01-14-2014, 08:42 PM | #1 |
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New 275/35 19 Michelin PSS for the F8X?
When I decided to switch to 275/35R19 tires on my E92, I did some in depth research to understand the differences between a 265/35 and a 275/35 regarding contact patch dimensions and tire weight tradeoff. I came to the conclusion that the 275 offered 20% more rubber on the road vs the 265 mostly due to smaller grooves in the thread.
http://www.m3post.com/forums/showthread.php?t=848092 Based on the picture from the Detroit release, it seems that the 275/35 on the F8X has the wider grooves of the 265 tire (also as on the 235/35, 245/35 and 255/35). See picture below of the 275/35 on my E92 vs the 275/35 on the F80. Last edited by CanAutM3; 02-13-2015 at 08:15 AM.. |
01-14-2014, 08:52 PM | #3 |
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01-14-2014, 09:03 PM | #5 |
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01-14-2014, 09:12 PM | #8 |
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01-14-2014, 09:14 PM | #9 |
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I'm sure tirerack could answer your question then.
Trying to judge this from differing distances with different wear patterns is only going to lead to guesses. |
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01-14-2014, 09:48 PM | #11 | |
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I'm actually putting on a new set of rears on this Friday after 24k miles on the first set. Superb tires. |
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01-14-2014, 09:54 PM | #12 | |
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Contact patch
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01-15-2014, 08:44 AM | #13 | |
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However here we are not discussing contact patch size. The contact patch is the the area where the tire deforms to contact the road. The pressure inside the tire times the contact patch area equals the load the tire is carrying (minus the load the sidewall is carrying). This area remains relatively constant regardless of the thread pattern of the tire; this because the air pushes on the inside of the tire and not on the individual thread blocks. So a slick tire will have the same contact patch size (tire deformation) than a wet tire with big grooves (assuming same inflation pressure and sidewall stiffness). However, since the slick tire does not have any grooves, it has much more rubber in contact with the road and therefore more grip. Comparing the two 275/35 PSS tires above, both will have essentially the same contact patch area, but the one with the smaller grooves will have more rubber in contact with the road, hence more grip. Last edited by CanAutM3; 12-28-2015 at 10:12 AM.. |
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01-15-2014, 01:42 PM | #14 |
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More rubber in contact with the road does not mean more grip. It means the total distribution of weight is over a larger surface area, so less downward pressure per square inch.
Measuring grip is much more complex than that. |
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01-15-2014, 02:42 PM | #15 | |
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A tire gripping the road is more than just normal force times the friction coefficient as you imply. There are two major components to tire grip: standard friction and rubber element interlocking with the pavement irregularities. The later is directly related to how much rubber is contact with the road. Otherwise, why would race cars use slicks? Last edited by CanAutM3; 01-15-2014 at 03:48 PM.. |
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01-15-2014, 03:59 PM | #16 |
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This is the part where I hijack the thread and complain that Michelin has yet to develop a 285/30-19 application of the PSS.
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01-16-2014, 02:09 AM | #17 |
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Let's not forget correcting the very common misconception that a wider tire has the same contact area as a narrower tire at the same inflation pressure. This is certainly a bit OT to the OP but was being discussed. This "fact" works for things like spherical balloons, not tires with heavy steel belts, stiff side walls and stiff solid rubber tread blocks.
This myth is very clearly refuted here.
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