Veloce Raptor

Here is my definition: when they howl all throughout the corner rather than just on corner entry! Another definition might be that they are experiencing a slip angle in excess of their ability to grip.

Van

I would say it goes beyond the howling, and starts when the tires really start loosing grip -- like you turn the steering wheel more, and the car doesn't... or when the rear starts to slide out on turns and you have to countersteer to save it (that 930, yellow bird (?), comes to mind...)

Veloce Raptor

Hence my 2nd definition.

sjanes

To me, that's not at the limit but over it. At the limit, the tires doesn't have much left to give, but can be driven like this for 30 minutes without destroying it. I doubt the tires in the yellow bird video were useful after 20.

10 GT3

The general rule is 2 seconds on a 1 minute track.

As to some of the comments above, I can understand goign faster on KD's than A032R. The A032R was specifically designed as a wet race tire. In autocrossing, I went much faster on them in the wet that RA1s and Victoracers. Both these tires were far superior in the dry. Road racing tires are different than autocross tires as heat cycling and construction need to both be different. An autocross tires needs transitional response as the priomary characteristic, while peak grip is more important on the circuit. Hence is the reason Hoosier R6's don't make the best autocrossing tires, while A6's are the best.

David Ray

This is by far some of the best feedback I've read on Street vs. R compound tires. First, understanding the limits of your street tires makes a better transition to track tires (R-comp). I've been experimenting between street and R-compound tires at the AX scene for the past year (and a new car half way through). However, at the track I run Toyo RA-1s exclusively.

Second, USED street tires are a very inexpensive way of experiencing the differences. You can get a good “used” set of street tires at many tire shops and only pay for mounting. Great way of trying several different brands and rubber compounds.

Third, the difference among “street” tires is astonishing. This past year I've tried: Pirelli’s, Bridgestone, Goodyear, Toyo’s, and Conte’s. Biggest inconsistency is that the AX track configurations change and the attitude of the turn’s changes. That said, at AXs I had the best times in the Continentals and Toyos Mxs. I drive a 1995 993 C2 with full suspension and alignment mods.

Noel

This is a very interesting thread.

I have always enjoyed using street tires since I got my 911, six years ago. I used to use R compounds prior to that with my previous non-porsche track/autocross car. I had so much fun learning how to drive the 911 with streets that I never went back. I'm still faster than half my run group with streets in the dry and nearly the fastest in the wet, so I have not felt much pressure to switch (Plus, my brakes would be no match for the increased work load/heat that an R compound would create).

This leads me to my next question, why then do most people from the White run group and higher (Black and Red on the East Coast) run almost exclusively on R compounds? In fact, more than half of the Blue (Sometimes called yellow) run group at Mid-Ohio last weekend were on R compound tires.

RonCT

Noel, you raise an excellent point. When I had my E46 M3 I seriously considered running 4x 275 PS2s on my track wheels. Almost as fast in the dry and far quicker in the wet than PSCs. Wear longer, more feedback, etc. The wonder-tire! Well, now I wonder why I'm like most - wanting that last extra 2 seconds off a lap at Lime Rock. It's part of the sickness...

FTS

I had some data collected in the past over a season, based on 60-sec course using a 4WD drive car that was ~3500 lbs, same suspension and chassis bits, alignment adjusted according to tire requirements, same drivers, nearly same weather conditions, same asphalt:

- Street tires, 140 treadwear: base (225/40/17 square setup)
- Toyo RA1: 1.5 secs faster than streets (245/40/17 square setup)
- Hoosier 305s hard compound: 1.6 secs faster than Toyos (245/40/17 square setup)
- Hoosier 305s soft compound: 1.8 secs faster than Toyos (245/40/17 square setup)

All data was recorded after tires reached optimum temps.

KRA993tt

I have not tried street tires with my new car, 1982 911sc. On my previous car braking and cornering was just superior with R's vs streets. IMHO I have destroyed street tires in one or two sessions at a de. You are continuously scrambling for grip. Chunking just made me know I was asking to much from the street tires I was using. Is this fun and instructional, yes, but the R's just hold up better under track conditions for me. I'm too cheap to buy lots of street tires too gain inferior performance. For wet conditions full tread R's seem ok. I have not tried the Hoosier wets but understand they are nice.

JackOlsen

Also understand that the treadware rating is primarily a marketing tool used by manufacturers. It does not necessarily correspond to any wear rate or compound softness level at all. There is no industry-wide standard for those numbers.

chrisp

Jack, I am with you. Treadware as I understand it is within their own product line and is linear. A 300 lasts twice as long as a 150 but one brand's 150 is not comparable to another's 150. That said, I wonder how SCCA can, in the name of equality, create rules involving treadware ratings.

chrisp

I use DOT-R because they are more of a "right tool for the job" than a street tire is. Outside of the higher grip threshold, they are more consistent. Street tires do not like being cycled up to high temperatures. Plus once a tire starts chunking you want to get off it....which easily happens to a street tire on a hot day.

Chris M.

Like THIS? Driver is Greg Fishman in my car at Mid Ohio.

Noel

Interesting. Which Street tires? Which track? How long was the lap?

Great comments from all. I haven't had any chunking problems with my street tires (AVS Intermediates and now Kumho MXs) over the past several years, then again I've never really driven in ambient temps >90F since I mainly run in the Spring and Fall in New England and in Ohio.