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"El Whatever"
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Discussion Starter · #1 ·
I'm thinking about designing a Brake duct for bake calipers cooling.

Would you buy one???

I think this would be very useful in DH and for folks with long descents. It would only collect air from the front of the bike and force it to flow around the brake caliper which would be fitted with some fins. It would attach to the lowers assy on conventional forks and to the bottles on inverted (or even to the lowers, maybe) This is for the front.

For the rear I would use only cooling fins as I think the air is too turbulent and slow to take advantage of a caliper cooling duct and would interfere with pedaling.

The benefits would be an additional removal of heat off from the caliper which eventually would avoid brake fluid to heat up and avoid fade.

What you guys think?? Am I crazy or just an idiot??? Would it work??

Any input is welcome.
 

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sounds like a good idea, but also sounds like another thing to break :eek: I know for me my brakes do not fade and i am pretty sure it is the same w/ others as well. It is different from a car or somthing with lots of mass/momentoum behind it. A bike's momentum is so much less than that of a car for instance, that the size of the rotors are able to create a great amount of friction without heating up unbarably. :cool: good thought tho.
 

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ballbuster
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Sure, I guess....

Warp2003 said:
I'm thinking about designing a Brake duct for bake calipers cooling.

Would you buy one???

I think this would be very useful in DH and for folks with long descents. It would only collect air from the front of the bike and force it to flow around the brake caliper which would be fitted with some fins. It would attach to the lowers assy on conventional forks and to the bottles on inverted (or even to the lowers, maybe) This is for the front.

For the rear I would use only cooling fins as I think the air is too turbulent and slow to take advantage of a caliper cooling duct and would interfere with pedaling.

The benefits would be an additional removal of heat off from the caliper which eventually would avoid brake fluid to heat up and avoid fade.

What you guys think?? Am I crazy or just an idiot??? Would it work??

Any input is welcome.
but...

A: Is there a demand for such an item?

B: Is brake cooling that big an issue on bicycles?

The reason cars use ducts, is because Air Dams choke off the air to your brakes (creates low pressure under the car, which is against the way air wants to flow through the wheels, inside to outside) and ducts shoot the air directly to the front wheels... and sometimes rear on RWD racecars.

It would seem the issue of brake cooling on a bike would be taken care of more effectively and with less weight by using larger rotors with better venting to wick out more heat from the caliper.
 

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"El Whatever"
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Discussion Starter · #5 ·
but...

A: Is there a demand for such an item?


most Probably not... that's why I was asking.

B: Is brake cooling that big an issue on bicycles?

In hot places with long-brake-dragging descents could be. It could be good for hydros.

The reason cars use ducts, is because Air Dams choke off the air to your brakes (creates low pressure under the car, which is against the way air wants to flow through the wheels, inside to outside) and ducts shoot the air directly to the front wheels... and sometimes rear on RWD racecars.

I understand that... low inlet pressure is not the only reason they do. F1 use open wheels so that area still has a high pressure and yet they use braking ducts. F1 cars do not have like "big" mass (lowest weight admitted is 650kg with driver and fuel included). On the rear tires of a car cooling ducts are critical as air becomes very turbulent on that area so cooling is less efficient.

It would seem the issue of brake cooling on a bike would be taken care of more effectively and with less weight by using larger rotors with better venting to wick out more heat from the caliper.

At least, I would use fins over the caliper and the close to the caliper line in order to increase cooling and avoid fading. Hydros should be the more benefited by this. Mechs no so much.
 

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There's plenty of air flow already around the brake calipers on a bike. They're not buried deep inside the wheels out of the direct airflow like in F1 cars etc. I very much doubt a cooling duct would make any difference at all. Cooling fins on the caliper body are a better idea for improving caliper cooling on a DH bike. Interesting thought though.
 

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"El Whatever"
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Discussion Starter · #7 ·
uktrailmonster said:
There's plenty of air flow already around the brake calipers on a bike. They're not buried deep inside the wheels out of the direct airflow like in F1 cars etc. I very much doubt a cooling duct would make any difference at all. Cooling fins on the caliper body are a better idea for improving caliper cooling on a DH bike. Interesting thought though.
Thanks for sharing your thoughts UKTM... as you're a knowledgeable person they're still more welcome.

I have experienced some overheating on the rear brake which sometimes receives more turbulent and less air flow, sometimes uneven as they're "hidden" behind the frame, your calves and some other stuff you can think of.

I had dropped the idea of the ducts but some snap on caliper cooling fins might help. unfortunately those are a part just waiting to be damaged as those have to be very thin and in a good heat conducting material like copper or aluminum which are not very resistant though.

A good idea for the wrong application I think.
 

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Warp2003 said:
Thanks for sharing your thoughts UKTM... as you're a knowledgeable person they're still more welcome.

I have experienced some overheating on the rear brake which sometimes receives more turbulent and less air flow, sometimes uneven as they're "hidden" behind the frame, your calves and some other stuff you can think of.

I had dropped the idea of the ducts but some snap on caliper cooling fins might help. unfortunately those are a part just waiting to be damaged as those have to be very thin and in a good heat conducting material like copper or aluminum which are not very resistant though.

A good idea for the wrong application I think.
Yeah, I was thinking about it a little more and perhaps the duct idea might just be feasible on the rear. The biggest problem would be getting clean airflow into the duct entry. Funnily enough, this is also a problem on F1 cars. The rear duct airflow is always a loss less efficient than the front.

Ok some other brake cooling ideas:-

Insulated brake pads - using a ceramic pad backing material to reduce heat flow into the caliper piston. An alternative to this are ceramic caliper piston caps.

Thicker brake discs with internal radial cooling vents - They basically act like brake fans, but they would add some drag at high speed. Might be heavy too if not carefully designed.

Wider caliper body with extended pistons exposed more directly in the airflow.
 

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"El Whatever"
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Discussion Starter · #9 ·
uktrailmonster said:
Yeah, I was thinking about it a little more and perhaps the duct idea might just be feasible on the rear. The biggest problem would be getting clean airflow into the duct entry. Funnily enough, this is also a problem on F1 cars. The rear duct airflow is always a loss less efficient than the front.
uktrailmonster said:
Ok some other brake cooling ideas:-
Insulated brake pads - using a ceramic pad backing material to reduce heat flow into the caliper piston. An alternative to this are ceramic caliper piston caps.
You gotta reengineer the pad and rotor material to work on a wider range of temperature operation... maybe the rotor can whithstand it but I doubt it from the pads. I think it's doable. Pretty economic and simple solution.

uktrailmonster said:
Thicker brake discs with internal radial cooling vents - They basically act like brake fans, but they would add some drag at high speed. Might be heavy too if not carefully designed.
This one sounds pretty interesting... but as you said it's gotta be designed by a real genious. Too thick walls and too heavy, too thin and you'll distort the stuff. As for drag (you unveiled your background on this one :D ) the rider and stuff on the handlebar for example would make for more drag than that.

uktrailmonster said:
Wider caliper body with extended pistons exposed more directly in the airflow.
You're calling for crash damage.

As you mentioned brake fans, it came to my mind some kind of fan/blower disc attached to the rear wheel spokes. It would allow for get more flow onto the brake when you need it the most... at high speed. You don't need it when you block the wheel as no heat is generated then. The drawback would be some noise, unsprung mass, and drag (neglectible??).
 

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Motorcycles don't seem to make any use of such ducts, likely because they would add little brake effeciency over the already ample airflow. Instead, they simply use big enough brakes to avoid brake fade. More rotor / caliper mass = more kinetic energy absorbed with less temp rise. Bigger diameter rotor = more radiative area.
I'd think this would be the simplest and most weight efficient answer on a bicycle as well- if you have brake fade, use bigger (or, as tech advances, more temp tolerant) brakes. Even if it adds more mass than a duct would (doubtfull, or sport motor bikes would already implement it universally) who cares? Its only a problem on bikes that descend non-stop, which would tend to indicate weight is not so much an issue...
 

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Cooling fins on the calipers would probably be the simplest additional cooling that could be implemented.

However, when you read the specs nowadays, you see that manufacturers are trying to design the pistons such that the heat transfer into the caliper is minimal to avoid heating up the brake fluid and it boiling.

There is also a balance of needing the brakes to be hot in order to work well ( depends on the pad material i suppose too )


as already said I actually think that the best route would be to have rotors with a decent area of metal to sit on the inside of the swept brake area. This would act as an immediate heat dissipating area. Cross drilling would help cooling to on the dissipating area.
 

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Brake cooling?

I like the idea of an insulating layer for the pad btwn the friction pad and the caliper. You could use a room temperature superconductor with a surface extending past the edges of the pad to radiate heat into the environment. It would also tend to be protected by the caliper design from impact damage. The vortex effect from the spinning rotor should generate enough airflow to leach heat from a room temp. superconductor. Gawd! I sound like I work for NASA! I guess I'm just a computer geek "Clydsdale" mountainbiker that's into Strange thought paths! :p
Warp2003 said:
You gotta reengineer the pad and rotor material to work on a wider range of temperature operation... maybe the rotor can whithstand it but I doubt it from the pads. I think it's doable. Pretty economic and simple solution.

This one sounds pretty interesting... but as you said it's gotta be designed by a real genious. Too thick walls and too heavy, too thin and you'll distort the stuff. As for drag (you unveiled your background on this one :D ) the rider and stuff on the handlebar for example would make for more drag than that.

You're calling for crash damage.

As you mentioned brake fans, it came to my mind some kind of fan/blower disc attached to the rear wheel spokes. It would allow for get more flow onto the brake when you need it the most... at high speed. You don't need it when you block the wheel as no heat is generated then. The drawback would be some noise, unsprung mass, and drag (neglectible??).
 

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"El Whatever"
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Discussion Starter · #15 ·
stormcrowe said:
I like the idea of an insulating layer for the pad btwn the friction pad and the caliper. You could use a room temperature superconductor with a surface extending past the edges of the pad to radiate heat into the environment. It would also tend to be protected by the caliper design from impact damage. The vortex effect from the spinning rotor should generate enough airflow to leach heat from a room temp. superconductor. Gawd! I sound like I work for NASA! I guess I'm just a computer geek "Clydsdale" mountainbiker that's into Strange thought paths! :p
As weird as it may sound... it could be. Why not?
 

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ballbuster
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Brakes fade...

uktrailmonster said:
Yeah, I was thinking about it a little more and perhaps the duct idea might just be feasible on the rear. The biggest problem would be getting clean airflow into the duct entry. Funnily enough, this is also a problem on F1 cars. The rear duct airflow is always a loss less efficient than the front.

Ok some other brake cooling ideas:-

Insulated brake pads - using a ceramic pad backing material to reduce heat flow into the caliper piston. An alternative to this are ceramic caliper piston caps.

Thicker brake discs with internal radial cooling vents - They basically act like brake fans, but they would add some drag at high speed. Might be heavy too if not carefully designed.

Wider caliper body with extended pistons exposed more directly in the airflow.
... mostly because the brake pad compound turns to liquid and gas when it gets too hot, and becomes a less effective friction surface. If you made the pads out of a heat insulator, that would probably make the problem worse. In fact, many brake pads have copper backings, to conduct heat away to the caliper. A large alu billet caliper acts like a heat sink already.

The next point of failure would be when the caliper gets so hot that the brake fluid boils causing vapor lock. Personally, I have never had this happen, and I hammer my brakes pretty hard and have small brakes (Hope Mono Minis) and weigh nearly 200#. I've smoked and glazed pads, but never got to vapor lock.

Like I said before, with larger rotors and calipers, this is really not a problem, unless you are looking to make rotors and calipers smaller and lighter.
 

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Race cars use two different types of ducts, depending whether the rotors are solid or finned. Solid rotors use a 'can' that fits tightly over the rotor and tries to skim the hot gases off the rotor surface. Finned rotors use ducting to the center of the rotor that forces air through the internal fins. (or directs air to the caliper to cool it.) For a complete discussion with sketches, see Carroll Smith's "Prepare to Win". (He wrote a series of books on race car building that are kinda the bibles of how to do it, I am pretty sure brake systems are in this one. Other exciting reading includes "Bolts and Fasteners Handbook". if you are really interested.)

But there is no way I can see a bike requiring brake cooling.
 

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racer99 said:
Race cars use two different types of ducts, depending whether the rotors are solid or finned. Solid rotors use a 'can' that fits tightly over the rotor and tries to skim the hot gases off the rotor surface. Finned rotors use ducting to the center of the rotor that forces air through the internal fins. (or directs air to the caliper to cool it.) For a complete discussion with sketches, see Carroll Smith's "Prepare to Win". (He wrote a series of books on race car building that are kinda the bibles of how to do it, I am pretty sure brake systems are in this one. Other exciting reading includes "Bolts and Fasteners Handbook". if you are really interested.)

But there is no way I can see a bike requiring brake cooling.
Carroll Smith's books are an interesting read and there is a lot of valid practical stuff in them. However, they are also littered full of mistakes and basic lack of understanding of both physics and engineering. Beware, all that is written is not true!
 

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Examples?
I've built several race cars and have used many of Carroll Smith's ideas from his books. I haven't had a problem with any of his information. I was not building F1 cars, just SCCA road racers.
 

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ballbuster
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Yeah, I gotta agree with this...

uktrailmonster said:
There's plenty of air flow already around the brake calipers on a bike. They're not buried deep inside the wheels out of the direct airflow like in F1 cars etc. I very much doubt a cooling duct would make any difference at all. Cooling fins on the caliper body are a better idea for improving caliper cooling on a DH bike. Interesting thought though.
Your rear brake overheating is not because of a lack of airflow. It is more likely that you are biasing your rear brake too much.

Again, F1 brakes are tucked inside the body of the car (inboard brakes), so they do need ducting. They are not in the open air like a regular car, apart from some Alfa Romeos, Jaguars, and older Audis. A side note, my wife had an older Audi LS100 with inboard brakes, and a brake job was gonna cost her $800. They had to drop the tranny to change out the brakes. She dumped the car.

Other race cars have the brakes at the wheels, which again, is out of the airflow. That, and bikes are not seeing nearly the speed that cars do. The brakes are out in the open already. They are not behind baffles, splash guards, or ground effects, or anything like that.

Again, I don't see ducts as solving any actual issues here. I don't think that even a 10 or 20% increase in airflow will make any significant difference. Bikes rarely see more than 50 MPH, which is where the ducting would actually make a difference, and if a bike does see 50 MPH, it would not be for long on a DH course.
 
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