What on earth was that noise / vibration??

[pounamu]

I was driving to work this morning and had to break somewhat hard when a car in front of me stopped suddenly. Unfortunately, there was a ridged manhole cover on the road right in front of me. When I hit the breaks, I felt a very strong vibration right through the break pedal, almost like metal skipping over hard ridges, and heard a vibrating noise. It was very brief and stopped when the car stopped. So, I'm trying to figure out if this was traction control (I didn't notice whether the TC light was on at that moment), or if some part on the underside of the car came in contact with the manhole cover. I'm obviously hoping for the former - it's not like the Sonic's bottom sits so low that it will be in direct contact with the road, even during breaking? But if it's not TC, should I have someone check it out? The car drove fine afterwards.

(I will add that earlier this morning I had my first experience of traction control: the car decided that I was taking off too aggressively from a stop, and, the roads being a bit icy, it threw a fit. What a weird feeling, like being yanked back by a leash. I mean, fair enough, I guess, but in my defense, driving in the city of Boston is like some weird auto version of the Hunger Games, and sometimes one has to be a bit aggressive to make a light. Still, I was grateful for the "it's icy, stupid" reminder, especially since it's my first year of driving in winter conditions).

 

[TrippinGearz]

ABS I'd expect. Its no problem mine does it too altho, mostly on ice. But ABS activates when your rear end starts to detect sliding in which case gears kick in which makes the axle stop and start over and over which you can feel through your break pedal. I think anyway, that is my understanding of it.

 

[trollbait]

Sounds like it was just the ABS working as intended.

 

[ahtoxa]

Pounamu, is this your first car?

 

[pounamu]

Ahtoxa, how did you guess? It is indeed.

I'm one of those people who needs to understand everything about their technical toys, so I appreciate everyone's help!!

 

[pounamu]

Thanks guys. Good to know.

 

[ahtoxa]

Alright, I figured it was your first. It's been many moons since I've encountered anyone who was new to cars in general.

Your questions are just fine - it's great to know all about how your vehicle works. There are folks out there who care little and don't know know/forget specific features exist. I'm talking features that have buttons in the cabin, not something that works in the background and is obscure enough to forget.

 

[pounamu]

Thanks Ahtoxa! Yes, I believe that information is power... When you are informed, the likelihood of making mistakes or being swindled is greatly reduced! Also, as a young woman dealing with all things auto related, helps to have knowledge on my side when dealing with dealers and mechanics

 

[Blue hedgehog]

It was probably the abs. It doesn't engage gears though. It pulses the brake pressure extremely fast. Much faster than any human ever could. Causing the wheel that locked to spin allowing you to maintain control of the vehicle.

 

[pounamu]

Thanks so much. You all put my mind at ease!

 

[svzuki]

It is ABS.

Whenever ABS activates there will be a pulsation on the brake pedal. This is normal. There is also the sound of the ABS motor operating which is likely the odd sound you heard.

 

[pounamu]

Thank you!!

 

[Swordsmith]

Previous posters are right on ABS. Traction control, which you mentioned in your initial question, is a separate but related system. When your wheels spin instead of pulling the car forward as you try to accelerate, TC kicks in, reducing you to about 20 horsepower and keeping you there, barely able to accelerate at all, for a couple seconds. As you mention, it feels like someone yanked your leash hard and forced you to heel.

It is possible to turn TC off, a little button on the center consol behind the shifter and in front of the cup holders. Tapping this switch lights up a yellow warning on your dash, but with it off wheel spin won't engage the system, so you can just ease up a little on the pedal, regain traction, and take off, instead of dropping nearly dead while in the middle of pulling onto a road in front of a speeding Semi.

There is a third system, Stability Control, or SC. This one is supposed to help you out when it detects you are skidding, probably from taking a turn at too high a speed. Like TC, it cuts your power for a little while; it's also supposed to brake the wheels separately to correct, but there's no evidence the Sonic is actually able to do that. At any rate, this one comes up less often, but if you want to kill it as well, you can hold down the TC button for several seconds, and be rewarded by a second warning light.

ABS cannot be disabled from the driver's seat. You can kill it (and the other two systems, which all use the same circuit) by removing the ABS fuse under the hood. But I would advise against that, you're new at cars and the ABS system is inhumanly good at helping you stop your car in an emergency. Do, on the other hand, practice feeling it engage. Go out in slippery conditions to a wide open parking lot, drive at a modest speed and brake hard, feel what happens. The hammering, the noise, the tendancy to flick out sideways a little, can all be very disconcerting when you don't know what's going on.

Keep asking questions here, plenty of folks will be happy to help. We were all new drivers once, even if it was (for some of us) before the wheel was invented.

 

[svzuki]

Like TC, it cuts your power for a little while; it's also supposed to brake the wheels separately to correct, but there's no evidence the Sonic is actually able to do that.

It does brake your wheels in order to try to prevent an understeer event. ESC usually only operates down to 18kph or so. So for very slow speeds it won't help.

I have had it properly activate numerous times over the past few days.

 

[sx sonic]

It does brake your wheels in order to try to prevent an understeer event. ESC usually only operates down to 18kph or so. So for very slow speeds it won't help.

I have had it properly activate numerous times over the past few days.

Yep. and it makes all sorts of wonderful ABS noises too

I despise the system. It is extremely scary when it intervenes. It might be ok for someone who doesn't know how to handle a slide but it makes the car completely unpredictable for an experienced driver.