Weird automotive engineering solutions

  • Thread starter Thread starter Leonidae
  • 349 comments
  • 33,942 views
So if someone drove for a bit with rusted rotors yet didn't use the brakes...that could possibly tell us whether the pads are always in contact with the rotor or not?
 
And it's not a uniform spread of rust, it's in radial bands (think the rings of Saturn) so there are signs of it beginning to wear off, but not like it would if the pads were constantly in contact with the disk. You can probably see it on other cars too, it's just that i've noticed it on particular car because a) it's a decent car so i take notice it more and b) the after-market wheels it has fitted have narrow spokes leaving a good view of the large front and rear disks.
 
Sounds like the rotors have some grooves in them or something where the pads don't touch.

Actually after reading your post again I don't think I'm thinking what your thinking, I think.
 
On the subject of weird gearstick positions from the last page, how about the Citroen 2CV?

IMG_1921.JPG


Not only was it mounted on the dash (well, technically it kind of sprouts from the dash...), but the shift pattern was odd too - from wiki:

It had a strange shift pattern: the first was back on the left, the second and third were inline, and the fourth (or the S) could be engaged only by turning the lever to the right from the third. Reverse was opposite 1st. Although this may seem an odd layout, it is in fact brilliant. The idea is to put most used gears opposite each other - for parking 1st and reverse, for normal driving 2nd and 3rd. This layout was adopted from the H-van's 3 speed gearbox.
Click to expand...
 
Moisture can form overnight. My car has rust spots on the rotors after just one day of non-use.

And even if you don't drive that often... just a few kilometers of driving are usually enough to clear away rust... if you use the brakes. If you don't... it won't.

And if the rust is in radial bands, those discs are probably badly scored and in need of resurfacing or replacement.

I was going to add something slightly on-topic here... of newer cars actually applying the brakes lightly in the rain, to keep them primed for use and to prevent a film of moisture from building up between the pad and disc... I read about this somewhere about Mercedes brakes, but for the life of me, I can't find it now. :(
 
niky
I was going to add something slightly on-topic here... of newer cars actually applying the brakes lightly in the rain, to keep them primed for use and to prevent a film of moisture from building up between the pad and disc... I read about this somewhere about Mercedes brakes, but for the life of me, I can't find it now. :(
Click to expand...

Type in "mercedes dry-braking" on google and it comes up with a number of links. I couldn't find one concise enough to link to here though, apart from maybe this one on the Mercedes-Benz India site.
 
:lol: I'm surprised nobody else had thought of that one yet actually! I suppose having an entrance to the car that is the front of the car is pretty weird.

Here's a pic that I took of one at a car show - you can see, like in the second pic above, that the door brings the steering column with it to ease access.

DSC_0160.jpg


Isettas are awesome.
 
TheCracker
If pads do touch the surface of the disk, the disk surface would always be shiny and clean from the constant contact wouldn't they, even if the car is used infrequently (which is pretty criminal with the sort of car it is).
Click to expand...

The rotors on both my cars will get that haze of surface rust on them within hours of being parked. Besides, if that rust was there while driving, it would have been wiped clean by the last stop when the car was parked, not left by the pads not touching the rotors while driving.

I suspect we are arguing semantics or a minute difference. The thing that I'm just not sure that you guys are getting is that there is no device that retracts the pads from the rotor. Nothing pulls the pads away when you release the brake; they just relax their grip, so the gap (if any) is utterly miniscule.
 
Scaff
Carroll Smith says................

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

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

:)

Scaff
Click to expand...

That is interesting! And timely too, since my dad's Audi is showing symptoms....

About whether the pads are in contact with the disc - I was looking up proportioning valves to try and disprove PD but howstuffworks also maintains that the pads are in light contact with the disc, unless pushed out slightly by other factors as posted before.

I have to say it does make sense, using my admittedly basic logic when thinking of previous experiences. For example after fitting new discs on a car where the disc is fixed to the hub with something other than just the wheel bolts, the disc is easier to turn than when the pads have been installed and the system pumped. I can't think of any other source of friction, so it's not unreasonable to come to the conclusion that there is slight contact at all times.

Next time I'm in the garage the feeler gauge is going to be used in a way I don't think it ever has been :)
 
Duke
The rotors on both my cars will get that haze of surface rust on them within hours of being parked.
Click to expand...

Same here. Brake discs are notorious for their instarusting.

Duke
Besides, if that rust was there while driving, it would have been wiped clean by the last stop when the car was parked, not left by the pads not touching the rotors while driving.
Click to expand...

TheCracker's point is that if the pads are in contact with the disc, the spot where this occurs will not rust when parked - by simple dint of denying air access to the water/iron combination. When it's all rusted up, jack the car up and rotate a wheel forwards a quarter turn - if the surface which was under the pad is not rusted, the pad was in contact with the disc. If it is rusted, the pad was not in contact with the disc.

Duke
I suspect we are arguing semantics or a minute difference. The thing that I'm just not sure that you guys are getting is that there is no device that retracts the pads from the rotor. Nothing pulls the pads away when you release the brake; they just relax their grip, so the gap (if any) is utterly miniscule.
Click to expand...

But a gap, nonetheless... Still, I'm waiting on my tame technician to get back to me.

Edit: He returneth!

Bentley Head Technician
The dust boots and indeed flex on the seals is designed to pull the pad slightly back from the disc surface. If it remained in contact it would just eat away the pad, glaze itself up and generaly be quite miserable with itself. Almost like a sticking caliper.
Click to expand...

On the topic of strange car engineering - and solutions to problems no-one even knew existed...

AkinaGhost832.jpg

The Carver One. Only in a country where drug use is legal.
 
Last edited:
casey_2005
So if someone drove for a bit with rusted rotors yet didn't use the brakes...that could possibly tell us whether the pads are always in contact with the rotor or not?
Click to expand...

Taking the car out of winter storage, you always hear some rust getting grinded off when you move the car for the first time in six months. But it's first when you brake you really hear it.. :)

Bentley Head Technician
The dust boots and indeed flex on the seals is designed to pull the pad slightly back from the disc surface. If it remained in contact it would just eat away the pad, glaze itself up and generaly be quite miserable with itself. Almost like a sticking caliper.
Click to expand...

Yey.. :)
 
a112
Yeah,mostly because people use hydraulic e-brake.
Click to expand...

Indeed, the only time there will ever be two calipers on the rear brakes is when the rear disc (usually a high performance light weight type) does not make concessions for a drum type parking/emergency brake, the small extra caliper is used to provide a simple brake without the need to complicate the main caliper. I imagine this could also make sense for some drift cars where a higher performance e-brake is needed for the amount of use it gets.
 
Famine
The dust boots and indeed flex on the seals is designed to pull the pad slightly back from the disc surface. If it remained in contact it would just eat away the pad, glaze itself up and generaly be quite miserable with itself. Almost like a sticking caliper.
Click to expand...

Cool.

Yes I was bored enough at work to try with the feeler gauge, and it just happened that there was a Astra with new pads and discs in. Result? The second smallest could get about halfway down between the pad and disc and the smallest a bit further, so tighter than I would have ever thought had it not come up for discussion ;)
 
Bentley Head Technician
The dust boots and indeed flex on the seals is designed to pull the pad slightly back from the disc surface.
Click to expand...
Wouldn't the pad need to be somehow attached to the piston for this to be possible?

I should start getting sound clips of me spinning the wheels on each car I work on. You can CLEARLY hear a "ssssss" sound as the wheel spins around, which comes from the pads touching the rotors. I'm not saying the entire surface of the pad always touches the rotor, but I've never ran into one that wasn't touching at all.
 
Something interesting I've thought of due to a recent need for Spark Plugs on my part...

What's with some of these weird designs coming up, (your Bosch +2/+4, Splitfire, etc..,) ...and will they resist fouling in a cylinder that seems to have bad rings and thus oil blow-by, and the owner doesn't want to take the engine entirely apart because he doesn't have an alternative way to work and school?

as it is, I have to replace the set once a year, though this time, it's only #1 that was badly fouled.
 
Perfect Balance
Wouldn't the pad need to be somehow attached to the piston for this to be possible?

I should start getting sound clips of me spinning the wheels on each car I work on. You can CLEARLY hear a "ssssss" sound as the wheel spins around, which comes from the pads touching the rotors. I'm not saying the entire surface of the pad always touches the rotor, but I've never ran into one that wasn't touching at all.
Click to expand...
Yeah, as far as I've ever heard the pads are always in contact with the rotor. Not pressure necessarily, but just barely rubbing along.

And the idea behind these multi-electrode spark plugs is to spread out the spark and make it more powerful and better ignite the mix. But that's not what it does. The spark, as electricity does, only goes to the closest electrode. When that electrode wears out, or they move a bit with wear, it arcs to the next one, and so on.

So all they really do is last longer. But metals do make a difference, and platinum and iridium ones seem to work well. Besides that, I just stick with single electrode plugs. They're cheaper and more consistent.
 
EA11R
Asses? What did you think I meant?
Click to expand...

Do you genuinely not know or are you being sly?...

Re: Spark plugs - I guess an interesting engineering solution would be Alfa's habit of using two spark plugs per cylinder to apparently burn the fuel/air mix more efficiently. I'm guessing efficiently in terms of power, as they're generally nothing special on fuel consumption.
 
Perfect Balance
Wouldn't the pad need to be somehow attached to the piston for this to be possible?
Click to expand...

But if the piston is designed to retract a little, then those clips as eriksmil pointed out would push them off the rotor. Every set of brakes i've installed( obviously not near as many as you) have had the clips that connect the pads to each other and have enough spring to push them back against the piston.

Edit: I misread Famine's quote and thought it was saying the piston does move back a little. What are the dust boots and which seals flex?
 
Last edited:
homeforsummer
Type in "mercedes dry-braking" on google and it comes up with a number of links. I couldn't find one concise enough to link to here though, apart from maybe this one on the Mercedes-Benz India site.
Click to expand...

Thanks... that was driving me batty! :lol:

Jim Prower
Something interesting I've thought of due to a recent need for Spark Plugs on my part...

What's with some of these weird designs coming up, (your Bosch +2/+4, Splitfire, etc..,) ...and will they resist fouling in a cylinder that seems to have bad rings and thus oil blow-by, and the owner doesn't want to take the engine entirely apart because he doesn't have an alternative way to work and school?

as it is, I have to replace the set once a year, though this time, it's only #1 that was badly fouled.
Click to expand...

Change your rings.

I suppose they resist fouling better, but by-and-large, enough spark is enough spark. In most reputable tests I've seen, (done by independent buyers with nothing to sell) there is no power difference between plugs... or the difference is so slight that it falls within testing error on the part of the dyno.

Now fancier plugs may help with highly-strung turbocharged motors which run extra rich... but I've found some data which suggests why this might be so... the stronger spark may actually cause enough extra combustion to make the engine run slightly leaner... producing more power. To the tune of about 5 horses... on a 300+ horse motor. A gain so small that you'll never notice the difference. A gain you could achieve by retuning the engine, instead.

If your engine is properly tuned, in the first place (think modern Honda or Toyota, or an engine with aftermarket management, like mine), running with proper closed-loop feedback, better sparks equal zero gains... or close enough to zero that you can better spend your money elsewhere.

-

Oh, and that's just platinum / iridium / pulse / whatever plugs. Multi-tips? Not really worth it. Extended tips, though, sometimes have a good effect on certain engines... putting the spark closer to the center of the combustion chamber than standard tips.
 

Latest Posts

Back