I think the springs are somewhat of a one size fit's all type of deal. You just need to measure your piston diameter and cross reference the spring size on the AP site.

I got my springs locally at Brits Inc in Sonoma, CA. They had them in stock at the time.

 

Long term update on the knockback springs. They wear out over time...

I thought that they were becoming less effective because my pads were wearing down, but when I recently put in new pads, they still weren't working. I forgot how much I hate knockback. It's hard to charge into a corner when you don't know how your brakes will react (even with the pump method). It ultimately slows you down about a full second.

I came across PFC knockback springs. It says that they are made out of spring material rather than piano wire, so maybe they will last longer. They're also 6lbs vs the 4lbs that I have in there now.

In terms of brake wear, perhaps I got slightly more dust when the springs were working. I'm still on my original set of street pads after about 50k miles, so any extra wear is not an issue to me. I'm actually kind of waiting for the dusty axxis ultimates to wear out so I can put a more mild (street) pad on.



http://www.hrpworld.com/index.cfm?fo...action=product

 

Thanks for sharing dave. Sucks that this problem is so prominent. Hopefully those PFC springs work out better for you. I found out the hard way on my first trip to T-Hill with the stoptechs. Double pump method was used throughout the whole day. I even feel like I have to use it on the street sometimes. I think the Ultimates are partially to blame since they require less pedal effort vs a milder street pad. I'm in the same boat with you and want to switch the front pads to something more mild liek the Deluxe Plus but I can't get myself to dump a perfectly good set of pads.

 

That's interesting, I want to give this a try too. Which spring should we use from that link? The larger or smaller one?

 

I have been playing with the idea of making a set of billet spindles on the CNC for my Z, and set them up for the front wheel bearing off a different car to aleviate this issue, and also slightly raising the wheel bearing to drop the car a little without the adverse effects on geometry and alignment.

i wonder if there is any market for a product like this? it would be pretty expensive to retail, probably just over a grand for the pair, so probably not.

 

I ordered the larger size for my stoptech's. I've got the AP racing 35+mm in there right now so I'm hoping the slightly larger diameter PFC 36.5mm will fit.

 

i must say i have heard of knock back in my years of motorcycle racing but now to have it for myself on my 03 track is frustraiting. after driving a day a grattan i had to learn the tap drill on my own. now i just have to learn it with the left foot
kinda glad this thread popped up now i don't have chase another problem
thanks for the info guys

 

Update?

 

Update is that they work. They seem to be of the same construction as all other springs that I have seen. Knockback is gone once again. I also replaced seals and cleaned up the caliper so it might be a combination of the new springs and the caliper servicing. The old springs still felt like they were good, but I reality, it's hard to tell if they lost a pound of two of force.

 

I talked to Steve Mitchel at M-Workz to see if there is a stronger Nismo hub(which there should be) but he said no. He changes his hubs after every three events just because of the extra wear on the bearings.

 

FYI... the non-Brembo brakes don't have a knockback problem....

 

I've had this problem here and there - even on street tires at the Glen, and that was on almost brand new bearings. I do my bearings every year for safety's sake anyway but this is a frustrating issue. I didn't experience it at all on the two tracks I've run with the Pilot Sport Cups - NHIS and Dunnville - but they don't really have much in the way of high-load / high-speed sweepers (it was the Esses at the Glen that did it for me). We'll see this spring, I'm not opposed to doing springs when I rebuild my calipers this season, it's a track only car anyway... I'm just tired of the "few hundred here and a few hundred there for a stupid part" that should NOT be necessary...

LOL Coffey you're a jackass How do those non-Brembos do at stopping our fat pig of a car from 100+ repeatedly?

 

from a non-brembo usere here...........even with Hawk HP Plus pads they just don't have the stopping force I want. but who knows, maybe by non-brembo he meant stoptech or Project-Mu....idk

 

Bill,
Those Hawks just wont cut it on the non-Brembos as you know. I would try more agressive pads like the Carbotechs or Hawk HT-10s. Once the BHP pads come out, they will be good too.

 

Yeah but they have a stopping problem after repeated use

 

Especially when they catch on fire. Not a fun experience!

 

I have a 355mm Stoptech BBK. During Auto-X or track events when hitting the brakes hard coming into or during corners and slight high speed turns, I noticed that my brakes will lose pressure until I depress the brakes again. The car still brakes, but the pedal is basically to the floor. I have to tap the brakes once really quickly to get the pressure back up and then hit them again for the real braking. This only happens in turns. When I hit the brakes hard after a straightaway the pedal stays firm on the first pedal push. Is this a sign of hub flex or air in my lines?

 

Your description is a bit confusing because you really only notice pad knockback after a hard turn AND a straightway (because you don't brake while on the gas). But, I think I know what you're trying to say. If the brake pedal goes to the floor after a hard turn and ONLY after a hard turn, then yes, it most likely is pad knockback. If you're getting squishy pedal when street driving, it's air in the lines.

 

I just finished reading the Stoptech knockback writeup and I am pretty confident now it is pad knockback. I remembered that even if I hit the brakes on a slight turn(ie. S-Turns) they pedal would drop down. Btw, I meant if I hit the brakes hard during a Straightaway, the pedal was fine. Street driving is fine, the pedals stays firm everywhere. I do have to tap the brakes before any hard braking zones to make sure the pedal doesn't drop. Once I tap them, then the brakes stay firm throughout the turn.

Are the wheel bearings hard to replace? Is it mainly only the front wheel bearings that wear out? I don't think that I want to go to the spring option because my car is daily driven.

 

Ask RKnight, Paulie, Eagle1, and the guy driving a Porsche GT3 that got passed in turn 2 by my co-driver, Erik Messley at Cal Speedway last Saturday.

Ten 25 minute sessions using the base brake setup on a 2006 350Z. All I added was some custom cut Hawk DTC70/60 pads front and rear, Motul 600rbf fluid, and air ducting. My fastest speed through the oval was 136 and I got up to 145 before braking down to about 50 mph for the infield entrance (turn 3). Erik hit 152 mph through the oval and he forgot to check how fast he was going before braking for turn 3. Best lap time of the day for Erik was 1:56.6xx. Mine was a 2:01.xxx.

So yes, the non-Brembo OEM brakes work just fine if you upgrade the pads, fluid, and duct air to the fronts. Plus, knockback ain't an issue...