[utekineir]

Hi,

Have had my lightly used zl1 1le for about two weeks and 4 autocross events now, roughly 70 runs and 6 or so different people have driven it, last weekend myself and several other friends instructing at a school took runs in it.

The universal feeling is that the front tires are unhappy mid corner and chuffing without being pretty delicate. Surface is an old pavement runway in the northeast, temperatures are off summer peaks but pavement still is at a good point of heat.

Its first event the alignment was 1/8" toe in front at the suggestion of a friend. After that day the front has been 1/8" toe out. Rear has been 1/8" toe in and rsb on full soft every day. Front camber -3.5 range, rear -2.0 Pressures maintained around 32 cold front, 28 cold rear. Track mode, all nannies off.

First weekend tires were sticker 305/30/19 re71 at the front from tire rack clearance this summer and 2 325/30/19 several hundred run sc3 saved from scrap pile at the rear. Last weekend the tires were sticker 325/30/19 sc3 all the way around.

The car overall feels great, far more controllable than was ever expected (exhaust is partially corked on the npp valves to not pop sound limits) and hides the weight amazing.

Regardless of tire and front end alignment the chuffing from the front when not treating the car gently has persisted in significant cornering.

There appear to be about 6 threads left on the front spring perches to lower, however the current ride height is very functional without scraping the oem aero in day to day use and trailering/entering garage. So i'd prefer not to lean into using rake in this case.

The car overall feels great, but every driver has complained of the front end chuff. On my end i've found its mostly avoidable treating the car as the fat pig it should be treated like.

I'm guessing a bit more softness in the front would help alleviate the situation. As a kludge I'm thinking about experimenting with a bit stiffer setting on the rear bar and or seeing if there is enough space on the oem front bar to drill an extra set of holes further out or trying a different trim front bar. I also wouldn't be suprised if the issue goes away on concrete, however the one concrete site within 3 hours always schedules events that overlap with local ones 30 minutes away I'd prefer to attend.

Tldr.

Does anyone know the spring rates of a zl1 1le or the sway bar number specifics? My front end could likely benefit from a little softening for being a peasant driving around cones.

[utekineir]

Not sure if the front end noise evident in any of these. Still working on a better gopro mount position.

The hardo with orange gloves driving it like an str miata easily created the most front end unhappiness.

[5inn]

Did you try putting a big stiff bar in your rear?

[utekineir]

Originally Posted by 5inn

Did you try putting a big stiff bar in your rear?

I'd try a big stiff bar in your rear if you ever signed up for anything.

[Mountain]

If it were my car, I wouldn't soften the front bar, or soften the front suspension, especially for autocross. Why? You will hurt the car's transition response and also balance in putting power down. The ZL1 is 1. a front heavy car and 2. has a high-amount of low-end torque. In autocross, you are working with tight corners, fast transitions between direction and speed and the need for a lot more constant overlap in steering, throttle and brake than in a circuit/road course, to which the ZL1 1LE is more-so setup for.

You say that you've only run the OE rear ARB on full soft so far? If so, I'd start to play there. I would also suggest going closer to zero rear toe - try 1/16 or 0. Maybe some more messing with tire pressures. If none of that works, maybe look at a different rear bar, but I would say your options are pretty limited and, myself, I'd be very hesitant to do that if you also ever plan to take your car on a circuit/road-course often. My understanding is that a lot of the ZL1 1LE guys find the stiffest setting on the rear ARB too oversteer-like for them on track.

[utekineir]

Originally Posted by Mountain

If it were my car, I wouldn't soften the front bar, or soften the front suspension, especially for autocross. Why? You will hurt the car's transition response and also balance in putting power down. The ZL1 is 1. a front heavy car and 2. has a high-amount of low-end torque. In autocross, you are working with tight corners, fast transitions between direction and speed and the need for a lot more constant overlap in steering, throttle and brake than in a circuit/road course, to which the ZL1 1LE is more-so setup for.

You say that you've only run the OE rear ARB on full soft so far? If so, I'd start to play there. I would also suggest going closer to zero rear toe - try 1/16 or 0. Maybe some more messing with tire pressures. If none of that works, maybe look at a different rear bar, but I would say your options are pretty limited and, myself, I'd be very hesitant to do that if you also ever plan to take your car on a circuit/road-course often. My understanding is that a lot of the ZL1 1LE guys find the stiffest setting on the rear ARB too oversteer-like for them on track.

Thanks for the feedback.

On old pavement the car has an excessive amount of front end stiffness for autocross. I'm sure it would absolutely shine on track as is, but that isn't the goal here. One track day = about a full month of ax dickery and this is a short drive.

With that in mind I have 0 issue with tinkering on softening the front end. This isn't the first time setting up a car for this use or venue. This weekend if the weather is dry stiffening the rear bar and pressures will likely be tested.

If this post is correct the only softer front bar is an fe2 bar. I'd assume one can be found dirt cheap to mess with.

[VR Baron]

Originally Posted by utekineir

Thanks for the feedback.

On old pavement the car has an excessive amount of front end stiffness for autocross. I'm sure it would absolutely shine on track as is, but that isn't the goal here. One track day = about a full month of ax dickery and this is a short drive.

With that in mind I have 0 issue with tinkering on softening the front end. This isn't the first time setting up a car for this use or venue. This weekend if the weather is dry stiffening the rear bar and pressures will likely be tested.

If this post is correct the only softer front bar is an fe2 bar. I'd assume one can be found dirt cheap to mess with.

I was going to refer to those bar rates. On springs the only thing I have seen is Chevy site saying zle front springs were around 250 % stiffer then ss 1le rates. And those rates per a post in this forum saying the ss 1le at 178 lbs per ft.

My friends who autocross with me with zle’s use about your camber numbers, 305/30/19 all around(falcons now) and the rear bar set in the middle. Stiffer rear bar,especially with the square tire setup , and to much oversteer. And they are in the top 2-4 in our modern muscle group of 25-30 cars

[rotis]

In your shoes the first thing I'd try is adjusting the stock rear bar.

[utekineir]

Originally Posted by VR Baron

I was going to refer to those bar rates. On springs the only thing I have seen is Chevy site saying zle front springs were around 250 % stiffer then ss 1le rates. And those rates per a post in this forum saying the ss 1le at 178 lbs per ft.

My friends who autocross with me with zle’s use about your camber numbers, 305/30/19 all around(falcons now) and the rear bar set in the middle. Stiffer rear bar,especially with the square tire setup , and to much oversteer. And they are in the top 2-4 in our modern muscle group of 25-30 cars

Originally Posted by rotis

In your shoes the first thing I'd try is adjusting the stock rear bar.

Thanks,

This region has a great trickle down from the pointy end of national competition, great site, 8 great groups resulting in 2 events a weekend for the full seasson, many hardos. Theres enough success that big fish small pond syndrome isn't an issue.

Temperatures for sunday look to be the first day with a real drop off and its been cold recently, expecting the chuffing condition to be more prevalent atleast in the am. Likely will show up with one endlink on middle one on soft and go from there. I will smile, but 2 of the drivers (neither from above) in car sunday aren't going to do so well with cold temperatures and loose rear.

[utekineir]

Ended up bumping up the rear bar to both holes at middle. Car was worse in sweepers but enough better overall it felt worth it.

Finally this weekend I got around to spinning the front perches all the way down. Even with the colder temperatures the front end is feeling quite a bit better.

Will reevaluate in the spring, but no legitimate complaints as it sits.