CGexM5

Hi All,
I'm a newbie and have had my LS since 12/9/06. I now have about 2100 miles and have enjoyed the car tremendously with one glaring exception. I have noticed that with moderate to hard braking (not panic stops), braking pressure varies with pedal pressure remaining the same. It's as though I am applying varying pedal pressure when I am not. It's quite unnerving and results in, I believe, quite long braking distances. I am aware of Road and Track's braking distance from 60 to 0 number being quite high at 140 ft. and wonder if that is part of the reason. Is this normal and if so, why in the world would Lexus have a braking system like this?
Thanks for any thoughts on this.
CGexM5

rominl

iTrader: (4)

umm, have you gone to the dealer and have them check the brakes? i wonder if you have air bubbles inside the system. to me that's the main reason why you feel different braking power with the same pressure on the brake pedal.

regard R&T, i thought that's due to the tires?

btw, welcome to CL!

CGexM5

Thanks for the welcome and your input! I have not yet contacted my dealer about this but unless I hear otherwise from the Board members, I will assume that this is not normal and give them a call to bring it in for a check.
CGexM5

widlfiresd

The issue you described is normal. The technology is called adaptive braking (or in Lexus terms "Brake Assist"). Most premium cars have this technology now. It has been around for a few years. If the car senses you need to stop somewhat aggressively, it will assist you in providing additional brake boost in an attempt to slow the car down faster.

Research has shown that when a typical driver is in a panic stop situation, the ABS kicks in, the get scared and let off the brakes. They think the car is broken. The answer, if you slam on the brakes let us help you in case you chicken out.

Once you get used to it, you will appreciate it.

Lexus really needs to get a clue and offer driving schools like BMW. A day or two learning how your car performs is well worth it. Right now the only time a Lexus owner realizes the potential of the car is when they are in an accident, but by then it is too late because they have no training on how the car would perform during accident avoidance.

From Lexus web site...

"Brake Assist
In some instances, drivers fail to push the brake pedal hard enough to engage the Anti-lock Braking System (ABS). Brake Assist [1] senses a panic-stop scenario by judging how quickly and how forcefully the driver hits the brake pedal, automatically applying increased braking boost until the driver releases pedal pressure. "

dimapb

I'm having the same issue and that is what I've been told also. It's a feature not a bug. You'll get used to it.

Dmitry

CGexM5

This is not just increased brake pressure. It's increased and then decreased pressure. It cycles back and forth as though it can't make up its mind. I'm pretty familiar with how brakes should work having been to three Skip Barber driving schools (regular and high performance) and having had an M5 and gone through that two day new owners program back at the plant in Spartanburg, SC. This just doesn't seem right to me.
CGexM5

widlfiresd

When did you get your LS? Right when they came out? If you feel the car is not modulating the brakes correctly, there might be a software update to address the issue.

Of course, the system could be working as designed and you just do like it. In which case I would let Lexus know.

I have seen with my BMWs, even though something is working as designed, they do not always program the car to meet customer's needs adequately. i.e. touchy brakes, tranny shifts to rough or to mushy, etc. So BMW is known for coming out with software updates to modify the car's behaviour based on customer feedback.

CGexM5

I think I'll take it in just to be sure. It's possible I could subconsciously be decreasing and increasing brake pedal pressure to compensate for the action of the braking system. I'll try testing it again before I take it in. "Behaviour". Are you a brit by chance?
CGexM5

widlfiresd

Irish, and we can't spel either.


Behavior for you.

Barrynsh

I agree with you. Even prior to your first note about the brakes I noticed that when I spply even pressure to brakes, enough to slow the car down gradually and in a linear fashion that the amount of braking varies with time and frequently if I don't let up on the brakes the car, on its own will stop far short of the planned stop point. It seems that the braking gradually increasses by itself without increasing the braking. It does not feel natural. Possibly it is because was driving caddy's for the pasts 30 years and this has not been a problem.