point2point

I took the day off work to drive the local twisties free of traffic. Today's playground was the Ortega Highway (SR74).

I experienced something on this drive I've never felt before. On long sweeping corners, I could feel a buzzing sensation through the steering wheel. I'm not sure, but I think I could also hear it. This only happened with a good amount of cornering load and only after 30 minutes or so of spirited driving. The weird part is that it was intermittent through a single corner - buzz, pause, buzz, pause, buzz. Each time after feeling this, I would get a very solid brake pedal at the top of its travel. Could this be some driver assist electronic intervention?

This completely sapped my confidence, and I slowed things right down for the drive home.

sfo

how old are your front tyres? are they much different in thread depth and age compared to rear tyres?

last year I replaced my rear tyres, but not the front. Fronts still had 5mm depth despite having done about 15k miles (rear also did 15k miles).

When I was in the Alps driving spiritly, I experienced similar sensations to you, but not just high cornering loads. Felt like ESP or TC constantly active. Maddening and made the car feel really unstable. Horrible.

Replaced front tyres, all fine again.

Clearly, front tyres were dead as too many heat cycles.

point2point

It did feel like a front tire issue, but all four tires are pretty new. I think they only have around 1000 miles on them.

Larry Cable

I dont think that the (power) steering and braking (pressure) systems are connected so I am not sure what the cause would
be that resulted in the solid brake pedal.

I would be concerned that any such effect could be a serious issue, I presume there are no fault codes present?

what was the air/ground temperature??? (thinking acorns)

tire pressures?

did you try turning off the TC/SC - did you notice the dash light signalling its intervention?

PASM normal or sport?

sometimes the ball joints on the steering rack need lube which results in a "creaking" that you can feel thru the steering wheel when turning ...

Protocav

I had a very similar sensation which I thought was piston knockback, so I rebuilt all of the brake calipers. This did nothing. I took it out again, and turned the stability control off, and it went away. I think this is the computer interfering a little bit when it senses that the wheel speeds aren't where they should be. This can be from an aggressive alignment or possibly tires that aren't exactly what the computer expects.

point2point

Tire pressures were normal.

I didn't think to turn off TC/SC, but in hindsight I should have tested that. The dash light did not come on. In the moment, I feared it was some kind of mechanical fault. I had not thought of electronic intervention at the time because the cornering loads were not super high, and I had taken similar corners minutes earlier at much greater speed.

Protocav

The sensation would happen on mine at very low speeds and g loads, specifically on long sweepers. No dash light either.

Larry Cable

I would repeat the drive with TC/SC off to see if that makes a difference...

Larry Cable

re-reading this, I think that its significant that you only started to experience this once the car was "hot" *and* that you experienced a hard brake pedal... definitely leads me to think
that it may be brake and TC/SC related... note that not all
TC/SC intervention will result in lighting the dash indicator,
for example ABD does not... although ABD is relegated to
rear wheel only operation as I recall ...

CosmosMpower

I've never felt this before even with -3.5 camber in the front. I'd rebalance the tires anyway.

charles06

I experienced the exact same on my 2011 GT3. When I turned off SC, all was fine. After a new alignment (nothing aggressive/special), it seems to be gone. Not sure if this is the same as OP, but definitely the same as described in the quote.

point2point

I did the same drive earlier this week. The only difference is that I have a fresh alignment. About 20 minutes into spirited driving, I experienced the buzzing/chattering sensation again on sweeping corners. This time, I turned off SC. I had no issues whatsoever for the rest of my drive, even taking some turns at pretty high pace.

Larry Cable

H'mmm so probably not an issue with the power steering (since disabling SC negates this) ... has to be an issue with the PASM *and* SC ... can you try with PASM normal/sport toggled to see if the issue changes when the shock response is changed (with SC enabled)?

p.s chattering suggests perhaps ABS intervention to me ... buzzing not so much

nwGTS

next time can you apply VERY light brake pressure with your left foot while trying to replicate the situation? If you feel a pulsating in your foot coinciding with the sound/sensation through the steering wheel it may indicate ABS intervention as Larry said. i'd toss the wheel speed sensors on your 'to check' list too. i've heard (and read here) of issues with those playing havok with TC/SC systems.

steve porter