEM setup. Measuring at the jack points (yes I know this is not where you're supposed to measure), the rear jack points were 11 mm higher than the front.

To get these suspension specs, you’ll need to buy some aftermarket suspension parts to make it happen. This is what we did, but some items are optional. For example, you don’t need to go to the swift springs, or the moonball control arm ends even though I recommend them – the stiffer swift spring help with performance and better tire wear, the monoball lower control arm ends have a spherical bushing that doesn’t flex as much as the factory rubber bushing).

Front:

• Camber plates (race design)
• Thrust Arm Bushing (might be optional – depends on how much caster gets moved away from ideal when dialing in camber) + spacers for thrust arm
• Monoball end (longer LCAMBCUP ones needed for the increased camber)
• Front tie rod (longer 991.008.CLAMP.LONG needed for increased camber)
• Front drop links (for adjustable zero pre-load on the anti-roll bar)

Rear:

• Toe control arm (needed for increased camber) + toe link locking plate (optional; removes the eccentric bolt which can come loose)
• Rear drop links (for adjustable zero pre-load on the anti-roll bar)
• Non-cup monoball lower control arm ends (optional, not needed to get to the camber spec but removes the slop of the OEM bushing)

Shims:

• 11 mm shims
• Shim set

Springs:

• Spring upgrade kit (optional, but we found that they helped with tire wear and I thought the stock springs were a bit soft on track)

Brakes: Stock calipers are very good, but you’ll need to keep an eye out for cracked ceramic piston pucks (we upgraded to stainless steel pistons on our 981 and high temperature dust boots since the regular ones disintegrate)

• Cobalt Friction now has brake pads for the GT4 (and GT3) (I’ve been working with them to develop). The XR2 (front) and XR3 (rear) compounds are fantastic.
• I would recommend replacing the OEM rotors when they’re done with AP Racing rotors. They last much longer, are cheaper than OEM, have better feel, and actually help your brake pads last longer since they’re harder.
  • Front rotors – replacement rings are $399 each
  • Rear rotors – replacement rings are $399 each
• BTW I have an extra set of front hats that I'm willing to sell. PM me if you're interested.

I decided to replace the stock brakes with AP Racing BBK from Essex Parts on the new GT4. Great feel/feedback, lighter, and brake pads are much easier to change.

• Front: AP Racing by Essex Radi-CAL Competition Brake Kit (Front 9661/394mm)- Porsche 981/718 GT4, Cobalt Friction CRB-XR2-AP19-18.0MM pads
• Rear: AP Racing by Essex Radi-CAL Competition Brake Kit (Rear CP9449/380mm)- Porsche 981/718 GT4, Cobalt Friction CRB-XR3-AP2-16.5MM pads

Wheel and brake caliper studs: (optional, but because you’ll be removing wheels and brake calipers to change pads fairly often, I would recommend it):

• Wheel stud conversion kit
• If you're keeping the OEM brake kit, get these.
  • Brake caliper stud kit (62 mm front, 85 mm rear)
  • Brake line bracket stud kit

Harnesses: both for safety purposes but also for driving comfort.

• Rollbar: CMS or Cantrell; there are other options
• If the car you purchased has the lightweight bucket (LWB) seats:
  • Sub strap mount: CMS (as part of the roll bar order) or Cantrell
  • Harnesses: Schroth Profi 2x2 Porsche GT4 6 point (the lap belts attach to the LWB)
    • The passenger side LWB seat will require modification for the sub-strap; instructions are in the 981 GT4 forum somewhere
• Don’t forget to get a forward head and neck restraint like HANS, Simpson Hybrid S, or Necksgen

Trj

Thank you for the post. I had been reading on the 981 forum and had not seen anything this detailed on the 718 forum. Excellent detail. Thank you

gesmith55

This is great! Thanks for taking the time.

mgordon18

This is excellent info - thank you!

What tires are you planning on going to, now that RE-71s are disappearing? And what size(s)?

So many of the other tire threads are from 2016 and their recommendations are no longer valid.

Thanks!

ski35off

RE-71Rs are going away? Ruh-roh. I hope not, or if they do, I hope Bridgestone is coming out with something better. Toyo R888R might be an option but I've heard mixed reviews.

mgordon18

I'll find the thread...

Here it is: https://rennlist.com/forums/gt4/1196...continued.html
The original post is from last May, but it continues up until last week.

Also this: https://rennlist.com/forums/718-gts-...l#post17134048

six2six

wow.. great post! thank you for this

jmartpr

+1 on this....there's a sticky on the 981 GT4 forum about this with lots of info.

ski35off

Thanks for the links. Curious, I just bought a set from Discount Tire a few weeks ago, and just ordered another set today. Perhaps we're using up remaining inventory. I will say that I've never purchased an RE71R tire with a date code newer than early 2019.

mgordon18

Tire rack has them on "Closeout" and Discount Tire Direct only has them in 2 sizes. They happen to be the proper sizes for GT4 20" wheels, but that's it. No 19s. Did you buy them from them in 19s? Maybe you bought their last ones...

ski35off

2x 265/35R19, 2x 285/35R19. Said they had the rears in stock and the fronts are 5 days out. From my local Discount Tire. The customer rep didn't mention that they were in short supply even after I said that there are rumors that they have been discontinued.

mgordon18

BTW - My wheels are 8" in front and 11" in rear (they're old 997 wide-body wheels). I'd like to stick with them for at least this year if possible. Is 255/35R19 and 285/35R19 reasonable? Can a 255mm tire squeeze onto an 8" wheel?

ski35off

Have you test fit the wheels on your car yet? Assuming the wheels work offset/caliper clearance-wise, it depends on the tire. The recommended rim width range for the 255/35R19 RE71R is 8.5-10", so I think you might be (literally) stretching it there. You might be better off with the 245/40R19 (8-9.5"). Range for 285 is 9.5-11", so you should be OK there.

mgordon18

Yes. The wheels fit with a 7mm spacer in the rear to keep away from the toe link. I'm running winter wheels on a similar set (lobster forks) now and they're fine so far. Although I've only had the car for 5 days (and 100 miles, though)!

245/40 makes sense, if I can find any. [EDIT: Michelin doesn't make a MPSC2 245/40 19R] I'm trying to stay clear of MPSC2s just because they're so expensive and I've had them heat cycle out on me before the tread disappears. Don't last as long as I want them to for that price. But if RE-71s become unavailable, I have a feeling MPSC2s are it!

I'm also contemplating jettisoning the 19s and just using MPSC2s on the stock 20s all summer for street and track. But I worry a bit about rain in that case. I've run MPSC2s in heavy rain on track and they were surprisingly good, but that was in a Carrera 4S...

lovetoturn

Outstanding post. You pretty much covered it all.

I take it by your call sign and living in Woodinville that you all get up to ski at Steven's Pass. Grew up in Seattle many moons ago. Wish I lived an hour away from skiing.