Pilot Sport Cup Sizes
07-08-2009, 01:06 PM
#16
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Rennlist Member
Rennlist Member
NJ-GT,
It isn't the N-Spec that are discontinued, it is the better NON-N-Spec (softer compound) that are discontinued in GT3 sizes.
So you are pushing for the 265/325 combination for the 997 GT3. Few questions then before I order.
1. Do you see any negatives to running the softer Non-N-Spec 265 in the front with an N-Spec 325 in the rear?
2. Will this work with my current alignment, or should I make adjustments?
FRONT
Camber -3°00’ / -3°00’
Caster 9°50’ / 9°40’
Toe OUT -0°05’ (1/16”) / -0°05’ (1/16”)
Ride Height 93mm / 94mm
REAR
Camber -2°43’ / -2°43’
Toe IN 0°10’ (1/8”) / 0°10’ (1/8”)
Ride Height 118mm / 120mm
SWAY BAR FRONT: 2nd hole closest to elbow
SWAY BAR REAR: 1st hole closest to elbow (full stiff)
Thanks...
It isn't the N-Spec that are discontinued, it is the better NON-N-Spec (softer compound) that are discontinued in GT3 sizes.
So you are pushing for the 265/325 combination for the 997 GT3. Few questions then before I order.
1. Do you see any negatives to running the softer Non-N-Spec 265 in the front with an N-Spec 325 in the rear?
2. Will this work with my current alignment, or should I make adjustments?
FRONT
Camber -3°00’ / -3°00’
Caster 9°50’ / 9°40’
Toe OUT -0°05’ (1/16”) / -0°05’ (1/16”)
Ride Height 93mm / 94mm
REAR
Camber -2°43’ / -2°43’
Toe IN 0°10’ (1/8”) / 0°10’ (1/8”)
Ride Height 118mm / 120mm
SWAY BAR FRONT: 2nd hole closest to elbow
SWAY BAR REAR: 1st hole closest to elbow (full stiff)
Thanks...
2. perfect alignment, stay there
07-08-2009, 08:39 PM
#18
Rennlist Member
stock rims 8.5J n 12J .....245 n 325 are probably the max available
265 in the front is too squashed in and bear in mind that 265 of Cup tires are like 275 on street tires due to wider shoulder block
I m on 245 front and stock 305 rear..of course the 245 being non N-spec
Fits well n runs well but after trying both Corsa n MPSC, I prefer Corsa
265 in the front is too squashed in and bear in mind that 265 of Cup tires are like 275 on street tires due to wider shoulder block
I m on 245 front and stock 305 rear..of course the 245 being non N-spec
Fits well n runs well but after trying both Corsa n MPSC, I prefer Corsa
07-09-2009, 04:34 AM
#19
Banned
I ran the 265 MPSC on stock wheels at a heavy load high banking race track (California Speedway Roval). My lap times where under 1:50s. At the same track with my previous GT3 on Toyo RA-1 275/335 with 10"/12" x 18" wheels, my fastest lap time was 2.5 secs slower. Temperatures for both front and rear tires in the GT3 RS where in a 15 degrees Fahrenheit range, tire pressures at 32 psi front/ 34 psi rear hot (started at 26/28).
The 265 MPSC is a 265 wide tire, it is indeed narrower than other R-comp 265 tires. The 315 MPSC is much wider than the average 315 tire. The 345/19 and the 335/18 MPSC are also wider than average, with the 325/19 being narrower than the 315/18. This is information from tires measured side by side with measure tape.
A recent sample I took when testing fitments for the 997 GT3 RS and Cayman S, I found a 265 being narrower than a 235 from the same brand and model tire.
Most recently I ran the Pirelli Corsa system tires against Hoosier A6. Three different road courses, where I found the Pirelli being 5 to 6.5 seconds slower than the A6. At the same venue, I tested the MPSC multiple times against the A6 (same day, same car, same driver, same road course), and the difference per average 60 secs laps was in between 2.5 secs and 3.8 secs, when comparing the Hoosier A6 to the Michelin Pilot Sport Cups. The MPSC shows consistently faster lap times compared to the Pirelli Corsa.
The Pirelli Corsa tires are not remotely close to the MPSC & R888 lap times in my experience.
By the way, the 245/19 MPSC is not yet available as a full spec MPSC, it's not a N-spec either. It has an extra groove, and it is built as a BMW OEM optional tire in Europe. I have a set of 245/265x19 MPSC for my E92 M3 right here.
Some pics with the 265 MPSC on stock 8.5" wheels.
The 265 MPSC is a 265 wide tire, it is indeed narrower than other R-comp 265 tires. The 315 MPSC is much wider than the average 315 tire. The 345/19 and the 335/18 MPSC are also wider than average, with the 325/19 being narrower than the 315/18. This is information from tires measured side by side with measure tape.
A recent sample I took when testing fitments for the 997 GT3 RS and Cayman S, I found a 265 being narrower than a 235 from the same brand and model tire.
Most recently I ran the Pirelli Corsa system tires against Hoosier A6. Three different road courses, where I found the Pirelli being 5 to 6.5 seconds slower than the A6. At the same venue, I tested the MPSC multiple times against the A6 (same day, same car, same driver, same road course), and the difference per average 60 secs laps was in between 2.5 secs and 3.8 secs, when comparing the Hoosier A6 to the Michelin Pilot Sport Cups. The MPSC shows consistently faster lap times compared to the Pirelli Corsa.
The Pirelli Corsa tires are not remotely close to the MPSC & R888 lap times in my experience.
By the way, the 245/19 MPSC is not yet available as a full spec MPSC, it's not a N-spec either. It has an extra groove, and it is built as a BMW OEM optional tire in Europe. I have a set of 245/265x19 MPSC for my E92 M3 right here.
Some pics with the 265 MPSC on stock 8.5" wheels.
A 265 tire is not recommended to be mounted on an 8.5" rim. Also, the section width (and maybe tread width) of a tire will change depending on the width of the rim. If you want a wider front tire on the front of the GT3 such as a 265 (which I think is a good idea; I personally run a 255), it makes sense to increase the front wheel size so that the tire can set more squarely on the wheel and is not pinched. The section width can vary depending on the rim width a tire is mounted on. Also, by using a wider wheel, and thus allowing the tire to sit more squarely, the section width is wider but also has better contact across the entire width of the tread. I believe that ideally, the width of the wheel should be same as the section width of the tire (when it is not on a wheel) to take full advantage of its contact patch and to keep it square. I learned this from John at CCW.
I think that our 997 GT3's are a good example of this. Anybody ever wonder why the rear wheel is a full 12" for only a 305 tire? It will easily fit on an 11" wheel, and that is what I believe is used on the turbo. But with the GT3's wider wheel, the 305 tire sits much better and makes full use of that particular size tire. I do wonder why Porsche didn't go with a 9" on the front with a 245 (or even the 235), for this same reason and to help with the understeer issue. I know they try to be "safe" with factory understeer dialed in, but they know that 70% of GT3 buyers will track their cars and probably have more HP driving experience than any other street legal Porsche buyer. I guess it just takes that one guy to ruin it for all of us.
One other thing I would like to point out is the affect of the tire sidewall height (aspect ratio) on the section width. I have done a lot of research on the specs of tires that you can find on the manufacturer website and also on Tire Rack's website. Generally, a lower profile tire of the same width (235 35 18) as a higher profile (235 40 18), mounted on the same wheel, will have less of a section width. The higher profile has more sidewall to allow it to flare out, then the lower profile; but the higher profile will almost always weigh more (seems logical). Take the Toyo R888 315 30 18 vs the 305 35 18; the 315 is wider, yet it weighs a full 3 lbs less than the 305! And when you put them on the same width wheel of 11 or 11.5" (I forget which), the 305 is only 1/10 of an inch less than width than the 315. Why? Because it has a higher profile to allow it spread at the outer diameter of the tire, at the contact patch.
I use CCW 18" wheels with a 9" front and a 12" rear and run Toyo R888's with a 255 35 18 front and a 305 35 18 OR a 315 30 18 rear. I use these tires because I find them to be one of the best, if not THE best, choice of tires if you do not trailer your car and want a single tire wheel combo for both street and track use. I run them at 32 front and 34 rear hot on the track; go much higher and I notice a significant loss of grip. The only drawback with the Toyo's is that they are a heavy tire. I believe the 255 is around 26 lbs, the 315 is 30 lbs, and the 305 is 33 lbs in the 18" sizes. Compare that to the stock 19" GT3 tires and they come in at the front at 20 lbs for MPSC and 21 for Corsa, and the rear is 27 lbs for MPSC and 26 for Corsa. So with the wheel weight that I saved with my CCW C14 wheels, I got it all back with the heavy Toyos, and now the extra weight is on the outside of the wheel/tire setup, which makes it even worse! I think my CCW's with Toyos are a couple lbs heavier each in the front than stock, and only 1 lb lighter in the rear.
Now if you go with the super light 18" Champion RS98 or RG5 wheels along with the super light (and super duper sticky) R6 Hoosiers, then you can actually lose about 6 lbs per wheel/tire setup in the front, and about 12 lbs per wheel/tire in the rear when compared to stock!!! So don't forget to check those tire weights when comparing brands, they can vary just as much as wheels when going from cast to forged.
As for the 997 GT3 N spec MPSC's vs. the Corsa's, I think the Corsa's are superior both on the street (especially rain) and on the track. But I am sure that a full spec MPSC is different story alltogether.
Did anybody read all of this? Why do I always have to write essays???
07-09-2009, 06:46 AM
#20
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Rennlist Member
Rennlist Member
I measure my tires before and after mounting on the wheels, keep a spreadsheet of my measurements, and manufacturer specs. Weight, height, section width and tread width. For tread width I use the guides provided on most r-comp tires (continuous line or arrows), this thread width is what should ideally match your wheel width. A 8.5" wheel is a 9.5" wide wheel, the extra inch supports the sidewalls.
The 265 MPSC is narrower than the 255 Hoosier A6/R6 on 18". Per manufacturer specs, the 265 MPSC requires at minimum a 9" wheel, while the 255 R6/A6 requires at minimum a 8.5" wheel. The reality is that the 265 MPSC sits well on a 8.5" wheel, and the 255 A6/R6 requires a 9" wheel minimum.
Examples of messed up tire specs: The 235 Hoosier on 19" is wider and shorter than the 265 Hoosier on 19". 335/30 RA1 and 315/30 MPSC on 18" are as wide as each other. The 295/19 R888 is narrower than the 285/19 Pirelli Corsa System. The 345 Hoosier is 1.2" wider than MPSC 345.
Porsche uses a 325 MPSC on a 12" wheel with the 997 GT2. As long as your thread width (dismounted tire) doesn't exceed your wheel total width minus 1", I consider the DOT tire safe to mount on the wheel.
The 305 MPSC per Michelin should be used on a wheel up to 11.5", but Porsche mounts it on a 12", the tire is stretched beyond tire manufacturer recommendation but still works. The 345 MPSC is recommended for a wheel up to 12.5", but the reality is that the ideal wheel is a 13".
The fastest tires I ran in my RS where narrow 240/270 on 9"/11" x 18" wheels, not remotely close to Porsche OEM widths, diameter, specs, offsets, etc.
Manufacturer specs are mostly off, so use them at your own discretion. If you don't know much about tires (vast majority of people sadly), stick to the stock sizes, brand and model, and the stock tire pressures.
The 265 MPSC is narrower than the 255 Hoosier A6/R6 on 18". Per manufacturer specs, the 265 MPSC requires at minimum a 9" wheel, while the 255 R6/A6 requires at minimum a 8.5" wheel. The reality is that the 265 MPSC sits well on a 8.5" wheel, and the 255 A6/R6 requires a 9" wheel minimum.
Examples of messed up tire specs: The 235 Hoosier on 19" is wider and shorter than the 265 Hoosier on 19". 335/30 RA1 and 315/30 MPSC on 18" are as wide as each other. The 295/19 R888 is narrower than the 285/19 Pirelli Corsa System. The 345 Hoosier is 1.2" wider than MPSC 345.
Porsche uses a 325 MPSC on a 12" wheel with the 997 GT2. As long as your thread width (dismounted tire) doesn't exceed your wheel total width minus 1", I consider the DOT tire safe to mount on the wheel.
The 305 MPSC per Michelin should be used on a wheel up to 11.5", but Porsche mounts it on a 12", the tire is stretched beyond tire manufacturer recommendation but still works. The 345 MPSC is recommended for a wheel up to 12.5", but the reality is that the ideal wheel is a 13".
The fastest tires I ran in my RS where narrow 240/270 on 9"/11" x 18" wheels, not remotely close to Porsche OEM widths, diameter, specs, offsets, etc.
Manufacturer specs are mostly off, so use them at your own discretion. If you don't know much about tires (vast majority of people sadly), stick to the stock sizes, brand and model, and the stock tire pressures.
07-09-2009, 12:42 PM
#21
Rennlist Member
How are you measuring these tires? Is it on or off the wheels?
A 265 tire is not recommended to be mounted on an 8.5" rim. Also, the section width (and maybe tread width) of a tire will change depending on the width of the rim. If you want a wider front tire on the front of the GT3 such as a 265 (which I think is a good idea; I personally run a 255), it makes sense to increase the front wheel size so that the tire can set more squarely on the wheel and is not pinched. The section width can vary depending on the rim width a tire is mounted on. Also, by using a wider wheel, and thus allowing the tire to sit more squarely, the section width is wider but also has better contact across the entire width of the tread. I believe that ideally, the width of the wheel should be same as the section width of the tire (when it is not on a wheel) to take full advantage of its contact patch and to keep it square. I learned this from John at CCW.
I think that our 997 GT3's are a good example of this. Anybody ever wonder why the rear wheel is a full 12" for only a 305 tire? It will easily fit on an 11" wheel, and that is what I believe is used on the turbo. But with the GT3's wider wheel, the 305 tire sits much better and makes full use of that particular size tire. I do wonder why Porsche didn't go with a 9" on the front with a 245 (or even the 235), for this same reason and to help with the understeer issue. I know they try to be "safe" with factory understeer dialed in, but they know that 70% of GT3 buyers will track their cars and probably have more HP driving experience than any other street legal Porsche buyer. I guess it just takes that one guy to ruin it for all of us.
One other thing I would like to point out is the affect of the tire sidewall height (aspect ratio) on the section width. I have done a lot of research on the specs of tires that you can find on the manufacturer website and also on Tire Rack's website. Generally, a lower profile tire of the same width (235 35 18) as a higher profile (235 40 18), mounted on the same wheel, will have less of a section width. The higher profile has more sidewall to allow it to flare out, then the lower profile; but the higher profile will almost always weigh more (seems logical). Take the Toyo R888 315 30 18 vs the 305 35 18; the 315 is wider, yet it weighs a full 3 lbs less than the 305! And when you put them on the same width wheel of 11 or 11.5" (I forget which), the 305 is only 1/10 of an inch less than width than the 315. Why? Because it has a higher profile to allow it spread at the outer diameter of the tire, at the contact patch.
I use CCW 18" wheels with a 9" front and a 12" rear and run Toyo R888's with a 255 35 18 front and a 305 35 18 OR a 315 30 18 rear. I use these tires because I find them to be one of the best, if not THE best, choice of tires if you do not trailer your car and want a single tire wheel combo for both street and track use. I run them at 32 front and 34 rear hot on the track; go much higher and I notice a significant loss of grip. The only drawback with the Toyo's is that they are a heavy tire. I believe the 255 is around 26 lbs, the 315 is 30 lbs, and the 305 is 33 lbs in the 18" sizes. Compare that to the stock 19" GT3 tires and they come in at the front at 20 lbs for MPSC and 21 for Corsa, and the rear is 27 lbs for MPSC and 26 for Corsa. So with the wheel weight that I saved with my CCW C14 wheels, I got it all back with the heavy Toyos, and now the extra weight is on the outside of the wheel/tire setup, which makes it even worse! I think my CCW's with Toyos are a couple lbs heavier each in the front than stock, and only 1 lb lighter in the rear.
Now if you go with the super light 18" Champion RS98 or RG5 wheels along with the super light (and super duper sticky) R6 Hoosiers, then you can actually lose about 6 lbs per wheel/tire setup in the front, and about 12 lbs per wheel/tire in the rear when compared to stock!!! So don't forget to check those tire weights when comparing brands, they can vary just as much as wheels when going from cast to forged.
As for the 997 GT3 N spec MPSC's vs. the Corsa's, I think the Corsa's are superior both on the street (especially rain) and on the track. But I am sure that a full spec MPSC is different story alltogether.
Did anybody read all of this? Why do I always have to write essays???
A 265 tire is not recommended to be mounted on an 8.5" rim. Also, the section width (and maybe tread width) of a tire will change depending on the width of the rim. If you want a wider front tire on the front of the GT3 such as a 265 (which I think is a good idea; I personally run a 255), it makes sense to increase the front wheel size so that the tire can set more squarely on the wheel and is not pinched. The section width can vary depending on the rim width a tire is mounted on. Also, by using a wider wheel, and thus allowing the tire to sit more squarely, the section width is wider but also has better contact across the entire width of the tread. I believe that ideally, the width of the wheel should be same as the section width of the tire (when it is not on a wheel) to take full advantage of its contact patch and to keep it square. I learned this from John at CCW.
I think that our 997 GT3's are a good example of this. Anybody ever wonder why the rear wheel is a full 12" for only a 305 tire? It will easily fit on an 11" wheel, and that is what I believe is used on the turbo. But with the GT3's wider wheel, the 305 tire sits much better and makes full use of that particular size tire. I do wonder why Porsche didn't go with a 9" on the front with a 245 (or even the 235), for this same reason and to help with the understeer issue. I know they try to be "safe" with factory understeer dialed in, but they know that 70% of GT3 buyers will track their cars and probably have more HP driving experience than any other street legal Porsche buyer. I guess it just takes that one guy to ruin it for all of us.
One other thing I would like to point out is the affect of the tire sidewall height (aspect ratio) on the section width. I have done a lot of research on the specs of tires that you can find on the manufacturer website and also on Tire Rack's website. Generally, a lower profile tire of the same width (235 35 18) as a higher profile (235 40 18), mounted on the same wheel, will have less of a section width. The higher profile has more sidewall to allow it to flare out, then the lower profile; but the higher profile will almost always weigh more (seems logical). Take the Toyo R888 315 30 18 vs the 305 35 18; the 315 is wider, yet it weighs a full 3 lbs less than the 305! And when you put them on the same width wheel of 11 or 11.5" (I forget which), the 305 is only 1/10 of an inch less than width than the 315. Why? Because it has a higher profile to allow it spread at the outer diameter of the tire, at the contact patch.
I use CCW 18" wheels with a 9" front and a 12" rear and run Toyo R888's with a 255 35 18 front and a 305 35 18 OR a 315 30 18 rear. I use these tires because I find them to be one of the best, if not THE best, choice of tires if you do not trailer your car and want a single tire wheel combo for both street and track use. I run them at 32 front and 34 rear hot on the track; go much higher and I notice a significant loss of grip. The only drawback with the Toyo's is that they are a heavy tire. I believe the 255 is around 26 lbs, the 315 is 30 lbs, and the 305 is 33 lbs in the 18" sizes. Compare that to the stock 19" GT3 tires and they come in at the front at 20 lbs for MPSC and 21 for Corsa, and the rear is 27 lbs for MPSC and 26 for Corsa. So with the wheel weight that I saved with my CCW C14 wheels, I got it all back with the heavy Toyos, and now the extra weight is on the outside of the wheel/tire setup, which makes it even worse! I think my CCW's with Toyos are a couple lbs heavier each in the front than stock, and only 1 lb lighter in the rear.
Now if you go with the super light 18" Champion RS98 or RG5 wheels along with the super light (and super duper sticky) R6 Hoosiers, then you can actually lose about 6 lbs per wheel/tire setup in the front, and about 12 lbs per wheel/tire in the rear when compared to stock!!! So don't forget to check those tire weights when comparing brands, they can vary just as much as wheels when going from cast to forged.
As for the 997 GT3 N spec MPSC's vs. the Corsa's, I think the Corsa's are superior both on the street (especially rain) and on the track. But I am sure that a full spec MPSC is different story alltogether.
Did anybody read all of this? Why do I always have to write essays???
I have RG5's on my car ... but decided to stick with the 235 up front because
I was not happy with the apparent clearance of a 265 ...
