Car Unstable Under Full Throttle

[StlRomAniaN]

Originally Posted by WoodBoss

I bet your tires are shot. Black on the bumper seems like you lost significant rubber. Worn tires on these cars make them catch every crack and groove in the road.

I'm going to keep driving on these tires in hope that the tires even themselves out somewhat.

These rear tires are only 23 months old. I had 3 years out of my first two sets. If I do end up getting new tires, I believe I'm going to leave Pirelli and get some Michelin Pilot Super Sports--285/35R20 in the front and 315/35R20 (since they don't have a 305 available).

[JusticePete]

We need to be looking for wear like this.



The OP's Camaro is on OE rubber, but rubber wears too. The arms and links have to be removed so the can be inspected, taken out cleaned and inspected. You may need to chuck and arm in a vice and use a level to articulate the bushing to find a tear.

If the alignment is changing, it isn't a tire. Something is moving in the suspension that should not be moving. Loose bolts, bolts night tight enough to hold loads can feel tight, even with a spot check with a wrench. Bushings wear and tear. mI made these videos a long time ago.





These are Z/28 rear knuckles. Take a close look. Closer. How many monoballs are in the knuckle?



The OP writes there is 'no play in anything'. I am not picking on you, but yes there is play designed in the rear suspension brand spanking new. The six monoballs on the rear suspension, the rubber bushings and mounts are designed to allow movement, not much, but movement. When they wear, there is more movement. At some point you cross a line and the movement becomes too great and repairs need to be made.

Let's start again. Your rear end became 'loose'. You had an alignment and it was better for a short period of time and the condition returned?

[StlRomAniaN]

Thanks for all of the information.

Well, I noticed the issue when my rear bumper was turning black. It progressively got worse when the bumper got darker.

The alignment was done to spec., but the problem persists. It does sound like it can be a tire issue. If I had the alignment checked in a month or two and it was still spot on, can this eliminate broken/worn parts as the culprit and make the tires the blame here?


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[JusticePete]

Originally Posted by StlRomAniaN

Thanks for all of the information.

Well, I noticed the issue when my rear bumper was turning black. It progressively got worse when the bumper got darker.

The alignment was done to spec., but the problem persists. It does sound like it can be a tire issue. If I had the alignment checked in a month or two and it was still spot on, can this eliminate broken/worn parts as the culprit and make the tires the blame here?


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Done to spec... factory tolerances are a degree. A degree is HUGE. Can you post the alignment sheet?

[StlRomAniaN]

Yes. In a second. I used your aggressive street settings.


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[StlRomAniaN]

Before on the left and after on the right.




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[christianchevell]

The car sitting on badly worn tires that wore unevenly and that could be defective and is not the best way to start with alignment especially if out of balance too much as the tire may fit but it may never sit right..is kind of the point, tire wobble is not good, some people using low quality aftermarket knock off wheels in the past have reported problems. Your pics just show the average stock rubber bushings on the stock stamped steel weak toe and trailing arms that most upgrade if they are serious about keeping it planted IMO. While the alignment gets it into range for your car those specs change with lowering/ ride height and with adjustable coil overs your ride height may make a difference a bunch on handling IMO.....and feel, so its hard to tell what you have.... stock ride height coil overs......not likely ??? change in geometry and setting to the coil overs specs ....yes; add in rear end slop from stock rubber bushings and stock parts with stock maybe torque management and stabillitrac or who knows what.....

If I were you yes I would drive the suckers because you don't have a choice and look into the Phastek or other sites with so many good parts to make the rear especially perform better and check the wheels for cracks or dings or if its something else?????

Aggressive street driving with stock trailing arms,toes, upper a arm bushing/ all bushings being rubber prone to deflection, stock sways, stock end links, etc.....all things I myself plan on or have upgraded ....well not something I am too much into doing and expecting miracles from stock crap..... Heck my trailing arms and toes are a paper weight in the storage shed.... scrap. Good Luck to you! what ever you do remember everything takes money.... I know I am looking into the FAST intake and Nick Williams 102 with new fuel rails.... not cheap.

[JusticePete]

Originally Posted by StlRomAniaN

Before on the left and after on the right.




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The rear toe was really off on the before. The tech did a good job. To make this all really easy. Tak it back and have the alignment checked. If the toe is whacked again, we know exactly where to look.

[JusticePete]

Originally Posted by christianchevell

The car sitting on badly worn tires that wore unevenly and that could be defective and is not the best way to start with alignment especially if out of balance too much as the tire may fit but it may never sit right..is kind of the point, tire wobble is not good, some people using low quality aftermarket knock off wheels in the past have reported problems. Your pics just show the average stock rubber bushings on the stock stamped steel weak toe and trailing arms that most upgrade if they are serious about keeping it planted IMO. While the alignment gets it into range for your car those specs change with lowering/ ride height and with adjustable coil overs your ride height may make a difference a bunch on handling IMO.....and feel, so its hard to tell what you have.... stock ride height coil overs......not likely ??? change in geometry and setting to the coil overs specs ....yes; add in rear end slop from stock rubber bushings and stock parts with stock maybe torque management and stabillitrac or who knows what.....

If I were you yes I would drive the suckers because you don't have a choice and look into the Phastek or other sites with so many good parts to make the rear especially perform better and check the wheels for cracks or dings or if its something else?????

Aggressive street driving with stock trailing arms,toes, upper a arm bushing/ all bushings being rubber prone to deflection, stock sways, stock end links, etc.....all things I myself plan on or have upgraded ....well not something I am too much into doing and expecting miracles from stock crap..... Heck my trailing arms and toes are a paper weight in the storage shed.... scrap. Good Luck to you! what ever you do remember everything takes money.... I know I am looking into the FAST intake and Nick Williams 102 with new fuel rails.... not cheap.

A quality alignment does require the tires to be correctly inflated. Worn is ok if the diameters of the tires are close to even. moderate wear on the shoulders will no alter the alignment.

The parts coming from the factory are damn good these days. 1LE/ZL1/ Z/28 monoball toe links and Z/28 trailing arms the BEST solution for a street driven Camaro.

[StlRomAniaN]

Originally Posted by JusticePete

The rear toe was really off on the before. The tech did a good job. To make this all really easy. Tak it back and have the alignment checked. If the toe is whacked again, we know exactly where to look.

Yup. Strange that it was that off. I was surprised on how well they aligned it this time around.

If the alignment checks out when I take it back, then it's the tires/wheel balance issue? Could it be the differential like someone mentioned?

If the alignment is off again, then the bushings on the tie rods, etc?

The bushings is something I've ignored and I know it's the "lowest hanging fruit". Considering I have your coilovers and sway bars, which bushings package can "complete" my suspension.


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[JusticePete]

Originally Posted by StlRomAniaN

Yup. Strange that it was that off. I was surprised on how well they aligned it this time around.

If the alignment checks out when I take it back, then it's the tires/wheel balance issue? Could it be the differential like someone mentioned?

If the alignment is off again, then the bushings on the tie rods, etc?

The bushings is something I've ignored and I know it's the "lowest hanging fruit". Considering I have your coilovers and sway bars, which bushings package can "complete" my suspension.


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If the toe is off again, we have found a problem. There could be others, but we take this one step at a time.

If you brought it to my shop, we would

Do a visual inspection for broken or damaged
Lay a wrench on every nut and bolt to make sure they are good and tight, mechanic tight.
If we found nothing, pull a toe link and trailing arm to inspect the bushings.
Still nothing, road force the rear tires to see if they are bad.
Still nothing, continue on to the differential to inspect those bushings.
Still nothing, we are looking for a bad monoball so we check all six
We keep systematically digging until we find the source of the problem.

I'll be waiting to see what the alignment reads.

[Jrichards73]

23 months on tires!? How the hell?...

[StlRomAniaN]

Originally Posted by JusticePete

If the toe is off again, we have found a problem. There could be others, but we take this one step at a time.

If you brought it to my shop, we would

Do a visual inspection for broken or damaged
Lay a wrench on every nut and bolt to make sure they are good and tight, mechanic tight.
If we found nothing, pull a toe link and trailing arm to inspect the bushings.
Still nothing, road force the rear tires to see if they are bad.
Still nothing, continue on to the differential to inspect those bushings.
Still nothing, we are looking for a bad monoball so we check all six
We keep systematically digging until we find the source of the problem.

I'll be waiting to see what the alignment reads.

Thanks. I'm going to get the alignment checked after another week of driving. My bumper isn't black with tire rubber like it was before the alignment, but the shaking under full throttle still persists.

I'll get the alignment checked, as well as the balance of the wheels.

However, while driving, I do notice a bit of a hopping sensation in the rear when I let off on regular driving. For instance, if I'm in 3rd/4th gear cruising towards a stop light and I let off, there's a bit of a bounce/hop. It feels driveline-related, almost like the differential is moving.

But, this is all speculation. I'll report what I find out when I get the alignment and balance checked.

[StlRomAniaN]

I'm going to put my GoPro under my car this weekend and accelerate a few times. I'll make sure to get different angle. Left rear, right rear, differential/driveshaft, and on the fender looking at the outside of the wheel/tire. I'll then review and hopefully I'll see the movement/wobble/oscillation that I'm feeling.


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