i have a 04 coupe 6MT. when i'm taking a curve at around 30 to 50 mph (like on an off-ramp from the freeway) and if i brake a little bit at the same time, it feels like the ABS activates and locks up the tires. this happens regardless of whether the traction control is on or off. there's usually loud thudding noise, and the car jerks. it's quite unnerving. i took it to an infiniti dealer and they checked all the TC sensors and found nothing wrong. they only thing they could tell me is that maybe the non-OEM brake pads (i replaced the all 4 stock pads with Axxis Ultimates) are the culprit.

now, i'm thinking that this condition may be caused by the tires. i have yokohama avs es100 tire on one side of the front, and the stock michelin PS on the other. the rears are both yokos.

can anyone shed some light on what might be causing this condition? i suspect the mis-matched tires are the reason, but i wanted to see if anyone has had a similar problem. thanks.

 

I have mismatched tires, no problem here.

ABS works by monitering the speed at each tire, senses a skid, and tries to fix it.

I have on a few occasoins been taking offramps at pretty quick speeds, and was able to get the back end to come loose due to braking without the abs coming on. It only happened when I started braking well into the turn. Doing so, because the weight has not properly transfered to the outside wheels for optimum braking, causes a little bit of lateral skidding, but the tire continues to turn, at least enough not to induce ABS. Its somewhat complicated vehicle dynamics.

Anyways, when that occurs, releasing the brakes immediately causes the rear end to "snap" back in place, because the tires are already spinning, and the vehicle wants to quickly return to a "proper" path of least resistance, which is with the rotation of the tires. (Similar to spinning the tires, having the back end come out, then getting off the gas, the back end immediatetly lines back up with the front of the vehicle).

I *think what you are feeling is that snapping. ABS should in NO way make your wheels "lock" up, and if they did, you'd skid off the ramp, remember, skidding tires have NO turning ability, so you'd continue in a strait line from the bedining of the skid.

 

make sure you are not rubber. Might be your fenders. if not have your dealer take a look. good luck.

 

^^ what he said, because when your rubberized ankle tends to extend and retract at a high pace during braking, its not steady and will lock the wheels up accordingly.

Whenever ABS activates, it does not lock up the wheels, hence ABS=Anti-lock Brake System. Sometimes mismatch tires screw up the rotation and will interfere with the ABS.

Mismatch tires could have different diameter even though it has the same sidewall numbers. Example, my Toyo T1r sidewalls are thicker than the Pilot sport even though both is 45 series.

 

I bet the different tires are the reason. They are probably causing the wheels to turn at different rates. Also diff tires have diff braking characteristics, compounding the problem.

 

thanks everyone. so you all don't think it's the axxis ultimate pads that's causing the problem. that's good, because i like the axxis pads much better than the oem pads, and dont want to switch back to oem.

i'm gonna keep a close eye on the sole michelin ps on the front. the tread looked good last time i checked, but the car does have 35k miles and it might be time to change that out (with matching yoko avs).

the feeling is definitely that the brakes are being activated by the ABS. it doesn't lock up the tire (i misspoke in the original post), but the pads grab the rotor much harder than the pressure on the brake pedal with my foot, causing the car to jerk back and forth.

 

Your tires will ALWAYS rotate at different speeds when you turn, regardless of mismatched tires, thats not the problem (meaning causing ABS to kick in becasue of mismatched tires). Outside tires have a longer distance to cover in the same ammount of time as you turn, therefore they rotate faster.

By your second description, you're clearly loosing tractoin in the corners. Check your tire pressure. Have you changed anything in suspension?

 

Good point, im worried about this matter as Im considering replacing worn tires with bfg kdw t/a2's

 

With any system one tire will lock BEFORE another even in the exact same brand size there may be an age diffence and thus a difference in the coefficient of friction or a 0.1 degree difference in camber or caster or toe.

There will be a loaded weight diffence even 10 pounds is enough to change the friction. 1.0 psi tire pressure is enough to cause problems.

There can be a tread depth diffence and thus a diffence in friction.
Perfection requires perfection of all components.

Cars handle differently turning left from right [driver weight in seat] different as the gasoline level [weight] changes from consumption.

All a lock up tells you is that tire is slipping more than another