R Owners - 325s on the rear

[passwords]

@passwords So I just looked up the specs for the 325/30 SC3(nonR) vs my Conti SportContact. The GY has a 1/2" wider treadwidth (.5 exactly), but they boast the exact same section width on the same wheel size (11.5"). In that photo on your 12" wheel, they look ever so slightly stretched; which I like. but with the same section width, they should look and fit very similar as the Conti on my 11.5". I checked the 305 for the front also, and that had the same results.

The tire in that picture is the SC3R. They are on my Camaro ZL1 1LE (“ZLE” to avoid the alphabet soup). The ZLE (not to be confused with the regular ZL1) comes with the SC3Rs from the factory, and my ZLE is 100% bone stock down to the air cleaner - zero modifications including wheels and tires. I tried to get some better pictures today but I couldn’t get anything that shows a realistic view of the wheel/tire combo. I don’t see any stretch in the sidewall but the SC3Rs do have the sidewall that extends past the wheel rim to add some curb protection as part of the tire design, just like the Cup2s. But now we have pictures from OP to confirm the 325/30/19 SC3Rs do result in some poke. I personally would not want that on my R but I don’t track my R and the potential for paint damage would be my primary concern - the SC3Rs throw rocks every bit as bad as the Cup2s on the R. I would also be slightly concerned about damage to the quarter panel at full suspension compression on the rear, but I really don’t know whether the tire would contact the quarter panel at full squat.

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[AgSurfer]

Yeah I'm probably in for PPF on the R given I track the car and plan to do so even more often in the future. I'm running out of time to get all this stuff done.

 

[galaxy]

@passwords I don’t think I’ve seen one of those things with 19” wheels. Pretty sure every one I’ve seen has 20’s.

 

[passwords]

@passwords I don’t think I’ve seen one of those things with 19” wheels. Pretty sure every one I’ve seen has 20’s.

https://wildhammermotorsports.com/1...eel-kit-includes-4-front-rear-general-motors/



If you have seen a ZLE with 20” wheels the owner should be slapped (I’m kidding of course, mostly). Many ZLE owners who track their cars use the OEM wheels and tires for track duty since you can also use them to drive to and from the track, or they go to 18” BC Forged or Apex wheels and Pirelli DH slicks for dedicated track use since the slightly smaller diameter front rotor allows certain 18” wheels to be used, which opens up other tire choices. The OEM fronts are 19x11 ET11, rears are 19x12 ET41. OEM tires are SC3Rs in 305/30/19 on the front, 325/30/19 on the rear. If you haven’t heard/seen much about the ZLE it’s worth some time looking at on the interwebs.

The attached picture is slightly distorted but you can see the tire size and 3R logo on the side.

 

[drummerboy]

Thanks to you guys posting pics, very helpful.

Also found a pic in a thread that I can't find, showing that the 305 SC3R is wider than the 315 Cup2. It seems to me from all those pics/info that the SC3R in 305 would be a better fit on a 11.5" wheel than the 325 for track duty. From the pics it looks like that 325 is so wide that 12" would be the minimum wheel width ideally for track use. Please correct me if I'm wrong, about to order four to put on square 11.5"

 

[AgSurfer]

Thanks to you guys posting pics, very helpful.

Also found a pic in a thread that I can't find, showing that the 305 SC3R is wider than the 315 Cup2. It seems to me from all those pics/info that the SC3R in 305 would be a better fit on a 11.5" wheel than the 325 for track duty. From the pics it looks like that 325 is so wide that 12" would be the minimum wheel width ideally for track use. Please correct me if I'm wrong, about to order four to put on square 11.5"

Yes, others have mentioned running 305 square track set up with the Goodyear SC3Rs. Someone also mentioned running the 19x11.5" square setup for track, but, a spacer is needed for the front wheel. With respect to your comment on the Goodyear SC3R in 325/30/19 and needing a 12" minimum width rim, your statement is incorrect. The 11.5" rim is absolutely within spec. A 12" wide rim is not the "minimum width" needed for that tire. See Goodyear's website for verification. Approved rim width is 11.0" - 12.5". Measured rim width is 11.5".

Discount Tire Direct shows the rim width range of 10.5" - 12.5". The mid-point is usually the suggested rim width, which would be 11.5".

Let us know what you decide to do.

 

[GTX]

I just went to the track with SC3Rs in a 305 square set up and it certainly helped with understeer a bit. The car rotated better and just felt more balanced.

 

[Aaron1085]

I just noticed my Conti’s are a 345 tread wear!!! Woah? No wonder they’re doing soo great, LOL.

sorry … what model Conti’s?

 

[drummerboy]

A 12" wide rim is not the "minimum width" needed for that tire. See Goodyear's website for verification. Approved rim width is 11.0" - 12.5". Measured rim width is 11.5".

Agreed, it will surely fit fine. But going by the pics and info it just seems that the 325 might be wider than ideal on the 11.5" for track use. In regards to track use, wanting a little bit of stretch on the tire, the 305 already being wider than the 315 Cup2, and the 325's looking incredibly meaty even on a 12" (at least in the pics, hard to tell), it looks like the 305 is the way to go to me.

Thanks for the help - I haven't seen them in person, so I'm trying to get as much info as possible. I think the point alone about the 305 being wider than the 315 Cup2 is enough to make my decision 100% on the 305, but I wouldn't mind one last verification that this is in fact true.

 

[AgSurfer]

Agreed, it will surely fit fine. But going by the pics and info it just seems that the 325 might be wider than ideal on the 11.5" for track use. In regards to track use, wanting a little bit of stretch on the tire, the 305 already being wider than the 315 Cup2, and the 325's looking incredibly meaty even on a 12" (at least in the pics, hard to tell), it looks like the 305 is the way to go to me.

Thanks for the help - I haven't seen them in person, so I'm trying to get as much info as possible. I think the point alone about the 305 being wider than the 315 Cup2 is enough to make my decision 100% on the 305, but I wouldn't mind one last verification that this is in fact true.

Understood. I track my car as well and will be running it with the 325s on the rear and 305s on the front, and then after I burn those out, I'll swap back to the OEM CF rims with the Michelin SC2s - unless, I determine that I really like the Goodyear SC3Rs and want to keep running them all together.

 

[galaxy]

sorry … what model Conti’s?

The ExtremeContact Sport. I would have thought a lower number for this tire.

 

[passwords]

Agreed, it will surely fit fine. But going by the pics and info it just seems that the 325 might be wider than ideal on the 11.5" for track use. In regards to track use, wanting a little bit of stretch on the tire, the 305 already being wider than the 315 Cup2, and the 325's looking incredibly meaty even on a 12" (at least in the pics, hard to tell), it looks like the 305 is the way to go to me.

Thanks for the help - I haven't seen them in person, so I'm trying to get as much info as possible. I think the point alone about the 305 being wider than the 315 Cup2 is enough to make my decision 100% on the 305, but I wouldn't mind one last verification that this is in fact true.

I was going to reply the same way but you beat me to it…the 325 SC3Rs will fit on an 11.5” wheel no problem, but I don’t really know if it will make a noticeable difference as far as tire deflection/sidewall stiffness, so it may not be within the definition of ideal. It surely could but that’s way above my pay grade.

I can confirm that the 305/30/19 SC3R is slightly wider than the OEM 315/30/19 Cup2 on the R model, a little more than 1/4” on my set, and that’s on a 11.0” front wheel.

If it were me, I would go with the 305s square. I’m not sure the extra width with the 325s in the rear would be worth the potential fitment issues.

 

[AgSurfer]

I was going to reply the same way but you beat me to it…the 325 SC3Rs will fit on an 11.5” wheel no problem, but I don’t really know if it will make a noticeable difference as far as tire deflection/sidewall stiffness, so it may not be within the definition of ideal. It surely could but that’s way above my pay grade.

I can confirm that the 305/30/19 SC3R is slightly wider than the OEM 315/30/19 Cup2 on the R model, a little more than 1/4” on my set, and that’s on a 11.0” front wheel.

If it were me, I would go with the 305s square. I’m not sure the extra width with the 325s in the rear would be worth the potential fitment issues.

Thanks. So you're mounting the 305s on the 11 fronts and 305s on the 11.5 rears?

 

[drummerboy]

I was going to reply the same way but you beat me to it…the 325 SC3Rs will fit on an 11.5” wheel no problem, but I don’t really know if it will make a noticeable difference as far as tire deflection/sidewall stiffness, so it may not be within the definition of ideal. It surely could but that’s way above my pay grade.

I can confirm that the 305/30/19 SC3R is slightly wider than the OEM 315/30/19 Cup2 on the R model, a little more than 1/4” on my set, and that’s on a 11.0” front wheel.

If it were me, I would go with the 305s square. I’m not sure the extra width with the 325s in the rear would be worth the potential fitment issues.

Mirrors my thoughts exactly. I was originally having a tough time deciding til this thread and the others showing the size difference. The 315 Cup2 fitting the 11.5 so well and the 305 SC3R being 1/4" wider seals the deal. Thanks for your input.

 

[drummerboy]

Thanks. So you're mounting the 305s on the 11 fronts and 305s on the 11.5 rears?

That's what I would do, and since the wheel width is also affecting grip I'd expect the rears to have a bit more grip on that 11.5 than they would on an 11. If they offered a 295 to put on the 11 I wouldn't expect it would perform any worse than the 305 based on what I've read, but that's all just literature, no experience in this department.

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