Re: Simultaneous Application of Gas and Brake Pedals

Actually, not really. I never engineered a brake system from scratch, unless you count mixing amd matching parts on my own personal vehicles. But I have seen what happens when you get something a little off, like the MC bore size and your 70 MPH panic stop turns out to be a little more interesting than you planned on when the ABS' hydraulic accumulators suck all the fluid out of the MC. Whoopsie!

Keep in mind, however, that most of the stuff I worked on professionally was light trucks - these issues may not actually surface for passenger cars. The point that I was trying to make is, simply, that there really are good engineering reasons to use a power booster, and that they become more compelling when using disc brakes as opposed to drums.

Yeah... really, it boils down to how much room do you have between the top of the pedal stroke and the floor of the car (don't want to have the pedal too high, that would be bad ergonomically - you should be able to get your foot on it without taking your heel off the floor) and can you juggle your bore sizes and/or linkage to get a reasonable (or Federally mandated) pedal effort within those parameters while not having the pedal go to the floor either with one circuit failed or during a full ABS stop from whatever your maximum design speed is. If you can't, then you go to a power booster. I'm sure that someone could probably give a rough, hand-waving estimate (like I have above, but a more informed one) as to appx. what vehicle weight that starts to happen at... but the point is, that weight would be significantly higher for a drum brake car because a) they require less fluid movement (or should, if the shoes are properly adjusted - since they have positive return springs you really can't count on that though unless self adjusters are included) and b) they require less line pressure.

nate

And you still haven't. 8^) I was told that the trannies used in AMC vehicles (in my terminiology "AMC trannies") were what was used in the subject vehicle. At least two people reading did not take that to mean that AMC built those trannies. I wasn't intentionally being ambiguous, but I figured that anyone who knew the score would take it to mean what I had intended.

So let's see. To apply this rule, no one can ever refer to a wheel that fits Chevrolet vehicles (as well as certain other brands) as a "Chevrolet wheel", or a wheel that fits a Chrysler vehicle (as well as certain other brands) as a "Chrysler wheel"? Is that what we're saying here?

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')

One more thing I meant to add...

yet another reason why the "my '67 whatever had manual brakes and stopped just fine" does not translate over to a similar weight modern car *not* requiring a power booster... I've been told, although I have no hard numbers to back this up, that old asbestos brake linings actually have a higher coefficient of friction than most modern linings. I don't have enough experience to make a definitive statement on this but I will say that my '62 Stude with stock brake linings (still original, only 24K miles give or take a few) stops just fine without the power booster. However, I've heard people with near identical cars switching over to power because they claimed that the brakes required "too much effort." I suspect that that is because the brake shoes have been replaced with modern linings that work, but require more pressure to work *well.*

I can tell you that trying to stop a '64 Stude with *disc* brakes and a failed power booster is a firewall-bending exercise, but that's not entirely relevant to this discussion, other than the single data point that Studebaker apparently felt it necessary to mandate a power booster for all disc brake cars, for whatever reason.

Finally, stainless braided brake hoses are badass. This has *no* relevance whatsoever to this discussion, but I just felt like throwing that out there. I just replaced the front hoses on my 944 yesterday as the originals were well past their "best before" date (and the stainless ones were half the price of factory, even better) and the pedal feel is astonishingly good - and I haven't done the rears yet! Now the sludge that came out of the clutch slave when I bled it... that wasn't so badass. Hope that's not a sign of an impending future repair, 'cause it looks like a royal PITA, unless you pull the starter first. Why Porsche in its infinite wisdom didn't put the starter and the clutch slave on opposite sides of the bellhousing is beyond my ken...

nate

So you would *never* refer to certain wheels in a junk yard as "Chevrolet wheels" or "Ford wheels". You would first find out who manufactured the wheels and reference them that way. Or how about cell phone chargers? If I wanted to buy a charger for my Motorola cell phone, I would walk into a store and ask for a Kikosuki charger because they are the company who made it, and the store owner would immediately know it was for a Motorola phone even thought Kikosuki makes chargers for 3 other brands of cell phones. Let's get real.

Well - I agree with you on the under-engineered part - except for that tranny. It was ridiculous to put that tranny in that heavy a vehicle with no cooler. The proof in that pudding was having to replace the fluid every 20k miles in a time when no one ever changed ATF.

The over-engineered aspect of the IH vehicles was also their demise - their trucks and Travelalls could not compete with the lighter vehicles. Nor could the Scout compete witht he lighter more nimble competition. Not saying over-engineering is necessarily bad, just not competitive in a very competitive consumer market.

BTW - I did things to that Travelall that would have totally done in many other vehciles, so I hear you on the over-engineered thing. It was heavier than anything. IH dealers used to brag that "our engines are 600 pounds heavier than the equivalent Ford engine!" And that's what did them in. Same with the 1942 Gravely tractor that I used to cut the grass while growing up.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')

Ignoring the fact that I never said they were under-engineered, though I did point out that they put an automotive tranny in a tank with no cooler on it that needed fluid replacement every 20k miles. Yeah - I would call that particular feature under-engineered, though I had not called it that. Grossly under-engineered here, grossly over-engineered everywhere else - maybe the correct term for them would be "very unbalanced" (which is by definition "not competitive" as time proved).

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')

My dad had a whole fleet of their trucks in his mechanical contracting business. One small pickup truck had a four cylinder engine. It was obvious that they had taken the mold for casting a 304 CI V-8 and blocked off one whole side of the mold to create the 4-banger. We used to laugh at that.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')

There you are. Throw in your intial tolerance stackups/vehicle-to-vehicle variations on all that stuff, and then add the variations as things age, and you have no more design safety margins left, and you're eaten up with recalls and bad publicity.

So can anyone say how many models of mass-produced passenger vehicles sold in the U.S. in the last 10 years have disc brakes without boost of some sort? Is it more than zero?

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')

Yeah, eh? I try to avoid it, and I figure I'm about 80% successful. Nowtimes, I usually just killfile jokers who spoil for a credentials pissing match. "KaWALLski" doesn't really need to know why it's so laughable for him to try and argue headlamps with me, and "Loathesome Pawn" doesn't really need to know that I'm an appointed member of the National Academy of Sciences Transportation Research Board (Oops! Oh well, add that to the 20%!)

-DS (...he also doesn't need to know he misspelled "loathsome"...)

Sure you would. But you wouldn't refer to an "AMC starter" (it's a Delco) or an "AMC alternator" (it's a Motorola) or an "AMC carburetor" (it's a Carter or a Holley) or an "AMC transmission" (it's a Hydramatic or a Torqueflite).

You *would*, however, refer to an "AMC engine".

I'm sure you can understand the difference. The question is whether you'll choose to admit it.

Well, you'll have to tell the guy who was knowledgeable enough to know the different applications and conveyed that to me - except he's been dead probably 15 or 20 years. anbd which I understood what he meant - just as people here understood what was meant even though it was not quite up to the Stern standard for truth and excellence.

So is it because wheels are round and transmissions and alternators are irregularly shaped that there's a difference in how they are referred to? Just trying to figure out the rules. 8^)

Truth is Daniel, knowledgeable people all the time refer to such devices by application even though technically it's not up to your standards, and people all the time understand the information that is being conveyed (which is the goal most of the time. No different I guess in correcting someone when they refer to a "lash adjuster" as a lifter, or talking about torque in pounds, both of which I joke about all the time. Just depends on how anal we all want to be.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')

Hmmm - speaking of being anal - looking back at what I just posted - was a time I would have been mortified at the typos I made in that masterpiece. Oh well. In too much of a hurry. (and look at that - two incomplete sentences in a row! Wuff!

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')

I'll agree to an extent on disks needing more LINE PRESSURE. But there are ways to get line pressure without "needing" power assist.

And as for the amount of extra line pressure needed, I think that is minimized by the fact that disk calipers typically have a much larger piston area than do similar capacity drum brakes, which is part of the reason that the drums need to be self-energizing.

My comment was in reference to a '69 (so it does have a split braking system just like a modern car- which I can also see making quite a difference). I should also point out that it performs just fine with

*modern* lining materials- I'm not anal enough about it to dig up NOS brake linings from 1969! And besides, I like to DRIVE it not just have a trailer queen, which is what happens if you insist on NOS service items like brake linings, belts, and hoses.

Not at all- I'm saying that it will take MORE pedal travel, but that more pedal travel is a GOOD thing because it allows finer modulation of braking pressure. The pedal effort will depend on the amount of increase in the pedal stroke, and will typically be a little higher than a non-boosted system. But I think its quite safe to say that there are non-boosted cars out there that have less pedal effort than some boosted cars. There's a lot of overlap. I'll say again that people equate "power brakes with a failed booster" to "non-power brakes" and that's just flat WRONG. A failed booster makes pedal effort FAR higher than non-power brakes.

I didn't mean it like that... I do have all new, parts store belts and hoses on the car, I just didn't need to replace the original brake linings as they appeared to be essentially unworn. I have, however, heard complaints about the unboosted versions of my car being hard to stop many times - I think I'm about the only person I know still driving a drum-braked Stude without a booster, and that's the only logical explanation I can come up with - everyone else has probably replaced their linings at least once by now.

nate

So how do you feel about Hydrovacs? Don't hold back, keeping your feelings bottled up isn't good for you :)

nate

Yes, you keep laughing, I am still driving one. It is forty three years old, and I still hop in and drive it whenever I need to. It has been the most reliable vehicle I have owned (and I have owned alot) in the twenty two years since I got the first one.

Bernard

Nope, the difference is in how they are sourced and installed and how parts are cataloged for them. If you need an alternator for your BMW you may be asked if it is a Bosch unit or a Marshal because the alternator was purchased seperately and installed by BMW, not manufatured by them.

If you have a honda, and you need a cap and rotor, you will need to know who made your distributor, TEC or Hitachi, or perhaps Mitsuba. just calling it a "Honda distributor" will make the parts counter guy laugh, but will not get you the part

Not always, and specifically not in automotive applications

Nope, not always

(which is the goal most of the time. No different I guess in

You must be an engineer, lots of theory, no practical application as applies to automotive.

I know that some of the people who plst are engineers, but I have seen to much of this "really informed mis-information" from that particular class in my sixteen years of selling auto parts in Seattle (Boeing country) to miss making the observation.

Bernard

No opinion *yet*, haven't driven one.