More durable/affordable tire option?

[39PitCrew]

Handling: I think this is one of the most fascinating aspects of this tire. I have heard so many times that popping on a fresh set of RR’s will cure all of the car’s handling issues. People love how these tires handle when they are new and hate how they handle when they are all used up. Changing the overall amount of grip can have a small effect on handling balance but it shouldn’t dramatically change the handling.

I believe what is changing is the effective shape of the slip angle graph. The slip angle graph for this tire seems to have a pretty flat and wide peak on fresh RR’s. This wide peak allows good grip over a variety of slip angles and masks subtle balance issues and handling deficiencies. As more time/abuse is put into the tire, not only does the peak grip level dip down a bit, but the peak becomes sharper. This sharp fall off of grip past the peak quits masking issues and requires the driver to sense much more subtle inputs to keep the car near the peak grip level. The car is just flat harder to drive. The drop in performance depends not only on the condition of the tire but also the base handling of the car and the ability of the driver to deal with the sharper peak. If anyone has any further insights to expand or contradict this thought, I’d love to dig into it deeper.


On a practical application of this knowledge, we’ve found driving through a handling imbalance is a bad idea with these tires. One event at Cresson had Dan with a bit of understeer early in the weekend. He thought it was tolerable and didn’t want me to change anything. A couple of sessions later, he had abused the front tires enough that the front tires were signing off and the understeer was now magnified to intolerable levels. We made changes every session that should have made the car an oversteering pig with no success. I didn’t catch a clue to what was happening until we got back to the shop and looked at the differential tire wear front to rear. Now I hammer on balance with Dan early in the weekend and we often end up changing rear springs or sway bars during the event to keep on top of it. When the engine runs, anyway…


Richard P.

Richard, I'm not any sort of expert on any of this but the mechanic in me thinks what you say makes a lot of sense.
As I've read a couple of the tire threads here, I'm left to wonder about some things.

If I understand the issue: consistent performance over many driving cycles; where "many" is some arbitrary number, say 20.
The secondary issue: amortizing $$$$ spent across the # of driving cycles before the tire tread thickness reaches gone/cords
or the tire becomes substantially uncompetitive or dangerously unpredictable for door-to-door competition.

It seems to me that some of the discussion is adding in a performance component, that is, how "sticky" the tire is during it's usable life.
I think the primary goal of the discussion is two-fold - keep performance fair and keep the consumables budget reasonable.
So the dilemma is: the softer (stickier?) the tire, the faster it wears ($$$) but you get better (lower) lap times. But, a
soft tire also has a much smaller sweet spot related to it's maximum performance over a certain number of driving cycles.
A tire that has a harder compound will wear longer. But the trade off is that maximum acceleration, braking and cornering forces
are reduced by some amount. (And I get it, we're talking about race cars so it's hard to say higher performance is a bad thing.)

So, if the choice is made to use a harder compound tire, does it follow that the car's set up and the driver's racecraft must be better
to achieve the same performance (ie. lower lap times) that comes with a softer compound tire?
And a possible corollary: the more grip a tire has, the more wear/abuse the car's mechanical parts take.
So, more heat/wear in the brakes, diff and trans loads are higher, more heat and higher loads on wheel bearings, more chassis torsional forces, etc., etc. - right?
And based on threads here on the forum and many random discussions at the track over the years - car set up is hard. Well, mechanically
it's easy, dialing it it for optimal track performance is hard. Even NASCAR and F1 teams who have really smart people and spend millions of dollars
to figure that stuff out don't get it right every time.

Thoughts anyone?
Scott