Quote:
Originally Posted by PST
We've run nine hard, hot sessions on our RE71Rs (245/40R17) over the past month or so. Here's a graph showing lateral acceleration and speed:
Blue- Yesterday’s second morning session. 1:27.2
Orange- July 30th morning session. 1:26.4. RE71Rs & Tarmac 2s
Green- July 18th morning session. 1:28.1. RE71Rs & stock suspension
Track temps were within a few degrees of each other, so we can consider that a constant. G iven the setup changes, the Blue session should have been noticeably faster than the other two sessions, but it wasn't. Why? We simply were not developing the lateral load that we had been in previous sessions. The RE71Rs are still soft, and have about 4/32nds left (rough average). But the grip just isn't there.
Here's the IR tire temps of those same laps. The blue session was as warm as the orange session, with the exception of the big sweeper at the end of the lap where the orange temps got much hotter. I can't help but wonder if we wouldn't see the same thing on the left tires through that shorter sweeper a few turns earlier where the grip was noticeably higher.
You'd think the tire temps would get hotter as they dropped off, but it appears here that the temps aren't getting as high. It looks like since there's more sliding friction and less static friction, the specific µ is lower, the force being imparted on the wheels is lower (evidenced by the lower lateral acceleration), so less work is being done. That plateau through that last corner might be a visual representation of the limit of the tires.
Anyone have any input? |
what makes you think that you were not generating enough G load or Blue line should be faster? you know not all the setup changes yield gains, and it sometimes hurts.. and I am looking at two graphs I would interpret (as a data analyst, lol) as they’re pretty consistent and the only big difference between orange and the blue lines is where you see the orange line jumps ahead of the blue is about 8000 mark, which makes me think it’s probably because of a late brake/ trail braking since it looks like it carried out more speed throughout that specific corner (area under the orange and blue line is your difference) if you look at the IR temp graph (on a side note I don’t believe both IR or pyrometer readings since it’s almost impossible to read the temps properly, unless you have a racing team with specific equipment, even then those wouldn’t be 100% accurate) this also backs my suggestion since the sliding through that specific corner generates more heat ..
You do know that .8 secs of a difference can be caused by anything else correct ? such as 1-2 degree difference in ambient temps or driver confidence (or lack of confidence) combined with the possible reason I mentioned above
FYI, I personally never experienced that an Extreme performance tires heat cycle out (even some R comps don't even heat cycle out such as Nitto NT01 ), the tires (200 TW or above) typically feels greasy after couple laps because it's easier to overheat them not because they heat cycle out.. for that reason you can also destroy them easily, typically the good indicator for street tires and some streetable r romps is the treadwear not the sessions you put on them
I would personally keep using them to the cords they typically perform the best right before you see them corded
but that's just me