BBK Brake Bias List

I think you got the SSS and SSY interchanged in the top post.

PER SUBARU EBD is independent of ABS. EBD works all the time not just when ABS is deployed

Hello,

Talked to Tim at StopTech... someone with a brake kit would have to supply piston sizes - they don't publish that ever since a huge range of their products were copied by another brake manufacturer...

As for pad mu, he said the pads they use don't have a published mu, but anyway, the published mus are about as useful as dyno-hp numbers when it comes to comparing pads. Every pad manufacturer uses their own mu's and one company's 0.3 might be much stickier than another's 0.6.

That goes back to someone else's post - perhaps it's better to list mechanical advantages and then have pad mu's as a seperate chart? Or someone shlep a bunch of pads somewhere for mu-testing

And finally, on ABS, ABS is always better than no-ABS, ideal conditions or not, because the "threshold" you're braking towards on the right front tire is drastically different than the threshold at the left rear tire. If you want to beat ABS, you need 4 brake pedals, four appendages, and a really good butt-dyno so you can get all four wheels at their thresholds. If you exceed at any corner, you suddenly lose most of the braking at that corner.

Finally, as far as I know, EBD measures front and rear slip angles and uses the ABS to modify the front / rear bias by unclamping the rears, regardless of lockup - solely based on current slip angles. IE, without waiting for lockups, if the rears are decelerating too quickly relative to the fronts, they may be about to lock up, so release them to maintain better front bias.

Joel

hmmm, so EBD never worries about too much front bias?

I am going to leave the threshold vs. ABS out of this one. I would like to keep it on the the topic of what BBKs are out there, how their biasing compares to stock, and what pads are out there...

Any Stoptech owners want to measure pistons?

Ted

I am going to leave the threshold vs. ABS out of this one.

Another "worship the ABS God" clone.

Good call though.

Hello,

Praedet, EBD is a simple system that just compares relative slips and probably uses some kind of maximum slip LUT. So, yeah, it's fine with whatever brake mods you make, with the usual yadda yadda about not being optimized for non 100% stock systems.

LittleBlueGT: I only have half a decade of professional motorsports experience and only 3 years of that was as a funded factory team crew chief (Subaru of America), so I don't know everything, but I do know that in road racing, we'd take 100 lbs to get ABS any day. I've never seen a driver who posted slower times with ABS and usually, the improvement in times is significant.

Joel

LittleBlueGT: I only have half a decade of professional motorsports experience and only 3 years of that was as a funded factory team crew chief (Subaru of America), so I don't know everything, but I do know that in road racing, we'd take 100 lbs to get ABS any day. I've never seen a driver who posted slower times with ABS and usually, the improvement in times is significant.

 

Joel

I would send you a PM but they are not enabled. Not discrediting your experience, some people here seem to go on and on about things they know nothing about.

I actually agree with you, but ABS will not always stop faster as threshold braking is better. (Not talking about snow or gravel)

A properly set up F to R bias will allow straight line braking on an even surface to be better with threshold then with ABS. I gaurantee you that a good driver with a properly set-up system can out-brake a comparably equipped car on even pavement. Can he do it consistently? NO! Is ABS always better in Motorsports? If there are corners, yes. If there is uneven surfaces, yes.

But it will not always stop better.

Now for good drivers (ones that actually brake in corners, rather then the auto-cross beginners that brake only before corners) ABS will allow them to concentrate on the task at hand rather then if one wheel is about to lock-up (inside rear). Also, generally the ABS that racing crews use is a lot better grade then the stuff that we get in our cars.

Back to the topic at hand:

The EBD system our cars uses is very good. Much better then w/o. It is not perfect though. A brake system with proper f/r biasing will allow EBD to function better. If the inside rear is beginning to lock-up the EBD will help, but the car may still be de-stabilized enough to allow a little bit of unwanted oversteer. If the inside rear was about to lock-up becasue of too much rear biasing then a proper f/r ratio would help that problem.

Always better to have a system work at its peak w/o electronic interference, and then the electronic goodies just work better.

Thanks to praedet for posting this info as it will be of help to any of us upgrading our brakes.

Hello,

I would send you a PM but they are not enabled.

At gmail.com, I'm carguy.

I actually agree with you, but ABS will not always stop faster as threshold braking is better. (Not talking about snow or gravel)

I agree that in the totally un-real-world situation of a single braking event with perfect conditions, perfect road surface, etc., with a perfectly matched brake system that is designed around the specific spring rates and ride height, etc., of the car, threshold braking will be better.

As soon as you move to the un-ideal real world, though...

Now for good drivers (ones that actually brake in corners, rather then the auto-cross beginners that brake only before corners) ABS will allow them to concentrate on the task at hand rather then if one wheel is about to lock-up (inside rear). Also, generally the ABS that racing crews use is a lot better grade then the stuff that we get in our cars.

First, you'd be surprised - the cost of a properly designed ABS system is extremely expensive. I know first hand from the guys that did the brake system design for GM until recently, that they were approached by GM and asked to make a custom ABS program to account for the tires and chassis setup that the factory race teams were using, and in the end, it was decided that GM could not afford to give that custom programming to their teams... So most teams are running with suboptimal ABS programs that are designed around stock tires, stock weight balance, stock weight transfer, stock brake bias, etc., despite all those parameters being changed. Modern ABS systems are quite robust, including the Subaru one, though, as one expert told me, speaking about the WRX ABS, "I am sure the Subaru system is optimized for some set of conditions - I just have no idea what those conditions might be." Subaru ABS is strangely hypersensitive to bumps, which is not what you'd expect from a "rally car heritage."

Always better to have a system work at its peak w/o electronic interference, and then the electronic goodies just work better.

I 100% agree with this statement. There is a reason that StopTech brakes are on more podium cars in World Challenge and Grand Am these days... with a properly balanced brake system, you can work wonders in the braking zone. The fact that the exact same brake kit you buy for your street car is on cars winning World Challenge race cars (yep, even those WC cars are running stock rear brakes, often), is quite telling. Get the bias / balance right, and you have a winner. Get it right and the brakes work as good as it gets, whether you have ABS on or disabled.

And the electronics work by reducing braking somewhere. You'd be much better off with peak braking without reducing the braking, which is why it's so important to have the front-rear bias done right. Some of these BBK companies are basically slapping the same 2-3 piston sizes they have on a million different car kits and they're saying they developed their kits scientifically... sure! The science being "1. Post a lot on the internet, 2. ???, 3. Profit!"

Thanks to praedet for posting this info as it will be of help to any of us upgrading our brakes.

Amen.

Joel, still with stock brakes on both Subarus, though testing new pads on the STi for one of the brake manufacturers.

Hello,

 

Praedet, EBD is a simple system that just compares relative slips and probably uses some kind of maximum slip LUT. So, yeah, it's fine with whatever brake mods you make, with the usual yadda yadda about not being optimized for non 100% stock systems.

 

LittleBlueGT: I only have half a decade of professional motorsports experience and only 3 years of that was as a funded factory team crew chief (Subaru of America), so I don't know everything, but I do know that in road racing, we'd take 100 lbs to get ABS any day. I've never seen a driver who posted slower times with ABS and usually, the improvement in times is significant.

 

Joel

well, I am glad that at least one pro agrees with me regarding ABS. Also modern EBD does a lot more than you might think. Many EBD systems calculate bias based on expected weight transfer(ie spring rates) lateral load, wheel speed differentials( both actual and expected/anticipated) and the list goes on.

What does Subaru do? I do not know. they won't share their source code with me.

In any case mucking around with pads to adjust bia is at best a crap shoot. Kudos to the poster about threhold braking and four feet. I also was a professional racer(formula B&C) and (since you can SEE lock up) frequently wished for four feet and four braking systems!!!!!!

frequently wished for four feet and four braking systems!!!!!!

And a better CPU (better) to work the 4 feet!

First, you'd be surprised - the cost of a properly designed ABS system is extremely expensive. I know first hand from the guys that did the brake system design for GM until recently, that they were approached by GM and asked to make a custom ABS program to account for the tires and chassis setup that the factory race teams were using, and in the end, it was decided that GM could not afford to give that custom programming to their teams... So most teams are running with suboptimal ABS programs that are designed around stock tires, stock weight balance, stock weight transfer, stock brake bias, etc., despite all those parameters being changed. Modern ABS systems are quite robust, including the Subaru one, though, as one expert told me, speaking about the WRX ABS, "I am sure the Subaru system is optimized for some set of conditions - I just have no idea what those conditions might be." Subaru ABS is strangely hypersensitive to bumps, which is not what you'd expect from a "rally car heritage."

I run my ABS 99% of the time, but 1% still adds up to quite a few minutes. On my daily commute I routinely brake fairly hard just before a turn, of course there are train tracks there, with ABS on the car will go at least an extra 40 feet compared to ABS off. So I am just used to now turning it off there.

I have spent a fair bit of time behind the wheel of some BMWs, and there ABS just seems to work much better, not hyper-sensitive. I wish I knew why.

please...

I think the other thread is open still

I edited the iON offerings to reflect new data Jack sent me...

Ted

Jack just called me and said he has their LGT stock replacement brake pads in.

Don't quote me, but this is what he said:

About 75% higher co-efficient of friction then stock.

Very similiar to Ferrodo compounds.

***Higher mu in the rears then in the front***

The difference in mu is to compensate for what ION tested to be too much front bias from factory. It should be somewhere in the area of 5-10% higher in the rears.

That's excellent! How much? I might try those after I am done w/ my SS-Ms

Ted

I think they are $195 CAD fronts, and $135 CAD rears.

This is just vague memory, it is not accurate!

If someone will measure the piston sizes on the Stoptech for me, I will put it up. The problem is that Stoptech won't publish their piston sizes

Ted

Any chance we could add the upcoming Racing Brake bigger rear rotor upgrade kit to the bias list?

Same LGT rear calipers, just larger 316mm slotted rotors... more info in this thread.

What fronts do you want to see it with? I already have the calculations for it, I was just wondering what to match it with because it is pretty drastic...

Ted

What fronts do you want to see it with? I already have the calculations for it, I was just wondering what to match it with because it is pretty drastic...

 

Ted

Thanks,

George

I have Blitz Z1's 18.5 with a +51offset and I'm intrested in getting Project Mu big brakes for the car. Will the wheels clear the Project Mu Calipers??

Hubie