[Val Walkinshaw]

I've tracked my car a couple of times, autocross, many spirited trips to Tail of the dragon and so far with 22,000 miles on my 18 2ss m6 my brakes have been flawlessly smooth. Literally one day last week out of the blue a shimmy developed when braking at freeway speeds 65-75. Not below that though. It's noticeable even to the passenger and you can feel it in the seat and see it in the wheel. However it is not felt in the pedal. It's not obnoxious and it's something I can live with however it's clearly noticeable.

OEM pads and rotors. I'm running 1le size tires and aftermarket wheels all which are routinely checked and torqued to 140. Before I dive into this I'm looking for suggestions as to what I should be keeping an eye out for.

I saw where somebody had posted an article about brake deposit but I can't seem to find a working link.

With the different activities the Camaro has been involved in and my driving style I was rather surprised it took 22,000 miles before I felt anything like this. However it's surprised me to be out of the blue one day when I was just cruising around some Ohio back roads at leisurely speeds.

Thanks in advance .

[Alpha1BC]

Can you feel it in the steering wheel at all? Or in the shift knob if you've got a manual trans? I have no doubt it's rotors/pads if you only feel it when braking, but depending on where you feel it can help point at which axle the issue is on. You won't necessarily feel it in the pedal. Can try lightly sanding rotors to get rid of uneven deposits, or if you've got a dial indicator or something similar you can use that against the rotor face as you spin it to check for warping.

[WhiteMale]

You could try to bed the pads...do ~6, 60-10mph very hard braking runs. Don't come to a stop on the slow down. I think a warped rotor will vibe the steering wheel and not the pedal.

[Alpha1BC]

Originally Posted by WhiteMale

You could try to bed the pads...do ~6, 60-10mph very hard braking runs. Don't come to a stop on the slow down. I think a warped rotor will vibe the steering wheel and not the pedal.

I wouldn't advise that. Brakes will already be well bed-in at 22k miles (even if only gentle street driving) and doing hard stops like that with the current symptoms could make things worse.

[WhiteMale]

Originally Posted by Alpha1BC

I wouldn't advise that. Brakes will already be well bed-in at 22k miles (even if only gentle street driving) and doing hard stops like that with the current symptoms could make things worse.

It cost's nothing and won't make it any worse.

[Alpha1BC]

Originally Posted by WhiteMale

It cost's nothing and won't make it any worse.

If it's due to pads being at the end of their life or a warped/damaged rotor, it would make things worse and could even be catastrophic. Taking wheels off and checking the condition of components also costs nothing and doesn't risk brake failure at higher speeds in the process. If pad life is still OK (>3-4mm pad material remaining) and rotors show no sign of warping via a dial indicator or other wheel-off check then by all means try re-bedding. Given the age and heavier usage of the OE components, assuming original from the factory on a non-1LE SS, it's a pretty safe bet that something is at the end of its life which would pretty much be the worst possible time to try re-bedding brakes. I had completely used (<1mm pad left) 2 sets of front pads, one set of rear pads, and one set of front rotors on mine with moderate track use by the time I hit 11k miles. With OP having double that mileage, somewhat similar sounding usage, and brakes that wear slightly faster I'd be shocked if at least the front original brakes weren't due for replacement.

[Gunkk]

If it was in the pedal, you would expect varying pressure in the brake fluid, which would be caused by a warped disc pushing against the pistons. Since that's not the case here, then 90%+ chance this is just an uneven pad transfer "hot spot" on the disc. The binder material on the pad normally transfers a little bit to the disc and creates a thin film. This film is sticky, and if the transfer is uneven can create a "stick-slip" type of behavior that results in a shake/shimmy you can feel in the car. Such things can happen after a hard stop, driving in rain, washing the car, or just at random.

Pull the wheel, clean both sides of the disc well with brake cleaner, then re-bed the brakes.

[Alpha1BC]

Originally Posted by Gunkk

If it was in the pedal, you would expect varying pressure in the brake fluid, which would be caused by a warped disc pushing against the pistons. Since that's not the case here, then 90%+ chance this is just an uneven pad transfer "hot spot" on the disc. The binder material on the pad normally transfers a little bit to the disc and creates a thin film. This film is sticky, and if the transfer is uneven can create a "stick-slip" type of behavior that results in a shake/shimmy you can feel in the car. Such things can happen after a hard stop, driving in rain, washing the car, or just at random.

Pull the wheel, clean both sides of the disc well with brake cleaner, then re-bed the brakes.

You can still have a warped rotor and not necessarily feel it in the pedal with fixed calipers. With a "wavy" rotor you can still get brake torque pulses to cause a shake at the wheel but have the hydraulic pressure response to the pedal be nothing since fluid can transfer to the other half of the caliper instead of just back to the pedal like a floating caliper would. To get pressure pulses back to the pedal you'd need varying thickness in the rotor. Not trying to say it's definitely a warped rotor, but lack of pedal pulsing during braking isn't necessarily enough to rule it out (hence my initial suggestion to take the wheels off and inspect everything first before deciding what to do next).

If it's hot spots I wholeheartedly agree that taking wheels off and cleaning rotors is the proper next step, but I'd also stick by the sanding suggestion at the same time. In my experience, when the pad binding material transfers unevenly enough to feel significant pulses there are typically spots too hard to be removed without at least a light sanding to clean it off.