[QUOTE=ttx350z;1599246029]Heres the 315 on 10.5
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Well that looks like it will clear the fender lip. At last weekends AutoX another Z06 had the 315 on an 18x11 and he was rubbing ..... even after telling me he sanded the fender lip down after previous event.
What offset is that?

:cheers:
DH

The wheels themselves are 18x10.5 +56 (C5Z wheel spec) with a 12mm spacer so its effectively +44. I’ve got a 20mm spacer on the way since i slightly touch the wheel well housing at full lock. Just seeing if I can eliminate it. Real world driving on the road it doesnt touch.

Edit: that pic is with -2.3 camber

Sounds like the 71s were fresh and the 11s were possibly heat cycled out? Saw you’ve added a lot of power and aero in your profile pic so was curious as to what all mods you had done, if you had fresh 11s in the rear it might have been more balanced I’m thinking. It’d be like putting R compounds up front and street tires in the rear, that would be a very tail happy combo and one I wouldn’t recommend.

The 11’s were close the end of their life. I definitely accelerated wear with all the spins and drifts. The Rivals I put on where actually a used set if takeoffs since i just wanted a cheap set to try for the last 2 events of the year. The Rivals were close to what the 11’s wear wise when I put the 71’s on.

Mods is just cam, headers, fixed heads, msd, halltech, nw102. Aero mods were ZR1 splitter and side skirts.

https://cimg7.ibsrv.net/gimg/www.cor...cbd0c67217.png
Here’s yesterday’s results where he placed 4th in PAX out of 157 with the discontinued RE11s on the rear. It still has stock shocks, sway bar and no harnesses.

Stop showing off my slow 9th place finish on here Chris! I had a fast raw time atleast ....

Haha, you did and enjoyed a front row seat to your great driving! Thanks again for the ride, looking forward to hearing your feedback on the 1.5s once you run them. Hopefully I can break into the top 10 like you guys one day, haven’t gotten below 13th in BS, CAM-S or AS

I'm thinking about going with the bfg rivals. 315 30 18 and 345 30 18. Should be rather interesting to see how they handle.

The rear will be a 335/30-18 as a 345 does not exist. They will handle very good though for a street tire, lots of us do various 200tw race series on them (Optima, etc.)

Just finished up my first weekend with brand new still shiny 315 Rival S 1.5 on 18x10.5" front and (well worn used) 335 Rival S on 18x12" on the rear. On Viking coilvers 550 front/700 rear. Event is ran on a concrete pad that's used as a truck stop.

I have very limited experience with the Rival S on the front (275 on a 10.5" wheel) for like 8 runs in mid 30ºF weather.

I'll be referencing OUSC competitor Brandon Williams R35 GTR (335 Rival S squared/700+AWHP) quite a bit since he's got competitive experience and fleming23 should know who he is since they've competed in the same event before.

So Day 1, it was freezing. It was cloudy and snowing during registration with some moisture/puddles on the ground. Temps where in the 30's until about 1 pm. Of course I got shafted and was in the first run group. First heat was pretty much a lost cause as nobody could get their tires warm. Guys with RE71R's in second run group were only getting 60ºF tires temps after their hot laps. There was no grip at all. So not much to report on. The co-driven GTR was 1/2 after the first heat.

After lunch break, it warmed up into the 40's. Grip improved a little bit but there was still no grip for turn in. RE71's were just getting to 80ºF for the second run group. I ended up like 5th raw/pax time. Behind a shifter kart that set FTD, the GTR with both driver, 2 Miatas with RE71R's. Due to the weather and only 16 cars showing up, we finished early so we reconfigured the course to start another "event" it was about 45º at that point and a little overcast. I was able to set the second fastest time behind Brandon's GTR.

Day 2, it was 35ºF at the start of the first run, but sunny and no snow. Of course I was in the first run group once again. The main competitors on 71R's and the co-driven GTR was in group 2. The slightly warmer conditions made a huge difference. Turn in didn't just understeer into oblivion at 20mph like the previous day. I had the fastest time posted for run group 1, up on the GTR driven by the codriver .1 sec. I was in 4th at the lunch break, 1.6 seconds off the GTR with Brandon driving in group 2 with the same 2 RE71R shodded miatas ahead of me. Heat 2, warmed up and I was finally able to get a feel of what the car could do. Front end felt great, tires felt stiff and did not feel any sidewall flex/wallowing even mounted on the 10.5" wheels. Visual inspection after the weekend didn't show any signs of the sidewall rolling over and rubbing the ground. I didn't feel like I had any issues with precision as I was able to place the car where I wanted. I came into the weekend expecting it to have oversteer, but I'm happy to report that there was no snap oversteer on turn in or midcorner. Car was very neutral even around high speed (60 mph) sweepers, pulled 1.28G's according to the HUD and would scrape the airdam. Power delivery on exits were great and uneventful in second gear, wheelspin was easily managed even though the tires are at the end of their life. I'll probably do one more weekend with those rears before I get the new set mounted. At the end of the day, I finished 2nd in raw and PAX only behind the GTR with Brandon behind the wheel. I closed to gap considerably to finish .2 secs behind in raw time. I know it doesn't count, but I took off another .4 secs off my time during buck runs at the end of the day. So the cars potential is there, I just have to get up to speed quicker myself.

Times are based off of memory and it's been a long weekend. I'll post the times when their available.

On another note, the 315 on 10.5" +36mm wheels had ZERO rubbing at all. No rub while staging, hairpins, fully compression sweepers, nada, zilch. I know it's something people will deal with if they rub, but this is still sort of a daily car to me.

Great report. Thanks for all the info. :thumbs:
Do you think there would still be no outside fender rubbing with stock suspension vs your coil overs.

:cheers:
DH

I don't think it'll rub the fender with stock suspension. Now that the shoulders are worn, there'll be even more clearance.

I'm seeing recommendations in forums for re71r 275-35-18/305-30-19 with a slight edge to the rivals 275-35-18/335-30-18. Stock wheels in AS. Any reason not to use the re71r 285-30-18 up front? I assume they would be close in performance with slight edge to the 285. And if South Florida heat would favor re71r or rivals?

I’ve tried both the Rival S and RE71r in the sizes you list. I do prefer the RE71r for better feel and steering response. But high heat is better for the Rival S. They need some heat in them to work well, and the RE71r works better cold, but can get a bit greasy when hot. So you may like the Rival S better most of the year.

I have not tried the 285s up front because I think they are too short, but it’s possible they will work OK.

To support this statement, I have been working with a guy that won a national championship in a C5. His experience supports this, the RE71 are faster from the first run, but as temperatures build, he was noticeably faster with the Rivals. He runs Rivals for this reason, and because he can get contingency sponsorship to get free tires.

The first thing I would do is evaluate what temperatures you expect to be running under. If its typically 60 deg and cooler, I would go RE71, as getting heat into the Rivals is tough. If its warmer, I would go to question 2, tire sizing. I run Rivals 315 square, and in the first few events of the year I struggle to get any heat into them in the small courses we run. I am thinking of getting a set of Re71s in 285 square just to help them warm up faster and also get a co-driver to help warm tires.

At the end of the day, these tires are really good, and people can win on either one.

I assume you have to be running wider fronts to go 315. Vs the stock 9.5s. also wonder if running rival 275/315 would improve balance, less understeer, help rotation.

Im running a C4 with Forgstar F14s, 11" wide square. Running a 275 front would be more understeer then a 315 front. But maybe your not comparing the 275 to the 315?

Ya, i want to run the stock 9.5/12 rims. Was thinking maybe running 275 front 315 rear for better balance/rotation instead of 335 rear. Not sure if it will be faster overall though. Wondering what combination they're running at Nationals. I could see the top spots c6z have BFG.

Not new to autocross but will be new to the Vette. Hense some of the newbie questions.

I went with the shorter 285/30 up front since it keeps the ratio the same and lowers center of gravity with the 305/30 being shorter.

I agree hot temps with a co-driver on a grippy concrete surface and the new Rival 1.5s will be as fast and feel great I imagine, if it’s cold and your a solo driver in a big field on asphalt then I’m betting on the RE71R being faster.