Thread: Use of handbrake on downhill

So, to re-phrase an earlier question, is there anything to stop you if you have a catastrophic brake line failure (i.e. total fluid loss). If the handbrake works via ABS via brake pads, what would stop you?

Originally Posted by spudboy

So, to re-phrase an earlier question, is there anything to stop you if you have a catastrophic brake line failure (i.e. total fluid loss). If the handbrake works via ABS via brake pads, what would stop you?

The electric handbrake operates a separate drum brake inside the rear disc.
I didn't think the ABS system came into play when operating the handbrake as an emergency brake.......something else to test .

Originally Posted by TuffRR

I have the maxi-drive "rock crawling" gears in my auto Rangie. My biggest problem in low 1st on a steep descent is actually stopping the vehicle. At times I have needed to quickly throw it into neutral to get it to pull up.

I think they would be great in a manual with a standard motor but with 35's, a bucketload of torque from the 4.4, and a bloody low final drive, descending steep hills is not something that the gears have actually helped.

For pretty much anything else though they are awesome.

I have them also and find that problem.

With locking the torque converter the problem with mine is its been played with so has a monster stall setting. seems to vary between 200-300rpm. Gives great take of though!

Originally Posted by JDNSW

You're comments on the crossaxle situation are correct - but you have no engine braking either, so yoou will have to use the foot brake in any case.

With hand brakes operating on the rear wheels (or the transmission), if the vehicle is in four wheel drive, the hand brake is effectively operating on the front wheels if the centre diff is locked or if the gearbox is in gear and the clutch engaged even if the CDL is not locked.

From a functional point of view your argument against the transmission brake may have some merit, but actual function is not the only reason why most Landrovers have transmission brakes. The reason is partly history - when the Bantam Jeep was first designed in about 1940, transmission brakes were commonplace in the USA, probably because it was easier to fit one than to design a reliable wheel brake that reliably combined mechanical and hydraulic operation (and this still applies - many of us have memories of generations of Holdens and other cars with handbrakes that never worked because the mechanism rapidly rusted up and seized, especially the bowden cable bit of the linkage).

Since most four wheel drives until recently were direct descendants of the Bantam, many (including Landrover) retained the transmission brake because of its significant advantages in avoiding the problems with mechanical linkage to the rear brakes and dual function brakes, the latter becoming even more of a problem with the change to discs at the rear.
John

That does clear a lot up. I guess one other pragmatic point I've noticed (and someone with technical expertise might be able to explain) is that hand brakes are almost invariably drum brakes, even when discs are fitted all round. My Forester had a setup with drums-in-discs, and I see from this thread that the D3 does too (though with a lot more electronics). With a drum already engineered on the drive train, it saves a lot of R&D just to keep on using it, but with a clean sheet vehicle like the D3 a better ingineered solution can be had.

For my money, I'd take the Forester arrangement with completely independent brake circuits acting manually at the rear wheel in preference to either the D3 or Defender arrangements.

Steve

Originally Posted by scrambler

That does clear a lot up. I guess one other pragmatic point I've noticed (and someone with technical expertise might be able to explain) is that hand brakes are almost invariably drum brakes, even when discs are fitted all round. My Forester had a setup with drums-in-discs, and I see from this thread that the D3 does too (though with a lot more electronics). With a drum already engineered on the drive train, it saves a lot of R&D just to keep on using it, but with a clean sheet vehicle like the D3 a better ingineered solution can be had.

For my money, I'd take the Forester arrangement with completely independent brake circuits acting manually at the rear wheel in preference to either the D3 or Defender arrangements.

Steve

The problem with disc brakes for parking/emergency brakes is that the force that has to be applied to the pads is much greater than that which has to be applied to the shoes in a drum - and with the drum, the force is between two shoes pushing them apart, where with a discc it is between the two pads pulling them together, meaning that you need a very strong and rigid caliper, much heavier and more expensive than the backing plate plus expander of a drum. Where you are using a mechanical linkage, applying a higher force causes more problems because you have to have more leverage, which amplifies any lost motion and the effects of the mechanism flexing. Add to this, the advantages of disc brakes over drums are non-existent in this application - you can't simply make it self adjusting with mechanical operation, and since it is designed primarily as a parking brake the better cooling of the disc is irrelevant. While it is possible to make disc parking brakes, most manufacturers seem to have decided that it is easier and cheaper to use drums, this often being why they are retained for the rear wheels.
However, my preference is still for a transmission brake for off road use due to the lack of vulnerability of the linkage.

Originally Posted by JDNSW

The problem with disc brakes for parking/emergency brakes is that the force that has to be applied to the pads is much greater than that which has to be applied to the shoes in a drum - and with the drum, the force is between two shoes pushing them apart, where with a discc it is between the two pads pulling them together, meaning that you need a very strong and rigid caliper, much heavier and more expensive than the backing plate plus expander of a drum. Where you are using a mechanical linkage, applying a higher force causes more problems because you have to have more leverage, which amplifies any lost motion and the effects of the mechanism flexing. Add to this, the advantages of disc brakes over drums are non-existent in this application - you can't simply make it self adjusting with mechanical operation, and since it is designed primarily as a parking brake the better cooling of the disc is irrelevant. While it is possible to make disc parking brakes, most manufacturers seem to have decided that it is easier and cheaper to use drums, this often being why they are retained for the rear wheels.
However, my preference is still for a transmission brake for off road use due to the lack of vulnerability of the linkage.

I have a X-Eng disc handbrake on my rangie and it is very good. I intend to fit one to the disco soon.

No more problems with the handbrake not holding.

Here's a question from a novice.
I have a late series TD5 D2, auto. I've read for economy reasons the torque convertor locks up at a given speed ?
If this is true, then there should be a solenoid that controls this? Is this correct?
If there is a solenoid, would it be possible to wire in a switch to lock the torque convertor for down hill assents?
Cheers,
John

not too sure about the new autos but in the old school ones
the torque converter lock up is controled by the front speed govenor in the box and its driven directly by the output turbine of the torque converter so that when the converter output speed is high enough (turbine speed is aproximately equal to impeller input speed) it then locks up...

In most torque converters the lockup plate is not designed to cope with massively different plate RPM's...

Not being an autobox pro (read some of my rants I think they are eeeevil) if you like I can ask the auto specialist at work..