I own a 2006 Toyota Highlander Hybrid and yesterday someone cut me off at the mall and I was going about 25 MPH so I slam the brakes all the way and I saw the yellow sliding car indicator blink, but it felt like the front wheels locked up. Is that normal? I know the car I used to have an 04" Chevrolet Tahoe when you slam on the brakes it will pulse violently and none of the wheels would ever lock up. I am not sure if the tires actualy locked up or it just felt like it because I did not try to swerve, but it did feel like the front tires locked up.

 

The highlander Hybrid has a brake-by-wire system so the ABS activation does not pulse the brake pedal like conventional hydraulic brakes do.

 

But the tires are never supposed to lock?

 

ABS: Anti-Lock Braking System.

 

I disagree with Ron R. I put my 400h into an intentional skid a snow covered road to see how the ABS would work, and the brakes do pulsate in bringing you to a stop in those conditions. The pulsating is gentler than some vehicles I've had, and they kind of alternate left, right, left, right. They worked quiet well.

On dry road conditions, maybe it takes more to cause the pulsating to kick in, I don't know.

 

ABS kicks in When the tires lock. ABS is a compromise between maximum breaking and skidding.

 

The ABS does not pulse the brake pedal as a side effect of ABS operation as is common in conventional brake systems. The brake pedal remains relatively vibration-free during ABS operation due to the brake-by-wire system.

The ABS system in the Toyota hybrid vehicles pulses the wheel cylinders as all ABS systems do. The fact that the brake pedal does not violently vibrate under your foot when the ABS is pulsing the wheel cylinders may lead some to doubt that it is working.

 

How much wheel lock is the Highlander Hybrid supposed to allow?

 

When on very slick surfaces such as ice, the ABS pulsing of the brakes will be at a much slower rate than when on a wet surface with more friction.

The idea behind ABS is for the brake to actuate until the wheel begins to slip- then the brake releases to allow the wheel to begin rotating again - then the brake again actuates until the wheel again slips - and on and on.

On ice, a skidding wheel takes much longer to begin to rotate again after the brake is released because there is not as much friction with the road to get the wheel rotating as quickly. Thus, the ABS pulse rate naturally becomes slower as the road surface becomes more slippery.

The Highlander Hybrid uses the electric motors to help accelerate the wheels during ABS braking activation under very slick conditions by providing some torque to the skidding wheels when the brakes are released during each ABS brake pulse cycle. The faster the wheels can regain rotation between each brake pulse period, the more effictive the ABS effect will be.