BGOL

[jont]

Are you still in doubt about the benefits of separation after looking at the linked threads?

Yes! I understand "what" and "how" and "when" but I can't find "why".

Decelerating for a turn, braking and engaging the appropriate gear for exit from the turn, would seem to save time without any obvious dangers and maintain progress.

Still haven't found "why"!

Because if you're sticking to one pedal at a time (ie not heel and toeing), then BGOL results in dragging the clutch to match engine revs to road speed for the new gear. The only exception is at very low speed where the new gear approximately matches idle speed, or you are doing a partial overlap, so the revs can be raised before the clutch is brought up.
If you take an intermediate gear (without overlap), then the braking process ends up being done in stages - ie brake -> off brake/change gear -> brake -> etc. which is both less smooth, causing "nodding dog" for passengers, and potentially misleading for following drivers as they see your brake lights go on/off multiple times.

[TripleS]

Dave, do you accept that it is bad practice to change down without rev matching?

Yes, I certainly do. Rev matching is important if we are to drive in a mechanically sympathetic manner.

With all due respect to Michael, I would suggest that far more harm is done to clutches and other transmission components by making a down change and bringing the revs into line by re-engaging the clutch and letting the engine speed be dragged up to the new level in that way, than by the considered use of lower gears for speed reduction. Making a downward gearchange and failing to rev match to a decent standard could be a recipe for reduced stability, safety and passenger comfort; he's right about that.

Some time ago we had people on PH talking about cars being spun, due entirely to making a clumsy downchange into a low gear, so it can be a serious matter. I think they were talking about cars like a TVR - large, powerful V8 engine, rear wheel drive, lots of engine braking etc. I've no experience of TVRs and that type of car, but they will not be the sort of car that will forgive the ham-fisted driver.

Best wishes all,
Dave.

[Ancient]

The use of a lower gear to aid the slowing process (in lieu of braking) is acceptable when demonstrating "acceleration sense" but is inefficient in other circumstances and is not actually controlled. It also negates the advanced aspect of being in the right gear for whatever you may be doing which, ideally, should be achieved with just one gear change.

On one of my regular routes I enter a 30 limit from NSL just after a 40mph (ish, depending on conditions) bend, so that's a 4th to 3rd change for the limit. Aprox 150yds later (visible just after passing the 30 signs) is a steep downhill with a sharp left bend, a road entering from the right, parked cars and shops on the left just around the bend; a 20mph max corner then.
If you don't know the area, the first you see notice is the dip and bend ahead (shown by the upper stories of the houses across) so you'll brake then take 2nd (probably - at least in our cars) to approach the hazard, hopefully covering the brake in case the car on the right pulls out or an oncoming vehicle cuts the corner or... etc.
Since I know the hazard well I avoid making two changes and (in my car which is happy in 2nd to 40mph) simply select 2nd entering the 30 limit - this seems smoother to me and has a more responsive throttle (i.e. greater engine braking adding to the mix) before the components of the hazard are all in sight. But I'm using "a lower gear to aid the slowing process " Am I out of control?
(I'm also 'breaking the system' by selecting gears before speed: Naughty Boy!)

[GJD]

Decelerating for a turn, braking and engaging the appropriate gear for exit from the turn, would seem to save time without any obvious dangers and maintain progress.

Slowing for a turn into a side road with following traffic is one of the situations often given as an example of where BGOL might be useful because you get off the main road and out of the way sooner. I'm not sure whether BGOL vs no BGOL would make much difference to the overall time to get through the hazard and out the other side though.

I think the thing to do, rather than getting too hung up on examples where BGOL avoidance might seem counter-productive, is to think about the various benefits that slowing on the brakes in a single braking phase followed by a single gear change can offer and see where those benefits are useful in your driving.

[Horse]

Decelerating for a turn, braking and engaging the appropriate gear for exit from the turn, would seem to save time without any obvious dangers and maintain progress.

Slowing for a turn into a side road with following traffic is one of the situations often given as an example of where BGOL might be useful because you get off the main road and out of the way sooner.

Ah! is that why one of the main points of AD is improving forward obs and planning, because driving 'badly' takes less road space?

[trashbat]

Because if you're sticking to one pedal at a time (ie not heel and toeing), then BGOL results in dragging the clutch to match engine revs to road speed for the new gear.

This doesn't require H&T, depending on your definition of BGOL anyway. I regularly overlap clutch down and braking, but not clutch up and braking.

[zadocbrown]

(I'm also 'breaking the system' by selecting gears before speed: Naughty Boy!)

Not really - you go through the sytem twice, the 2nd time you happen to already be in the right gear. The system should be used flexibly.

[TripleS]

My experience is the same as Zadocbrown with my diesel. I wasn't putting the clutch down early enough. It's fine now and no BGOL.

But with the engine merely at idle 2nd gear does 12mph happily... So I sometimes have to use 1st gear for tight turns

I've only owned one diesel car (Pug 406 HDi, had it almost 13 years now) and I haven't found any particular difficulty with it. In 5th gear it does 28 mph/1000 rpm, and in some situations it will potter about quite happily in 40 mph limts, and even some 30s, using the highest gear.

Back in 2004/2006 I drove quite a few Mondeo TDCi models with the 130 PS engine and 6 speed gearbox, and I liked those. On that model 6th gear yielded about 37 mph/1000 rpm, so naturally it wasn't happy about the use of its highest gear in 30/40 limits: that would be asking a bit too much. I found built-up areas were best travelled in 4th gear with that model.

They might only be machines but we still need to find out what they are happy with. If we do that, we can get along pretty well with most things.

[GJD]

Slowing for a turn into a side road with following traffic is one of the situations often given as an example of where BGOL might be useful because you get off the main road and out of the way sooner.

Ah! is that why one of the main points of AD is improving forward obs and planning, because driving 'badly' takes less road space?

Afraid you've lost me there

[Horse]

Slowing for a turn into a side road with following traffic is one of the situations often given as an example of where BGOL might be useful because you get off the main road and out of the way sooner.

Ah! is that why one of the main points of AD is improving forward obs and planning, because driving 'badly' takes less road space?

Afraid you've lost me there

That help?

[Silk]

Because if you're sticking to one pedal at a time (ie not heel and toeing), then BGOL results in dragging the clutch to match engine revs to road speed for the new gear.

This doesn't require H&T, depending on your definition of BGOL anyway. I regularly overlap clutch down and braking, but not clutch up and braking.

As far as I'm concerned, what you have described is proper separation. It's completely pointless, in my opinion, to come off the brakes and go into a kind of "limbo" phase before going anywhere near any of the other controls.

I think that insisting on "full" separation at all times is down to misinterpretation as much as anything else.

As far as I'm concerned, if you're off the brakes and back on the power when the clutch is released, you've separated.

[Russ_H]

Here is an extract from High-Performance Driving for You, by Tom Wisdom. It is on page 78 of my copy. It is a transcription of a recording of a commentary given by John Miles.

...Jaguar falling away behind, no junctions. Speed now just coming up to 140 in top. Mirror. Nothing behind. Looking well ahead road curves away to left, still clear. It's not a bend, just a sweep and can see well across it. Holding my speed around the sweep. Way ahead there's a roundabout. Mirror. Nothing behind. Bringing my speed down now for the roundabout. Down to 80, 70, into third. Still braking. Going straight on so no need to signal. Bit of traffic on the roundabout and going around it at 20 mph...

Any thoughts on BGOL here?

[GJD]

As far as I'm concerned, what you have described is proper separation. It's completely pointless, in my opinion, to come off the brakes and go into a kind of "limbo" phase before going anywhere near any of the other controls.

I think that insisting on "full" separation at all times is down to misinterpretation as much as anything else.

As far as I'm concerned, if you're off the brakes and back on the power when the clutch is released, you've separated.

To be honest, I'm not sure much is made of the distinction between full and partial separation (yes, I know I introduced it in this thread ). I don't remember my RoSPA tutor talking about the distinction at all.

That said, I do try and fully separate sometimes as I find that rev matching the gear change can be easier if I start the process with my right foot on the accelerator so I don't have to pick the revs all the way up from idle.

[Silk]

Here is an extract from High-Performance Driving for You, by Tom Wisdom. It is on page 78 of my copy. It is a transcription of a recording of a commentary given by John Miles.

...Jaguar falling away behind, no junctions. Speed now just coming up to 140 in top. Mirror. Nothing behind. Looking well ahead road curves away to left, still clear. It's not a bend, just a sweep and can see well across it. Holding my speed around the sweep. Way ahead there's a roundabout. Mirror. Nothing behind. Bringing my speed down now for the roundabout. Down to 80, 70, into third. Still braking. Going straight on so no need to signal. Bit of traffic on the roundabout and going around it at 20 mph...

Any thoughts on BGOL here?

I'm guessing the driver has preselected third, ready to put the power back on once the braking phase was complete. Of course, I could be wrong but there's no evidence from this that the driver did a BGOL.

[Silk]

As far as I'm concerned, what you have described is proper separation. It's completely pointless, in my opinion, to come off the brakes and go into a kind of "limbo" phase before going anywhere near any of the other controls.

I think that insisting on "full" separation at all times is down to misinterpretation as much as anything else.

As far as I'm concerned, if you're off the brakes and back on the power when the clutch is released, you've separated.

To be honest, I'm not sure much is made of the distinction between full and partial separation (yes, I know I introduced it in this thread ). I don't remember my RoSPA tutor talking about the distinction at all.

That said, I do try and fully separate sometimes as I find that rev matching the gear change can be easier if I start the process with my right foot on the accelerator so I don't have to pick the revs all the way up from idle.

There are still come "conservatives" out there who insist that the braking phase must be over before a hand goes on the gearstick and a foot goes on the clutch, although they're very few and far between.