Dirty Howie

I have been asking and getting lots of info but I am hesitant to do the normal 18 inch (13/11) setup with Rivals (335/315). I don't want fender or brake duct rubbing issues and I want to retain some agility in the front end that I think is given up with the larger wheels. I also have an opportunity to get another set of new MMR wheels like you see in my sig for about $700 less than the F14 that everyone gets. AND I like the looks of the MMR which obviously should make me faster

Anyways the MMR will be 18x12 with 50 offset and the 18x10 with a 30 offset.

Question is: Which of the following setups will be faster for AutoX? I do this for fun not worried about classing or filling up my trophy room!!
1. Rival 1.5 in 335 and 275
2. NT01 335 and R888R 295 (love the NT01 but doesn't come in 295 front)
3. Rival1.5 in 335 and 285 RE71R

Thanks for any opinions


DH

eric1855

The Rivals will be much faster. They are a significantly faster tire, regardless of size

If you've not bought the wheels yet, you can also consider the RE71Rs which some testing has shown as being slightly faster than the Rivals. You can get a 275/35/18 front, 305/30/19 rear set up on oem sizes so you dont have to worry about rubbing issues.

Dirty Howie

So you think smaller 200 rated tires will be faster than larger 100 ??


DH

ttx350z

Yep. Those R compounds wont get up to temp unless your autocross is like 3:00+ lap time at high speeds.

R compound will also put you in SSM where you’ll need to run A7’s if you want to be competitive.

Edit: Didn't notice you said 275 Rival S up front. I would say go with the 285 RE71R up front with the 10" wheels. With the 335 Rival S on the back, the 275 71R worked better than the 275 Rival S out front.

Dirty Howie

thanks. didn't realize the 285 RE71R was an option. I will strongly consider that and add it to my list


DH

jesup16

IIRC, people were mostly mixing the RE71R and RivalS before BGF had a 275 option for the front. All the feedback I've "heard" is the mix of RE71R/RivalS is not ideal.

IMO, stick with the RivalS.

AND0

What's with the weird offset on the front wheel?
If I'm reading the specs correctly that 18x10 30mm offset wheel will stick out by almost an inch over the standard C5Z06 rear (18x10.5 58)
MORE likely to rub the front fender with something like that.

I've used RE71 285/30-18 fronts with 315 rival rears on an C5 Z06 AS set up, and I didn't like it only because I tend to overdrive and correct, and the RIvals seem to be more tolerant of that sort of behavior.

RE71s in 285/30-18 on a 10 front and 305/30-19 on a 11-12 inch rear would be a good combo

Currently I use the 315 rival on the C5 Z06 rear all around in CAM-S Works really well. They do rub on my DRM brake duct extensions just a bit on full lock, but not on the fenders.

Dirty Howie

This is for a C6Z06 front. 18x10 with 30 offset is pretty normal for after market wheels. I currently run 285x35x18 MPSS on the front in this size as seen in my sig with no rubbing at all.


DH

jesup16

I'm not a C6Z06 expert, but isn't 10" front conservative? I thought you could fit a lot more. Not uncommon to see 18x11 w/ 315's on the front of a C5!! For autoX, you are going to want a lot more front wheel/tire. Are you just trying to make a set of wheels work?

Al.B

I'm trying to decide between the two also. From all the reading i like these two options best. For stock class that is. 9.5/12" rims.
1)Re71 285/305
2) rivals 275/335
I'm leaning towards the re71 because it seems that they would be better balanced (more neutral I'm guessing) compared to the rivals slight understear nature with this tire size combo. I also like the 285 over 275 re71 only because it will more closely match the tire diameter ration F/R to stock. The 275-35 and 305-30 are about the same height vs stock rears being about an inch taller. Not sure if that small change will throw any Dynamics off but I figure it's a safer gamble to keep that factor similar.

jesup16

Stock diameter ratio is 25.6 / 26.7 or a difference of 1.1". You're right about being closer to the stock diameter ratio, but is that really the ULTIMATE factor???

RE71R - 285/30/18 is 24.8 and 305/30/19 is 26.2 diameter. That's a difference of 1.4 " You can get a 275/35/18 for the front, too.

BFG RivalS - 275/35/18 is 25.6 and 335/30/18 is 25.9 or a difference of .3". Keep in mind you'll need to down size to an 18" rear wheel. HOWEVER, there is now a 305/30/19 RivalS on tirerack now. Also, a shorter rear tire may be helpful to provide better acceleration... specifically talking to the 335/30/18.

I think more important than keeping the ratio is understanding the nature of these tires:

RE71R: Come to operating temperature faster. Better for single driver autocrossers. Ultimate level of grip might be a tad better. Don't multi-task as well. Tend to have "Knife-edge" characteristics... meaning when you overheat or overdrive, then go off quick.

RivalS: Handle heat better but take longer to heat up. Multi-task really well: can handle some slip angle while providing longitudinal grip. Ultimate grip level might not be as high as the RE71R.

Also, consider the surfaces you run. I think the difference in ultimate grip favors the RE71R on asphalt surfaces. Concrete plays a little more to the BFG given the feedback I've heard.

Dirty Howie

I'm surprised no one would select the Nt01/R88R combo. Its 100 TWR instead of 200. To be clear this is not for sanctioned competition but rather to beat you buddies ..... run what yo brung cash on the line fun !!!!!!!!!!!!!!!!!!!!


DH

ttx350z

Not sure why Hoosier A7’s aren’t an option. They should be the only choice if you want to win.

jw1

Because it would be slower for an autocross..

18x11s don't rub on the front of my C6 GS with factory springs and shocks so there isn't a need to limit to smaller wheels, especially if you want to go fast. Since this isn't sanctioned, the fastest streetable tires for autocross are the V720 ACRs, but you would need 19" wheel F & R for those.

Kubs

Those 100TW options are not true 100TW tires from my experience. They will not be as fast as a Rival or RE-71R.

The way the UTQG determines the tread wear rating is by running a wear test. That is supposed to be an indication of how long the tires will last, and tire companies are not allowed to mark it HIGHER than the tested result. However, there is nothing against marking it lower. Before the 200TW class wars came about all the companies were marking their summer tires 180, 150, 120 etc to make the buyer think they were softer. Now that SCCA and USCA are mandating 200TW or higher, companies like BFG and Bridgestone are actually making tires that dont test higher than 200 on the wear test (or not by much), and these tires are significantly faster than a lot of options marked 180 or lower. Just going by what us stamped on the sidewall is not a good indication.

AutoX-Z06

Anyone have experience running the RE71R 305 squared? C5/C6

Ahrmasos14

https://www.corvetteforum.com/forums...-in-my-c5.html

305/19 square BS re-71

Dirty Howie

Two reasons:
1. I drive to the track
2. I want to give the other guys a chance !!


DH

jesup16

If you're so competitive, then why not build to a class and see how you stack up?

Dirty Howie

Thanks, thats a good reason.
Even with our the 11's I see brake duct contact. Most guys see this and some even consider the brake duct a consumable. Just don't want to get into that.....


DH