Talk:Disc brake

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This page is awfull there is almost no mention whatso ever of motorcycle disk brakes, which are completly diffrent from car ones. There is also next to no mention of the matreials used or their structure ect, sorry but this page is poor and almost useless. someone sort it out. —Preceding unsigned comment added by (talk) 10:42, 2 December 2007 (UTC)

One item that is very important to the development of disc brakes is the inverted caliper, it is most commonly used on the Buell motorcycle. The design allows an immense rotor to be used within a specific wheel size.

Another interesting note is the recent bonding of steel to aluminum discs, reducing the weight of the vehicle. —Preceding unsigned comment added by (talk) 05:30, 15 July 2010 (UTC)

Full-Circle/Annular brakes?[edit]

User: added a large discussion of "full circle" disc brakes including a single external link to a company that makes (?) them. Sounds like a real technology, but has never been mentioned by autoweek or ward's. Google didn't have anything like it in the top 10 in a search for '"full circle" brake'. I've never heard of it. I removed it. What do you all think? Reminds me of Quasiturbine... --SFoskett 03:13, Jan 28, 2005 (UTC)

Exactly. Come back when people have heard of you. —Morven 10:01, Jan 28, 2005 (UTC)

they're called "full contact disc brakes" —The preceding unsigned comment was added by (talkcontribs).

Wasn't that in PM or PopSci a few yrs ago, a spl ish on "future car" tech? (Anybody remember what ish that was?!) Trekphiler 17:38, 21 August 2007 (UTC)

In wheels?[edit]

The picture caption states "On automobiles, disc brakes are located within the wheel". Is that always the case? Doesn't Jaguar use a rear axis where the discs are located almost at the differential? // Liftarn

Good catch - inboard brakes. --SFoskett 15:46, Apr 6, 2005 (UTC)

yes have a Jaguar XKE 1967 and it has inboard brakes located at the rear differential.

Alfa Romeo did, can't remember which model though. The idea is to reduce unsprung mass. —Preceding unsigned comment added by (talk) 05:50, 26 April 2011 (UTC) Citroen used the same "discs near differential" on their smaller cars. "Oltcit", licensed Citroen made in Romania, used the same technology. Unfortunatelly, the stress on CV axles is very high during breaking.

Pinion mounted disc brakes are used on many off road vehicles. These vehicles are modified by using Rockwell 2-1/2 ton axles from military trucks. To reduce weight, the stock drum brakes are removed, and a disc brake set up is mounted on the pinion of the differential. — Preceding unsigned comment added by Somebodyalreadytookmyclevername (talkcontribs) 20:55, 13 December 2011 (UTC)

Recent additions[edit]

Do some of the recent additions/changes seem a bit dodgy to anyone else? At a minimum, there's now grammar cleanup that's needed, and I'm not sure I agree with the technical accuracy of some of the changes.

Atlant 20:28, 7 September 2005 (UTC)

fudu —Preceding unsigned comment added by (talk) 11:16, 18 October 2009 (UTC)

Concerns about runout[edit]

I'm new here, so I was hestiant to make changes myself, but I agree. Particularly, the setench about how .007 inch thickness variation can be felt - this is entirely dependant on the rest of the braking system. I was going to change it to this:

The thickness variation can often be felt by the driver when it approaches or exceeds the maximum allowable value specified by the manufacturer.

but thought I should get some feedback here first, seeing as I'm new :)

--Emesis 16:08, 19 March 2006 (UTC)

You might keep the data that's there now by including something like: "when it approaches or exceeds the maximum allowable value specified by the manufacturer; .007 inches is a typical maximum value allowed."
Atlant 16:44, 19 March 2006 (UTC)

Disc Brakes on Bicycle[edit]

There is a lot of information about disc brakes and how they are used for motorized vehicles (e.g. cars), but how about disc brakes used on bicycles, because surely they are not the same.

Actually, the basic operating principle is identical; only the implementation details vary. You know: master cylinder, hydraulic fluid, caliper, disc. But please, be bold and add to the article as you see fit!
Atlant 16:46, 19 March 2006 (UTC)

Bicycle disc brakes work in an identical way to cars, in that they all have a master cylinder, a disc (known as a rotor on a bike) and a caliper, interconnected by brake fluid, which operates the pistons. The main difference is the mounting and the overall size and weight of the brake. The bicycles' rotor is mounted on the wheel therefore making it easier to replace the brake pads. Also, the brakes are considerably lighter, approximately 300 grams for each brake, although this excludes the rotors. The size of the rotors also differ, from 140mm to 225mm in diameter. The brakes are not vented either unlike a car that has effectively two rotors attached with a gap in between, although new brake designs are being released by the likes of Hope Technology, which are vented. All bike rotors are cross-drilled, reducing the build up of gasses which can affect braking performance, and it also helps to keep both the pads and the rotor cooler, by increasing the surfac area they have to cool down. —The preceding unsigned comment was added by (talkcontribs) .

Re: Materials used for bicycle disc-brake rotors. While it's true that stainless steel is preferable to mild steel for disc rotors, in my experience it's incorrect to state that most rotors are currently made of stainless steel - most of them are mild steel as a quick glance at the rusty discs on many MTBs at a meet, or at a shopping centre, will readily attest. Further, there's also currently no in-line citation to support this assertion. Chapter 11, page 13 (11-13), however, of Sutherland's Handbook for Bicycle Mechanics (7th Edition) states that "Stainless steel is preferred due to its anti-rust properties." Therefore, citing Sutherland's Handbook, I intend to amend the current assertion that "Most bicycle brake discs are made of stainless steel, ..." to "Most bicycle brake discs are made of steel. Stainless steel is preferred due to its anti-rust properties." (talk) 15:01, 8 October 2011 (UTC)

Cross Drilling[edit]

Why do my edits regarding cross drilling keep getting removed!

The drilling of discs is to remove/vent high temperature gases from the brake pad/disc surface. They also increase the discs surface area allowing more heat to transfer to the atmosphere.

Any effect on unsprung mass is negligible/incidental. They do not 'in the main crack', this is dependant on use and manufacturing quality.

"Manufacturers use drilled discs if they determine that the average owner of the vehicle model will not overly stress them"

Is that suggesting that manufacturers send out marginally safe vehicles based on an estimate of the owners driving style?
Dispite the poor wording, the phrase does get at a very important fact. Manufacturers base brake system design around what the vehicle is expected to be used for. Try and take a minivan out to racetrack and run 25 hard laps in a row. I can nearly guarantee the brakes will not function 100% properly by lap 25. — Preceding unsigned comment added by (talkcontribs) 04:17, 8 December 2010 (UDT)

This article is grossly inaccurate, I am a highly qualified vehicle engineer with nearly 25 years experience in the industry.

Thank you for the completely unhelpful insult. Maybe help improve instead of talking trash on the article?

I see your point but contact area is not a major factor. The arguments for/against cross drill include 1) removal of metal lowering thermal mass.... If you work this out for ordinary cars this is small and accounts for about 0.004 material spread across the disc, using my estimates. This is small compared to a typical thickness spec that allows 0.040 removal per side of material due to wear and machining. 2) Increasing air movement and surface area helping cooling.... surely this is small.. forgot to sign this...Ianhenderson007 (talk) 13:12, 9 July 2010 (UTC) I see the comment about pad temp going up, I think the area change is small, and the contact is wiped across the pad, so surely the pad temp is dependent on the rotor temp and physics of the interface being the overwhelming factor.Ianhenderson007 (talk) 13:12, 9 July 2010 (UTC)

Might I ask what qualifications the author of these half baked opinions holds? —Preceding unsigned comment added by Goldenthesarge (talkcontribs) 11:22, 30 June 2008 (UTC) Surely this is a format for brain storming, we should be bring opinions and then facts to this discussion. (I see lots of this but not much half backed ideas.) hopefully a better public page then emerges, or am i stating the obvious.Ianhenderson007 (talk) 13:26, 9 July 2010 (UTC)

I added some information about cross-drilled rotors under the "Discs" subsection. I'd like to add something somewhere that brakes work by converting the car's kinetic energy to thermal energy; a dramatic illustration of this can be seen here: Just not so sure where. Riddlefox 21:03, 6 April 2006 (UTC)

'Sounds like an item that belongs near or in the lede. Of course, one might also argue that that's info that's already in the cross-referenced (I hope!) article on plain-old-brakes. ;-)
Atlant 23:35, 6 April 2006 (UTC)

What's that nonsense about "heat dissipation"? Cross-drilling does not improve heat dissipation. Quite the opposite, disk brakes with cross-drilled disks are more prone to overheating due to lower contact area and, consequently, higher heat accumulation in the pad. — Preceding unsigned comment added by (talkcontribs) 04:17, 8 December 2010 (UDT)

—Preceding unsigned comment added by (talk) 20:03, 19 May 2008 (UTC)

My understanding is that the real purpose of cross-drilling or cutting grooves is to dissipate offgasing that occurs under severe braking. Since the heat dissipates primarily through conduction and then convection, the drilled holes may actually restrict the flow of heat through the rotor disk. The vents in vented rotors adds convective heat transfer to the cooling process.--THE FOUNDERS INTENT TALK 13:24, 20 May 2008 (UTC)
I'm sorry, but outgasing has not been an issue for >30 years. Modern brake pads do not break down the same way the adhesives in 1970s brake pads did, outgasing was solved by revision of the compound which brake pads are composed of a few decades ago. This is a common misconception about modern brake systems. It was the original reason for cross-drilling on race cars. Now that the problem has been eliminated, so have the gains.... but that is another whole argument. — Preceding unsigned comment added by (talkcontribs) 04:17, 8 December 2010 (UDT)
Cross-drilling is actually to help remove rainwater from the disc when on wet roads, reducing the film of water that builds up under the pad. It was first used on aircraft discs in conjunction with the Dunlop Maxaret system. The film of water is forced into the holes, where it becomes one larger, heavier drop, which then gets flung-off by the centrifugal force. — Preceding unsigned comment added by (talk) 22:08, 25 September 2011 (UTC)

Bedding Rotors to reduce Squeal[edit]

Pad and rotor bedding procedures are often overlooked by drivers. In performance automobiles, properly bedding new pads in old rotors is essential for performance, comfort and squeal reduction. Is it appropriate to add a procedure to the article? Wpjonathan 13:27, 11 April 2006 (UTC)

Unfortunately, it is unrealistic to expect most drivers to go through the complicated and time consuming process required to bed the pads. 500 miles (as I have read in one source) is rather long to expect the average driver to pay attention to bedding pads. Frankly I wouldn't expect my wife to drive more than 5 miles before she decides it's been long enough. --THE FOUNDERS INTENT TALK 13:28, 20 May 2008 (UTC)

Most/ some? manufacturers give a simple 10 stop procedure for this. So any recommendation should refer to the manufacture's specification for bedding in.Ianhenderson007 (talk) 21:45, 8 July 2010 (UTC) —Preceding unsigned comment added by Ianhenderson007 (talkcontribs) 21:22, 8 July 2010 (UTC)

Brake repair and maintence[edit]

Having recently shelled out ~$90 to replace a "brake switch" I'd like to see more general information on the parts that go into the brakes and how to replace/repair them. So if someone could add a section for this, that'd be nice. Also, after poking around a bit most places seem to have "brake light switches" for about $3 and they go into the main fuse box under my hood...takes a good 3-4 seconds to replace it. Am I getting hosed on this deal or is the "brake switch" something different? -Anon 12:33, 2 May 2006 (CST)

Old joke:
The big factory has been shut down for a while, costing the company millions of dollars a day. They call in the consultant who arrives, looks at the situation, pushes one switch, observes the factory start working again, and presents his bill: "$50,000 for services rendered".
The CEO says "That's outrageous! I won't pay it! Break it down so I can see just where my $50,000 went!"
The Consultant re-writes his bill:
  1. Pushing Switch: $2
  2. Knowing which switch to push: $49,998
You're kind of in the same boat. By the way, I doubt the replacement switch was $3, but let's say it was $10. Where did your other $80 go? It went to knowing what part to replace and how to replace it correctly. For some switches (the mechanical kind that are operated by the brake pedal lever), that means knowing how to adjust it. For others (the hydraulic kind), that means knowing how to replace it without introducing dirt or air bubbles into your brake fluid or knowing enough to bleed the brake system afterwards.
Brakes are pretty serious stuff; you do want the technician who works on your brakes to know their stuff, right? ;-)
You may also have been hit with a "minimum shop time" charge. When my Audi dealer works on my car, the minimum workshop time is one hour at $90/hour. no matter how long the repair takes. But no matter what type of brake switch you had, you can trust that it probably took more than "3-4 seconds".
Atlant 17:52, 2 May 2006 (UTC)

Early History[edit]

Crosley's '49-50 discs were not "a type of" but true modern discs: Examination via a '35-53 MOTOR manual diagram further proves this fact. The apologetic wording "type of" needs to be stricken. Sorry, Jag. Imperial's '49-53 disc brakes should by right be mentioned, though those DO fit the billing of being "a type of", as they were fully enclosed with dual expanding full-circle pressure plates. WQ59B 03:02, 16 June 2006 (UTC)

yes but they were fixed brakes that also floated, they were fixed directally on but relied on one piston contacting the rotor first then pulling the other one in... believe me that was my uni thesis for engineering science.
So yes they were the first "modern brakes" however they were not under the general specification headdings and so are not recognised.

Pad retraction?[edit]

  • How do the brake pads retract after application - are springs or negative hydraulic pressure used? What stops the brakes staying "on"? 06:46, 8 December 2006 (UTC)
They don't ever really retract (well, more than an infinitesimal amount). It's just that once you stop putting pressure on them (with the brake fluid or air pressure), they have no normal force relative to the rotor surface and so they exert essentially no friction force on the rotor. And the slight non-planarity of the rotors then drives the pistons back an infinitesimal amount, leaving a slight clearance with the rotor except at the rotor's "high spots". That the pads remain almost in contact with the rotors is actually useful as it helps to keep the rotor "swept" of any significant thickness of water and also prevents the intrusion of sand, grit, and other road debris.
When you finally change out worn pads and rotors, you use a clamping mechanism (of various sorts) to force the pistons back into the calipers. (Or, for calipers equipped with parking brakes, you often screw the piston back into the caliper.)
Atlant 12:42, 8 December 2006 (UTC)

In fact the Dunlop Brakes on my 1964 MkII Jaguar had a mechanism to retract the pads away from the Disc / Rotor. The Spec on this pull back was 0.010 inches. This was achieved using a pin and hat holding the pad to the piston.Ianhenderson007 (talk) 13:19, 9 July 2010 (UTC)

And I think its worth discussing the knock back that occurs on typical Automobile brakes. The small amount of play in the bearings knocks the pads back away from the rotor, and with no clamping force they effectively do not cause drag. It is also possible that lateral run-out does the same thing.Ianhenderson007 (talk) 13:19, 9 July 2010 (UTC) Ianhenderson007 (talk) 21:38, 8 July 2010 (UTC) —Preceding unsigned comment added by Ianhenderson007 (talkcontribs) 20:56, 8 July 2010 (UTC)

The brake pistons retract because of the elasticity of their seals. Pads stay behind, pushed away initaially by the uneven rotor and after that by the air wedge created at high rotating speeds. Lubicating the guides helps.


One of the sections near the end makes reference to the acronym 'DTV' but it's not readily apparent what this is. Either I'm blind or the article could use a bit explaining it :) Ayocee 16:41, 27 April 2007 (UTC)

DTV = Disc Thickness Variance, and refers to a condition where there are different thicknesses (high/low spots) across the face of the disc —Preceding unsigned comment added by (talk) 05:57, 26 April 2011 (UTC)

Liquid cooled disc brakes[edit]

One of my friends has developed a liquid cooled disc brake ("liquid cooled drive line" I think is the official description) called the "D-Brake." It attaches to the tail end of the vehicle's transmission and applies braking force to the drive shaft. Is this technology worth noting in the article? I don't know if this is the first of its kind or not, but I have detailed information available should it be deemed noteworthy. --Jack 22:27, 3 September 2007 (UTC)

Use on trains[edit]

This article completely overlooks the use of disc brakes on modern passenger trains a "hole" that needs to be filled by an expert in the field. Peter Horn 14:23, 26 March 2008 (UTC)

Picture of carbon disc brakes from the Concorde airliner?[edit]

The article on the Concorde uses a picture of its disc brakes, which are made out of carbon because of the high temperatures they must withstand when stopping a nearly-200 ton airliner. Would it be useful to put that picture in this article? Ilikefood (talk) 17:43, 28 August 2009 (UTC)

Concorde undercarriage Speyer 02 with disc brakes.JPG

Article content and quality[edit]

This article has some major problems.

  • Almost no coverage of non-automotive disc brakes. Disc brakes are widely used in aircraft, railroad and industrial applications. Yet, other than some coverage of a mountain bike application, I see little that would even indicate that disc brakes are used in other applications.
  • Little description of how disc brakes actually work. Some illustrations of a disc brake assembly cross-section would be very helpful.
  • Way too much information on failure modes. I doubt that most readers are that interested in details about how to measure rotor runout. Speaking of which, I've never seen anyone do that sort of thing in some 40 years of working around high performance cars. If there's ever any suspicion in that regard, the rotor is turned or replaced.
I work as a brake product manager in a big auto firm, and we sell quite a few run out dial gauges so i suspect someone still does this! (talk) 05:59, 26 April 2011 (UTC) Rob S
  • The history section is hard to follow and, again, ignores anything other than automotive applications.

Bigdumbdinosaur (talk) 22:07, 2 September 2009 (UTC)

Callipers or Calipers?[edit]

The British standard is 2 Ls, the American standard is with one. Both spellings are present in the article? Should it be standardized?

If so, to the American or British spelling? —Preceding unsigned comment added by Kopitarian (talkcontribs) 16:03, 9 September 2010 (UTC)

If we were going to follow the Wiki Guidelines for spelling and grammar then yes it should all be one convention - the American standard as is mandated.

That will never happen nor will you get the moderators to agree to use one spelling here - unless of course we ignore the fact that 70%+ "English" speaking people in the world are using American and just put the article in British standard. It would make the British and Aussies happy but would annoy the hell out of everyone else. Of course it is only a matter of time until every article is just that. It is almost impossible to find an article very accurate — Preceding unsigned comment added by (talk) 13:39, 23 April 2012 (UTC)

'48 Tucker[edit]

Didn't the Tucker Torpedo use disc brakes? — Preceding unsigned comment added by (talk) 00:07, 27 May 2011 (UTC)

Yep. TREKphiler any time you're ready, Uhura 11:09, 10 July 2011 (UTC)
Tucker suspension units
This photo suggests not. Andy Dingley (talk) 19:28, 12 July 2011 (UTC)
It appears my source is wrong. :( TREKphiler any time you're ready, Uhura 19:51, 12 July 2011 (UTC)

No mention of Elmer Ambrose Sperry[edit]

In 1889 Elmer Ambrose Sperry of Cleveland invented a disk brake for his electric car which employed electrically actuated pistons to clamp down on the disk. This is a known and widely accepted fact. In 1902 F. W. Lanchester received a patent for a nonelectric disc brake system that employed copper linings that clamped upon a metal disc. There are two types of disk brakes, Spot type and clutch types, again there is no mention here. I suggest that this page needs to be reworked and properly referenced. (( Jacob805 (talk) 07:14, 10 July 2011 (UTC)

Sperry received GB 189901116  Improvements in or relating to Motor Road Vehicles and Devices for Controlling the Various Operations relating to Starting, Stopping, Accelerating, and Retarding the same.
Frederick William Lanchester received many patents, but I think the one that relates is GB 190123500 . LeadSongDog come howl! 18:17, 23 August 2011 (UTC)

Uncited sections[edit]

Many sections of this article lack any references, and should be deleted if inline citations are not added. Of 31 citations, the brake judder section contains the majority. --THE FOUNDERS INTENT PRAISE 14:27, 22 August 2011 (UTC)

That's a fairly radical view, IMO. The guideline IIRC says "if likely to be challenged". AFAIK, none of it is. TREKphiler any time you're ready, Uhura 22:28, 22 August 2011 (UTC)
Information in articles are to have citations to support them, otherwise it could be challengeed as OR. A vast majority of the text is uncited. There is nothing radical about what I'm suggesting. --THE FOUNDERS INTENT PRAISE 15:19, 23 August 2011 (UTC)
Could be challenged for a number of reason, yes. That's what the cite tags are for. To remove it absent challenge is going a bit far IMO. TREKphiler any time you're ready, Uhura 23:17, 23 August 2011 (UTC)
Please go ahead and at {{cn}} wherever there's any real doubt of the accuracy. LeadSongDog come howl! 00:06, 24 August 2011 (UTC)

No mention of aircraft brakes?[edit]

I was surprised to read nothing in the article concerning disc brakes as used on aircraft. Despite their early origins in automobiles, I'm pretty sure the first practical disc brakes were used on airplanes because of their thin profile and light weight, and it was at least 20 years before they were used on cars. I do have plenty of knowledge of the subject, but I unfortunately don't have much time to dig up source material. Are there any other aviation buffs on here that can at least provide some source material to at least give aviation a mention here? Shreditor (talk) 07:38, 24 June 2013 (UTC)

Yes, it's a big omission, especially as this is where disk brakes started. R.A. Beaumont's Aeronautical Engineering is the usual 'entry level' source for 1930s stuff like this, as it's detailed, well written, but pretty common, so many editors have a copy of it. Aircraft in the 1960s should also cover the development of multi-disk packs, antilock brakes and exotic materials for brake disks. Andy Dingley (talk) 08:49, 24 June 2013 (UTC)

"Cryogenically treating" Brake Discs - validity thereof[edit]

Whilst searching for some replacement brake discs for my motor car I became aware that some performance part suppliers are offering discs that have been treated by taking them down to a low (sub -200°C ?) temperature for a time seemingly of hours or a couple of days (?) possibly with a further post refrigeration heat treatment. This is supposed to improve them by making them more uniformly hard so that they wear less and last longer or perform better at high temperature/loading. Is there any evidence that can be linked in to support such claims, if so then it is a topic that would be a useful addition to this article in my opinion. (talk) 18:54, 15 June 2014 (UTC)