Weird automotive engineering solutions

[stumpydino]

Still, they're always in contact. Throwing the whole "warping from city driving" thing out the window.

yes but there is no pressure.
and its quite possible warping from city driving, if hard and with all the stop starting that goes on, my sister has managed it with her car, the wavering squeeking noise appears after a short while of warming up...

 

[Famine]

You should be able to slide a piece of paper between the disc and both pads when the brake pedal is not applied. If not, there's something amiss - the pad should never contact the disc unless you're applying the brakes.

 

[Sniffs]

I must be the only one who doesn't automatically screw up on the window switches (the ones on my 4Runner are push down, pull up, rather than a two peice rocker...that's my Power locks). some of us tend to REST things on the center console, where my back window switch, power mode switch, and shifter ovveride are. console switches can get jamed out by dirt and use VERY fast

Famine: LOL had that problem mainly with Fords. everybody sets their controlls differently, depending on manufacturer and Market

btw, am I the only one who worries less about the controlls and more about the mechanicals? I take the time to actually read the manuals!

 

[Scaff]

Err, no.

I can't cite any specific instances of discs warping from this - or any other - practice but then most people known to me are British and don't generally ride the brakes at stoplights

(I'll also add that it's recommended that, after track use, you park the car with the handbrake off to prevent the heat dissipation through the braking system melting the quite crappy handbrake drums)

yes but there is no pressure.
and its quite possible warping from city driving, if hard and with all the stop starting that goes on, my sister has managed it with her car, the wavering squeeking noise appears after a short while of warming up...

Carroll Smith says................

http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml

..........brake discs don't warp.



Scaff

 

[Famine]

Yeah, I didn't really want to get into that. As phrases go it does the job - getting across the message that habitually clamping hot pads onto one spot on the disc is bad - while being a little inaccurate with regards to exactly why it's bad.

 

[Scaff]

Yeah, I didn't really want to get into that. As phrases go it does the job - getting across the message that habitually clamping hot pads onto one spot on the disc is bad - while being a little inaccurate with regards to exactly why it's bad.

Sorry............just one of those things I have heard so many times over the years in dealerships that it now bugs me a little.




Scaff

 

[niky]

It's funny - I was used to seeing the console-mounted window buttons from our friends' European cars growing up, though we never owned one. I always thought it was a good idea to simplify wiring. But our American and Japanese cars had armrest-mounted window switches, so I was used to driving that way.

Now I have a BMW (console mounted, which I like) and an Acura (armrest mounted, which I'm used to).

So why do I ALWAYS reach for the wrong location, no matter which car I'm driving?!

I always look for a footbrake in my sedan... reach for the handbrake in my crossover, and sit there, confused, while trying to remember whether it's a footbrake, handbrake or a twist-and-pull parking brake on my truck.

On occassion, I actually reach for an imaginary twist-and-pull lever on the crossover.

At least I don't try to stomp on the non-existent clutch, anymore.

 

[Perfect Balance]

You should be able to slide a piece of paper between the disc and both pads when the brake pedal is not applied. If not, there's something amiss - the pad should never contact the disc unless you're applying the brakes.

After doing easily 100+ on-car rotor resurface jobs, not to mention having to check the brakes on every car I work on as part of a mandatory, free inspection we provide, I can confirm that the pads touch the rotor on 100% of the cars I've worked on (literally thousands). You could probably get a piece of paper under there with little effort, but they do touch the rotor.

 

[neanderthal]

The whole heating up your discs at a traffic light argument is bollocks. No motion= negligible friction= negligible heat. And by the way, the heat is dissipated throughout the disc brake, not just on the "hot spot" where the pads happen to be clamping the disc. If you heat up a pot of water in just one spot, the heat travels throughout the pot and the water and heats up the whole thing, not just where the heat is applied.

Its not just the brakes that are holding the car in place but also inertia. A body will naturally resist a change in motion. Sure, there is some slight forward motion from the engine under idle but its usually not enough to get the discs glowing hot.

Unfortunately though, many aren't. Many seem to have the "press once for on, a second time for off" pedal, which means the hill-start procedure (if you're parked, not if you've just stopped in traffic) would require holding the normal brake as you release the e-brake, putting it into gear, and then jumping from brake to throttle and the correct biting point of the clutch before the car rolls back half a foot or more. Doable, but not nearly as simple or smooth as having it in gear and at the correct biting point whilst holding it on the handbrake, and then a smooth transition off the brake and moving off.

Actually, ALL Mercedes emergency brakes are hand released. It might seem like I am belabouring a point but you specifically mentioned Mercedes in your post.

I agree that many NON Mercedes foot operated parking brakes are also foot released.

 

[neanderthal]

Deleted double post. Thanks sucky internet service!!!!!!

 

[Famine]

After doing easily 100+ on-car rotor resurface jobs, not to mention having to check the brakes on every car I work on as part of a mandatory, free inspection we provide, I can confirm that the pads touch the rotor on 100% of the cars I've worked on (literally thousands). You could probably get a piece of paper under there with little effort, but they do touch the rotor.

I checked this with Milford before I posted - neither of us is a professional mechanic, nor have had the volume of cars pass through our hands that you have, but we have both worked on our vehicles' brakes specifically. No car we've ever seen has any contact twixt either pad and disc without the brake pedal pressed.

The whole heating up your discs at a traffic light argument is bollocks. No motion= negligible friction= negligible heat. And by the way, the heat is dissipated throughout the disc brake, not just on the "hot spot" where the pads happen to be clamping the disc. If you heat up a pot of water in just one spot, the heat travels throughout the pot and the water and heats up the whole thing, not just where the heat is applied.

You misunderstand. Pressing the brake pedal while at rest generates no heat. That's not what's going on though. Keeping the brake pedal pressed while at rest after having decelerated there has generated the heat associated with the deceleration action. And now the disc is trying to do its job, as you state, of dissipating the heat throughout from a single very hot spot, rather than by circulating the heat through the disc as it rotates on the hub.

To extend your analogy, if you plunge a red hot poker into a pot of water, the whole pot will eventually reach the same temperature (for a pot of about 20 litres, probably something around 40 degrees Celsius) but the spot into which you plunged the poker will reach several hundred degrees instantly and boil off.


Now, we're not talking about such ethereal temperatures - pads operate at a couple hundred degrees Celsius and iron brake discs have a melting point of about 1,500 degrees. But the principle is the same - you're asking the discs to dissipate heat in a manner for which they aren't designed. They're meant to rotate through the pads so that the "hot spot" is spread evenly, in a continuous arc, throughout the length of the disc while it dissipates, and not remaining in a single spot.

 

[eiriksmil]

I thought of something yesterday, while we're on this.. Do auto drivers go through more pads than manual drivers?

 

[TheCracker]

After doing easily 100+ on-car rotor resurface jobs, not to mention having to check the brakes on every car I work on as part of a mandatory, free inspection we provide, I can confirm that the pads touch the rotor on 100% of the cars I've worked on (literally thousands). You could probably get a piece of paper under there with little effort, but they do touch the rotor.

If a brake pad was constantly touching the surface of the disk it would not only wear out very quickly, it would also cause considerable friction and overheat the pads, and therefore the fluid, even under normal driving conditions. Pads naturally sit very close to the surface of the disk, but if they touched you'd not be able to rotate the (undriven) wheel when up on axel stands, which you obviously can.

 

[Famine]

eirik- Be a bit difficult to say - you'd need a like for like comparison for a start.

But taking PB's data and my experiences at face value - he's done hundreds of rotor resurfacing jobs and is in a culture where this habit (and the automatic car) is commonplace; I've never heard of anyone I know having "warped" discs and live in a culture where the habit is rare and will fail your driving test for you - it would seem there's a correlation.

 

[homeforsummer]

I always look for a footbrake in my sedan... reach for the handbrake in my crossover, and sit there, confused, while trying to remember whether it's a footbrake, handbrake or a twist-and-pull parking brake on my truck.

On occassion, I actually reach for an imaginary twist-and-pull lever on the crossover.

At least I don't try to stomp on the non-existent clutch, anymore.

The only problem I've ever had hopping from car to car is when some older Japanese cars have the indicator stalk on the right-hand side of the steering column. I can forget that the damn thing is on the right between setting the indicator and cancelling it. I'll turn the corner and then try and hit the wiper stalk to cancel it!

Never had any problems going for imaginary clutch pedals or window switches though.

Actually, ALL Mercedes emergency brakes are hand released. It might seem like I am belabouring a point but you specifically mentioned Mercedes in your post.

It's funny how you say that, yet the post of mine you quoted didn't have a single reference or even hint that I was talking "specifically" about Mercedes. All I did was quoted a picture of a Merc that you'd posted, but my post, with complete lack of mention of Mercedes, was talking very generally. So when you say this:

I agree that many NON Mercedes foot operated parking brakes are also foot released.

...that's exactly what I was talking about. And regardless, it doesn't take away that having a foot-operated brake in a manual transmission car is still a dim idea (which is what my original comment was centered on), because it's different to what 99% normal manual cars are like. I agree Merc do make a compromise with the hand release lever, but somehow I doubt this offers you quite as much control as a normal handbrake with which you can vary the pressure. I'm assuming the lever is basically like an on/off switch?

 

[eiriksmil]

My daily has the window winders and the release handle opposite of all other cars. What's up with that? And those right indicator stalks on the right, brrr.. The Colt in Cyprus has it.. Changing from a LHD to a RHD Toyota is worse enough, I always think they are opposite because you're changing side. And then I learn that it's no difference. Then I get into the Colt.. Blah

eirik- Be a bit difficult to say - you'd need a like for like comparison for a start.

But taking PB's data and my experiences at face value - he's done hundreds of rotor resurfacing jobs and is in a culture where this habit (and the automatic car) is commonplace; I've never heard of anyone I know having "warped" discs and live in a culture where the habit is rare and will fail your driving test for you - it would seem there's a correlation.

Yeah, seems like it. I mean, I've never driven an auto on the road, but I'm under the impression that you can't slow the car down by just changing gears, you need to brake a bit for it to change down, and then it might change up again if you're on a downhill. You've got to hold the car back at light. I've felt from the valet parking-experience I have with autos that the brakes really need to hold back forces. While auto seems more relaxed when you're driving, it seems more stressed at stops. I could be wrong of course..
Sounds like I'm an auto hater, just gotta say I'm not. I even want an auto box for my daily, it'd suit its character I think..

 

[Famine]

I've driven only three automatic cars (Ford Explorer 4.0, Jaguar XJ 3.2, Jaguar S-Type R) and none were that stressy to stop. Though the S-Type had a bloody stupid pushbutton handbrake (because a LIGHT is going to stop you, right?).


Incidentally, all three were also my dad's cars and we both went to press imaginary clutch pedals - moving our hands over to the gear lever at the same time - at various points while driving them. I also have gone to change up to 6th and caught myself in time in both my own MX-3 (that I've had for 6 years) and daan's 406 Coupe, which only have 5 speed boxes, but only after owning the 6-speed ST220 for a while

 

[homeforsummer]

When I drive autos I avoid going for an imaginary clutch pedal by keeping my left foot firmly on the footrest.

 

[Famine]

I avoided it by left-foot braking. Slight disadvantage in generally having the owner of the car (my dad) in it at the time, major advantage in that he preferred it that way

 

[eiriksmil]

I have four gears and the reverse down right, imagine the look on my face when I think something's broken when going for 5th after having driven something else..

I need to drive an auto some day, get the feeling with them, even though you can't base that opinion on one car. I think I'm gonna love it and hate it at the same time, you know? There should be a button for when you want to be in auto mode, and one for manual mode. Not talking autos with buttons here..

 

[bergauk]

I avoided it by left-foot braking. Slight disadvantage in generally having the owner of the car (my dad) in it at the time, major advantage in that he preferred it that way

ReL Left foot braking. My brother yells at me when I do this at low speeds. Is it such a bad thing?

 

[eiriksmil]

If you're like me it's a bad thing, I've got absolutely no control over my left foot when I use it on the brake.. If it's sweet, you've got him beat..

 

[Famine]

ReL Left foot braking. My brother yells at me when I do this at low speeds. Is it such a bad thing?

Pretty much this:

If you're like me it's a bad thing, I've got absolutely no control over my left foot when I use it on the brake.. If it's sweet, you've got him beat..

Generally our left feet are used to either doing squat (automatic) or mashing a pedal flat to the floor (manual) - we don't have the finesse we do with our right feet, simply because our right feet have been trained to have that finesse (and most people, even left-handers, are right-foot dominant).

IF, however, you can generate the same level of control, there's absolutely no reason not to do it. The public road isn't, generally, a good place to see if you can do it or not but I see nothng wrong with doing it on public roads if you know you can. If it were a fundamentally dangerous technique, they wouldn't teach it to our top public road drivers (police pursuit, fire response, paramedic first responder)*...


*Though the official line is it's "not the done thing" - it's taught, but not recommended for road use

Edit: Though now we're getting WAAAY off track! There's a car control/driving technique thread around here somewhere... Let's shunt back to odd engineering

 

[Duke]

I thought of something yesterday, while we're on this.. Do auto drivers go through more pads than manual drivers?

No. Unless you're driving offroad or on steep downgrades, you shouldn't be using downshifts for deacceleration anyway; just for preparing to accelerate again.

But taking PB's data and my experiences at face value - he's done hundreds of rotor resurfacing jobs and is in a culture where this habit (and the automatic car) is commonplace

Resurfacing (turning) the rotors is standard practice when you have a commercial brake job done, at least here in the States. It's one of the reasons I never have my brakes done commercially: 90% of the time they don't need it, and 10% of the time you should just replace the rotors.

[edit] RE: automatics and braking forces

Automatics do not generate a lot of force at idle. The torque converter is set up to barely generate any force when the engine is ticking over. It's only when you give it a little throttle that the car really moves forward; it will only idle forward at a mile or two an hour. So it hardly takes any additional brake power to hold the car stopped, or slow it down from speed (as long as you take your foot off the gas).

Not taking your foot all the way off the gas is one of the reasons that left-foot braking is discouraged among non-race drivers.

 

[TheCracker]

With all this talk of handbrakes and using them for hill starts etc, it's just reminded me of a nifty feature my Forester has. Subaru call it the Hill Holder system, where when you are stopping on a hill (facing up it) as long as you have the clutch in, you press the brake pedal to draw to a halt and you can then release the pedal and the brakes stay on until you move away again. It means you don't have to fanny about with the handbrake or juggle your feet whilst burning out your clutch either. It's such a simple solution that just works perfectly. I don't know why other manufacturers don't use a similar system. Trouble is, you get so used to having it, when you come to drive other (manual) cars you invariably begin rolling backwards on hill starts!

 

[eiriksmil]

No. Unless you're driving offroad or on steep downgrades, you shouldn't be using downshifts for deacceleration anyway; just for preparing to accelerate again.



Resurfacing (turning) the rotors is standard practice when you have a commercial brake job done, at least here in the States. It's one of the reasons I never have my brakes done commercially: 90% of the time they don't need it, and 10% of the time you should just replace the rotors.

[edit] RE: automatics and braking forces

Automatics do not generate a lot of force at idle. The torque converter is set up to barely generate any force when the engine is ticking over. It's only when you give it a little throttle that the car really moves forward; it will only idle forward at a mile or two an hour. So it hardly takes any additional brake power to hold the car stopped, or slow it down from speed (as long as you take your foot off the gas).

Not taking your foot all the way off the gas is one of the reasons that left-foot braking is discouraged among non-race drivers.

I live in Norway - it's just one steep hill really..
Regarding turning or replacing the rotors, I've experienced that most big garages just replace discs and calipers and won't turn the discs or repair the calipers.

Regarding the torque converter, when you release the brakes it sounds like when you're braking down a really steep hill, like there's a lot of stress on them. I dunno though, and that torque converter seems pretty nifty - lugging without actually lugging.

But like Famine said, we're pretty off topic now..

 

[Famine]

I've never had my discs resurfaced. Or even been offered it!

In fact, I've only ever replaced one pair of discs - and that was because I wanted to upgrade them!

 

[TheBook]

Running back a little bit (or not, really); why do some manufacturers (with automatics) put the shifter on the steering column, while others put it on the floor?

Since I've gotten my Escort (floor shifter), I've gone for the column shifter more than 10 times, 'cause that's where the Blazer's was.

 

[homeforsummer]

Running back a little bit (or not, really); why do some manufacturers (with automatics) put the shifter on the steering column, while others put it on the floor?

Since I've gotten my Escort (floor shifter), I've gone for the column shifter more than 10 times, 'cause that's where the Blazer's was.

I think the column shifter came about when bench front seats were popular as there was nowhere better to put the shifter. As we moved to individual seats the logical place to put it would be the centre console, as that's where manual shifters live.

I can see the advantages and disadvantages of both - If I were to have a MPV or maybe even an SUV and would like a big, flat floor, then a column shifter seems like a great idea. In most normal cars I prefer the idea of having a normal centre-mounted lever.

 

[Jim Prower]

What surprises me most is that a Moderator has allowed the thread to get this far off topic.

Enough about Brakes, who's right or wrong, dazzling people with your taillights, etc. Let's get back to Automotive oddities, people!!!