19" Tire Dilemma - Best Option?

Apex_Missing_Ape · 05-08-2019, 04:18 PM

I've got 19" wheels coming in factory SS 1LE offsets/widths that I will use for my track-only setup (so only want track-ready tires). I want to be as close as possible to the factory front:rear tire height ratio so that I don't screw with whatever algorithms are used when the PTM is doing its job.

So, in factory spec the rear tires are about .4" taller than the front, and I am assuming the computer factors this into its program. With the 19" wheels, I can't find track tires that maintain around that same ratio (30 series tires front/rear). The closest I can find are 285/35/19 front and 305/30/19 rear. That means the front tire will be about .6" taller than the rear tire.

I have two concerns with this:
1) it will affect the PTM system because it thinks the rear tires are spinning faster than the front (i.e. loss of traction event). I doubt it will cause issues in normal driving but may make traction control kick in earlier than normal in racing events.
2) the taller-than-factory 35 series tire will feel sloppier on turn-in.

A potential fix for maintaining the front:rear height ratio is putting a 295/30/19 up front paired with the 305/30/19 rear. That will keep it similar to factory spec since the rear tire is .3" taller. That will probably keep PTM happy. The problem is putting a 295 on a 10" wide wheel. Will that be worse than the 35 series on turn-in feel? Will that tire bulge cause a lot of rolling?

So which is the lesser or two evils?

BradfordCamaro · 05-08-2019, 06:02 PM

Way over thinking it.
.2"....Thats not even 3mm difference. Won't even notice.

Same with the minuscule difference in sidewall height.
Not going to cause any issue.

Apex_Missing_Ape · 05-08-2019, 07:06 PM

Quote:

Originally Posted by BradfordCamaro

Way over thinking it.
.2"....Thats not even 3mm difference. Won't even notice.

Same with the minuscule difference in sidewall height.
Not going to cause any issue.

It's not .2", it's .6", and it's on opposite ends of the car. Compared to the factory spec, it's like having 20s on the front and 19s on the rear.

vtirocz · 05-08-2019, 08:15 PM

I looked into this a little and this was one of the things holding me back from the 19" setup. There's not many options in 305/35/19 that I liked.

Also, with the Apex recommended tire size, there's a 5% error in the speedometer.

Apex_Missing_Ape · 05-08-2019, 08:56 PM

Looking around a bit more I found that the Hoosier A7/R7 in 295s and 315s are actually recommended to be mounted on 10" and 11" wheels according to their website, and both are about 26.1" diameter. That would prevent any kind of PTM imbalance, but I've never used slicks before and don't feel that I'm ready for them at my skill level. And I don't want to lose a whole track day to break them in properly, plus it looks like they only last 4-5 HPDE days. Also, they require more camber than my 1LE can manage without camber plates.

Maybe Provoste can chime in with his experience. I know he's ran a few different setups at the track.

ICTsccaCamaro · 05-09-2019, 07:59 AM

I'm running 305/30R19's front and rear on Bridgestone RE-71r's
https://www.tirerack.com/tires/tires...1RXL&tab=Sizes

Alpha1BC · 05-09-2019, 08:30 AM

You're not going to upset the car control systems as much as you think. These systems (ABS/TCS/ESC) function more off of wheel speed gradient (i.e., how fast the wheel speeds are changing) and accelerometers rather than just raw wheel speed values. Yeah, changing tires like that will throw off some of the optimized parameters such as the brake pressure build profile for an ESC hit, but that'll happen even from keeping OE tire sizes and changing rubber compound. Not that these systems won't work because of it, they just won't be 100% optimized and I'm willing to bet at least 90% of people who try it wouldn't notice because it's such a small drop in performance.

You're also not going to fault out any of these systems with that tire size difference. You need a much larger % difference in speed front to rear to mess that up. Tires you mentioned are 2-3% different front to rear, you'd need >10% at least.

FNxR3DNECK · 05-09-2019, 08:48 AM

Quote:

Originally Posted by Alpha1BC

You're not going to upset the car control systems as much as you think. These systems (ABS/TCS/ESC) function more off of wheel speed gradient (i.e., how fast the wheel speeds are changing) and accelerometers rather than just raw wheel speed values. Yeah, changing tires like that will throw off some of the optimized parameters such as the brake pressure build profile for an ESC hit, but that'll happen even from keeping OE tire sizes and changing rubber compound. Not that these systems won't work because of it, they just won't be 100% optimized and I'm willing to bet at least 90% of people who try it wouldn't notice because it's such a small drop in performance.

You're also not going to fault out any of these systems with that tire size difference. You need a much larger % difference in speed front to rear to mess that up. Wheels you mentioned are 2-3% different front to rear, you'd need >10% at least.

This right here!! A bunch of us are running square setups for track use so front/rear diameters are the same, PTM/ABS/whatever has absolutely no issues with it, all you have to deal with is the speedometer being off slightly.

I would recommend find whatever type of tire you want to run (200TW/R-Comp/Slicks) and throw the widest ones that will fit on the wheels, and just remember some tires run wider than others. For example: the 305 RE71R is only slightly wider than the 285 GYs and about smaller than the 305 GYs.

If you want 200TW I would recommend the RS4s, R-Comps: GY SC3Rs, Slicks: Pirelli Scrubs (though hard to find for 19s).

Don't over think it!

Apex_Missing_Ape · 05-09-2019, 10:38 AM

Thanks for the input, guys. I won't run a tire combo that makes the front higher than the rear (i.e. 285/35 with 305/30) and my offsets/widths won't support a square setup, so it looks like running a 295/30 on the front with a 305/30 on the rear is the way to go for me. I don't feel comfortable running a 305 on a 10" (front).

RS4s and RE-71s don't have the sizes I'm looking for. Have you tried the Toyo R888Rs? I've seen some ZO6 guys praise them...

Markoz28 · 05-09-2019, 11:02 AM

295/30 should fit a 10” rim fine. I wouldn’t go wider than that tho. I don’t know the width of the rear rims but 305/30 is perfect for an 11” wheel. Could even do 315 on that.

FNxR3DNECK · 05-09-2019, 12:17 PM

Quote:

Originally Posted by Apex_Missing_Ape

Thanks for the input, guys. I won't run a tire combo that makes the front higher than the rear (i.e. 285/35 with 305/30) and my offsets/widths won't support a square setup, so it looks like running a 295/30 on the front with a 305/30 on the rear is the way to go for me. I don't feel comfortable running a 305 on a 10" (front).

RS4s and RE-71s don't have the sizes I'm looking for. Have you tried the Toyo R888Rs? I've seen some ZO6 guys praise them...

R888Rs are a good R-Comp but they are pricey and won't last you very long. IMO the extra pace is not worth the extra cost vs. a 200TW tire.

For example R888Rs in 295/305 are $327/429 so that's roughly $1500. RS4s in 305 are $335. According to TireRack the 305/30/19 RS4s are good on 10-12" wide wheels, and their tread width is 11.4", where with the R888Rs you get 11.3" & 11.8" tread width. Based on that I would go square RS4s if I were you (even though you can't rotate them).

All tires aren't the same, some 305s will fit fine on a 10" wide while others will bulge.

Apex_Missing_Ape · 05-09-2019, 01:01 PM

Quote:

Originally Posted by FNxR3DNECK

According to TireRack the 305/30/19 RS4s are good on 10-12" wide wheels, and their tread width is 11.4", where with the R888Rs you get 11.3" & 11.8" tread width. Based on that I would go square RS4s if I were you (even though you can't rotate them).

All tires aren't the same, some 305s will fit fine on a 10" wide while others will bulge.

Damnit, you mentioned this earlier and I meant to look into that. Thanks for doing my research for me! I'm going to pull the trigger on RS4s.

FNxR3DNECK · 05-09-2019, 04:22 PM

Quote:

Originally Posted by Apex_Missing_Ape

Damnit, you mentioned this earlier and I meant to look into that. Thanks for doing my research for me! I'm going to pull the trigger on RS4s.

Happy to help! You won’t be disappointed in the RS4s!

eimarshall · 05-13-2019, 11:55 PM

Quote:

Originally Posted by FNxR3DNECK

Happy to help! You won’t be disappointed in the RS4s!

Have you run anything more than auto-X? I worry about the 305 on 10” combo for possible road course or track work. I really like the RS4s though.

05-08-2019, 04:18 PM	#1
Apex_Missing_Ape Drives: 2018 2SS 1LE Join Date: Jul 2018 Location: Birmingham, AL Posts: 117	19" Tire Dilemma - Best Option? I've got 19" wheels coming in factory SS 1LE offsets/widths that I will use for my track-only setup (so only want track-ready tires). I want to be as close as possible to the factory front:rear tire height ratio so that I don't screw with whatever algorithms are used when the PTM is doing its job. So, in factory spec the rear tires are about .4" taller than the front, and I am assuming the computer factors this into its program. With the 19" wheels, I can't find track tires that maintain around that same ratio (30 series tires front/rear). The closest I can find are 285/35/19 front and 305/30/19 rear. That means the front tire will be about .6" taller than the rear tire. I have two concerns with this: 1) it will affect the PTM system because it thinks the rear tires are spinning faster than the front (i.e. loss of traction event). I doubt it will cause issues in normal driving but may make traction control kick in earlier than normal in racing events. 2) the taller-than-factory 35 series tire will feel sloppier on turn-in. A potential fix for maintaining the front:rear height ratio is putting a 295/30/19 up front paired with the 305/30/19 rear. That will keep it similar to factory spec since the rear tire is .3" taller. That will probably keep PTM happy. The problem is putting a 295 on a 10" wide wheel. Will that be worse than the 35 series on turn-in feel? Will that tire bulge cause a lot of rolling? So which is the lesser or two evils?

05-08-2019, 06:02 PM	#2
BradfordCamaro SABIO Drives: 2016 CAMARO 1SS Join Date: Jul 2015 Location: Bradford, ON Posts: 5,012	Way over thinking it. .2"....Thats not even 3mm difference. Won't even notice. Same with the minuscule difference in sidewall height. Not going to cause any issue. __________________

05-08-2019, 08:15 PM	#4
vtirocz Drives: 2017 Camaro 1SS M6 Join Date: Apr 2015 Location: Indy Posts: 2,460	I looked into this a little and this was one of the things holding me back from the 19" setup. There's not many options in 305/35/19 that I liked. Also, with the Apex recommended tire size, there's a 5% error in the speedometer. __________________ 2017 Camaro 1SS, M6, Hurst shifter, Hyper Blue, NPP, Gray Split Spoke Wheels Best 1/4 Mile: 12.24 @ 115.9 mph

05-09-2019, 07:59 AM	#6
ICTsccaCamaro ITCRNRS Drives: 2018 ZL1 1LE Join Date: Jun 2012 Location: Wichita KS Posts: 1,575	I'm running 305/30R19's front and rear on Bridgestone RE-71r's https://www.tirerack.com/tires/tires...1RXL&tab=Sizes __________________ 2018 ZL1 1LE Ordered 6/29/17 Built 11/6/17 Delivered 12/7/17, Summit White, PDR, NAV, https://www.youtube.com/c/tylerpotter SOLD: 2014 Summit White 1LE 2SS/RS, Recaros, NPP, NAV, KONI Yellow's SOLD: 2012 Black 2LT/RS, Fully 1LE swapped, Brembo swap

05-09-2019, 08:30 AM	#7
Alpha1BC Drives: 2017 1SS 1LE Join Date: Jun 2016 Location: Detroit, MI Posts: 1,001	You're not going to upset the car control systems as much as you think. These systems (ABS/TCS/ESC) function more off of wheel speed gradient (i.e., how fast the wheel speeds are changing) and accelerometers rather than just raw wheel speed values. Yeah, changing tires like that will throw off some of the optimized parameters such as the brake pressure build profile for an ESC hit, but that'll happen even from keeping OE tire sizes and changing rubber compound. Not that these systems won't work because of it, they just won't be 100% optimized and I'm willing to bet at least 90% of people who try it wouldn't notice because it's such a small drop in performance. You're also not going to fault out any of these systems with that tire size difference. You need a much larger % difference in speed front to rear to mess that up. Tires you mentioned are 2-3% different front to rear, you'd need >10% at least. __________________ 2017 SS 1LE. Last edited by Alpha1BC; 05-09-2019 at 08:42 AM.

05-08-2019, 08:56 PM	#5
Apex_Missing_Ape Drives: 2018 2SS 1LE Join Date: Jul 2018 Location: Birmingham, AL Posts: 117	Looking around a bit more I found that the Hoosier A7/R7 in 295s and 315s are actually recommended to be mounted on 10" and 11" wheels according to their website, and both are about 26.1" diameter. That would prevent any kind of PTM imbalance, but I've never used slicks before and don't feel that I'm ready for them at my skill level. And I don't want to lose a whole track day to break them in properly, plus it looks like they only last 4-5 HPDE days. Also, they require more camber than my 1LE can manage without camber plates. Maybe Provoste can chime in with his experience. I know he's ran a few different setups at the track.

05-09-2019, 10:38 AM	#9
Apex_Missing_Ape Drives: 2018 2SS 1LE Join Date: Jul 2018 Location: Birmingham, AL Posts: 117	Thanks for the input, guys. I won't run a tire combo that makes the front higher than the rear (i.e. 285/35 with 305/30) and my offsets/widths won't support a square setup, so it looks like running a 295/30 on the front with a 305/30 on the rear is the way to go for me. I don't feel comfortable running a 305 on a 10" (front). RS4s and RE-71s don't have the sizes I'm looking for. Have you tried the Toyo R888Rs? I've seen some ZO6 guys praise them... Last edited by Apex_Missing_Ape; 05-09-2019 at 11:14 AM.

05-09-2019, 11:02 AM	#10
Markoz28 Drives: 18 ZL1 nightfall grey A10 Join Date: Apr 2018 Location: RGV Texas Posts: 1,527	295/30 should fit a 10” rim fine. I wouldn’t go wider than that tho. I don’t know the width of the rear rims but 305/30 is perfect for an 11” wheel. Could even do 315 on that.

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