Well, I ran my first event with my new front Stoptech BBK, and experienced pad knockback at every long sweeper. I just read a bit about this phenomenon in the stoptech website, and just wanted to find out whether all of you track regulars are experiencing this as well.

It's a bummer because I never experienced it on the stock single piston brakes. Now, I have to tap my brake once or twice before my next braking zone.

How about you folks with the oem brembos or other BBK models? Are you guys and gals experiencing pad knockback? If it's happening with the Stoptech's, it should be happening to every brake system out there.

 

This kit uses Wilwood sl6 front and I find no pad kick back. I can hammer the brakes at 125 and slow to 45. It is great.

sorry to hear of your problem. Does Stoptech offer a fix?

 

Pad knockback is pretty common with the Track Brembo brakes as well. I think there is a whitepaper on Stoptech's website on some solutions...you found one of them..left foot tap(s) to bring your pistons to your pads and pads to your rotors. Another option, they make springs that go behind your pistons to make sure they keep the pads against the rotors...however, this creates drag and will wear your pads down quickly.

I find the left foot tap works well and especially down long staights, it's good to make sure the brakes are still home anyway

 

After doing StopTech's 13" kit up front, this is really my only significant complaint (although better description/pictures of the brake hose routing would help).

My concern is what this actually means - ie, the reason this is happening is because there is something flexing under the lateral loads the car is generating. My real concern is this is happening with Falken Azenis. I can only imagine with R-compounds and bigger rubber how much worse this is going to get. And will something finally 'give'. Makes me nervous.

ahm

 

I'd have to 2nd that concern. If I'm getting this much pad knockback with street tires, I can't imagine what R-compounds would do.

I talked to one of the track instructors regarding this issue, and he said that he has run accross a lot of people who have complained about the Z's propensity to flex at the hub. He also said that his Viper doesn't exhibit any significant knockback.

Well, I guess you get what you pay for....Thanks Nissan for using another Altima component!

 

C Ray --

This is not a Wilwood v. Stoptech v. Brembro issue. The issue is with the hub of the car flexing allowing the rotor to knock back the pads. This is an issue endemic to fixed caliper systems (i.e., all BBK's).

If you have not experienced it -- it is only because you are (a) not putting enough lateral (turning) g-forces on the car to cause it (you will only get it in long sweepers on the track -- very unlikely to see it on the street), or (b) your hubs may not be flexing (that's a good thing).

 

I experience this every time, it's nothing to be afraid of. Ever watch those Best Motoring videos? Watch the foot cams, they'll requently show the guys tapping the break pedals on the straights. This is to get the pads back where they belong. This is happening to everyone who tracks their car.

 

Just so you know -- as I understand it -- the knockback issue may be exasserbated on our Zs because of the position of the caliper. Instead of being at 9 or 3 o'clock relative to the ground, it is actually at 10 or 2 o'clock. So when providing the rotor with more leverage to push the pad back.

I only seem to get it as my pads are wearing down -- and then only mildly. It get used to it and it really does not affect braking power -- only the feel of the pedal.

 

hrm.. wonder if there is any way of fixing this. has anyone determined where/what component(s) is flexing? any of the folks running in t2 or other series (using at least similar to stock suspension components) seeing this and/or feeling the need to address it.

with the amount of knockback i'm seeing - a trait I never had in my wrx, and i beat the crap out of that car on the track - i am really quite concerned something will let go at a less than opportune moment. not exactly sure when the opportune moment is to have a piece of the suspension fissure, but trail braking into turn one somewhere isn't on my list of possibles.

i guess the more direct question is, has anyone actually had a part of the suspension cease to be whole in operation?

ahm

 

I've discussed this with a number of you on the phone, email, and in person. My engineering team is working on a universal fix. At this point however, it's just something that we Z folk will have to deal with. Another poplular platform that has the same problem is the Subaru WRX. Actually, it's a bit worse on that car. The 300ZX was also significantly worse than the 350.

Don't worry guys, I'll keep you updated on any progress in this area. I drive my car on the track all the time, so I'm well aware of the issue. It's not quite as bad on the 332mm kit as it is on the 355mm kit, but it will still sneak up on you if you don't keep it in mind after a series of S turns or sweepers.

As for the entire suspension failing...I wouldn't worry about that. It does flex, but I don't think we need to worry about anything letting go.

 

I spoke to jritt over the phone earlier this week. Thanks for taking the time to explain it. Now that I know what it is, I am less worried about it.
One thing he mentioned is that the race teams blueprint their hubs. Not an option for us common folk.

 

Odd - I had a WRX wagon that I beat the P*SS out of, and I NEVER noticed this problem. Stock calipers/rotors though...

Appreciate your thoughts, but I'd like to hear from people really racing the car - routinely pounding the curbing at full load, probably with much stiffer suspension (hence transferring more load into the hard parts). I drive fairly hard at track days, but with a heck of a lot less fervor do I make decisions than I do in my race car.

ahm

 

Stock sliding calipers will not exhibit the pad knockback concern--only on fixed caliper applications, as Skrill and JRitt have explained.

The WRX application to which Jeff was referring was the Stoptech BBK, not the OE setup. Both Skrill and JRitt both have significant track experience, both of which experience this pad knockback. I too notice it on my car, even with the stock Brembos. Pad knockback is apparent even in R32 Skylines--NOT a car created with Altima components, as you indicate.

 

i have the knockback problem on my stock brembo's, due the my 20" low profile tire setup. there is no give in the tire since the sidewall is so stiff, which increases the moment on the hubs. i just use the "tap" method, and everything seems to work out fine.

in fact, i seem to "tap" on every car that i drive, just out of habit. so i guess once you get used to doing it, it's just routine.

Chad

 

First, I know this thread is as old as the internet.

I see that it just drops dead with no fix.

It seems these are the only options but I can't find anyone using them. . . besides #1

1. Left foot tap to set brakes.
2. Brake Knock Back Springs behind the pistons
3. Wilwood brake knock back check valve


Is this a dead topic? Or has anyone used #2 or #3?

 

Option 4 - ST now offers a bracket that clock the calipers at 3 and 9 o'clock instead of the oem location. They are the only one that offers relocation of their bbk iirc. I've had mine for couple years if not longer. No knockback issues.

 

does that work with the brembo calipers? Or do I have to purchase their calipers too?

 

Interesting. Ive heard the opposite, that you will still get knockback even with re-positioned ST calipers, on hoosiers though. Knockback springs are effective, but not a good solution for a dual purpose car.



Franken, I suggest you google the topic and it is universal, not just 350z specific.

There are even some other decent threads on this site.

 

Oh man, I googled a bunch on this already. Not just relying on forum members comments. What I found is what I posted in the post 15. Not much out there.

Not sure what else there is to do.

 

I have installed the 2 psi Wilwood residue pressure valve on my front brake line circuit (right after the master cylinder) for two racing seasons and problem solved.