I know I get this, as well as you Brembo boys and girls. For those who are not familiar and wonder what's happening when the pedal goes soft on an otherwise perfect brake package...

Knockback

 

Droideka- Great article- I love my StopTech's but admit the minor knockback caught me off guard at first. Now that I'm used to it I don't even notice anymore. Thanks for posting.

 

Great article! Thanks for sharing!

I "tracked" at Gingerman in my Z. I experienced the same thing. I Never experienced the problem at Blackhawk Farms......... I thought it was caused by the power brakes, vacuum controlled, causing the problem, as WOT produces NO vacuum. Nick at H-Tech is working on a vacuum tank for curing this.


BTW, Gingerman was the first time I documented slipping the tire on the wheel from braking. Sooooooo, I (ab)used my StopTechs with Panther +'s.


What the heck is really happening?

 

Are some kits more given to knockback than others?? A friend has an AP kit and seems to be sufering of severe knownback, for what he claims...

I would assume material (thicknes, quality) of the rotors could make for major knockback issues...

 

per my other post...

This is definitely knockback. Knockback is not a 'kit-specific' phenomena...it is a platform specific phenomena. In other words, it's not the fault of the AP kit per se, but a fault of the 350Z design. We've heard of knockback occuring with our kits, AP kits, and stock Brembo kits. The bigger rotors do tend to exaggerate the problem vs. the smaller rotors because the lever arm is longer.
What is the solution? Well, there really isn't a great one at this point. Knockback is something that OEM's have been dealing with for a long time. If you ever watch pro racing, you'll see drivers tap their brake pedal before they go to full stop on the pedal...the taillights will flash, pause, and then go on. That is the driver making sure his pedal is there when he needs it!

On the 350Z, there is some play in the bearing and hub assembly. This is also a problem on the WRX and a few others. The only solution right now is to basically take up as much slack in the tolerances as possible. A pro race team with a Z would disassemble the hub, etc. and blueprint the whole thing to 'tighten' up the tolerances. That means less flex in the system as a whole, and less knockback. For the average Joe, this is not a reasonable solution.
My advice would be this: If you are on a track with a sequence of left right switchbacks, followed by a straight with a big brake zone at the end...you might want to check your pedal before you hit the turn full blast. That would be the worst case scenario where knockback would occur and may catch you out.

My engineers are working on a solution to this problem as we speak.

 

intersting read. The same thing happens when I race my motorcycle on the track. After a big "tank slapper", where the bars deflect violently upon existing a bumpy turn on the power, the pistons and fluid pressure get pushed back slightly. Next time you pull in the brake lever, you have nothing.....very scary if you are going 160mph at the end of a straight away...and need to slow down to 40.

 

Awesome article! I experienced this exact problem after doing figure of eights around cones during a HPDE event in my Track Z with Brembo's!

At that time, about a year ago, I asked alot of folks but no one really knew what was going on. Now I know!

If someone comed out with a fix, I'd sure like to know.

Thanks again.