Brake Pads

Faults and Technical chat for the Volvo XC40
Deleted User 3629

Post by Deleted User 3629 »

Have stated before - oddly, the XC40 is the first car where more brake dust, and brake disc wear, happens on the rear brakes than on the front - indicating - a higher force distribution to the rear than the front and subsequently more wear the rear pads than front, and as is indicated by service inspections.

blastpipe
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Post by blastpipe »

Oldie wrote: Sat Nov 20, 2021 9:49 am Ok but they also explain - The energy efficiency of a conventional brake is only about 20 percent with the remaining 80 percent of its energy being converted to heat through friction. The important thing about the regenerative braking is that it may be able to capture as much as half of that wasted energy and put it back to work. This reduces fuel consumption by 10 to 25 percent , hence regenerative braking system plays an important role in the regenerative system. ???
I've never heard of energy efficiency of brakes. They are not normal regarded as an energy device. I prefer to know their efficiency at braking.

Yes agreed rgenerative braking is all about capturing the energy that normally the brakes would dissipate through heat if used to slow the car. If there is an alternative method of slowing the wheel such as by induction motor then that can generate electrical power and be used to put energy in to a battery. The pads play no part in this as they would just stop the regenerative braking getting any electrical input.

'Braking' doesn't have to use brake pads...there are other methods of slowing a car down some of which can put power back in to the car.

As a rule a car with regenerative 'braking' should expect a longer life on their brake pads.

Does the T3 doesn't have regenerative braking?
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blastpipe
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Post by blastpipe »

Oldie wrote: Sat Nov 20, 2021 9:55 am Have stated before - oddly, the XC40 is the first car where more brake dust, and brake disc wear, happens on the rear brakes than on the front - indicating - a higher force distribution to the rear than the front and subsequently more wear the rear pads than front, and as is indicated by service inspections.
There is more than one reason why rears might show more wear than front. Hill hold assist only operates on the rears I believe. The parking brake and its automatic release is on the rears. The car also has Electronic Brake Distribution.
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Deleted User 3629

Post by Deleted User 3629 »

True I guess - remember, don't make em only drive em
Deleted User 3629

Post by Deleted User 3629 »

blastpipe - energy cannot be created or destroyed, only converted from one form to another, efficiency is a measure of how much useful energy is converted. Braking converts kinetic energy into thermal energy, normally this thermal energy dissipates to the atmosphere in the form of waste heat, however if you can capture this thermal energy and convert into electricity via a thermoelectric device you can then measure that conversion rate to give you a braking efficiency value???
Felindre
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Post by Felindre »

Such a device would have to be physically located on the brake pads to achieve what you say. As I said, it's regenerative 'braking' using the engine to retard the speed by increasing the load the alternator is applying while generating more electricity.

I don't understand why you're so determined to stick to the original story of the brake pads when there's no visible mechanism to support the energy recovery.
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blastpipe
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Post by blastpipe »

Oldie wrote: Sat Nov 20, 2021 2:44 pm blastpipe - energy cannot be created or destroyed, only converted from one form to another, efficiency is a measure of how much useful energy is converted. Braking converts kinetic energy into thermal energy, normally this thermal energy dissipates to the atmosphere in the form of waste heat, however if you can capture this thermal energy and convert into electricity via a thermoelectric device you can then measure that conversion rate to give you a braking efficiency value???
Yes I know that. You canna change the laws of physics even though some seem to ignore them or fail to understand them. There are more forces than friction that can be used to slow things down.

But surely true brake efficiency is how much the speed is reduced and how quickly, for a given input from the driver.

Perhaps Volvo need to run some cooling pipes to the brakes, which can generate steam, which can power turbine to generate electricity.

However Volvo do not use the brake pads to provide regenerative power so I really can't see what you're saying and how it relates to question at the start of this thread. Especially for a T3 model that has no regenerative functionality.
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Deleted User 3629

Post by Deleted User 3629 »

Am not and never have been and don't care a hoot anyway - simply responding to points raised i.e. blastpipe hadn't heard of energy efficiency of brakes, so explained the theory - however, having driven many many cars the XC40 is a first for me to have a reverse logic to brake wear - i.e. rear's wearing out before the fronts - don't care why, don't matter why - they just do - and seems expensive to replace too - oh, and in the world of thermoelectric devices seems you only need nano-semiconductors to convert, and guess they would be very small???
Felindre
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Post by Felindre »

Won't give up will you? Yes there are devices, anyone got one if those stove top fans that rotate from the heat that travels up to the semiconductor? (I have 2)

However, there's no such thing fitted to the brakes of the XC, neither front nor rear. It's not about what could be possible, only what's actually there.
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Deleted User 3629

Post by Deleted User 3629 »

Back to the original post, 7k miles and 40% worn is in my view far too excessive, especially when the lower end of average life expectancy is 30k miles - however guess its also very subjective to types of journey and driving style??? - just think of all that break dust venting to the air and being breathed in - wonder if that can be re-used to generate power!!!
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