Specific heat absorption capacity of disc brakes

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Re: Specific heat absorption capacity of disc brakes

Post by Chalo » Mar 16 2018 3:44pm

Raisedeyebrows wrote:
Mar 16 2018 3:38pm
I really liked the rim brake you machined back in the day, the one you posted a photo of sometime ago, was that just a one-off you made for yourself?
Yes, that's right. It was made to fit the arch mounting points of the suspension fork I used, so it isn't adaptable to other uses. I made a lighter version for a friend of mine who rode observed trials.
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Re: Specific heat absorption capacity of disc brakes

Post by liveforphysics » Mar 16 2018 4:37pm

In practice, stainless only works well for very thin brake rotors that need the strength.

Brake rotors thick enough to vent, but not with the budget to run sintered ceramic rotors (like F1) run special alloys of grey cast iron engineered for dimensional stability under large a rapid heat deltaTs without cracking, and being capable of getting parked with hot and clean brake rotors to get rain splashed on them and not rust to a structurally significant depth.

Stainless rotors also have a meaningfully different traction coefficient with various pad materials that the ductile grey cast iron alloys are specially designed to keep a grippy surface grain structure.

Most brake rotor alloys start with "BR" or "DB" in the alloy because it's specific towards that single applications use. Example, Dura-Bar G20 is a common performance vehicle brake rotor material, yet has pathetic tensile strength properties that would make it a terrible choice for a thin bicycle rotor application.
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Re: Specific heat absorption capacity of disc brakes

Post by DRMousseau » Mar 16 2018 7:13pm

Chalo wrote:
Mar 16 2018 2:53am
speedmd wrote:
Mar 15 2018 9:44pm
Stainless in general is a slippery material ( I deal with several grades daily ) and may be just a poor choice for ultimate performance and mainly used for cosmetic considerations.
It's true that my best motorcycle disc brakes were some kind of carbon steel, made by EBC. They were better than stock in pretty much every regard I can think of.

Stainless alloys seem to tolerate surface wear relatively well; not as well as bearing bronze but better than plain steel. I'd be willing to try Ampco bronze or similar for disc rotors (expensive, but wear resistant and thermally more interesting than stainless). I've wanted to try that for a coaster brake hub shell for a long time.

I've never come across M2 high speed steel in any other state than glass hard, even after getting red hot in an ugly machining scenario. But I suppose that it's steel after all and thus can be annealed to some degree or another.
Well proven materials automotive and motorcycle industries have typically been cast iron,... strong, holds it's shape well at glowing hot temps, good wear resistance (even at those hot temps), but it's brittleness and low corrosion resistance is a huge liability in the thin forms of current exposed bicycle disk designs.

Carbon steels would certainly be better than cast for thin steel disks, depending on the crystalline structure and designed controls of expansion that causes deformation under stresses of high heat,.... and corrosion resistance lacks a bit.

The "self-healing" slippery qualities of stainless alloys and Aluminum/bronze such as the various Ampco materials is indeed desirable, but I'm not so sure they are even close in comparability in that thin disk design, where stainless will certainly excel.

As I was about to post this, I notice speedmd posted with further considerations of high speed steel and various stainless alloys, (and problems thru out the day tryin' to get back to this) as well as the post above by liveforphysics, and I wholeheartedly agree with both! I do think some of the 430 alloys would be excellent, as would the better 440 series,... with proper brake pad compounds of course. You do have to consider the designed system as whole. I probably wouldn't be so fond of costs in such products, but they'd likely be much less than other exotics above, and I'd luv to try a few!

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Re: Specific heat absorption capacity of disc brakes

Post by wturber » Mar 16 2018 8:07pm

I checked the discs on my bike on the way out the door this morning and they are magnetic. That is consistent with martensitic (400 series) grades of stainless steel.
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Re: Specific heat absorption capacity of disc brakes

Post by speedmd » Mar 16 2018 8:31pm

Not sure that 440c would be better than 410, 409 or 12c27 in this app. Yes it is stronger, harder, and overall a much better pc of metal, but the increase in chrome is not what you want here IMO. You need some strength at temperature in these thin highly cutout rotors and don't want them to change hardness much or develop carbide growth. The lower grades would be less likely in general to do that. To Lukes point, it would certainly be worth looking at coarse grain sintered grades to get closer to the friction of cast iron.

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Re: Specific heat absorption capacity of disc brakes

Post by DRMousseau » Mar 16 2018 8:34pm

wturber wrote:
Mar 16 2018 8:07pm
I checked the discs on my bike on the way out the door this morning and they are magnetic. That is consistent with martensitic (400 series) grades of stainless steel.
Wow! Jus checked mine and found the same. Rather surprised as it's jus a basic BB-7 set, nothing out of the ordinary.

I did mangle a disk once, the first one. Dang thing gripped good, but the cheap caliper mounting adapter for none disk forks (hahaha :lol: ) slipped badly,... what can I say, I was curious and lookin for a cheap way out. DAMN was that costly!

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Re: Specific heat absorption capacity of disc brakes

Post by Raisedeyebrows » Mar 16 2018 8:42pm

wturber wrote:
Mar 16 2018 8:07pm
I checked the discs on my bike on the way out the door this morning and they are magnetic. That is consistent with martensitic (400 series) grades of stainless steel.
After reading your comment I had to go check mine too, magnet wanted to stick to them.
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Re: Specific heat absorption capacity of disc brakes

Post by eCue » Mar 16 2018 11:02pm

I happen to have a magnet in my pocket :D I checked the trp rotor and it stuck like regular steel. It sticks much less to the kitchen sink. Watch it slip off the Chinese Rotor

I know how to test now haha
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Re: Specific heat absorption capacity of disc brakes

Post by eCue » Mar 18 2018 3:20pm

I figured out my brakes today..

The braking issue turned out to be larger then just rotor size its the SPYRE brake altogether , its for road bike levers.

I bought it after a recommendation a few pages back :D and apparently without checking for lever requirements.
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Re: Specific heat absorption capacity of disc brakes

Post by Chalo » Mar 18 2018 6:12pm

eCue wrote:
Mar 18 2018 3:20pm
I figured out my brakes today..

The braking issue turned out to be larger then just rotor size its the SPYRE brake altogether , its for road bike levers.
Get a set of old style 4 finger MTB levers with short pull (cantilever, not V-brake). Those should work great with Spyre calipers at reasonable cost.

These, for example.

For what it's worth, most of the e-brake brake levers that come with conversion kits have a pull ratio that will work for your brakes.
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Re: Specific heat absorption capacity of disc brakes

Post by eCue » Mar 19 2018 10:02pm

So the Spyre comes in 3 version one for a MTB the pull length looks oddly the same just the cable mount looks different. I have bought the road version ... that apparently canti levers will work with. I have tried it with the levers in a few modes first mode the lever was solid from start to end with no modulation at all
Current mode is better but not great. I need to check what mode Im in now.
The levers have 3 modes one for roller brakes which apparently are touchy and engage fast so should have a longer pull then the canti and vbrake setting if Im not mistaken. Hope I find a mode that works.

I will try switching brake modes from Vbrake to canti to RB be nice to get more leverage
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Re: Specific heat absorption capacity of disc brakes

Post by Raisedeyebrows » Mar 19 2018 10:20pm

Chalo wrote:
Mar 16 2018 3:44pm
Raisedeyebrows wrote:
Mar 16 2018 3:38pm
I really liked the rim brake you machined back in the day, the one you posted a photo of sometime ago, was that just a one-off you made for yourself?
Yes, that's right. It was made to fit the arch mounting points of the suspension fork I used, so it isn't adaptable to other uses. I made a lighter version for a friend of mine who rode observed trials.
As far as MTB rim brakes go do you have any you highly recommend if a person wanted to get the best thing available off the shelf? XT's about the top of the heap?
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Re: Specific heat absorption capacity of disc brakes

Post by eCue » Mar 19 2018 10:32pm

Alright i have hope right now its in Vbrake mode the first mode I tried must of been RB from the factory , Canti mode here I come :D
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Re: Specific heat absorption capacity of disc brakes

Post by Chalo » Mar 20 2018 12:48am

Raisedeyebrows wrote:
Mar 19 2018 10:20pm
As far as MTB rim brakes go do you have any you highly recommend if a person wanted to get the best thing available off the shelf? XT's about the top of the heap?
I haven't kept up with the latest generation XT V-brakes. The early ones with "parallel push" were bunk-- all the added free play from the linkages made them grabby and squeal prone. But to be honest there doesn't seem to be a dime's worth of difference among better linear-pull brakes. I've been super happy with Deore V-brakes, as long as they're fitted with Kool Stop pads and a booster arch of any kind. Tektros are also good.

Basically, I can get fine performance out of almost any linear-pull brake that retails for more than about $15. The really expensive ones are less of a sure thing, because they're more likely to be "enhanced" with unhelpful contrived features.
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Re: Specific heat absorption capacity of disc brakes

Post by eCue » Mar 28 2018 1:12am

Today got a chance to test the brake in cantilever mode with a extra 50 lbs of weight. It made a big improvement Big now the lever feels light with good bite closer to the end of travel. When the lever was in vbrake mode I had to pull hard to get a bite especially with extra weight.
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Re: Specific heat absorption capacity of disc brakes

Post by eCue » Apr 10 2018 10:38am

The 203 Rotor arrived , after checking for flatness on a table (it was flat vs trp disc that was not) did a side x side magnet pull test and noted they had identical strong magnetic properties :shock:

With luck this means it will be as silent as the trp rotor is performing.

Image

A simple explanation of magnetic stainless

The two main types of stainless steel are austenitic and ferritic, each of exhibits a different atomic arrangement. Due to this difference, ferritic stainless steels are generally magnetic while austenitic stainless steels usually are not. A ferritic stainless steel owes its magnetism to two factors: its high concentration of iron and its fundamental structure.

I will add its chromium and nickel content also play a part

Now im waiting for the 203mm adapted
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Re: Specific heat absorption capacity of disc brakes

Post by liveforphysics » Apr 10 2018 8:28pm

Inconel is perhaps the best of the stainless options if you're going for ultimate performance without regard for cost.

It's still likely under $100 for the Inconel to make a thin bicycle brake rotor, but can be difficult to source and always a challenge to machine.


DRMousseau wrote:
Mar 16 2018 7:13pm
Chalo wrote:
Mar 16 2018 2:53am
speedmd wrote:
Mar 15 2018 9:44pm
Stainless in general is a slippery material ( I deal with several grades daily ) and may be just a poor choice for ultimate performance and mainly used for cosmetic considerations.
It's true that my best motorcycle disc brakes were some kind of carbon steel, made by EBC. They were better than stock in pretty much every regard I can think of.

Stainless alloys seem to tolerate surface wear relatively well; not as well as bearing bronze but better than plain steel. I'd be willing to try Ampco bronze or similar for disc rotors (expensive, but wear resistant and thermally more interesting than stainless). I've wanted to try that for a coaster brake hub shell for a long time.

I've never come across M2 high speed steel in any other state than glass hard, even after getting red hot in an ugly machining scenario. But I suppose that it's steel after all and thus can be annealed to some degree or another.
Well proven materials automotive and motorcycle industries have typically been cast iron,... strong, holds it's shape well at glowing hot temps, good wear resistance (even at those hot temps), but it's brittleness and low corrosion resistance is a huge liability in the thin forms of current exposed bicycle disk designs.

Carbon steels would certainly be better than cast for thin steel disks, depending on the crystalline structure and designed controls of expansion that causes deformation under stresses of high heat,.... and corrosion resistance lacks a bit.

The "self-healing" slippery qualities of stainless alloys and Aluminum/bronze such as the various Ampco materials is indeed desirable, but I'm not so sure they are even close in comparability in that thin disk design, where stainless will certainly excel.

As I was about to post this, I notice speedmd posted with further considerations of high speed steel and various stainless alloys, (and problems thru out the day tryin' to get back to this) as well as the post above by liveforphysics, and I wholeheartedly agree with both! I do think some of the 430 alloys would be excellent, as would the better 440 series,... with proper brake pad compounds of course. You do have to consider the designed system as whole. I probably wouldn't be so fond of costs in such products, but they'd likely be much less than other exotics above, and I'd luv to try a few!
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Re: Specific heat absorption capacity of disc brakes

Post by MadRhino » Apr 11 2018 9:40pm

The future of brake rotors is CMC (ceramic matrix composite).
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Re: Specific heat absorption capacity of disc brakes

Post by DRMousseau » Apr 12 2018 12:44am

MadRhino wrote:
Apr 11 2018 9:40pm
The future of brake rotors is CMC (ceramic matrix composite).
I wondered why I hadn't seen some kind of ceramic composite brake-pad for bikes yet,... but I'm thinkin' they're not nearly as effective on stainless disks as on grainy cast materials. I've found ceramic composite pads to be excellent in some automotive applications,... and I've no experience in motorcycle uses.

And while $1000 CMC disks might be considered by some in specialized motorcycle applications, I'm not so sure we'll see them in e-bikes for quite some time. And mostly because of the expensive delicate nature in the thin-disks of bike designs. Even stainless is somewhat delicate in thin-disks of bike designs, susceptible to bending deformations on impacts. When thin CMC's can resist equivalent impacts without damage,... they'll gain a huge, although expensive, advantage over current stainless designs.

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Re: Specific heat absorption capacity of disc brakes

Post by MadRhino » Apr 12 2018 1:04am

DRMousseau wrote:
Apr 12 2018 12:44am
MadRhino wrote:
Apr 11 2018 9:40pm
The future of brake rotors is CMC (ceramic matrix composite).
I wondered why I hadn't seen some kind of ceramic composite brake-pad for bikes yet,... but I'm thinkin' they're not nearly as effective on stainless disks as on grainy cast materials. I've found ceramic composite pads to be excellent in some automotive applications,... and I've no experience in motorcycle uses.

And while $1000 CMC disks might be considered by some in specialized motorcycle applications, I'm not so sure we'll see them in e-bikes for quite some time. And mostly because of the expensive delicate nature in the thin-disks of bike designs. Even stainless is somewhat delicate in thin-disks of bike designs, susceptible to bending deformations on impacts. When thin CMC's can resist equivalent impacts without damage,... they'll gain a huge, although expensive, advantage over current stainless designs.
There were some ceramic composite brake pads for some bicycle brakes and I believe that some still can be found, but they wear the rotors quickly and make a lot of noise. Magura was the first to offer them, and abandoned them after 2 years.

CMC discs, like most composite parts, will become affordable pretty soon, and their performance could be changing the bicycle brakes for the best. Smaller, thicker rotors, with big carbon calipers. Maybe I am too old to live to see it, but I believe it will happen.
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Re: Specific heat absorption capacity of disc brakes

Post by liveforphysics » Apr 12 2018 1:37am

Life's short, we gotta ride together before you die my friend, I will fly out there to Canada if I have to, but I bet you would enjoy the experience of riding California more, and Ive got some suitable steeds for you here so you don't need to bring a bike.

Also, I agree ceramic composites will be the ultimate evolution, likely mounted on floating bush/rivets on a spider of some high toughness material.

Before that level, a disc of Inconcel floated on a rigid spider should be able to sustain strength to double the temperature of most bike rotors. A carbon ceramic matrix can of course beat it by a few thousand degC.
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Re: Specific heat absorption capacity of disc brakes

Post by DRMousseau » Apr 12 2018 10:13am

MadRhino wrote:
Apr 12 2018 1:04am
CMC discs, like most composite parts, will become affordable pretty soon, and their performance could be changing the bicycle brakes for the best. Smaller, thicker rotors, with big carbon calipers. Maybe I am too old to live to see it, but I believe it will happen.
The amazement of age, is seeing for ourselves the unexpected and incredibly rapid advances in technology and everyday applications! Like coaster brakes, sealed-beam headlights were a long established and common standard for nearly half my life,.... then suddenly SEVERAL various technologies evolved jus in the years since!!!

I DO feel the thin-disk standards today WILL eventually evolve into something more durable to accommodate new technologies. And given increasingly rapid advances currently seen,.... it jus may be sooner than we might expect! The standards of bicycles are becoming greatly varied and broader. AND, E-bikes will certainly contribute some wonderful specialized needs to everyday use, WITH unique standards of their own. We all know and have experienced the shortcomings AND DANGERS, of DYI conversions, that lead to innovative adaptions.

Being "old" usually means I'm slower in adapting new technology till it's rather well established. But these development ALWAYS excite me!

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Re: Specific heat absorption capacity of disc brakes

Post by MadRhino » Apr 12 2018 5:01pm

liveforphysics wrote:
Apr 12 2018 1:37am
Life's short, we gotta ride together before you die my friend, I will fly out there to Canada if I have to, but I bet you would enjoy the experience of riding California more, and Ive got some suitable steeds for you here so you don't need to bring a bike.
I don’t plan to die anytime soon, but I always knew it could happen anytime. My girlfriend’s father died last Thursday, he was one year younger than I. Makes me think of some things I’d like to do before the last jump. Spending some winter time riding away from the cold is one of them, and I have no doubt that you are a challenging riding partner. 8)
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