I have a 2003 performance and after every time I hit the brakes in order to stop suddenly, the next time I touch them they are very sensitive. If I as much as touch the brakes after, the entire car seems to come to a halt.

Is there a reason for the brakes acting this way?

Does everybody else have the same occure to them?

Anything I can do to continue the brakes consistency in feel?

Thanks for all your input and assistance with this matter.

 

I have noticed on my Touring 6 speed that the brakes are a little soft when first used then firm up if I press them again. This tells me there is air in the lines. Dealer said there was no issue -- yeah right.

Try this:
1. Bleed brake fluid from all 4 wheels and see if any air comes out. If you get some air then that is the problem. Note also that there could be some air in the ABS unit and may need a special bleeding procedure.
2. If no air comes out then it is possible one of the calipers has a sticking piston. Have the brake pads inspected for wear. If there is a problem with one of the calipers then the pads will have unusual wear compared to the other caliper on opposite side of the car.
3. If you want more consistent brake feel then stainless steel lines are the way to go. Stoptech sells some very nice as well as tirerack.

Ja

 

That's the way they are supposed to be.....not soft and pushy. These are very good brakes. You just need to learn to modulate them.

I wish they grabbed better on the initial pump.

 

This has to do with the brake booster, regardless of whether you have the stock brembos or not. I have the same issue on my car and it drives me nuts. I like 1 inch of travel and then wham! brakes. The only fix that I can think of is to adjust the nut on the brake input rod. It is located at the top of the brake pedal. You simply disconnect it and then twist it a turn or two. PLEASE NOTE: I have not done this and if you over do it, you may lock your brakes. Be carefully and for the love of God you are at your own risk.

The other option is to put in a thicker aftermarket pad. I put on Ferodos for the track and the initial travel was much shorter. However, as the pad wears away, the travel will become longer. In addition, my review of the Ferodo DS2500 is that they are not streetable. You may find another brand that is.

 

How many miles on your car? If your car is new, the piston seals may not have broken in completely and they could still have a strong "spring" action, causing the pistons to retract slightly after you release the brakes. This means that your first application of the brakes requires some extra travel to get the pads back in contact with the rotors. A second application of the brakes immediatly afterward will not require as much travel and the brakes may feel more sensitive. If so, this should go away or be reduced after you put some miles on the car.

You could be describing a phenomenon known as "pad knockback" where the pads are pushed back into the caliper body by runout in the rotor. The runout can be caused by thickness variation on the rotor surface, runout on the hub to which the rotors are mounted, or deflection of the wheel bearings caused by turning forces.

 

I currently have approxiamtely 3900 miles on the Z.

I don't think it might be pad knockback because I can slam the brakes and have a much shorter brake pedal travel till the brakes engage (violently), park the car for about 8-9 hours, get in drive and still have this issue until a while after driving it normally. Basically, I just have to drive the car for the brakes to go back to normal.

I'm going to the dealership this Thursday and I'll ask them, but frankly I put more trust into some people on this site than I do the dealers.

 

I asked my dealer, who seemed reliable in thier statements, about the stiffining brake issue and they said that its normal for the non-brembo 350zs.

They seemed very eager to assist me with everything else that I had, so it doesn't seem like they would just make up some story just to not deal with the issue.

 

Hey dudes, it is not that complicated about bleeding brakes, pads, calipers, etc. It is simply called a lack of available vaccuum on the initial pump and then it builds up when you pump them up. Turn the car off and pump the brakes. The brake pedal will get solid. The motor takes vaccuum to run. So do the brakes. You take vaccuum from the motor to run the brakes. The first pump has less vaccuum dedicated to the brakes because the motor has been running. On most cars, don't know about the Z, you can make the idle move by pumping the brakes when stopped. That's all it is. All cars react this way.

 

I think it's the electronic brake force distribution that is causing that. Not 100% sure tho.

 

All that does is redistribute braking force from left to right and front to back based on weight and where the load is (full tank of gas/empty tank, lightened body parts/stock ones, passenger/none, etc.) It does not change pedal feel.

 

That sounds really familiar. I think that is what the dealer explained it to me as being.

 

Sounds like you've owned a bunch of 4-cylinder cars! Time to step up to some V8 power!

 

No actually I have owned/own about 15 V8's and have had one 4 cylinder and one 6 cylinder (Z). Sorry. And, what you talkin bout Willis? This is a Z forum! We don't have V8s. I really wish we did. I am sure they could add two more cylinders and still make the motor smaller and make it fit. I would have paid more.

 

LOL!! Well, at least we know they will have a turbo or twin turbo out eventually for those of us with greater pwer requirements.

Neither my 1996 Impala SS nor my 2001 BMW 540i 6-Speed idle even budges when I apply the brakes. However, my older, open loop (carburated) cars used to do that. In fact, I recall the idle fluctuating when I used my turn signals! It's possible that the added current draw from the brake lights was causing more parasitic drag from the alternator and slowing down the idle. A little experiment to determine contribution of vacuum production to idle slowdown would be to pull the brake light fuse and see if the idle still drops and by how much. That would isolate the vacuum effect from the parasitic drag/alternator effect.

 

Geez I would hope electronics would not vary the idle anymore. The alternators are sure putting out a lot more than they used to though so I would think it would be less of an issue... But I do think that the mechanical aspects involving vacuum still share. But anyways.