I'd be surprised if the rears are the culprit, since nobody complains of this on a stock setup.

As far as rears, most options for fized calipers are tough unless you're willing to have no e-brake.

 

When is this and what organization are you running with? I might go also

 

I wouldn't be surprised but I won't say I'm 100% correct - the telling story will be from those with fixed rear calipers commenting on this.

I've changed the pads a lot of times - and when the adjuster,(parking brake) isn't fully seated - there is no question more pedal travel to take some of that up - so now I make 100% sure I take all the free play out of the adjuster if I can, and use the parking brake a lot to ensure all that slack movement in the piston is taken up.

And I can physically move the entire caliper with very light force by my hand when the parking brake is off and no pressure is applied - so it is most certainly moving around when the pistons are released causing the rear pistons to retract some. I have 3 FD's right now, and all three have that much free play in the rear calipers,(some have more than others, but its more than any other car w/sliding calipers I've owned - BMW's most noticeably).
I'm OK w/a lack of parking brake if it removes much of the required pedal pumping.

Pumping the pedal EVERY single corner on the track is not piston kickback in the front calipers. It is obvious on some corners when that is in play. I ran through this pretty extensively with my BMW's, (lots of E36 track time).
When you have a corner which is after a light or quick left or right and you have to pump the pedal just as much as a hard corner - the front upright isn't moving that much.
That is where my comment on up to half or more of the required pedal puming is from the rear calipers.
The telling part of this is to take your car out on a long straight road - run up to 120 or so, brake really hard to about 40,(w/a few pumps to the system first), now accel as hard as you can back to 120 again and repeat.
Now do the same test, but leave about 1/2 mile in-between the braking after you hit 120, (simulating a long straight). In my case, I have to pump the pedal much more. - so the front upright movement is isolated in this instance.

Again, I'm not happy with the rear brakes on this car - I'd much rather switch to something else,(not to mention limited rear pad choices).
I really want to hear from anyone who has a fixed rear caliper setup,(2 or 4 pistons).
The front uprights/bearings do move around, but not every corner - and it shouldn't be the same after a lightly loaded corner vs. a very heavy corner. (say a .4 g corner vs a 1.1g corner). I can tell when I've gone through a particularly hard corner, (very high lateral G loading), and the pedal goes much further than other corners if I don't pump it up. It is very different from other corners on the track and most certainly piston kickback in the fronts.

Again, I'd really love to hear from those who have a fixed rear piston setup and have tracked their car.
-Bob

 

Let me split the difference between Bob and Peter above. I think it is worth noting that people tend to suffer more knockback when they add a front BBK while keeping the rears stock. So I can see Peter's point.

However, at my last Laguna test I was experiencing the worst knockback yet. I had to really aggressively tap up on every corner. I was frankly getting pretty depressed. So while in the pits I jacked the car up to see if I could spot an issue. And what did you know...both of the rear wheels had bearing play. Not a massive amount, but it was definitely there.

Turns out that despite staking the axle nuts, they had backed off perhaps 5-10 degrees. Not enough to lose the wheel, but enough to allow some play that you could feel.

So I re-torqued the rear nuts before my Thunderhill event and staked them about 10x harder than before. And what do you know...the knockback was greatly reduced.

So I think that Bob is correct insofar as the rear calipers are susceptible to knockback, perhaps even more sensitive than the fronts. But I think that even if you completely eliminated the issue in the back, the front uprights are definitely flexing enough to ensure that knockback will still be an issue.

Unless you go the piston spring method.

-ch

 

I was scheduled for the big event in late August (Speed Ventures) but I had to cancel due to a conflict. So it may be until the November timeframe, unless something comes up.

-ch

 

Here is a link from Max Cooper's site on a rear brake setup using a Wilwood caliper
http://www.maxcooper.com/rx7/how-to/...ear/index.html

Whatever happened to Max?

 

That is something I'll have to check into - esp. with the high torque of the LS loosening things up everywhere....
Sounds like we are on the same page - the rears are contributing to at least 1/2 of the required pumping - but maybe not for 100% of the reason I thought.
That's something I'll be checking before my next event.

 

redline track events are good for testing because they allow you alot of freedom on the track, but safety is not as good with them as nasa (for this reason and them being small)

 

He's lurking. He was on as recently as the 16th, but hasn't posted in over 2 years.

 

Yeah, I'd be dead without the ducting. Intake is via an unmodified R1 spoiler to a fiberglass pickup of my own design, with the orange hose to NTech backing plates. Anyone interested in details can search my old posts.

The crack pattern is also very different. Your rotor cracks are also much more spider-like, and from your picture it looks like it doesn't crack as much near the slots - perhaps the rotor is cooler there?. Mine are all clearly radial, and you can definitely catch a fingernail in the worst ones (not shown in my pics). I've run them until they cracked through, so know from experience when to chuck'em

So little that I've never bothered to measure. The Carbotech XP10 pads are very easy on the rotor. Next track day I'm going to try the more aggressive XP12 pads, but I doubt if it will matter much - the rotors will cook and crack long before they ever wear out. Given the cost of the pads vs. rotors, I'd happily trade rotor wear for pad wear if I could figure out how.

For my low HP setup the system brakes very well - no fade at any time. The only real downside is the pads wearing out so quickly. And I also have a 929 MC. I found even the minor knockback of the stock system annoying and the larger MC is a huge improvement.

 

If you don't mind second hand, a bloke running 4 pot Harrops in the rear over here, after going through the AP and Alcon options, still has knockback requiring the confidence pump. From my conversation with him, the fronts are the ones causing the grief....much more than 50%, rotors in the 350 range I believe though.

 

Say "hi" to Aaron Bitterman of Speed Ventures. I did a couple of trackdays with him when I was in Santa Barbara. He went to school with some friends of mine.

:-) neil

 

No updates. I was supposed to go to the track for the first time this year on Sat, but NASA didn't get enough people to register so the event was cancelled. Damian is trying to get enough people together to rent the track ourselves, but it isn't looking good. My next opportunity to head to the track will be the 19th/20th of July if this weekend is scratched entirely.

In the meantime I had a companion flange issue (the harmonic dampener broke) so I've been fixing that and getting the car ready to go with the new DTC pads. My rotors still look almost exactly like they did in those pictures, I've probably only driven the car 50 street miles (With HT-10 pads) since those were taken. The cracking has started to go away with street driving, even only 50 miles worth, so I'm not worried about the rotors yet at all. The reputation I've heard with respect to DTC pads is the same as you say, that they are generally very friendly.

 

That is good news Chris!

So what pads do you run on the street now?

 

I'm running the Hawk HPS. To be honest, I'm still not happy with the feel of the brakes in street driving. The OEM brakes had an immediate, hard bite when you got into the pedal, while these brakes feel more like my STI did; there is about 1" of pedal travel where the brakes begin to engage but aren't really slowing down the car. Then, as you apply the pressure, the braking force builds up.

I suppose this makes them easier to modulate, but for my style I'd rather have something that engages faster and produces greater stopping force at lower pedal force levels.

I may try the HP+ pads next, but I feel that this shouldn't be necessary...

I'd love to meet up with someone else in the bay area that has this kit installed so I can evaluate my setup back-to-back. (Mark: HINT, HINT.)

-ch

 

If a bunch of us Bay Area Racing Brake guys want to meet up to do some testing I'd be down. I have ET300 and 700 pads.

 

This sounds like an excellent idea. I'll be happy to organize. Anyone else interested? Send me email at chris@rs-engineering.com.

-ch

 

I'd be up for that.

 

^Me too.

I have the Hawk HPS, ET500 and Hawk HT10 pads.

 

Or you can install an e-brake kit.
http://daliracing.com/v666-5/catalog...cfm?focus=414-

 

I had a chance to test out my RB BBK on the racetrack. My pad selection was DTC 70 front and DTC 60 rear. My first event with these this kit was Mid Ohio about 6 weeks ago. My second event was VIR this past weekend.

Mid Ohio is a shorter track that is harder on tires than brakes. I had a few problems with the rear brakes prematurely locking up. My rear alignment was a little off so I wasn't going to place the blame on the brakes until I got the car realigned. Other than prematurely locking the rear brakes, the setup displayed no fade and performed very consistently. I didin't measure the pad wear, but it appeared as though I used up about 15 to 20% of the front pads during the 3 day event.

VIR is very tough on brakes. There are two straights where you must brake from 145+ MPH. Unfortunately I had the same brake bias problems. I was effortlessly locking up the rear brakes under heavy braking at several locations on the track. I found myself braking earlier and squeezing them much more gently, trying to prevent the rear from locking up. By the end of the weekend I had flatspotted my rear tires.

On a positive note, even with the bias problem, I experienced no brake fade and performance was a huge improvement over stock brakes with Hawk blues. It was a very hot weekend and I was driving the car hard. Instead of worrying about whether I had enough brake to stop, I found myself concentrating more on the next turn knowing that brakes would be there and perform constently. I haven't measured pad wear yet but there are no visible cracks or premature wear on the rotors.

For those wondering why my brakes are locking up... for some reason after the BBK install my ABS light came on and my ABS hasn't been working since. I just haven't had time to troubleshoot the ABS but will be doing everything I can to get it working again during the next couple of weeks.

I emailed RB and am awaiting a suggestion. I will most likley change my pad compound in the rear to something with a little less bite, maybe DTC 30.

My alignment settings are as follows:
Front: camber -2.7, caster ~6 degrees, Toe slightly in (0.1 degrees)
Rear: camber -2.5, zero toe

I may experiment with taking out some neg camber, especially in the rear. This should help with rear traction under braking. I really don't want to get into brake bias valves unless it's the only option.

Has anyone experienced this problem? If so, what was the solution?

Josh

 

If your ABS isn't working then you will have brake bias problems. Get the ABS fixed and you'll be good to go. You probably pulled the wire on one of the ABS sensors on the hub during the install. It doesn't take much stress on those wires to have them break internally and cause a fault.

 

I will get that fixed before i make any changes.

I did get a chance to look over the tire wear a little closer today when I put my street wheels back on the car. It appears that I flat spotted the fronts pretty badly. This happened during my final session so I just pulled off and put the car on the trailor without taking a good look at everything. It sure did feel like the rears where locking but evidently the fronts were locking up too. I wasn't applying very much pedal pressure when this happened. The less torque DT60 might be a better option for me in the future.

I think my brake problems at the track were more related to me getting used to the new braking system and not having ABS operational.

 

Just a quick update, was at Autobahn CC outside Chicago this past weekend with the car and the new DTC-60 pads from Racing Brake. I will have a detailed post and data forthcoming. But the short version is: Pads worked great, no brake issues for the entire weekend, nothing but high hard pedal and great feel.

More to come.

 

Man... I really wish I got in at the GB price. Does anyone want to sell their RB BBK? PM me.