Can hydraulic brake levers get hot when brakes overheat?
If your hydraulic brakes get hot, can this heat ever travel to your brake levers. Can your levers feel hot or is this my imagination?
hydraulic-disc-brake
edited 5 hours ago
Criggie♦
44.7k573151
asked 14 hours ago
johnjohn
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If your hydraulic brakes get hot, can this heat ever travel to your brake levers. Can your levers feel hot or is this my imagination?
hydraulic-disc-brake
edited 5 hours ago
Criggie♦
44.7k573151
asked 14 hours ago
johnjohn
61
New contributor
john is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
3
Your hands can get hot, from the muscles working, the friction between hand and lever, and the lack of airflow.
– Daniel R Hicks
14 hours ago
2
The fluid will expand a bit and your hands will feel the levers becoming stiffer which feels like they're pushing back out on their own a bit. Could that be causing a perception of heat ?
– Criggie♦
5 hours ago
add a comment |
If your hydraulic brakes get hot, can this heat ever travel to your brake levers. Can your levers feel hot or is this my imagination?
hydraulic-disc-brake
edited 5 hours ago
Criggie♦
44.7k573151
asked 14 hours ago
johnjohn
61
New contributor
john is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
If your hydraulic brakes get hot, can this heat ever travel to your brake levers. Can your levers feel hot or is this my imagination?
hydraulic-disc-brake
hydraulic-disc-brake
edited 5 hours ago
Criggie♦
44.7k573151
asked 14 hours ago
johnjohn
61
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edited 5 hours ago
Criggie♦
44.7k573151
asked 14 hours ago
johnjohn
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edited 5 hours ago
Criggie♦
44.7k573151
edited 5 hours ago
Criggie♦
44.7k573151
edited 5 hours ago
Criggie♦
44.7k573151
44.7k573151
asked 14 hours ago
johnjohn
61
New contributor
john is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 14 hours ago
johnjohn
61
asked 14 hours ago
johnjohn
61
61
New contributor
john is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
john is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
john is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
3
Your hands can get hot, from the muscles working, the friction between hand and lever, and the lack of airflow.
– Daniel R Hicks
14 hours ago
2
The fluid will expand a bit and your hands will feel the levers becoming stiffer which feels like they're pushing back out on their own a bit. Could that be causing a perception of heat ?
– Criggie♦
5 hours ago
add a comment |
3
Your hands can get hot, from the muscles working, the friction between hand and lever, and the lack of airflow.
– Daniel R Hicks
14 hours ago
2
The fluid will expand a bit and your hands will feel the levers becoming stiffer which feels like they're pushing back out on their own a bit. Could that be causing a perception of heat ?
– Criggie♦
5 hours ago
3
3
Your hands can get hot, from the muscles working, the friction between hand and lever, and the lack of airflow.
– Daniel R Hicks
14 hours ago
Your hands can get hot, from the muscles working, the friction between hand and lever, and the lack of airflow.
– Daniel R Hicks
14 hours ago
2
2
The fluid will expand a bit and your hands will feel the levers becoming stiffer which feels like they're pushing back out on their own a bit. Could that be causing a perception of heat ?
– Criggie♦
5 hours ago
The fluid will expand a bit and your hands will feel the levers becoming stiffer which feels like they're pushing back out on their own a bit. Could that be causing a perception of heat ?
– Criggie♦
5 hours ago
add a comment |
2 Answers
2
active
oldest
votes
I've never heard of anyone having that issue before. The heat would have to travel all the way up the hose, even then still having to warm up all of the body of the brake lever before heating the part that you would pull. If you're pulling your brakes very hard for a long time, then it's more likely to be related to the strain of pulling them or cutting circulation.
answered 14 hours ago
Carbon side upCarbon side up
1,872316
6
Since the brake fluid is constrained in a narrow tube, the transfer up it would have to be entirely by conduction: there'd be no appreciable convection. That conduction would be slowed by the cooling effect of air passing over the brake line. So I agree that it's very unlikely that brake heat will reach the levers.
– David Richerby
14 hours ago
add a comment |
No, the thermal conductivity of brake hose/fluid is way too low.
I've run the numbers on this -- very roughly to make the calculations simpler. I've assumed the hose isn't cooled by airflow for some reason and a solid hose or equivalently that the fluid has the same thermal conductivity. Even the lever is assumed not to lose any heat to the air. All these assumptions maximise the amount of heat delivered to the lever.
Lets assume the hose is PTFE, which decomposes at 200°C and has a thermal conductivity of 0.5 W/m.K (the highest value I saw). I'll take a hose outside diameter of 6 mm, length 1 m. To feel warm the lever would have to get to something like 40°C, giving a temperature drop of 160°C at the point where the caliper end of the hose got so it it would be giving off toxic fumes, i.e. the absolute maximum.
Working this through, you'd be conducting 2 mW of heat to the lever. If the lever is 100 g of aluminium with a specific heat capacity of 900 J/kgK, this 2 mW it would take 12.5 hours to warm by 1°C.
Some steels have 100× the thermal conductivity of PTFE. Brake cables could conduct 200 mW for the same caliper temperature, and only take 7.5 minutes to warm by 1°C - but still an hour or two of non-stop braking to get from ambient to warm.
answered 10 hours ago
Chris HChris H
23.9k138105
add a comment |
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2 Answers
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2 Answers
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I've never heard of anyone having that issue before. The heat would have to travel all the way up the hose, even then still having to warm up all of the body of the brake lever before heating the part that you would pull. If you're pulling your brakes very hard for a long time, then it's more likely to be related to the strain of pulling them or cutting circulation.
answered 14 hours ago
Carbon side upCarbon side up
1,872316
6
Since the brake fluid is constrained in a narrow tube, the transfer up it would have to be entirely by conduction: there'd be no appreciable convection. That conduction would be slowed by the cooling effect of air passing over the brake line. So I agree that it's very unlikely that brake heat will reach the levers.
– David Richerby
14 hours ago
add a comment |
I've never heard of anyone having that issue before. The heat would have to travel all the way up the hose, even then still having to warm up all of the body of the brake lever before heating the part that you would pull. If you're pulling your brakes very hard for a long time, then it's more likely to be related to the strain of pulling them or cutting circulation.
answered 14 hours ago
Carbon side upCarbon side up
1,872316
6
Since the brake fluid is constrained in a narrow tube, the transfer up it would have to be entirely by conduction: there'd be no appreciable convection. That conduction would be slowed by the cooling effect of air passing over the brake line. So I agree that it's very unlikely that brake heat will reach the levers.
– David Richerby
14 hours ago
add a comment |
I've never heard of anyone having that issue before. The heat would have to travel all the way up the hose, even then still having to warm up all of the body of the brake lever before heating the part that you would pull. If you're pulling your brakes very hard for a long time, then it's more likely to be related to the strain of pulling them or cutting circulation.
answered 14 hours ago
Carbon side upCarbon side up
1,872316
I've never heard of anyone having that issue before. The heat would have to travel all the way up the hose, even then still having to warm up all of the body of the brake lever before heating the part that you would pull. If you're pulling your brakes very hard for a long time, then it's more likely to be related to the strain of pulling them or cutting circulation.
answered 14 hours ago
Carbon side upCarbon side up
1,872316
answered 14 hours ago
Carbon side upCarbon side up
1,872316
answered 14 hours ago
Carbon side upCarbon side up
1,872316
answered 14 hours ago
Carbon side upCarbon side up
1,872316
1,872316
6
Since the brake fluid is constrained in a narrow tube, the transfer up it would have to be entirely by conduction: there'd be no appreciable convection. That conduction would be slowed by the cooling effect of air passing over the brake line. So I agree that it's very unlikely that brake heat will reach the levers.
– David Richerby
14 hours ago
add a comment |
6
Since the brake fluid is constrained in a narrow tube, the transfer up it would have to be entirely by conduction: there'd be no appreciable convection. That conduction would be slowed by the cooling effect of air passing over the brake line. So I agree that it's very unlikely that brake heat will reach the levers.
– David Richerby
14 hours ago
6
6
Since the brake fluid is constrained in a narrow tube, the transfer up it would have to be entirely by conduction: there'd be no appreciable convection. That conduction would be slowed by the cooling effect of air passing over the brake line. So I agree that it's very unlikely that brake heat will reach the levers.
– David Richerby
14 hours ago
Since the brake fluid is constrained in a narrow tube, the transfer up it would have to be entirely by conduction: there'd be no appreciable convection. That conduction would be slowed by the cooling effect of air passing over the brake line. So I agree that it's very unlikely that brake heat will reach the levers.
– David Richerby
14 hours ago
add a comment |
No, the thermal conductivity of brake hose/fluid is way too low.
I've run the numbers on this -- very roughly to make the calculations simpler. I've assumed the hose isn't cooled by airflow for some reason and a solid hose or equivalently that the fluid has the same thermal conductivity. Even the lever is assumed not to lose any heat to the air. All these assumptions maximise the amount of heat delivered to the lever.
Lets assume the hose is PTFE, which decomposes at 200°C and has a thermal conductivity of 0.5 W/m.K (the highest value I saw). I'll take a hose outside diameter of 6 mm, length 1 m. To feel warm the lever would have to get to something like 40°C, giving a temperature drop of 160°C at the point where the caliper end of the hose got so it it would be giving off toxic fumes, i.e. the absolute maximum.
Working this through, you'd be conducting 2 mW of heat to the lever. If the lever is 100 g of aluminium with a specific heat capacity of 900 J/kgK, this 2 mW it would take 12.5 hours to warm by 1°C.
Some steels have 100× the thermal conductivity of PTFE. Brake cables could conduct 200 mW for the same caliper temperature, and only take 7.5 minutes to warm by 1°C - but still an hour or two of non-stop braking to get from ambient to warm.
answered 10 hours ago
Chris HChris H
23.9k138105
add a comment |
No, the thermal conductivity of brake hose/fluid is way too low.
I've run the numbers on this -- very roughly to make the calculations simpler. I've assumed the hose isn't cooled by airflow for some reason and a solid hose or equivalently that the fluid has the same thermal conductivity. Even the lever is assumed not to lose any heat to the air. All these assumptions maximise the amount of heat delivered to the lever.
Lets assume the hose is PTFE, which decomposes at 200°C and has a thermal conductivity of 0.5 W/m.K (the highest value I saw). I'll take a hose outside diameter of 6 mm, length 1 m. To feel warm the lever would have to get to something like 40°C, giving a temperature drop of 160°C at the point where the caliper end of the hose got so it it would be giving off toxic fumes, i.e. the absolute maximum.
Working this through, you'd be conducting 2 mW of heat to the lever. If the lever is 100 g of aluminium with a specific heat capacity of 900 J/kgK, this 2 mW it would take 12.5 hours to warm by 1°C.
Some steels have 100× the thermal conductivity of PTFE. Brake cables could conduct 200 mW for the same caliper temperature, and only take 7.5 minutes to warm by 1°C - but still an hour or two of non-stop braking to get from ambient to warm.
answered 10 hours ago
Chris HChris H
23.9k138105
add a comment |
No, the thermal conductivity of brake hose/fluid is way too low.
I've run the numbers on this -- very roughly to make the calculations simpler. I've assumed the hose isn't cooled by airflow for some reason and a solid hose or equivalently that the fluid has the same thermal conductivity. Even the lever is assumed not to lose any heat to the air. All these assumptions maximise the amount of heat delivered to the lever.
Lets assume the hose is PTFE, which decomposes at 200°C and has a thermal conductivity of 0.5 W/m.K (the highest value I saw). I'll take a hose outside diameter of 6 mm, length 1 m. To feel warm the lever would have to get to something like 40°C, giving a temperature drop of 160°C at the point where the caliper end of the hose got so it it would be giving off toxic fumes, i.e. the absolute maximum.
Working this through, you'd be conducting 2 mW of heat to the lever. If the lever is 100 g of aluminium with a specific heat capacity of 900 J/kgK, this 2 mW it would take 12.5 hours to warm by 1°C.
Some steels have 100× the thermal conductivity of PTFE. Brake cables could conduct 200 mW for the same caliper temperature, and only take 7.5 minutes to warm by 1°C - but still an hour or two of non-stop braking to get from ambient to warm.
answered 10 hours ago
Chris HChris H
23.9k138105
No, the thermal conductivity of brake hose/fluid is way too low.
I've run the numbers on this -- very roughly to make the calculations simpler. I've assumed the hose isn't cooled by airflow for some reason and a solid hose or equivalently that the fluid has the same thermal conductivity. Even the lever is assumed not to lose any heat to the air. All these assumptions maximise the amount of heat delivered to the lever.
Lets assume the hose is PTFE, which decomposes at 200°C and has a thermal conductivity of 0.5 W/m.K (the highest value I saw). I'll take a hose outside diameter of 6 mm, length 1 m. To feel warm the lever would have to get to something like 40°C, giving a temperature drop of 160°C at the point where the caliper end of the hose got so it it would be giving off toxic fumes, i.e. the absolute maximum.
Working this through, you'd be conducting 2 mW of heat to the lever. If the lever is 100 g of aluminium with a specific heat capacity of 900 J/kgK, this 2 mW it would take 12.5 hours to warm by 1°C.
Some steels have 100× the thermal conductivity of PTFE. Brake cables could conduct 200 mW for the same caliper temperature, and only take 7.5 minutes to warm by 1°C - but still an hour or two of non-stop braking to get from ambient to warm.
answered 10 hours ago
Chris HChris H
23.9k138105
answered 10 hours ago
Chris HChris H
23.9k138105
answered 10 hours ago
Chris HChris H
23.9k138105
answered 10 hours ago
Chris HChris H
23.9k138105
23.9k138105
add a comment |
add a comment |
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3
Your hands can get hot, from the muscles working, the friction between hand and lever, and the lack of airflow.
– Daniel R Hicks
14 hours ago
2
The fluid will expand a bit and your hands will feel the levers becoming stiffer which feels like they're pushing back out on their own a bit. Could that be causing a perception of heat ?
– Criggie♦
5 hours ago