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radensb · 04-30-2016, 05:28 PM

Well, unfortunately this thread didnt get more "traction" (

...sorry), but I did learn some stuff and figured I'd share in case others had questions or were curious.

I ended up getting the Michelin Pilot Super Sport. I got XL's all around. All I can say is WOW. What a difference from the worn out, NANKANG tires that were on the car when I got it. The PSS looks great and handling is night and day better. And they are QUIET! Huge improvement. I can actually use bluetooth in my car now. They are a bit loose on traction, but that is expected with new tires until they are broken in. I expect that to get much better.

With regards to the XL vs SL matter for our cars, the Z34 does not need the XL rating. Factory tires are SL rated, however, MFG's do not make SL in all sizes. This is what lead to my initial confusion. For Michelin PSS, the stock front tire size only comes in XL, while the rear size come in both. That's why the auto-matching on sites like Tire Rack and America's Tire selected XL's for fronts and SL for the rears. When I checked other tires and brands, I saw SL/SL, SL/XL, XL/XL combinations, so it was clear that any combination was acceptable. However, the recommendations I got were to keep the Load Ranges consistent between the front and backs. While mixing them are OK and still within OEM spec, it will change the handling and feel of the car as the fronts will be more ringed than the rears. This may not have been a huge deal, or even noticeable, but I didnt want to take a chance and Im glad I didn't. Going from XL/SL combo to XL/XL is a definite improvement to me. Sure, its also a way better tire in general, but the back doesn't sway as much. The XL's have a higher load index at a higher pressure than the SL's (35PSI vs 41PSI), but even at 35psi, you are still within OEM load specs of 94 and 96 respectively as the load capacity to inflation pressure is linear.

Stock Tires (from door jam):
Fronts: 94W (Rated at 1477lbs @ 35psi)
Rears: 96W (Rated at 1565lbs @ 35psi)

MPSS:
Fronts: 98Y (Rated at 1653lbs @ 41psi)
Rears: 100Y (Rated at 1764lbs @ 41psi)

XL's have a higher load capacity at a higher pressure of 41psi, but have the same load capacity as an SL tire at 35psi. (source)

In general, what the XL's provide is a more robust, more ridged tire with reinforced sidewalls that improve cornering performance by reducing tire deflection and are more resilient to road hazards. They are also a bit heaver, which is expected due to the added materials to make them more robust and handle the extra pressue. Also, in the case for the MPSS 275/35R19's, they were about $35 cheaper. Oddly, the above source claims that XL's actually hurt performance as they are thicker and retain heat. However, not by any noticeable difference. Its also the only source that I have read that claims that. Everything else I have read states that performance is better, especially for sports cars, and from what I have experienced so far, they are correct. Perhaps this varies from vehicle type?

04-30-2016, 05:28 PM	#5 (permalink)
radensb Base Member Join Date: Jan 2014 Location: California Posts: 148 Drives: 09 Nissan 370Z GM M6 Rep Power: 6721	Well, unfortunately this thread didnt get more "traction" (...sorry), but I did learn some stuff and figured I'd share in case others had questions or were curious. I ended up getting the Michelin Pilot Super Sport. I got XL's all around. All I can say is WOW. What a difference from the worn out, NANKANG tires that were on the car when I got it. The PSS looks great and handling is night and day better. And they are QUIET! Huge improvement. I can actually use bluetooth in my car now. They are a bit loose on traction, but that is expected with new tires until they are broken in. I expect that to get much better. With regards to the XL vs SL matter for our cars, the Z34 does not need the XL rating. Factory tires are SL rated, however, MFG's do not make SL in all sizes. This is what lead to my initial confusion. For Michelin PSS, the stock front tire size only comes in XL, while the rear size come in both. That's why the auto-matching on sites like Tire Rack and America's Tire selected XL's for fronts and SL for the rears. When I checked other tires and brands, I saw SL/SL, SL/XL, XL/XL combinations, so it was clear that any combination was acceptable. However, the recommendations I got were to keep the Load Ranges consistent between the front and backs. While mixing them are OK and still within OEM spec, it will change the handling and feel of the car as the fronts will be more ringed than the rears. This may not have been a huge deal, or even noticeable, but I didnt want to take a chance and Im glad I didn't. Going from XL/SL combo to XL/XL is a definite improvement to me. Sure, its also a way better tire in general, but the back doesn't sway as much. The XL's have a higher load index at a higher pressure than the SL's (35PSI vs 41PSI), but even at 35psi, you are still within OEM load specs of 94 and 96 respectively as the load capacity to inflation pressure is linear. Stock Tires (from door jam): Fronts: 94W (Rated at 1477lbs @ 35psi) Rears: 96W (Rated at 1565lbs @ 35psi) MPSS: Fronts: 98Y (Rated at 1653lbs @ 41psi) Rears: 100Y (Rated at 1764lbs @ 41psi) XL's have a higher load capacity at a higher pressure of 41psi, but have the same load capacity as an SL tire at 35psi. (source) In general, what the XL's provide is a more robust, more ridged tire with reinforced sidewalls that improve cornering performance by reducing tire deflection and are more resilient to road hazards. They are also a bit heaver, which is expected due to the added materials to make them more robust and handle the extra pressue. Also, in the case for the MPSS 275/35R19's, they were about $35 cheaper. Oddly, the above source claims that XL's actually hurt performance as they are thicker and retain heat. However, not by any noticeable difference. Its also the only source that I have read that claims that. Everything else I have read states that performance is better, especially for sports cars, and from what I have experienced so far, they are correct. Perhaps this varies from vehicle type?