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I would aim for low 30s hot on the track or about 30 PSI after cool down lap and heading to paddock (inexact science). 25 psi cold may be too high depending on ambient temps and how hard you are working the car--- but a decent place to start. Manual (9-6) says to start at 26, FYI.
Michelin says Cup 2s should run 38 psi hot on the track. I ran a few week ago at Mid-Ohio and not surprising the recommended 30 psi cold got me within a few pounds of 38 hot. You need to stay within a 36 to 40 psi hot window to keep max tire grip.
This is generic guidance, so perhaps GaryChurch has Z06 specific guidance, but I have not seen that published by Michelin. In Owners Manual GM says to start at 26 cold. Manual does NOT recommend 30 cold for track use. As noted above, see Manual at Page 9-6
This is generic guidance, so perhaps GaryChurch has Z06 specific guidance, but I have not seen that published by Michelin. In Owners Manual GM says to start at 26 cold. Manual does NOT recommend 30 cold for track use. As noted above, see Manual at Page 9-6
Chris...
Let me give you my sources, experience and opinion. The tire pressure decal on the driver door sill recommends 30 psi cold. The Cup 2 tires on the sidewall are marked Max Pressure 51 PSI. My owners manual on page 10-57 states, although it appears to apply to highspeed highway (i.e., Autobahn, Autostrada, etc.) and not to an aggressive track environment.
"The tires require inflation pressure adjustment when driving the vehicle at speeds of 160 km/h (100 mph) or higher, where it is legal. Set the cold
inflation pressure to the maximum inflation pressure shown on the tire sidewall, or 265 kPa (38 psi), whichever is lower. See the
example following. Return the tires to the recommended cold tire inflation pressure when high-speed driving has ended."
I talked with two Michelin tire engineers at this year's Daytona Rolex 24 briefing the Porsche and Corvette Club Members on their tire technologies and specifically asked about hot track tire temps for the Cup 2. They advised 38 psi hot was the target temp for max track performance.
I have been Club Racing for 20 years. When using non street legal slicks most manufacturers recommend 30 to 32 psi hot (i.e., Michelin, Hoosiers, Dunlops and Yokohama) However, when using DOT street legal competition tires these recommended temps have been higher, such as 40 psi for the Hoosiers.
Based on this information I am going to continue to target my Corvette Z06 with Cup 2 tires for 38 psi hot on track. Starting at about 30 psi, the recommended cold tire pressures seems to get me to the 38 psi hot target. That said, at Mid-Ohio the left front tire hit a high of 41 psi and was bled down to 38 psi. This would have actually represented a cold starting temp for this tire of about 27 psi cold. As you know depending on the track the tires on all four corners of the car get a different workout and generate heat and tire pressure separately.
I hope that clarifies my experience. Like all things different people, different experience, different opinions.
As an additional follow up I copies the Michelin reference you cited below. Obviously Michelin should know. That said, they do caveat their recommendations with, "Use cold tire pressures recommended b manufacturer", which is 30 psi recommended for the Z07 Cup 2s. it would seem that the discussion hinge on whether 36 or 38 psi is the correct hot psi for the Corvette. I do know that tires are like supplemental springs and to a degree within about a 4 pound operating range centered on target temps change the balance of the car. Ehat a little less understeer for example lower the front tire pressures a coupl of pounds. This used to be good advice before today's electronic controls, I am not sure it is appropriate advice for the electronic stabilization and traction controls on the Z06.
INFLATION PRESSURE ADVICES
On the track for majority of car (*)
Cold tires
• Inflate the MICHELIN Pilot Sport Cup2 with a pressure between 1.7 bar (24 psi) and 1.8 bar (26 psi) front & rear
• Never allow the pressure to be below 1.5 bar (22 psi)
Hot tires
• The optimal operating pressure of the MICHELIN Pilot Sport Cup2 must be between 2.3 bar (33 psi) and 2.5 bar (36 psi) Front & Rear
• Never allow the tyres to run below 2,0 bar (29 psi) HOT
Road use
• Use the cold pressures recommended by the car manufacturer
INFLATION PRESSURE ADVICES
On the track for majority of car (*)
Cold tires
• Inflate the MICHELIN Pilot Sport Cup2 with a pressure between 1.7 bar (24 psi) and 1.8 bar (26 psi) front & rear
• Never allow the pressure to be below 1.5 bar (22 psi)
Hot tires
• The optimal operating pressure of the MICHELIN Pilot Sport Cup2 must be between 2.3 bar (33 psi) and 2.5 bar (36 psi) Front & Rear
• Never allow the tyres to run below 2,0 bar (29 psi) HOT
Road use
• Use the cold pressures recommended by the car manufacturer
The "use cold pressure recommended [by GM]" is clearly under the "Road use" heading and not "Track use." GM says start at 26 for track. No one is saying to NOT use 30 psi cold for the street.
You say target 38. GM and Michelin say otherwise.
If your grip and tire wear are to your liking, do what you want.
My experience (not an expert, but 10 years of being a casual HPDE driver-- many of those driving a 911 Turbo on Cup1 tires) is that low 30s hot is better (for grip and wear) than high 30s, but I acknowledge that I could be wrong about this. When in doubt, I look for manuf data first, then supplement with paddock advice and tweak with my personal experience.
See screen shot below from "Track and Competitive Driving" in the owners manual:
I find 32-33 hot for cup 2's to be ideal on my c6z07. This is going at a competitive pace. Hotter than that and the tires were starting to give up grip quickly. Ymmv.
Slightly off topic but when it says to keep the oil level 1/2 qt above the max fill line, do we still use the "wait 5 min after shut down and then check" technique?
06-01-2015, 07:31 PM
