Auto driving help wanted

[deman]

How can automatic drive be held when going down a long steep hill without relying on braking? I am new to auto driving.

 

[Miffy]

if you have tiptronic, knock the gear lever to the left to manually drop a gear.

 

[gladholm]

Pre select - going downhill in an auto...

Normally at the top of a hill, at appropriate speed having braked to slow down if necessary, move selector to 4, 3 or 2 as appropriate. Do not touch the brakes or ride the brakes down the hill. If the downhill speed is too fast for the gradient, brake to slow the speed, and downshift again, and let the engine do the work.

Don't worry if the engine appears to be highly revving, that is the effect of engine braking. At the bottom of the hill, select the next higher gear or D as appropriate. Sit back smugly knowing that you descended without wearing out your brake pads like everyone else!

 

[television]

We have 2 different gear boxes on our cars, the boxes before the 722.6 gave engine braking, plus you could lock the car into a lower gear.

Boxes after 06-96 all have to be selected on the shift, but one should remember that it is far cheaper to replace brake parts than auto box parts.

This use of engines braking is not allowed on an airplane when not run in, the reverse thrust causes the piston rings to oscillate with damage to the bores

 

[Juddian]

Bearing in mind the brakes fitted to our cars are more than capable of handling anything you want to throw at them, i'd rather use the brakes for slowing and not put unecessary wear on the box.

The brake pads all round for my car are approx £40/£50 for Textar or equivalent good make, and another £100ish for discs all round.
I haven't priced a gearbox overhaul and don't have any intention of finding out the hard way....sufficient knowledge being it will be the cost of dozens of brake sets.

 

[Alex M Grieve]

Bearing in mind the brakes fitted to our cars are more than capable of handling anything you want to throw at them, i'd rather use the brakes for slowing and not put unnecessary wear on the box.

I've cracked this one! I do use brakes, just not very often. :Oops:

Pads last 44,000. I have never had to replace discs. And that helps reduce tyre wear too.

 

[GRAHAME2001]

I've cracked this one! I do use brakes, just not very often. :Oops:

Pads last 44,000. I have never had to replace discs. And that helps reduce tyre wear too.

Errrrr Which one's the brake then? :lol:

 

[Miffy]

isnt that called the BMW in front?

 

[Alex M Grieve]

isn't that called the BMW in front?

I can imagine you seeing small ones in your mirror Mark - but one in front?

 

[Miffy]

oops, of course, fancy me admitting in public that i let a bmw get in front eh lol

 

[mikestrivens]

The Institute of Advanced Motorists recommends that you use the brakes for all but exceptional conditions (e.g. snow, slippery conditions, very steep gradients) as brake pads are far cheaper to replace that gearbox parts.

 

[teddycatkin]

Autos only have two pedals stop and go --easy !
Where are these long downhill slopes that you need to slow down on in a mercedes ?
(Mine all go a bit slower uphill -but like sh-- off a shovel downhill)
I only use the big pedal for stopping.

 

[television]

(Mine all go a bit slower uphill -but like sh-- off a shovel downhill)
.

Thats odd,wonder whats wrong with it

 

[jberks]

Bottom line, if you roll down a steep hill in 5th in a manual, it will pick up speed. You can select 4th, 3rd etc by shifting the lever. There is no difference with an auto. You can equally select any gear on a tip shift model by knocking the lever to the left. Equally you can slide a non tip lever back one or two notches to select a lower gear. So there really isn't any difference. That said, we generally don't bother and just ride the brake.

 

[woodley_bob]

Agree with the general advice so far - use brakes to slow down, but use a lower gear hold to maintain the lower speed once you have slowed down. I'm an observer with the Advanced Motorists and that's agrees with the official guidance they have issued (as per mikestrivens' post).

However, I've only recently got my first Merc (W211 E220 diesel - 5 speed) and was a bit confused by the gearbox doing some of this for me automatically. Specific example:
- driving along happily on the flat, let's say about 45 in 4th
- start going downhill and car starts to speed up
- come off throttle, steep hill now so car keeps speeding up
- touch brake to keep control of speed
- gear box changes down to lower gear itself during braking!
It doesn't do this when braking on the flat, so there's obviously a bit of computer logic going on in there. It seems that technology has moved on a lot since my last Auto (old BMW E32 730 from about 1990).

I do use the manual holds a bit, but the behaviour above makes it a bit confusing as tiptronic will change one gear lower than you are at the moment - even if it's just changed down itself - result, sudden engine braking. As a result I find that letting the box do its stuff works better in the "going down a hill" scenario.

Anybody know when this behaviour came in?

 

[Alex M Grieve]

Bottom line, if you roll down a steep hill in 5th in a manual, it will pick up speed. You can select 4th, 3rd etc by shifting the lever. There is no difference with an auto. You can equally select any gear on a tip shift model by knocking the lever to the left. Equally you can slide a non tip lever back one or two notches to select a lower gear. So there really isn't any difference. That said, we generally don't bother and just ride the brake.

I originally learned to drive in HM Forces, courtesy of Her Majesty. Learning on a truck with a crash gearbox (Commer Q4), I was taught that the correct technique was to descend hills in the same gear as you would use to go up them - particularly important if you are carrying a full load and with the drum brakes of that era.

It is a rule that still holds true in mountainous terrain, although you might not need to revert to it in Essex too often. Try it when next in the Alps. Works a treat.

 

[st4]

The Institute of Advanced Motorists recommends that you use the brakes for all but exceptional conditions (e.g. snow, slippery conditions, very steep gradients) as brake pads are far cheaper to replace that gearbox parts.

A modern car has more than sufficient brakes to slow itself down without the use of engine braking. So long as the brakes have sufficient power to lock the wheels (which they do hence the need for ABS) then they are the only thing you need to slow the car down.

 

[Rory]

However, I've only recently got my first Merc (W211 E220 diesel - 5 speed) and was a bit confused by the gearbox doing some of this for me automatically. Specific example:
- driving along happily on the flat, let's say about 45 in 4th
- start going downhill and car starts to speed up
- come off throttle, steep hill now so car keeps speeding up
- touch brake to keep control of speed
- gear box changes down to lower gear itself during braking!
It doesn't do this when braking on the flat, so there's obviously a bit of computer logic going on in there.

There's a steep downhill run on one of the approaches to my house and my car (late 04 C270CDi) doesn't downshift itself - perhaps it's the higher speed, it's a 70 limit but the car will soon be doing 90 if you don't hold it back. The bottom of the hill is a favourite speed camera van spot.

However it does seem to downshift unexpectedly early when braking on the flat - there's a long run up to a set of lights near home and trying to slow for those without stopping forever catches me out as the car downshifts and slows itself more than I want it to.

 

[television]

As I said earlier there are differences in our boxes in the way that they perform.

A simple test is to go down a hill and slip into N, the go back to D, watch the rev counter when doing this, if the engine speeds up as you go back to D then you have some automatic engine braking (early cars) on later cars the rev counter will not change from idle

 

[st4]

As I said earlier there are differences in our boxes in the way that they perform.

A simple test is to go down a hill and slip into N, the go back to D, watch the rev counter when doing this, if the engine speeds up as you go back to D then you have some automatic engine braking (early cars) on later cars the rev counter will not change from idle

In my car it depends on the mode.

In S mode mine reverts to idle speed (880rpm) when decsedning a steep hill-approach at 30mph in 4th it will gain then the RPM drops. On the same steep hill in C mode it holds 1200rpm (30mph in 4th). 3rd holds 30mph