Autobox Manners

Just been thinking about this recently, but I always leave my box in D with my foot on the footbrake when in traffic - this is the best way to treat the autobox isnt it? Shifting it into Neutral when in traffic doenst do it any good does it?

Do you know what? (spooky), I was thinking that today as I was sitting in traffic, love to know the answer

It's the normal way to drive an auto, tbh, but there's no harm in pulling it out of D to take the strain off the brakes and box.

i asked this before and everyone told me to leave it in D opposite to a manual car where you would put it in manual. So leave it in D.

It all depends on how long you're sitting in traffic for.

If you're going to be stationery for more than a couple of minutes then I would put it in neutral.

This eases the stress placed on the gearbox so less wear and tear.

Other auto cars that I've driven have said this in the handbook

just to add i have also been thinking this! ive only had my baby just over a week i want to know how to treat her properly! At the mo i try to put her in neutral as much as poss and put the handbrake on. I have a J spec with the big uk brakes, i heard if you keep the foot brake on you can warp the disks.........

CW once advised that leaving in D was best as this is what the new-york yellowcab drivers advise and they know how to maximise the life of their autoboxes

i heard if you keep the foot brake on you can warp the disks.........

every case of "warped brake disc" that I have investigated, whether on a racing car or a street car, has turned out to be friction pad material transferred unevenly to the surface of the disc

i heard if you keep the foot brake on you can warp the disks.........

I had forgotten to consider this when replying, but it is something that I am always aware of. If I have braked heavily, I will always apply the handbrake, and therefore usually (but not always) drop into Neutral.

Daman, Have a read of this article from the StopTech web site: "Warped" Brake Discs And Other Myths

 

Jake, it goes on to say..

..material transfer between the two materials can take place in a random fashion - resulting is uneven deposits and vibration under braking. Similarly, even if the brakes are properly broken, if, when they are very hot or following a single long stop from high speed, the brakes are kept applied after the vehicle comes to a complete stop it is possible to leave a telltale deposit behind that looks like the outline of a pad.

So I guess what it's saying is that "warped discs" is a myth, but "vibration under braking due to holding the brakes on when discs are warm" is genuine.. so the problem still occurs, it's just not what we thought it was, right?

edit: but then, what's the point in using Dial Test Calipers to measure disc runout, if it never happens?

Just been thinking about this recently, but I always leave my box in D with my foot on the footbrake when in traffic - this is the best way to treat the autobox isnt it? Shifting it into Neutral when in traffic doenst do it any good does it?

I've been wondering about this myself actually (never had an auto before)

There must be a time 'threshold' where it becomes beneficial to change into "N"

I have 2 supra autos.

Always leave in drive and leave plenty of room behind slow moving traffic or at traffic lights so i can let the car creep so as not to have to keep my foot on the brakes and heating them up, i personally never use the handbrake either ever unless parked on steep incline for safety.

My red n/a had for 5 yrs now and no probs silver turbo for 3 yrs also with no probs.

Bear in mind that with your foot on the brake it can dazzle drivers behind, which is impolite.

The supra was built tough for a reason, because the Toyota engineers knew the car would be "driven". I've owned several autos and never had a problem with leaving it in Drive, foot on the brake. However, as stated, if you're in a traffic jam and it looks like you'll be sitting for awhile, N+parking brake is the smart way to go. If you're worried about wear and tear, keep in mind that constant shifting to and from Drive and Neutral will cause wear to the tranny syncros so pick your option carefully. Personally, I'll be sticking with the D + brake option. You boys with the bigger UK brakes shouldn't worry. Again as stated, warped discs is most often caused by over-heated brakes during heavy braking and worn pads, not sitting still.

Aye, you only warp discs while braking hard from very high speeds (do it a few times in a row and your discs are toast)

It's inconceivable to warp discs just by pressing the pedal while sitting in a queue.

It's inconceivable to warp discs just by pressing the pedal while sitting in a queue.

Heat can't escape from under the pad?

So you've got a really HOT spot in the rotor metal under the pads and COLD everywhere else?

I wouldn't bet money on this, heat travels fast in such thick metal objects and it spreads quickly. So it would be dissipated pronto.

We're talking about tiny amounts of heat, too, the car is practically stationary.

I'm not saying it's true, I'm saying that is the theory as I understand it.

I can easily imagine circumstances where a car could have have very hot discs and pads at a standstill.

Heat can't escape from under the pad?

So you've got a really HOT spot in the rotor metal under the pads and COLD everywhere else?

I wouldn't bet money on this, heat travels fast in such thick metal objects and it spreads quickly. So it would be dissipated pronto.

We're talking about tiny amounts of heat, too, the car is practically stationary.

I think it's more about braking fairly heavily, for example at the end of a sliproad coming off the motorway, then keeping the pedal down as the lights are red. The brakes are hot from the stop you just did, and you haven't let off the brake while the disc is cooling. The area under the pad cools at a different rate to the rest of the disc.

That's the theory anyway, but the document Jake has just linked to suggests that this kind of braking does indeed cause a brake vibration phenomenon, but that it's actually due to pad friction-material getting baked onto the disc in the area under the pad, rather than the disc itself warping.

The last time I warped my front discs I kicked myself because I knew exactly how I'd done it. I anchored on from 140 down to 0 in a test of the brakes, then tootled back to my housing estate, garaged the car and thought "hmm, I wonder if the brakes have cooled down adequately...". I was about to touch them to test for heat and wisely stopped and put some spit on my finger first. Imagine my shock when, a good 5 minutes of slow driving and gentle braking after the hard stop, the spit flash boiled in the time it took me to remove my finger from the brake disc and squeal like a girl.

Stupidly, I then left the car there Unsuprisingly, I got the brake disc judder straight after that. I actually measured the runout on the discs, and both of them were thicker around about 1/4 of the disc - suspiciously close to a brake-pad sized chunk of disc. This correlated with:

1) every other time I warped my brake discs

2) the fact that I haven't warped them since because I do a looong cool down drive after caning them

3) seeing people on track days fail to do a coast down lap and ending up with discs so warped you can hear the pads catching the disc surface once every wheel rotation (scrape, scrape)

4) what Chris Wilson told me when I first warped my MkIII Supra discs

I don't think that just holding your car on the brakes will cause that problem, though, not in normal driving. You'd have to brake down to a dead stop from a high speed then sit like that until the discs had pretty much cooled. If you do end up in the situation, just leave a gap and then creep forwards half a wheel turn every couple of minutes to equalise the cooling

-Ian

I warped a set of disks in a single stop from 160+ down to 60-odd, with a big long cool-down period after.

Mind you, that was with shite Porterfield pads.

That's the theory anyway, but the document Jake has just linked to suggests that this kind of braking does indeed cause a brake vibration phenomenon, but that it's actually due to pad friction-material getting baked onto the disc in the area under the pad, rather than the disc itself warping.

Personally I've never seen that phenomenon on any of my discs, I've never heard it mentioned before, and as pad material is designed to be ablative and discs are designed to be the ablater, I can't see it happening - the stuck-on pad material would be eroded off with one good anchors-on moment.

-Ian

If you do end up in the situation, just leave a gap and then creep forwards half a wheel turn every couple of minutes to equalise the cooling

-Ian

call me anal, but that's exactly what I do

On similar lines, another dodgy situation can arise when you get home after a high speed run where you've used the brakes quite a bit, then park the car and pull the handbrake.

It got me first time round, I hadn't realised that it's a bad idea to engage handbrake with hot discs (hadn't crossed my mind at all, I was young and dumb )

Live and learn.

Some very interesting points made here.