2014 2SS - Best wheel/tire size for tracking?

[Balok]

Originally Posted by Dropspeed

I will know tomorrow if the Z/28 305/30/19 setting is in there. If not, it can be done with an aftermarket flash.

Those are some badass looking tires! I I necro'd another very old thread along these lines last night, and posted what's below. Do you know if what I'm asking is correct or am I off my rocker, lol.

Here's the quote:

The Camaro ABS/Stabilitrack/Traction Control system is programmed to read wheel speeds at each corner. In order for this to function properly, you need to maintain similar tire heights at all four corners. At least within 0.5" difference, to be safe.

So, I looked at my stock setup and I have 245/40ZR21's on the front, and 275/35ZR21's on the back which according to the chart linked here are 28.7" and 28.6" in height. So I can see where they're almost the same height.

Now, my question is this: As long as the height on all 4 corners is within the specified limits, does it matter the size of the wheel/tire combo? In other words, lets say I went to a 19" wheel with 295/30ZR19's all the way around, would it still throw the sensors off? Is the computer calibrated to expect to read readings from a 21" tire and base it's calculations off of that, so that even if all 4 19" tires are the exact same size it would throw it off because they're 19" and it's looking for 21"?

Thanks!

[TLSTWIN]

The tires from the factory are almost all the same outside diameter regardless if they are 18's, 19's, 30's, or 21's. At least they used to be. That is why the tire sizes are all over the place.

Now, as long as you keep all 4 tires on your car within that 1/2" that you quoted, you'll be fine. If you could fit 15" tires on there it wouldn't make a difference other than your speedo.

I believe it can be calibrated, or information updated with the current tire size if needed.

Try this
http://tire-size-conversion.com/spee...r-calibration/
http://www.onlineconversion.com/bigger_tires.htm

[Dropspeed]

Originally Posted by Balok

Those are some badass looking tires! I I necro'd another very old thread along these lines last night, and posted what's below. Do you know if what I'm asking is correct or am I off my rocker, lol.

Here's the quote:


So, I looked at my stock setup and I have 245/40ZR21's on the front, and 275/35ZR21's on the back which according to the chart linked here are 28.7" and 28.6" in height. So I can see where they're almost the same height.

Now, my question is this: As long as the height on all 4 corners is within the specified limits, does it matter the size of the wheel/tire combo? In other words, lets say I went to a 19" wheel with 295/30ZR19's all the way around, would it still throw the sensors off? Is the computer calibrated to expect to read readings from a 21" tire and base it's calculations off of that, so that even if all 4 19" tires are the exact same size it would throw it off because they're 19" and it's looking for 21"?

Thanks!

It is not a specification that reads inches, it is actually a % diff and there was a discussion on FB with my GM calibrator friends trying to decide if it was 3% or 5% for the ABS system on most GM vehicles

A ZL1 is only about 2% with the 285/35 and 305/35....

The 1LE has a specific ABS program based on a square tire set-up...

Matt

[Balok]

Originally Posted by Dropspeed

It is not a specification that reads inches, it is actually a % diff and there was a discussion on FB with my GM calibrator friends trying to decide if it was 3% or 5% for the ABS system on most GM vehicles

A ZL1 is only about 2% with the 285/35 and 305/35....

The 1LE has a specific ABS program based on a square tire set-up...

Matt

OK great, I do understand that it's a %, but I'm still unclear as to whether going from a 21" to a 19" would make a difference if all 4 19" tires are the exact same size. There would be nothing for it to to scream about unless it was looking for a size based on a 21" tire, right?

[hookdup]

Contact John at CCW,
H e will make a set of wheels that you can run 315 , if you are capable, and
clear calipers

[Balok]

Originally Posted by hookdup

Contact John at CCW,
H e will make a set of wheels that you can run 315 , if you are capable, and
clear calipers

Yeah, I'm not spending $2000 to $4000 (or more) for a set of rims to run on the track. But thanks anyway!

[Dropspeed]

Originally Posted by Balok

OK great, I do understand that it's a %, but I'm still unclear as to whether going from a 21" to a 19" would make a difference if all 4 19" tires are the exact same size. There would be nothing for it to to scream about unless it was looking for a size based on a 21" tire, right?

Correct: The ABS, traction and stability should work fine

The only thing that should be calibrated for the tire Overall Diameter (OD) is the speedometer and if an automatic the transmission.

From a quick Google, you should have a 245/40/21 front and 275/35/21 rear tire the ODs are 28.71" and 28.57"

[Balok]

Originally Posted by Dropspeed

Correct: The ABS, traction and stability should work fine

The only thing that should be calibrated for the tire Overall Diameter (OD) is the speedometer and if an automatic the transmission.

From a quick Google, you should have a 245/40/21 front and 275/35/21 rear tire the ODs are 28.71" and 28.57"

Thanks Dropspeed, that's what I was hoping. And yes, those are the exact tires that it's currently calibrated for. I could probably live with the aids being off as I was planning on running them off next time anyway. But yeah, it's an automatic with paddle shifters and the last thing I want to do is tear the transmission out of my new car, lol.

I spoke with the service manager where I bought the car, and he rattled off all these certifications and years of experience he had, blah, blah, blah, but in the end he made sure I knew tracking the car would void any warranty for something I broke on the track, and basically said he didn't know if it could be reprogrammed like I want and I would have to bring it in and hook it up to see for $80.00. That's a LOT cheaper than buying a set of wheels and track tires, so I think I'm going to let them look at it and see what they can do. I'll update this thread when I find out.

Thanks again!

[Norm Peterson]

Originally Posted by Balok

OK great, I do understand that it's a %, but I'm still unclear as to whether going from a 21" to a 19" would make a difference if all 4 19" tires are the exact same size. There would be nothing for it to to scream about unless it was looking for a size based on a 21" tire, right?

If the 19" tires are enough shorter than the 21's, there is some possibility that the ABS could activate a little sooner than it should. But running 4 x whatever 19's under any normal situation short of extreme braking shouldn't light up the dash.

A small-diameter tire will drop revolutions faster than the standard tire, which ends up being interpreted by the ABS as a slightly more aggressive braking event than is actually the case. I think you'd need to know whether the ABS was primarily calibrated to activate at a specific maximum deceleration (as indicated by the rate at which the sensor pulses decrease) and what that deceleration was, or if seeing the pulses from one or more sensors which are already decreasing at some rate suddenly decrease dramatically is what mainly triggers it. I wish I had a better answer.


On edit - I'm currently scuffing in a set of tires that will see track use and which are nearly 5% shorter than my car's OE tires. So far, there haven't been any ABS events in some fairly hard stops. YMMV, though I doubt there are huge differences among the OEs.


Norm

[Dropspeed]

Originally Posted by Norm Peterson

On edit - I'm currently scuffing in a set of tires that will see track use and which are nearly 5% shorter than my car's OE tires. So far, there haven't been any ABS events in some fairly hard stops. YMMV, though I doubt there are huge differences among the OEs.


Norm

Most programing for ABS/stability is done by a Tier 1 that helps develop the system and they usually work with more than one OEM.... In one of the GM Z/28 videos there was an acquaintance that worked at a supplier and helped dial in the Z, he was hired direct by GM after.

[elbob]

I have ordered these for the track
4-19x10 Forgestar CF5V
with Toyo Proxes R888 295/30ZR19

I wanted a square setup I could rotate and these should also lower the car 1" for track day.

Can't tell you how they work yet but I'm hoping they will show up soon.

[Orange Crush 1LE]

Guys,

I'm running 315/30-18s super-sticky Hoosiers all the way around. These are 2.6" diameter smaller than the OEM 285/35-20s, and I have NO ABS issues. The car is very well balanced and predictable, no complaints on braking or funny ABS behavior. So I can't imagine there being an issue with going with 19s, which are only about 1.3" diameter smaller than stock.

[Balok]

Originally Posted by Orange Crush 1LE

Guys,

I'm running 315/30-18s super-sticky Hoosiers all the way around. These are 2.6" diameter smaller than the OEM 285/35-20s, and I have NO ABS issues. The car is very well balanced and predictable, no complaints on braking or funny ABS behavior. So I can't imagine there being an issue with going with 19s, which are only about 1.3" diameter smaller than stock.

OC, did you have to reprogram anything when you switched?

[Orange Crush 1LE]

Originally Posted by Balok

OC, did you have to reprogram anything when you switched?

No, not required but I wanted to have my speedo correct at the track. But that means my speedo is incorrect on the street when I have my stock 20" wheels on. That was a good trade-off for me. I would think that others wouldn't want to correct their speedo unless their car is primarily a road course car like mine.