The G Man

Does anybody feel like the ABS system is overly active on the Q5. We have brake in a few snowy situation where the ABS kicked in and we were going very slow. I did not feel any skidding, I know that sometimes you do not feel it, but I do think the ABS is activated faster than most other cars that I have driven.

kleinbus

And the tires are?

No one can really help you as non of us weren't there on same conditions as you were.

All I can say is that I had my crappy all-seasons on for 2 hours to test them, traction control and ABS was on when ever I hitted gas or the brakes.

Swapped to real winter tires and now it is like it's supposed to be and on bare snow I really have to floor it to get traction control active and well the braking is normal winter braking, meaning slow down early

All-Seasons are doable, you just need to adjust your driving style the way when ever ABS comes on it means you were going too fast for conditions and tire traction.

No matter of all these fancy electric gadgets, ABS, ESP, ASR few to mention, we should drive the car like we used to drive on old days without ABS brakes and other safety features.

There was no traction control so we spun the wheel and got stuck and hopefully learnt how to avoid it in future. Same was with brakes, slam the brakes and locked them, either slid off the road or learnt to release them and have somekind of control of the car.

ABS actually does not give you shortest stopping distance as when ABS is active, it does "free-lock-free-lock-free" cycle and that makes stopping distance longer than braking the way ABS does not come active, like we all used to brake when there was no ABS systems.

Now this sweet spot of pedal where it provides highest braking and allows wheels rotate and does not activate the ABS, works well for normal smooth surfaces where all wheels have equal traction.

Well there is times when one side of car is on more slippery than other side so ABS comes on anyway and there not much we can do. Mostly there is no space to move sideways so we have to stick on path we are, sometimes there is room on each side so we could release brakes and move car feet or two either side to search better traction and then brake again.

Below is photo from icy road where car tires have grinded ice off all the way down to black pavement that happens to be really icy and more slippery than the white part. Up north where this road weather camera photo is, I used drive on that black rail and it is smoother than white part but when ever I need to slow down, first I came off from black rail and while on white, I applied the brakes and had no issues to slow down.

guyguyke

up to now, the ABS works just fine, I had to brake harder than necessary to verify it worked
I've no winter-tires and drive carefully on snow
the (virtually new) Dunlops Sport /19" cope reasonnably good with icy roads, due to quattro...
I feel much safer than in my former A4 (FWD)
PS : ABS is not less intended for braking than for guiding the car: on very icy roads, the ABS only helps making the braking distances ... longer

flogsta

I have All-Seasons on and it shows just like The G Man describes. I agree with Kleinbus - I adjusted my driving style. Not so much a problem here in Toronto if the main roads are clear of snow. Most likely will get Winter Tires ;-)

kleinbus

ABS is one darn good aquipment when each wheel have different traction as vehicle without ABS brakes would locks those wheels on pure ice and brake wheels in more tractive snow.

Though there is one condition where ABS sucks and it is more dangerous than vehicle without it. Normal gravel road and generally sand surfaces are worst as ABS does not allow the wheel lock and dig in. I have had so many hairy moments on gravel when rocks behave like a little roller bearings and ABS just keeps its sound and barely slows down. Later another day I happened to drive same gravel roads with old car without ABS brakes and once wheel locked, it digs in and stops like nothing.

This gravel issue caused some manufacturers to add gravel program to ABS system and for example, VW Tiguan with Track & Field package (not sold in NA) and Touareg haves that feature.

The G Man

I have the Good Year Eagle LS, its didnt get very good rating for light snow. I have own other Audi with all season tires as well as other SUVs. It just seems to be that the Q5's ABC is over active. Just wondering if other owners have the same experience.

kleinbus

I saw similar debates about ABS over-sensitivity on other VW and Audi forums and it got a bit flamy so I'm not trying to have a camp fire here….


First folks, watch these few videos, sure not Audi but points out the difference between tire types.

The last test, going around the curve is worth of attention.
http://www.tirerack.com/videos/index.jsp?video=23&tab=winter

Ice hockey rink,
http://www.tirerack.com/videos/index.jsp?video=26&tab=winter


I'm design engineer and currently working on 18 wheelers emission control, drivetrain and brake systems (including ABS).

Generally speaking ABS system consists brake unit that haves wheel sensors on each wheel, computer controlled pump and valves to decrease and increase brake pressure individually on each wheel ( on 18 wheelers I would say on each hub as there is single wheels and dual wheels depending axle).

The computer monitors and compares rotation against each wheel every 0.01 second (or so) and during deceleration, compares vehicle acceleration sensor, steering wheel shaft angle, tire rotation and locking between each wheel.

Modern cars have even acceleration sensor the way even if some weird way wheels would be locked while car goes 40 mph on pure ice, acceleration sensor would tell computer that the vehicle is still moving so release the brakes. Among that there is steering angle sensor and bunch of others that works along with stability control etc.


Now to the topic itself, the over-sensitive ABS system.

Before I go further, how and where this over sensitive situation happened?

Different situation affects different way and for example,

a) Slamming the brakes on straight road and ABS comes on and it is truly depended on tires and road surface.

b) Cornering a bit too hard on icy road the way tires already are on its friction limit and then slamming the brakes and nothing barely happens as there is no enough friction.

c) Coming from main street to go over the curb to driveway. Driver slows down and turns same time and speed drops below 5 mph to go over the curb. ABS system stops functioning below 5 mph and if pedal is still pressed it will act as normal brakes and lock the wheels and make car slide.

B may activate the stability control as it is trying to keep the vehicle on curve as most of activity goes to control the wheels to align and keep the vehicle on its own lane and barely uses brakes to slow down.


This slow speed locking can be seen on that ice hockey rink test, vehicle haves slow speed momentum but the wheels are completely locked.

There is no sensitivity adjustment on ABS system as the wheel either slips or not and only sensitivity is via tires and current conditions. Normal snowy road gives relatively good traction but powder snow on top of ice is one of the worst.


Even my ABS comes on once awhile no matter I’m trying to drive to way it does not activate as to me it is sign I’m going way too fast for conditions. Like when I came home today, slowed down on main street and turned to side street and then turned to our street and while slowing down to turn to ours, one of the front tires hit the patch of melting snow-slush stuff and front tire ABS came on, I eased the brake till I released it completely and rolled to our street and went home.



Now to compare 18-wheeler against the passenger cars, the unsprung mass it the key and that is also the reason that big-rigs should be driven the way ABS does not come on.


On passenger car where tire-rim-brake disc-hub combination weights about 50 lbs (or what ever, just to point out it is relatively light) the lock-free-lock cycle is fast and while on normal snow surface, once ABS pump releases the brake pressure on locked wheel, it gains rotation within few inches and that allows maneuverability and then it locks again.

On 18-wheeler, the single wheel-rim-brake drum-hub combination is about 200 lbs and dual wheels are about 500 lbs, so when dualie is doing its lock-free-lock cycle, the higher mass takes longer to gain the rotation and so 18-wheeler maneuverability is much slower than small cars. Sure empty versus loaded is another story...

<O</O

The G Man

I feel the over active ABS mostly on just straight stop on a red light. Again I am comparing the Q5 to other AWD sedans and SUVs with different tires.

ttman00

I find the same thing on my 2011 Q5.. I Have Blizzak tires and there have been times the vehicle rolled me right through an intersection and it didnt even seem that slippery out.. Wheels never locked just he ABS rolling me through. Anyone else find this? Is there a problem with the ABS?

motoguy128

Early season storms bring 2 things, ice, and heavy wet snow and higher ambient temperatures. The warmer snow and ice are, the less grip they have... generally.

Most ABS system are pretty comparable these days.