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I've been using 645-18 and 680-18 for 8 track days. No ABS issue until the very last day which was self-induced when I switched the rear pads to a more aggressive compound that developed mild ice mode that only happened in the first 2 laps in the morning session when the surface was damped and cold. After 2 warm up laps the tire grip came in and braking was fine. I might switch the rear pads back.
I also have customer using 645-18 and 660-18 with no braking issue.
Can anybody explain the method to those tire sizes? Why don't they go with the standard DOT method?
accuracy is all relative. A Pirelli DH 315/680-18 actually measures 687mm tall (27.04”) which makes it the tallest of the 680s..
Concur. It is good practice to inflate tire to target hot pressure then use a high quality tire measuring tape to measure the circumference and divide by pi to come up with the "actual" diameter. The actual diameter is important for setting ride height accurately when changing the car's setup. Usually when I make setup changes, by calculations with accurately measured numbers I can nail it the first time.
__________________
PCA National Instructor
TPC Racing stats:
2023 Porsche Sprint Challenge 992 Cup Am Champion
2023 Porsche Sprint Challenge GT4 Pro-Am Team Champion
2022 Porsche Sprint Challenge 992 Cup & 991 Cup Champion
2020 IMSA GT3 Cup Challenge 2nd Championship
2018 IMSA GT3 Cup Challenge 2nd Championship
2016 IMSA GT3 Cup Challenge Champion
2013 IMSA GT3 Cup Challenge Champion
2006 Rolex-24 @ Daytona GT Champion
2004 Grand-Am SGS Class Champion
Here's the updates from Wednesday and Thursday nights' work-
Replaced the busted up rads.
On these cars its not a simple radiator swap like on a Honda or something. Each radiator has to be built up to an assembly before it goes on the car. During race events Porsche Motorsport and race teams have complete assembles in the trailer to reduce the replacement time.
I am switching to .2 ducting(upper portion of image). The difference in the duct openings is huge. Not that I've ever had overheating with the .1 ducting but I'd image the increased air flow will help cooling the brakes since the air exiting goes to the brake duct.
Hey Tom, did you go back with oem radiators? I'm smelling a little coolant around mine and somewhere I've heard the oem's fail so I may change them out while I have the bumper cover off. Do you recommend oem or aftermarket?
Thanks
Tom, do you remember the brand of the 997.1 GT3 RS wing you had on your former black 997? And do you still use redline engine and gear oil in your GT3?
Hey Tom, did you go back with oem radiators? I'm smelling a little coolant around mine and somewhere I've heard the oem's fail so I may change them out while I have the bumper cover off. Do you recommend oem or aftermarket?
Thanks
Hi Paver. I replaced all 3 rads with OEM. The rads that were replaced looked to be the original ones from 2007. The center rad was leaking from frontal impact. The side rads has zero leak, I proactively replaced them to ensure optimal cooling. With 3 new OEM rads and with the fender liner openings cut out à la Cup car, my car runs on the cooler side even on hot Summer track days. If I run my car in cold weather I'd tape off some of the rad opening like this car in image below.
I have seen some OEM rads leak at the seam where the aluminum core meets the plastic end tank. Typically the sealant used at the seam deteriorates causing small leak or weep. Of the ones I've seen leaked there's usually tree leave fragments and other debris trapped in the corner of the seam. I think the acidity from the tree leaves packed in that dark corner with moisture from car washing or driving in the rain accelerates the deterioration of the sealant. So it is a good idea to occasionally remove the front bumper to blow out those corners and the rad cores with compressed air like we do on Cup cars.
I've heard positive things but I don't have experience with aftermarket rads. We have only used OEM rads for street cars and Cup cars.
Tom, do you remember the brand of the 997.1 GT3 RS wing you had on your former black 997?
It was from Getty Design.
I didn't use the supplied universal mesh screen, instead I got OEM screens trimmed them to fit then used epoxy to secure them in place.
Originally Posted by sumbaco
And do you still use redline engine and gear oil in your GT3?
Since my 4.0L engine rebuild I've been using Mobil 0w40 because the engine bearing clearances are tighter than before. On an aging engine will looser clearances a thicker viscosity oil such as Mobil 5w50 or Redline 5w40 can be a good option.
For the gearbox I've been going back and forth between Mobil and Redline 75w90. I think they're both good, their limited-slip additive is different which slightly changes the diff lock up.
Thanks for the reply. That 997 you put together was amazing. But not as amazing as your current car. I'm taking a .1 GT3 on track this year, so have been re-reading this thread.
Thanks for the reply. That 997 you put together was amazing. But not as amazing as your current car. I'm taking a .1 GT3 on track this year, so have been re-reading this thread.
My pleasure. Thank you for reading this thread.
Originally Posted by PTSGT3
Love seeing new updates to this thread.
Updates will come soon. Been deciding on next round of mods.
Originally Posted by PTSGT3
Tom, do you have a build thread on your old black 997?
The work on the black C2S was done before I became a RL member so I don't have a build thread. I do have a photo album of the work with notes in my personal facebook page. I don't know how share the album without friending the entire community LOL!
Hi Paver. I replaced all 3 rads with OEM. The rads that were replaced looked to be the original ones from 2007. The center rad was leaking from frontal impact. The side rads has zero leak, I proactively replaced them to ensure optimal cooling. With 3 new OEM rads and with the fender liner openings cut out à la Cup car, my car runs on the cooler side even on hot Summer track days. If I run my car in cold weather I'd tape off some of the rad opening like this car in image below.
I have seen some OEM rads leak at the seam where the aluminum core meets the plastic end tank. Typically the sealant used at the seam deteriorates causing small leak or weep. Of the ones I've seen leaked there's usually tree leave fragments and other debris trapped in the corner of the seam. I think the acidity from the tree leaves packed in that dark corner with moisture from car washing or driving in the rain accelerates the deterioration of the sealant. So it is a good idea to occasionally remove the front bumper to blow out those corners and the rad cores with compressed air like we do on Cup cars.
I've heard positive things but I don't have experience with aftermarket rads. We have only used OEM rads for street cars and Cup cars.
Tom, thanks for all the info and techniques you've put in this thread!
Spring isn't here yet but the weather has been pretty decent so its time to come out of hibernation. Here's the "to do" list in two categories, the mundane essentials and fun mods-
And now the fun stuff Desired items:
-Delete carpeting and plastic trim panels to reduce weight and for racy look(following the idea of the new factory Clubsport models)
-Race car style floor board
-Raise gas pedal by 1/4 inch
-Convert 4-point roll bar to 6-point
-Exit screens for side radiators
Coming out of hibernation after 5 months.
Here's a pic of the interior pics before the conversion.
The DAS Sport 4-point bolt-in roll bar has been one of the best mods I've done. Perfect fit, never had any creaks in 5 years, and made the chassis very noticeably stiffer during cornering. I am keeping it in case things doesn't work out as intend with the next mod. I highly recommend DAS Sport for anyone looking for well-made and effective bolt-on roll bar solution.
11-25-2019, 11:24 PM
