Why does the rear of my vehicle sink when I apply the handbrake on a downward gradient?
This is something that I've always wondered. I'm no mechanic (web developer, actually) with very basic knowledge of vehicle mechanics so I can only guess at something like brake pipe pressure being involved, but that's about as far as I could guess. I can't find any article on the subject either, though I admit it's quite a niche question.
Case in point; I'm leaving the motorway via a downhill off-ramp and come to a stop in the queue using the foot brake (still downhill) - I shift into neutral, apply the handbrake and release the foot brake. As I release the foot brake the rear of the car sinks, as though the suspension was being elevated by the foot brake, though I've no idea how this is possible.
I apologise in advanced if this is rudimentary to those versed in vehicle mechanics and may be obvious. I've come to the assumption that it's normal behaviour and not an issue, but I can't remember whether or not this occurred with my previous two cars.
If it's relevant, here's my vehicle information:
Citroen Xsara Picasso Exclusive, 2006 (06),
1.6 HDI (Diesel) - 92HP,
Manual Transmission
manual-transmission handbrake stopping
edited yesterday
motosubatsu
4,2651826
asked yesterday
Kallum TantonKallum Tanton
15816
New contributor
Kallum Tanton is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
This is something that I've always wondered. I'm no mechanic (web developer, actually) with very basic knowledge of vehicle mechanics so I can only guess at something like brake pipe pressure being involved, but that's about as far as I could guess. I can't find any article on the subject either, though I admit it's quite a niche question.
Case in point; I'm leaving the motorway via a downhill off-ramp and come to a stop in the queue using the foot brake (still downhill) - I shift into neutral, apply the handbrake and release the foot brake. As I release the foot brake the rear of the car sinks, as though the suspension was being elevated by the foot brake, though I've no idea how this is possible.
I apologise in advanced if this is rudimentary to those versed in vehicle mechanics and may be obvious. I've come to the assumption that it's normal behaviour and not an issue, but I can't remember whether or not this occurred with my previous two cars.
If it's relevant, here's my vehicle information:
Citroen Xsara Picasso Exclusive, 2006 (06),
1.6 HDI (Diesel) - 92HP,
Manual Transmission
manual-transmission handbrake stopping
edited yesterday
motosubatsu
4,2651826
asked yesterday
Kallum TantonKallum Tanton
15816
New contributor
Kallum Tanton is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
This is something that I've always wondered. I'm no mechanic (web developer, actually) with very basic knowledge of vehicle mechanics so I can only guess at something like brake pipe pressure being involved, but that's about as far as I could guess. I can't find any article on the subject either, though I admit it's quite a niche question.
Case in point; I'm leaving the motorway via a downhill off-ramp and come to a stop in the queue using the foot brake (still downhill) - I shift into neutral, apply the handbrake and release the foot brake. As I release the foot brake the rear of the car sinks, as though the suspension was being elevated by the foot brake, though I've no idea how this is possible.
I apologise in advanced if this is rudimentary to those versed in vehicle mechanics and may be obvious. I've come to the assumption that it's normal behaviour and not an issue, but I can't remember whether or not this occurred with my previous two cars.
If it's relevant, here's my vehicle information:
Citroen Xsara Picasso Exclusive, 2006 (06),
1.6 HDI (Diesel) - 92HP,
Manual Transmission
manual-transmission handbrake stopping
edited yesterday
motosubatsu
4,2651826
asked yesterday
Kallum TantonKallum Tanton
15816
New contributor
Kallum Tanton is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
This is something that I've always wondered. I'm no mechanic (web developer, actually) with very basic knowledge of vehicle mechanics so I can only guess at something like brake pipe pressure being involved, but that's about as far as I could guess. I can't find any article on the subject either, though I admit it's quite a niche question.
Case in point; I'm leaving the motorway via a downhill off-ramp and come to a stop in the queue using the foot brake (still downhill) - I shift into neutral, apply the handbrake and release the foot brake. As I release the foot brake the rear of the car sinks, as though the suspension was being elevated by the foot brake, though I've no idea how this is possible.
I apologise in advanced if this is rudimentary to those versed in vehicle mechanics and may be obvious. I've come to the assumption that it's normal behaviour and not an issue, but I can't remember whether or not this occurred with my previous two cars.
If it's relevant, here's my vehicle information:
Citroen Xsara Picasso Exclusive, 2006 (06),
1.6 HDI (Diesel) - 92HP,
Manual Transmission
manual-transmission handbrake stopping
manual-transmission handbrake stopping
edited yesterday
motosubatsu
4,2651826
asked yesterday
Kallum TantonKallum Tanton
15816
New contributor
Kallum Tanton is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited yesterday
motosubatsu
4,2651826
asked yesterday
Kallum TantonKallum Tanton
15816
New contributor
Kallum Tanton is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited yesterday
motosubatsu
4,2651826
edited yesterday
motosubatsu
4,2651826
edited yesterday
motosubatsu
4,2651826
4,2651826
asked yesterday
Kallum TantonKallum Tanton
15816
New contributor
Kallum Tanton is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked yesterday
Kallum TantonKallum Tanton
15816
asked yesterday
Kallum TantonKallum Tanton
15816
15816
New contributor
Kallum Tanton is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
Kallum Tanton is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Kallum Tanton is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
With the handbrake on, the rear wheel is not able to rotate. When the foot brake is released the car will try to move forward. This will cause a rotational force on the rear tire. Since the rear tire cannot turn, the rotational force will be transferred to the axle mounting point 'A' which will cause the road spring to compress, hence lowering the car body. If you did the same thing going up hill, you will find that the body raises instead.
answered yesterday
HandyHowieHandyHowie
9,80511235
13
The design of the rear is the main reason for this. Being on a swing arm causes the squat. Vehicles without this design, namely those with a solid 4-link or those with independent rear suspension (IRS) will not incur the "squat" you'd get here.
– Pᴀᴜʟsᴛᴇʀ2♦
yesterday
3
@Pᴀᴜʟsᴛᴇʀ2's comment is critical for this answer's explanation. I drive a pick-up and was confused when trying to think through this explanation in my head. (I was already confused by the question, but assumed it was just something I hadn't noticed before.)
– Zach Mierzejewski
23 hours ago
Indeed. It's the trailing-arm suspension that causes this effect. IIRC my old Peugeot 106 did the same thing.
– spender
3 hours ago
add a comment |
When you stop the car using the footbrake, all four wheels are held stationary by the brake. When you apply the handbrake, this locks the rear wheels only (in most cars) - as you then release the footbrake, this releases the front wheels, allowing them to turn ever so slightly. Gravity is still trying to pull the whole car downwards, and so it settles down on the rear suspension - it's something that's hard to describe!
answered yesterday
Nick C♦Nick C
25.4k44291
1
Ah, that makes perfect sense and, while I agree that is difficult to describe, I understand you. I was thinking the suspension was expanded and was settling back to rest, however you've shown that it was at rest and the cars front moving forward slightly is actually compressing the rear suspension - if I've got that right! Thanks again.
– Kallum Tanton
yesterday
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
With the handbrake on, the rear wheel is not able to rotate. When the foot brake is released the car will try to move forward. This will cause a rotational force on the rear tire. Since the rear tire cannot turn, the rotational force will be transferred to the axle mounting point 'A' which will cause the road spring to compress, hence lowering the car body. If you did the same thing going up hill, you will find that the body raises instead.
answered yesterday
HandyHowieHandyHowie
9,80511235
13
The design of the rear is the main reason for this. Being on a swing arm causes the squat. Vehicles without this design, namely those with a solid 4-link or those with independent rear suspension (IRS) will not incur the "squat" you'd get here.
– Pᴀᴜʟsᴛᴇʀ2♦
yesterday
3
@Pᴀᴜʟsᴛᴇʀ2's comment is critical for this answer's explanation. I drive a pick-up and was confused when trying to think through this explanation in my head. (I was already confused by the question, but assumed it was just something I hadn't noticed before.)
– Zach Mierzejewski
23 hours ago
Indeed. It's the trailing-arm suspension that causes this effect. IIRC my old Peugeot 106 did the same thing.
– spender
3 hours ago
add a comment |
With the handbrake on, the rear wheel is not able to rotate. When the foot brake is released the car will try to move forward. This will cause a rotational force on the rear tire. Since the rear tire cannot turn, the rotational force will be transferred to the axle mounting point 'A' which will cause the road spring to compress, hence lowering the car body. If you did the same thing going up hill, you will find that the body raises instead.
answered yesterday
HandyHowieHandyHowie
9,80511235
13
The design of the rear is the main reason for this. Being on a swing arm causes the squat. Vehicles without this design, namely those with a solid 4-link or those with independent rear suspension (IRS) will not incur the "squat" you'd get here.
– Pᴀᴜʟsᴛᴇʀ2♦
yesterday
3
@Pᴀᴜʟsᴛᴇʀ2's comment is critical for this answer's explanation. I drive a pick-up and was confused when trying to think through this explanation in my head. (I was already confused by the question, but assumed it was just something I hadn't noticed before.)
– Zach Mierzejewski
23 hours ago
Indeed. It's the trailing-arm suspension that causes this effect. IIRC my old Peugeot 106 did the same thing.
– spender
3 hours ago
add a comment |
With the handbrake on, the rear wheel is not able to rotate. When the foot brake is released the car will try to move forward. This will cause a rotational force on the rear tire. Since the rear tire cannot turn, the rotational force will be transferred to the axle mounting point 'A' which will cause the road spring to compress, hence lowering the car body. If you did the same thing going up hill, you will find that the body raises instead.
answered yesterday
HandyHowieHandyHowie
9,80511235
With the handbrake on, the rear wheel is not able to rotate. When the foot brake is released the car will try to move forward. This will cause a rotational force on the rear tire. Since the rear tire cannot turn, the rotational force will be transferred to the axle mounting point 'A' which will cause the road spring to compress, hence lowering the car body. If you did the same thing going up hill, you will find that the body raises instead.
answered yesterday
HandyHowieHandyHowie
9,80511235
answered yesterday
HandyHowieHandyHowie
9,80511235
answered yesterday
HandyHowieHandyHowie
9,80511235
answered yesterday
HandyHowieHandyHowie
9,80511235
9,80511235
13
The design of the rear is the main reason for this. Being on a swing arm causes the squat. Vehicles without this design, namely those with a solid 4-link or those with independent rear suspension (IRS) will not incur the "squat" you'd get here.
– Pᴀᴜʟsᴛᴇʀ2♦
yesterday
3
@Pᴀᴜʟsᴛᴇʀ2's comment is critical for this answer's explanation. I drive a pick-up and was confused when trying to think through this explanation in my head. (I was already confused by the question, but assumed it was just something I hadn't noticed before.)
– Zach Mierzejewski
23 hours ago
Indeed. It's the trailing-arm suspension that causes this effect. IIRC my old Peugeot 106 did the same thing.
– spender
3 hours ago
add a comment |
13
The design of the rear is the main reason for this. Being on a swing arm causes the squat. Vehicles without this design, namely those with a solid 4-link or those with independent rear suspension (IRS) will not incur the "squat" you'd get here.
– Pᴀᴜʟsᴛᴇʀ2♦
yesterday
3
@Pᴀᴜʟsᴛᴇʀ2's comment is critical for this answer's explanation. I drive a pick-up and was confused when trying to think through this explanation in my head. (I was already confused by the question, but assumed it was just something I hadn't noticed before.)
– Zach Mierzejewski
23 hours ago
Indeed. It's the trailing-arm suspension that causes this effect. IIRC my old Peugeot 106 did the same thing.
– spender
3 hours ago
13
13
The design of the rear is the main reason for this. Being on a swing arm causes the squat. Vehicles without this design, namely those with a solid 4-link or those with independent rear suspension (IRS) will not incur the "squat" you'd get here.
– Pᴀᴜʟsᴛᴇʀ2♦
yesterday
The design of the rear is the main reason for this. Being on a swing arm causes the squat. Vehicles without this design, namely those with a solid 4-link or those with independent rear suspension (IRS) will not incur the "squat" you'd get here.
– Pᴀᴜʟsᴛᴇʀ2♦
yesterday
3
3
@Pᴀᴜʟsᴛᴇʀ2's comment is critical for this answer's explanation. I drive a pick-up and was confused when trying to think through this explanation in my head. (I was already confused by the question, but assumed it was just something I hadn't noticed before.)
– Zach Mierzejewski
23 hours ago
@Pᴀᴜʟsᴛᴇʀ2's comment is critical for this answer's explanation. I drive a pick-up and was confused when trying to think through this explanation in my head. (I was already confused by the question, but assumed it was just something I hadn't noticed before.)
– Zach Mierzejewski
23 hours ago
Indeed. It's the trailing-arm suspension that causes this effect. IIRC my old Peugeot 106 did the same thing.
– spender
3 hours ago
Indeed. It's the trailing-arm suspension that causes this effect. IIRC my old Peugeot 106 did the same thing.
– spender
3 hours ago
add a comment |
When you stop the car using the footbrake, all four wheels are held stationary by the brake. When you apply the handbrake, this locks the rear wheels only (in most cars) - as you then release the footbrake, this releases the front wheels, allowing them to turn ever so slightly. Gravity is still trying to pull the whole car downwards, and so it settles down on the rear suspension - it's something that's hard to describe!
answered yesterday
Nick C♦Nick C
25.4k44291
1
Ah, that makes perfect sense and, while I agree that is difficult to describe, I understand you. I was thinking the suspension was expanded and was settling back to rest, however you've shown that it was at rest and the cars front moving forward slightly is actually compressing the rear suspension - if I've got that right! Thanks again.
– Kallum Tanton
yesterday
add a comment |
When you stop the car using the footbrake, all four wheels are held stationary by the brake. When you apply the handbrake, this locks the rear wheels only (in most cars) - as you then release the footbrake, this releases the front wheels, allowing them to turn ever so slightly. Gravity is still trying to pull the whole car downwards, and so it settles down on the rear suspension - it's something that's hard to describe!
answered yesterday
Nick C♦Nick C
25.4k44291
1
Ah, that makes perfect sense and, while I agree that is difficult to describe, I understand you. I was thinking the suspension was expanded and was settling back to rest, however you've shown that it was at rest and the cars front moving forward slightly is actually compressing the rear suspension - if I've got that right! Thanks again.
– Kallum Tanton
yesterday
add a comment |
When you stop the car using the footbrake, all four wheels are held stationary by the brake. When you apply the handbrake, this locks the rear wheels only (in most cars) - as you then release the footbrake, this releases the front wheels, allowing them to turn ever so slightly. Gravity is still trying to pull the whole car downwards, and so it settles down on the rear suspension - it's something that's hard to describe!
answered yesterday
Nick C♦Nick C
25.4k44291
When you stop the car using the footbrake, all four wheels are held stationary by the brake. When you apply the handbrake, this locks the rear wheels only (in most cars) - as you then release the footbrake, this releases the front wheels, allowing them to turn ever so slightly. Gravity is still trying to pull the whole car downwards, and so it settles down on the rear suspension - it's something that's hard to describe!
answered yesterday
Nick C♦Nick C
25.4k44291
answered yesterday
Nick C♦Nick C
25.4k44291
answered yesterday
Nick C♦Nick C
25.4k44291
answered yesterday
Nick C♦Nick C
25.4k44291
25.4k44291
1
Ah, that makes perfect sense and, while I agree that is difficult to describe, I understand you. I was thinking the suspension was expanded and was settling back to rest, however you've shown that it was at rest and the cars front moving forward slightly is actually compressing the rear suspension - if I've got that right! Thanks again.
– Kallum Tanton
yesterday
add a comment |
1
Ah, that makes perfect sense and, while I agree that is difficult to describe, I understand you. I was thinking the suspension was expanded and was settling back to rest, however you've shown that it was at rest and the cars front moving forward slightly is actually compressing the rear suspension - if I've got that right! Thanks again.
– Kallum Tanton
yesterday
1
1
Ah, that makes perfect sense and, while I agree that is difficult to describe, I understand you. I was thinking the suspension was expanded and was settling back to rest, however you've shown that it was at rest and the cars front moving forward slightly is actually compressing the rear suspension - if I've got that right! Thanks again.
– Kallum Tanton
yesterday
Ah, that makes perfect sense and, while I agree that is difficult to describe, I understand you. I was thinking the suspension was expanded and was settling back to rest, however you've shown that it was at rest and the cars front moving forward slightly is actually compressing the rear suspension - if I've got that right! Thanks again.
– Kallum Tanton
yesterday
add a comment |
Kallum Tanton is a new contributor. Be nice, and check out our Code of Conduct.
Kallum Tanton is a new contributor. Be nice, and check out our Code of Conduct.
Kallum Tanton is a new contributor. Be nice, and check out our Code of Conduct.
Kallum Tanton is a new contributor. Be nice, and check out our Code of Conduct.
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