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Old 09-14-2017, 02:57 PM   #115
Zefy
Scooby Specialist
 
Member#: 105104
Join Date: Jan 2006
Chapter/Region: VIC
Location: Coquitlam, BC, Canada
Vehicle:
1979 BRAT / 01 RSTI
99 2.5TS (DEAD)

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The next event I did was at Mission Raceway Park. This track is one that I have far more experience at and I actually have data from other events to compare with. It was another decently warm day and the tires had about one and a half months of street driving on them and a couple of heat cycles. At this track the tires still had the nice break away characteristics and took heat well. I dropped the tire pressure to 30psi front and 33psi rear.

At Mission I was able to get down to a 1:21.7. Unfortunately I had mechanical troubles and lost boost. I was essentially running an N/A car for the remainder of the day. I'm positive I could get it into the 1:20's. But even so, here is the GG diagram from my fast lap. Looking at later sessions it looks like I found a bit more grip but the lap was overall slower because of the reduction in power.

mission Gredge by Greg Petroski, on Flickr

Let's compare that one to my fast lap at mission on Bridgestone RE71R tires. My fastest lap time to date is a 1:19.3. Keep in mind, this is with a little more power and a 10mm wider tire. Definitely not a true apples to apples comparison. However the GG diagram cares less about the amount of power you're making.

mission RE71R by Greg Petroski, on Flickr

So it's pretty clear that the bridgestones have more grip. I'm able to consistently pull 1.2-1.3g in the bridgestones where as the Zestinos I'm able to get about 1.1-1.2g. This is a really good result for the Zestinos. Especially given the 10mm less width and the 240tw hard compound.

Another noteworthy point that we can see from the GG diagram is the transition from cornering to braking. In the Zestino chart, you can see the long arcing line going from the top to the left. This is turn 1 at Mission and I'm probably using as much grip as those tires can muster. My transition with the RE71R is not as arced showing I'm giving up cornering speed as I trailbrake into the turn. I feel like the Zestino is giving better feedback and inspires more confidence as the breakaway of the tire is so gradual. It makes it really easy to ride the edge of grip without going overboard.

This is how the Zestinos looked after 5 sessions at mission. They definitely got more abuse put into them compared to Area 27, but overall they held up very well. No weird wear patterns or problems with the rubber or overheating. My car is relatively gentle on tires. My RE71R tires have lasted me far longer than I thought they would. If your car is camber challenged I'm sure you could burn through these just as fast as any other tire.

20170626_145709_HDR by Greg Petroski, on Flickr

Conclusion:

The Gredge 07R is a decent track day and daily driver tire. You won't be setting any records with these (at least not the hard compound) but I am very happy with how easy they are to drive at the limit of grip. Very wide transition with lots of feedback in the wheel and in your ears. On top of that, they seem to take heat like a champ and wear really nicely.

As we head into the winter months, I will look further into the wet and cold performance of these tires.
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