Cal Club Autocross Forums

Steve Coe wrote: what else is coming out?


Steve

Jason Isley BS RX8 wrote:BFG.

Max Hayter wrote:

Steve Coe wrote: what else is coming out?


Steve

Bill Schenker }:)

Jonathan Lugod wrote:Dunlop Direzza Z2 (not labeled star spec)
Bridgestone RE11A
Kumho V720
BFG

Kurt Rahn wrote: Is the Kumho 720 a replacement for the 710, or will it be ST-legal with treads and all that stuff?

Max Hayter wrote:

Steve Coe wrote: what else is coming out?


Steve

Bill Schenker }:)

Bill Schenker wrote:

Max Hayter wrote:

Steve Coe wrote: what else is coming out?


Steve

Bill Schenker }:)

Hey! Keep that crap for Facebook (where we regularly humiliate you...)

Bobby Beyer wrote:Well I just picked up a set of z2's for street/backup duty. Wonder how they'll compare to the R1R's, I'm guessing slower but it'll be interesting either way.

Byron Goodman wrote:The Dunlop Direzza ZII is out too. Anyone see any reviews on these? Sadly, it seems the BFGs won't be out in my size for while.
http://www.tirerack.com/tires/tires.jsp ... irezza+ZII

-B

Back from Daytona...sorry for the delay. Working on getting tires to test for GRM, but dates are fluid.

At the launch event, I was the lucky dog. I was there a day early for some on-camera interviews, and while watching the BFG lead test driver gathering on-track comparison data between the Rival and a set of Z2's they had just acquired, I was asked if I wanted a go at it. Hmmm...let me think...yeah, sure ok. With only one set on hand, the Z2 was not used in the main event at all.

Preface: Prior to this I had zero on-track time at NOLA and none in an MX5 Cup car. Plus, the car didn't quite fit right (I have short legs). But with the Rivals on the car I came up to speed pretty quickly on the track...or so I thought. Their test driver and I swapped seats and he promptly showed me that I was not pushing the tires nearly enough. There was a whole nuther level that I was not exploring, as I had been backing off when I started to hear some squeal and feel some slip angle build. Turns out, the Rival is a massive talker (like the Kumho XS) and will deliver even when slip angles get quite large. The latter is similar to an R1R, except in the case of the Rival, you aren't destroying the tire as you run that large of an angle.

I then did another 6 laps or so by myself and got to the real limits. For example, 90 mph through the backside esses with total confidence. After that, we swapped to the Z2 and I tried to replicate what i had been doing with the Rival for another 10 laps. First couple of times I turned in, I had to turn right back out again....as first one end, and then other end of the car would get upset. The Z2 is very peaky in its grip delivery versus slip angle, while the Rival has a broad plateau. And with a well-balanced car like the MX5, you have to keep both ends of the car in the narrower band with the Z2 in order to stay at max lateral. That also makes it more setup dependent, whereas the Rival will likely be more setup-agnostic. I never got the car out of sorts with the Rival, but got each end to misbehave with the Z2.

In short, the Rival is a bolt-on-and-go performance enhancer for the "everyman", whereas the Z2 is more of a delicate instrument that can perhaps be careful wielded by a "skilled professional" to great effect. And some of the things that make the Z2 less confidence-inspiring on the track, may actually make it more lively on an autocross course. If you can handle it.

Bottom line: I was a full second faster on the Rival than the Z2 on a 2:08 lap time. And more consistent.

As for heat, discussion with the engineers suggested that the tire did not need a lot of heat to work, yet could tolerate it well. We did overheat a set on the BMW E46's with many back-to-back runs. I was first driver out and got back in later after a couple dozen runs (and smoking brakes) and the car drove nothing like it did earlier.

My takeaway is that BFG built a better RS3. Doesn't need heat to work. Tolerates lots of heat. Will work at least passably in the wet. Wears like iron. Easy to drive. Consistent and confidence inspiring.

Remember when the Kumho V710 first came out? It made heros out of zeroes. The Rival is like that in its driveability, if not in overall grip level.

Oh yeah, and for those claiming the Rival is some sort of cheater r-comp: baloney. Not only does it meet the rules, the 200 treadwear is no joke. The thing wears even better than an RS3 despite being abused. Truly incredible. And when compared on a skid pad to the R1-S r-comp and Comp 2 street tire, it fell much closer in grip to the Comp 2. .95 vs 1.0 vs 1.2g.