[Flycaster]

Originally Posted by stretch

...Lastly, just subjectively, I hate ABS. This is my first car with it, and I always feel it engages too early. It probably isn't, but I'd love to, someday, actually measure for myself how much improvement it makes.

In really slippery conditions, I can come close but not beat a good ABS system. On dry pavement, I'm able to consistently beat it. For an average driver (one that doesn't race much, or at all), it's a helluva system. It has saved my wife's life on 1 occasion, and has helped her to avoid a major incident on several others. Personally, I'm a believer.

[MGizzle]

Stretch, great points that you mention. As far as the transient time, you have less weight (car is lighter) hence reaching weight AT the tires to the optimum will take slightly longer than with a heavier car. I am not sure this is bad but in my opinion you want to reach peak ASAP so that ABS kicks in ASAP as well. However, think about this now. We have progressive springs, which are SIGNIFICANTLY softer in the initial loading. Hence, going lighter will pick up our car and making the intial compression softer as compared to stock. Now, do softer or stiffer springs transfer weight faster?? The stiffer ones do, hence why I was saying you could effect transients a bit.

I am not sure what the deal with European tires is but the cal guys at my work keep saying that they calibrate them differently because tires are so similar. We do have the same tires in NA (north america) but with our heavier average vehicles I think it might have something to do with that. Not sure, honestly. Just something they mentioned when I talked to them.

As far as braking better than ABS I believe it with R compunds. I don't on street tires. As far as Chrysler not tuning for max grip I am not sue about that but I know that on SUV's and bigger cars they actually design tires with LESS grip so that the car doesn't roll over etc. due to too much grip. Yeah, kinda ironic.

Anyhow, I am hoping they will get back to me with the exact logic during calibration. Also, please keep in mind that ABS is not really meant to decrease your distance as much as keep the car controlable. You think you can brake and steer without ABS?? Nope. You think you can keep a car with soft suspension straight without ABS? Sometimes, but more so not. You would be suprised how much these systems help.

[Flycaster]

Originally Posted by MGizzle

...As far as braking better than ABS I believe it with R compunds. I don't on street tires...

Perhaps not with the newer generation systems, but at a customer test day with a 1997 Audi A8, two of us consistently beat the in-car system in straight line brake testing on the OEM tires. The sales manager was not happy - he insisted it "couldn't" be done, at least in front of the other customers. Later, in private, he acknowledged that the factory drivers could also do this, and probably a helluva lot better than we could.

I haven't tried this with a new system, so you're probably right. With the ABS engaged, the brakes on the Audi were "late" and the pedal was horribly spongy, whereas the system in my Sti is much more "immediate" and the pedal is rock hard. 10 years is looong time in terms of electronic development.

And, no, neither one of us bought that overpriced tub of an Audi.

[MGizzle]

My brother has a 1996 C36 AMG and it has ABS on it and let me tell you what a difference it is to the systems we have now a days. They are way too slow in response but these systems back then were made to allow you to turn and CONTROL your car while you are on the brakes by not leting you lock up your tires. Go try to take a corner while all 4 wheels are locked up....you go where inertia wants you to.

They system on the STi is not bad at all and is currently what the industry sees. However, the new stuff coming out is just going to blow it out the water (car brakes by itself when it notices car ahead of it slowing down on free ways....car holds brakes while you are on a hill stop so no more rolling back....brakes are held while CRUISING down hill etc. etc.). A lot of new stuff....

If you rally or drive in dirt ABS will defenately give you LONGER distances all the time since locking up tires builds up dirt or whatever in front of tire, giving you more force than any tire can generate. However, good luck turning again unless you do it with the throttle

[Flycaster]

Originally Posted by MGizzle

...However, the new stuff coming out is just going to blow it out the water...

And how much of this new gagetry would be necessary if they would only outlaw cell phone use like they do in much of rest of the civilized world, or if people actually learned how to properly drive a car? None of it. Hell, 'hill starts' were part of the frigging driving test when I first got my license...

What ever happened to "paying attention?"

[stretch]

So how could more aggressive pads also not screw up the system? You're changing the coefficient of friction, which doesn't only change how quickly the brake bites, it also changes the amount of bite for a given brake pressure. Is this not just as bad as altering the pressure versus volume curve of a caliper? I would think larger diameter rotors would have the same effect, too. Really, I can't think of a single thing that wouldn't alter the ABS calibration.

(Where I differ is that I highly suspect the ABS calibration needs alteration since Flycaster reports being able to beat ABS, and I subjectively feel it engages early. For this reason, higher friction pads seem desirable because they'd alter the calibration.)

Originally Posted by MGizzle

Also, please keep in mind that ABS is not really meant to decrease your distance as much as keep the car controlable. You think you can brake and steer without ABS?? Nope. You think you can keep a car with soft suspension straight without ABS? Sometimes, but more so not. You would be suprised how much these systems help.

Actually, yes. Like I said, this is my first car with ABS, and I find its brakes inferior to my last (which was softly sprung, too, btw). Autocrossing taught me to modulate the brake and about the tire's friction circle. Maybe ABS can do better than me of allowing steering at threshold braking, but I don't think that is as important as squeezing every bit out of straight-line braking. What especially bothers me is this:

If you rally or drive in dirt ABS will defenately give you LONGER distances all the time since locking up tires builds up dirt or whatever in front of tire, giving you more force than any tire can generate.

I swear the STI accelerates in snow faster than it brakes! This very obviously shouldn't be. I think the ABS on slippery roads (mainly snow) is dreadfully bad and a bigger issue than the marginal decrease in steering that a good driver sees when self-modulating the brakes in the dry. Besides, even dry roads are subject to sand or leaves that seem to puzzle ABS.

Anyway, I digress- I don't mean to discuss the merits of ABS, just how to deal with it when making the car brake better. Besides, I realize I'm not a typical driver.

[MGizzle]

Pads and rotors will not effect the ABS if weight and dimensions are kept the same (inertia). Better pads and rotors will lock your brakes sooner, which will cause you to engage ABS sooner (or later if you have worst pads and rotors). It will not INCREASE your deccel rate since this is tire dependent, right? There is really no other variable that better pads and rotors effect (better is kinda hard to find sometimes though ).

Tires do effect more variables and with better compounds you obviously want better pads and rotors to achieve same torque output. It takes more brake torque to hold of stickier tires but the question we are trying to answer I guess is will the ABS unit allow the better tire to reach that max torque or will it let go at the torque the OEM tire maxed out at (calibration related). I am still trying to figure out how Slip Control is calibrated and what (if any) tire parameters they are using.

[MGizzle]

Originally Posted by Flycaster

And how much of this new gagetry would be necessary if they would only outlaw cell phone use like they do in much of rest of the civilized world, or if people actually learned how to properly drive a car? None of it. Hell, 'hill starts' were part of the frigging driving test when I first got my license...

What ever happened to "paying attention?"

I honestly feel like all this "gagetry" is complicating cars for us enthusiasts a lot but they are demanded by the "general" public because of fuel savings and increased safety requirements. Having the computer brake for you while you are in "cruise" saves gas supposedly. I actually drove a car towards a wall with this sytem engaged and it will stop completely for you....was a bit scary.

Hill assist etc. is just trying to take stress and such off the components while making people feel safer at the same time. It has no additional components and uses the same ESC units we have but is just another software addition.

The way I look at it is, people don't have to be good drivers anymore. Look at the GT-R. You don't need to know how to launch or downshift. It does it for you. It also balances the car for you so you honestly don't have to be a good driver to drive good. I think that is the worst aspect of all this gagetry but in "general" it is safer and safes lives.

UPDATE: Talked to the ABS cal guy and he stated "it depends on how your ABS unit is calibrated". He stated that some companies do use tire slip as a variable and it can play a big variable but this is something that we can not find out as consumers (unless we do some serious testing). However, he also stated that even without using tire slip in the ABS calibration, "stickier" tires can hurt depending on the characteristics of the tire (hot vs. cold vs. optimum operating temp). He stated that R compounds can hurt if you are doing a panic stop without the tires being heated to operating temp. That makes sense of course. He also stated that it can hurt you even when hot but not significantly. Some testing data was shown to me on a truck where with stickier tires it had a longer average stoping distance by about 1m hence not really significant but the point to iterate here IT DID NOT REDUCE STOPPING DISTANCE. He didn't elaborate on why exactly but just mentioned that with some slight calibration work you could change that.

I am going to bug him some more on details of the algorithms used on the ABS hoping to find something there that will explain better.

[stretch]

Bumping this thread since MGizzle edited his last post with more info 6 days after the original reply. Interesting info. Anything else to add? I'm all ears on this subject, and I'd absolutely love to see data if you happen to get some.

[Flycaster]

I'll bump it along too. This thread has given me a lot to think about. Any new info, Mgizzle?