Hyundai i20 Handbrake

System

IanMSpencer wrote: »

I think it is important that such an operation was brought to the attention of the owner. It is not something that is taught.

Yet it is in the manual of pretty much every car with a park brake that operates on disc brakes and has been for many years. That example I posted was in both my MX5 and my Ford Mondeo manuals.

Consider if you hired an i20. Would you read the manual before driving off to find that there was a recommended technique for a handbrake requiring the pressing of the foot brake? Or what about the first journey home from the dealership?

Given how almost every car requires it and people seem unaware then it suggests very few people ever read a manual to their car. Perhaps they should and then it'd stop them doing things that cause problems. Quite why you'd not read a manual for something which is the most expensive thing you'll ever buy after your house I don't know.

Generally, I think these instructions are simply excuses for them recognising that they have designed a handbrake system that requires more force than some drivers can readily apply.

It is nothing to do with that at all and everything to do with the laws of physics. You need to apply more force than you can on just the handbrake alone in order to push the pistons in the caliper further out because the discs shrink as they cool down but the pads remain in the same position. You therefore need to put more pressure on when you apply the handbrake and the discs are warm so there's sufficient pressure to hold the car when the discs have cooled and the pressure from the pads is less.

As for the interlock it adds unnecessary expense, complexity and another failure point and do we really need everything dumbing down to the levels they do in the USA with their cars?

oldagetraveller

"Yet it is in the manual of pretty much every car with a park brake that operates on disc brakes and has been for many years. That example I posted was in both my MX5 and my Ford Mondeo manuals."

It is no doubt additionally advised for cars where the parking brake is operated by shoes in a drum incorporated with the disc.
It was actually my Toyota Yaris manual where the advice I quoted came from - that has drum rear brakes. I'm sure the advice, if memory serves, was also given in older cars with drums all round. That was to apply the brakes using the foot pedal, then take up the slack in the cable to avoid over stressing it. i.e. the hydraulics do the work, not the cable.
If steel cables don't stretch these days then they must be using really super duper non stretch strands. If so there's no point for handbrake cable adjustment to compensate for stretching which is still fitted to cable operated handbrakes.
As you say, Tarambor, the advice has been in the manual of just about every car I've owned over many years, from various manufacturers.
Maybe Ian should contact a few manufacturers to tell them of their error?

nickcc

Had a similar experience many years ago with a Vauxhall Chevette. Parked on hill applied handbrake, came out of shops and thought car stolen. Ran home, about half a mile, and phoned Police and reported car stolen. Police arrived and told me car found and to come with them. Long story short, car had rolled back down road and stopped on wall, fortunately no damage, turns out when I got out of car tension had been taken of handbrake cables allowing car to roll back, still got fined £20 for insecure handbrake. As a mechanic I was always taught never to leave vehicle parked in gear when in workshops for safety reasons, something that has always stuck with me.

Car_54

nickcc wrote: »

Had a similar experience many years ago with a Vauxhall Chevette. Parked on hill applied handbrake, came out of shops and thought car stolen. Ran home, about half a mile, and phoned Police and reported car stolen. Police arrived and told me car found and to come with them. Long story short, car had rolled back down road and stopped on wall, fortunately no damage, turns out when I got out of car tension had been taken of handbrake cables allowing car to roll back, still got fined £20 for insecure handbrake. As a mechanic I was always taught never to leave vehicle parked in gear when in workshops for safety reasons, something that has always stuck with me.

But presumably you were also taught to leave it in gear when parked on a hill ...

nickcc

Car_54 wrote: »

But presumably you were also taught to leave it in gear when parked on a hill ...

Certainly never part of my driving instruction way back in 1963, nor in fact part of my advanced driving, defensive driving courses, HGV or PSV/PCV training. In fact if the hand/parking brake is incapable of holding the vehicle then it shouldn't be on the road.

BeenThroughItAll

nickcc wrote: »

Certainly never part of my driving instruction way back in 1963, nor in fact part of my advanced driving, defensive driving courses, HGV or PSV/PCV training. In fact if the hand/parking brake is incapable of holding the vehicle then it shouldn't be on the road.

Hence the name... parking brake

Car_54

nickcc wrote: »

Certainly never part of my driving instruction way back in 1963, nor in fact part of my advanced driving, defensive driving courses, HGV or PSV/PCV training. In fact if the hand/parking brake is incapable of holding the vehicle then it shouldn't be on the road.

Even in 1963 the Highway Code was part of the driving test.
"Rule 252

Parking on hills. If you park on a hill you should:

• park close to the kerb and apply the handbrake firmly
• select a forward gear and turn your steering wheel away from the kerb when facing uphill
• select reverse gear and turn your steering wheel towards the kerb when facing downhill
• use ‘park’ if your car has an automatic gearbox."

But it would be undestandable if you'd forgotten in the ensuing half century.

Deneb

nickcc wrote: »

Certainly never part of my driving instruction way back in 1963, nor in fact part of my advanced driving, defensive driving courses, HGV or PSV/PCV training. In fact if the hand/parking brake is incapable of holding the vehicle then it shouldn't be on the road.

But conversely was part of my police driving instruction since 1978 from standard through to advance level and refreshers. Not just on hills, but taught to always leave the vehicle in gear with parking brake fully applied when parked, and always check that the parking brake is fully applied and the gearbox is in neutral before starting. Manual gearbox obviously.

IamNotAllowedToUseMyName

oldagetraveller wrote: »

If steel cables don't stretch these days then they must be using really super duper non stretch strands. If so there's no point for handbrake cable adjustment to compensate for stretching which is still fitted to cable operated handbrakes.

Compensation is for pad wear, component wear and initial installation. Steel cables do not stretch significantly - certainly not in the sense that having been put under tension they do not return to the same length each time, there is of course some lengthening under strain. The idea that a hard pull on a handbrake avoids that x% extra force that would permanently lengthen a cable is nonsense. If a brake cable is significantly stretching and not returning to its original length, then it suggests it is failing - corrosion, broken strands and so on.

In your school days, this was the thing that Young's Modulus was on about - did you ever apply weights to a copper cable and measure each time? There is a point beyond which the strength of the cable is overcome. Brake cables are not like guitar strings which do stretch because they are made of different materials. Brake cables are made from the same sort of steel you use on cable cars, which are very long yet barely change in length under load. Haven't found any tables specific to diameters relevant to brake cables, but you are probably talking of forces more than 10 times that you can apply with a handbrake to get the cable to fail - think about it - if a hard pull was enough to induce cable stretch then what tolerance against failure has the braking system got?

With regard to using the foot brake to help hold the brake, it doesn't really make sense as people describe it. The force to clamp the brake once the foot brake is released has to be generated in the cable itself and is not generated by pressing the foot brake.

For pressing the foot brake to make a difference in the handbrake holding, there has to be a significant opposite force it is overcoming, not just the friction in the system of applying the brake. So if people are saying that to generate enough force in the cable, you use the foot brake to compensate for the opening force, then that can make sense (but then that is only the force that one would normally apply when going through a normal stopping routine), if people are saying that you have to use the foot brake to get the initial force in place, then that doesn't make sense, as once the foot brake is released, the only clamping force that remains is the hand brake.

Theories of simply closing the calipers on brakes don't make sense in terms of force applied, once the pads are in contact with the disc, pressing the foot brake can't generate more force in the cable which is what is required.

My understanding is more that the reason for failure on disc brakes is that you cannot rely on the braking force being applied when first set being retained. All the fluff above is about getting an initial force. Pressing the brake might help gain extra force on the brake, but if the user doesn't then put the full force into the hand brake cable, then it doesn't make any difference, you still end up with a hand brake that is not fully applied.

Therefore, the basic advice is that you must always apply a handbrake to its full extent, not simply assume that a handbrake that holds can retain the same holding force.

almillar

What car was that then?

Most modern cars that still have handbrakes tell you NOT to press the button.

This includes your favourite car, BeenThroughItAll, the Renault Zoe. Anyway, just parking in gear prevents these problems