[KL01]

After installing some taller tires in the rear I'm getting abs/stabilitrak/traction control off lights go off on my 2019 Camaro. I can adjust the tire size but was confused if I should also [scale the transmission] . I was just going to [adjust the speedometer calibration] The transmission has also been tuned. Also would like to add, the front tires are 26.7 inch tall and the rear were 27.2. New rear tires are 28.4 inch tall according to the tire size calculator. Really want to avoid getting front tires too due to them being less than 10k miles.

[arpad_m]

Unfortunately, the ECM is only willing to adapt to different front-to-rear tire ratios within a ~3% range, if you exceed it (which, although you didn't disclose exact sizes, you most likely did), ABS and Stabilitrak errors occur. If you stay close to the edge, the errors will be intermittent, if you grossly exceed it, they will pop up all the time.

The real fix is to change the front-to-rear ratio again to remain within 3% of stock. You need to either sell the rear tires and get shorter ones, or get taller front tires. Alternatively, you can try to change the driven and non-driven tire circumference parameters in the tune as an attempt to get rid of the errors (I have not tested this approach).

[KL01]

I went with 555R2 305/35/20 in the rear. Since they been out of stock for some time, once I found them new I jumped on it. The original size was 305/30/20. The front tires are 285/30/20. How do people with Drag packs do it? Do they do the same thing and keep the tire size similar?

[grampa_ss]

Some go with 17x10 rears and 18x5 fronts and use 28” tall tires for both.

[arpad_m]

Yeah, that's what they do, they keep the ratio in check no matter the absolute heights.

You reduced front size by 3.6%, and with these new 35 aspect ratio tires you increased rear size by 2.9%, which is a total delta of 6.5%, way more than what the car allows (~3%).

Going with 305/30/20 in the rear would bring this total to -2.2%; upping the fronts to 285/35/20 while keeping your current rears would do the exact same thing, but in the other direction (+2.2%), so both are equally viable. If possible, I'd reduce the height instead of going taller, that's better from every point of view except maybe a tiny little bit of ride quality due to shorter sidewalls. Taller tires are also a very tight squeeze and you may have some rubbing up front if you go with 285/35/20s.

It's no coincidence that the 1LE uses 285/30/20 and 305/30/20.

[KL01]

Originally Posted by arpad_m

Yeah, that's what they do, they keep the ratio in check no matter the absolute heights.

You reduced front size by 3.6%, and with these new 35 aspect ratio tires you increased rear size by 2.9%, which is a total delta of 6.5%, way more than what the car allows (~3%).

Going with 305/30/20 in the rear would bring this total to -2.2%; upping the fronts to 285/35/20 while keeping your current rears would do the exact same thing, but in the other direction (+2.2%), so both are equally viable. If possible, I'd reduce the height instead of going taller, that's better from every point of view except maybe a tiny little bit of ride quality due to shorter sidewalls. Taller tires are also a very tight squeeze and you may have some rubbing up front if you go with 285/35/20s.

It's no coincidence that the 1LE uses 285/30/20 and 305/30/20.

Well due to me purchasing rear tires new from someone local (not a shop) I might have to purchase the new front tires. I'll see what my tuner says tomorrow about changing the sizes. Some people on HPtuners said I can change the numbers so it can work, some said I can't. We will see.

[cjperformance]

I had tried swapping the stock sizes on my 2SS with the 1LE sizes... it had some intermittent wierdness on the street when I'd do a hit with the nannies on, but at the track it would completely freak out and activate torque management and even (i suspect) the ABS. I have some youtube vids of my track pass with the 1LE size and you can clearly see the camera shake in 1st gear. I thought it was wheel hop, but now im thinking it was ABS kicking in and chattering the front brakes. Plus it would close throttle and pull timing even with the nannies off...

The 1LE sizes are about 1" difference front to rear, where the normal SS sizes are much closer to the same. Long story short, i thought I'd be safe with the 1LE size, but still had some issues. I havent tried reprogramming the tire sizes in the ECU, but I have since swapped to the tire/wheel combo in my sig. They are only about 1/2" difference front to rear, and the weirdness on a hit on the street has gone away. I havent been able to get to the track to retest yet. Another board member had these sizes and said they ran fine, so i copied his setup.

Im not convinced that reprogramming the ECU only will work. I feel like there are probably other modules like the ABS that probably also have tire dias programmed into it, but its just a suspicion.

Its on my todo list to put those 1LE sizes back on and test reprogramming the ECU, but not super high priority right now. The 1LE size wheels i had were Racestar Recluse and heavy as hell, so i didnt bother figuring this out with them. The Forgestars are much lighter.

[wnta1ss]

If you are going to adjust the speedometer tire size, my suggestion is to also adjust the tire circumference section. This was not available years ago and I adjusted what was available at the time (speedometer only) for a rear tire size change. The stabilitrack freaked out driving less than a mile, lights flashing and lack of response to throttle, had to completely turn off stabilitrack (7~10 sec hold of T/C button) just to drive the car. See pic of tune below, circled part has front (undriven) and rear (driven) tires, note the 2150mm for the 748.34 rev/mi that is in the speedometer for the rear tires. Whatever you put in the speedo section, try putting the same mm equivalent in the driven tire section.

[KL01]

Originally Posted by wnta1ss

If you are going to adjust the speedometer tire size, my suggestion is to also adjust the tire circumference section. This was not available years ago and I adjusted what was available at the time (speedometer only) for a rear tire size change. The stabilitrack freaked out driving less than a mile, lights flashing and lack of response to throttle, had to completely turn off stabilitrack (7~10 sec hold of T/C button) just to drive the car. See pic of tune below, circled part has front (undriven) and rear (driven) tires, note the 2150mm for the 748.34 rev/mi that is in the speedometer for the rear tires. Whatever you put in the speedo section, try putting the same mm equivalent in the driven tire section.




Attachment 1136040

Mine has those options in red but I am able to change them. The math seems off since for both of mine shows 2266mm for both driven and non-driven.

[KingLT1]

2266mm is 28.4" height which is correct for drive tire. change the non-drive tire to 2130.565 and see what that does.

[KL01]

Originally Posted by KingLT1

2266mm is 28.4" height which is correct for drive tire. change the non-drive tire to 2130.565 and see what that does.

Will try that. These are the numbers from the factory. Might be different for the 1LE rims which I never had any issue with. Factory are 245/40/20 fronts, 275/35/20. Then i put the 1LE 285/30/20 front, 305/30/20 rears with no issues. Only changed the rear to a 305/35/20 which cause problems. Sorry for long explanation, just want to be clear of the situation. When I change the non- driven, did that change the tranny or just ecm?

https://imgur.com/a/qb1cN09

[KL01]

Originally Posted by KingLT1

2266mm is 28.4" height which is correct for drive tire. change the non-drive tire to 2130.565 and see what that does.

Still gave me the same issue..

[ZL1C7]

I played with these settings on my Gen5 Camaro until my fingers bled. I haven't bothered with my Gen6 but fairly sure that there is nothing you can do to make it work. Sometimes turning traction control all the way off will help, just like we do on the dyno. The wheel sensors sample the difference between speed on all 4 corners. The body module and ABS module take over primary duty to keep wheel speeds in check. The modules don't care about what is entered for gear ratio/aspect/circumference. It all comes down to wheel sensor speed. Someday I will remove the ABS module and play with it more but for now its all about keeping the tire diameters close. On the Gen5 when we were way off on tire size it would turn ABS on and kill the power steering. It wasn't a bad deal because I had skinnies up front and it wasn't kicking in/out of traction control. When we were just out of range on tire size it would randomly kick into traction control. Everyone said to pull the ABS fuse but that would also disable power steering.