Drum Brakes
 

I wont by a car anymore that has them! Its a shame there even made for automotive use anymore. And a marketing tool at that.

If drum brakes where so good they would still be on the front wheels on cars and Large aircraft would use them still. I cant imagen having drum brakes on a motorcycle now days.

Drum brakes dont deal with water worth a hoot. They have a propensity to lock due to shoe shift in the drum. You have springs that fail alot more often that folks want to admit. They only use about 1/2 of the shoe surface in braking. Just look at the shoes sometime. Only the top half of the show wears. The bottom half is barely used unless there is a lower cam that moves the lower part of the shoe into action. also if you look at a worn shoe you more than likely will see that the inner part is worn a bit more than the outer part. This is due to flex in the drum that happens during braking.

My brother is a tool and die man and shop manager. He quotes jobs makes dies runs production, buys matrials and such.

We talked about this very same subject. Hes with me on this issue and cant figure out why cars are even built with drums anymore. So I asked him to do a mock quote on production of the two brake systems. Are drum brakes really cheaper to produce than disk? I also asked my father inlaw the same question as he owns a foundry. So casting the drums, rotors and calipers would be right up his alley. he and my brother worked on this as if they where both supplying for a large automive company.

The answer was socking! Over all drum brakes cost more to produce!

The disk and caliper casting cost more to produce than the drum. But there also a much higher quality casting and peice of work. Then it ends. The back plate of a drum brake cost alot more to stamp ot then a light weight sheild used on on a disk brake system. The brake pads of a disk brake cost almost half as much as a drum shoe to produce. Then theres the springs, pins and other small hardware in a drum system. Spring winding machines cost alot to run and maintain at a level of producing brake parts. Theres alot of quality control issues from bulk spring wire stock to production of said springs. Alot of springs if tested right would be culit. The piston in a caliper is cheaper to make than the pistons in a common drum brake. Valving and control circuts are about the same for both.

In there little excersise they came up with drum brakes costing about 20% more to produce than disk brakes. Also there was more product liablity in the drum brake systems.

I think market dept's use drum and disk brakes as a trim adder for a excuse to charge more for something that cost less to produce. IMHO drum brakes should never be used on a new production auto.

Drum brakes and disk brakes are kinda like floresent lighting and power compac floresent lighting. Or even LCD panels verses CRT.

Older flo-light systems cost more to make than compac-flo-light systems. The newer lightes put out more light per watt used! A electronic ballist is far cheaper to make than a old style ballist and the bulb production is basicly the same.

Same with LCD's and CRT's. A CRT cost far more to make than a LCD. Just making the glass tube cost more than anything in a LCD panel of the same size.

In the LCD/CRT issue Im guilty of buying a CRT recently over a LCD. No way in hell Im paying 2500 bucks for a 32" wide LCD panel to watch TV on. So I purchased a 36" Sony Vega CRT for 700 bucks. I will never ever move that god awful heavy TV again. I will take it out of this house in peices when its time comes and it leaves.

But I will never purchase a car or truck again with drum brakes. My last drum brake purchase was my 00 Ranger. I only bought it new cause I got it for under 15k new. And truley wish I had not bought it. The drums are awful on it.

I understand a lot of your issue with drum brakes. I'm shocked that new cars are made with them, as disc brakes require less maintenance and are easier to work on.

That being said, I will not be swapping rear disc brakes onto my car. There is a weight differerence of around 25lbs between the disc brakes and the drum brakes. Every little bit of unsprung weight that I can save the better.

I don't know what you are complaining about. The only problem i have with brakes is I think ABS should be standard on all cars.

I have drum for the rear and discs for the front. My front disc brakes are huge. I can easily lock my tires at any speed, these *****es hold. I erased my last set of tires when I braked on the freeway to avoid a dog. Since then I have gotten rid of my warped disc problem and upgraded to racing pads. The pads are a little bit too much, they grip a lot more.

I'm fine with drum brakes in the rear, just make ABS because evrytime I slam the brakes my tires gets erased.

your tires vanish whenever you slam on the brakes? how weird.

Yea, with the new brakes it's even worse. If I slam at 5mph I can give anybody sitting in the car whiplash.

Compaq

You need to learn to quiver. Folks have known for years that a locked up wheel dosent stop as good as a ever so slightly rotating wheel. Train engineers, truck drivers and race car drivers lives have depended on it for years. ABS is the modern I dont have to think to hit the brakes system. And its great if people use it right.

The quiver is simply that. If you hit the brakes hard you figure out just how you have to land your foot on the pedal at hard pressures to make your leg quiver. This has a effect on the braking system like ABS. The slight quiver helps you to not lock up the brakes so early, but still allow max braking. Quiver isnt the best way to do it. Buts it the simplist. Once you find the place in your foot and leg position that causes it. It will become natural to you.

you mean make my leg spasm so it acts like a ABS system?

The downside to disk brakes for me is that they're open to the elements. When you don't drive every day (and then when you do drive, you don't use the brakes much or very hard) the disk surface rusts.

Streamlining my wheel covers helped with this a little, but the front brakes are still kind of grumbly for the first km or so when I fire up the flea.

I don't mind my drums because they can stop my car. I think I should go and say I'll never buy another car over 2100 pounds, :p

I could swap as well, but the weight isn't worth it to me.

I'm also not a fan of ABS for myself. I am in general cuz it keeps most "slam-the-brakers" from hitting me, but I have found the point where I can stop without locking up the brakes.

*shrug*

Static friction > kinetic friction.

lightness
 

How much more weight would rear disk brakes add compared to a drum brake setup. I was wanting to add disks in the back of my civic. I never thought of the extra rotating mass. :(

It's about a 25lbs difference overall from what I understand.

I don't like disk brakes because they alwas drag, it is part of their design to have close pads, if they came up with a design for disk brakes that was lighter then drums, and that the pads were able to fully retract, then I would think about them, but as they are they weigh more, and slow you down, try it, coast to a stope, and feel your wheels, if you have disk brakes they will all be warm, and the drums cold.
how much more does it cost to put a cable operated hand brake on a disk brake set up? was that included in your cost comparison?

I agree that disk brakes on the front of a motorcycle are nice, I've riden ones with every configuration, altho I never had an issue with the duel trailing pad front drum brake on my honda, the nicest thing about disk brakes on the front is that it's really hard to lock up the front wheel, and that is the only reason I would want them on a car or a motorcycle, but just like automatic transmitions, disk brakes are an extreamly problem filled part, I would say they require at least twice as much. attention/matence/tossing at of money then drums, altho

drum brakes have too much play.

pedal
 

I would love a firmer pedal. It just feels safer. That is one of my main quibbles about drum brakes...the soft feel of them is just unassuring. I had my brakes resurfaced, bled, and resurfaced last year. Still soft. It was dissapointing. I haven't done any shopping, but I know I would want it at some point.

It's possible that your flex lines are doing just that! They do go bad and get weak and will expand under pressure. You could switch to braided steel lines for a rock hard peddle.

good points everyone, but in the end regen owns all!

There was a toyota prius II at over 100,000 km that showed no signed in brake wear unless you put a microscope to it. Regen braking is truly the bomb and all drums should be installed for maximum weight reduction! Well I save gas so I barely go fast anyway so my front discs and rear drums are good enough.

i drove a car with 4 corner drums recently. horribly unsafe. i would take out airbags and seatbelts before going drums on all 4 corners. i dont understand how there is an argument for all drums in a street car.

even with stainless brake lines, it still will have the play, all drums do this. it is the nature of the beast.

haveing drum brakes on all 4 corners is not something that I would push for, drum brakes are to good at locking up wheels, where disk brakes are better at slowing you down without lock up, disk brakes make lousy parking brakes from what I've seen, and it's nice not to have the wheels you use to steeer with locking up.

as for disk brake being cheaper, to replace my entire brake system,
drum brakes cost $187.30 per wheel to buy all new brake drums, wheel bearings, mud guards, brake shoes for the rear.
disk brakes cost $325.97 per wheel for disks, calipers, bearings, pads, guards.
they still use drum brakes on the rear of vehicles like the Honda Insight, and they went to great laingths to make that vehicle safe, and light weight.

braided steel lines
 

Not many parts are actually available for my 4 door civic. They are few and far between. Anybody know any decent brands??

I have been able to get a lot of the item's for my 89 Honda, from a place called Autohaus AZ. They are available in Phoenix, or over the internet. So far all of the part's have been very high quality, at very reasonable price's, which is not easy to do for Honda part's, generally. They don't alway's have every thing I have needed, but I've gotten all of my ring's, bearing's, head gasket's, water pump's, oil pump's and thing's like that from them and I've been very happy with the quality. (This is not a pitch, it's just my experience!)

Honda parts
 

I get alot of my parts from honda dealers, https://www.hondaautomotiveparts.com/ is who I got the price for brake parts from, their 3-4 day shipping however takes around 12 days.

Even my n600 has front disc brakes. Sure, they're as tiny as hell, but they're disc brakes.

Just imagine how small the rotors have to be to fit underneath the 10 inch rims.

Ditto, for most of the general population's driving needs on city streets, drums are fine. I suppose during race conditions drums can heat up quite a bit, but given advances in materials since the disk brake was introduced, fade isn't what it used to be and they're actually suitable for some racing as well. According to the d00d that built this car.

All of your points were exactly spot on. :thumbup:
For FE machine drums are the way to go !!!! no question about it.

Discs brakes rely on the disc knocking the pads back into the caliper for clearance drums dont.
This means there is ALWAYS more resistance on a disc brake setup as the brakes always drag a little.

With steel lined vented alloy drums supporting a twin leading shoe arrangement stopping power is good.

Manufacturers went to discs BECAUSE IT WAS CHEAPER FOR THEM !

The corvair probably would have locked up anyway.(as you say)
Race car disc systems are manufacured to very high standards and are not the same as on our shopping trolleys.
If we had these brakes ,OK , discs are kool , but we dont., we have cheap immitations.
Its sure that because of racing success discs have been encouraged to put onto passenger cars also . but the cost of making a brake system (at teh wheels end) with only a few moving parts is a lot more economical idea than a drum setup which may have 10 or 20 moving peices.

As you say , drums can stop well.
On the front twin leading shoes have a power assistance type of effect often meaning no vac booster is required (especially on a light car)

Hey I think I have a quick fix for your problem . . . go up a hill where you can stop and roll backwards without anyone behind you and pump your brakes firmly several times. This adjusts your rear drum brake shoes and should take out most of the pedal travel, then as they wear and you do it a few more times they will get firmer.

Many , if not most drum brakes get adjusted when you apply the handbrake.

True, but the old chevys adjusted when you backup and hit the brakes.

BMWs have disks in the front and rear, and an set of extra drums in the back for the hand brake.

This is a vented alloy drum with fins if some readers are not familiar with what I have been talking about.

https://www.plminishop.com/images/SUPERFINS-PL.jpg

On small FE cars they could return.
Remember that in the old days machining and materials werent as good as what can be done today.

Ime sure if they put their thinking caps on they could make a nice drum system now days.

Lets not get too carried away one way or the other. Drums are better for FE, but should never be on the front of a car anymore. A pair of drums on the back never hurt anyone (unless you're racing), and they normally make for a much more effective e-brake.

For street driving, there should be nothing wrong with rear drums. If stopping in rain or dry is an issue, then there is probably a problem with the brakes or with the tires. Many people like to overlook the tire. If you are running 155's for FE, don't get pissed at your drums if you're not stopping. Short of running an r-compound tire, 155 mm is just not enough of a contact patch to stop your car on the dime (unless your car is in the sub 1800 lbs range).

The drum brake is going to be lighter and brake harder initially than a disc brake of equal size because their is a greater friction area. However, this causes heat build-up faster and degrades the performance very quickly. Rear brakes never support much weight during breaking and therefore will not heat up as fast. When braking the majority of the weight goes to the front of your vehicle, so drums in the front will heat up very quickly and can degrade your braking performance in just one hard stop.

I didn't really get any sleep last night so don't just my ability to string words together too harshly. :-p

And just how many high speed emergency stops would one be anticipating in a high FE car ?
-- and that is why (if done properly) a drum setup could be viable on a FE car.


PS - I know a whole bunch of disc front ends that will fade to NOTHING in less that 1 hard stop.

I am confused with this logic.

If I turn this around you are saying that disc brakes are less prone to fade because they have smaller friction area.,, so less area is better.
If that true , I should cut half the surface off my brake pads , then ide have super brakes.

That just doesnt make sence.

as I see it the area that rear disk brakes have an advantage is if you are doing alot of speeding up then slowing down (to go around corners?) or are takeing a fully loaded car down moutan roads, but a few days ago when I went over the rocky moutans in a civic with rear drums that was loaded slightly over the recomended gross vehicle weight, we had no problems at all slowing down or stoping at any point in time, as I see it they are strickly a stelling poing, a style point, like those little rear air fin tails, they are shiny, and look pretty on the rear, compared to my rusty drum brakes.

Brake fade, and brake fluid
 

I thought that brake fade was largely caused by brake fluid boiling. If so, than one key factor in brake fade, would be how much heat is produced by brake friction (which isn't necessarily how much you slow down/stop with the brakes), and how much of that heat is removed by brake cooling (which is one reason some people think smooth hubcaps are a bad idea, because they trap extra heat in the brake system).

BUT, if you are worried about brake fade, it seems like you have one easy/cheap solution that many people totally forget about. If you have some reason why your system causes (or traps) extra heat in the brake line, just use a quality brake fluid and change it out every year or two. While doing so doesn't lower the heat in the system, it does an amazing job of raising the boiling point of your brake fluid. And remember, it's not heat (per se) that causes brake fade, so much as heat that exceeds the boiling point of the fluid in the lines! So by greatly improving the heat handling ability of the brake fluid, you increase the total capacity of the brake system.

NOTE: Changing the fluid out every year or two is even more important than using a quality fluid. While you can "get away with" running brake fluid for 10+ years, it's boiling point will be noticeably diminished with just a year or two (because the brake fluid attracts water, and water in the fluid greatly lowers the boiling point). So the "frequent" fluid changes are more important than the quality of the fluid used (although both help). Happily, even decent quality brake fluid is CHEAP (often under $10 for a quart, and many brake systems use less than a quart total), so there is no real excuse to forget to change the brake fluid!

NOTE: If it's a hassle (or a fair cost from your mechanic) to totally bleed the brake system, you can just take a $2 turkey baster (don't use it for food afterwards, or you will poison yourself) and suck out all the fluid you can from the brake fluid fill location (and then replace with fresh). This isn't nearly as good as a complete flush (in some cars you can only get around 1/3 of the fluid at a time this way), but it will still help a lot by (easily) replacing some of the brake fluid in the system with fresh. And mixing fresh brake fluid in with the old (i.e. diluting the old fluid with fresh) will still help to refresh the brake fluid (raising the overall boiling point, getting some dirt out of the system, and generally making the brakes work better). And using "the turkey baster method" to your brake system, is almost as easy as filling your washer fluid reservoir. Just be sure to have a real mechanic occasionally (every 5 years or so?) do a total bleed of the brake system (as there will be some fluid damage and dirt/junk that "the turkey baster method" doesn't properly address).

WARNING:
Do NOT use DOT 5 brake fluid in any system originally designed for any other brake fluid (i.e. most brake systems). It's OK to upgrade from DOT 3 to 4 (or even 5.1, which is not the same as 5), but don't use DOT 5 brake fluid as its makeup doesn't mix properly with the residue of other brake fluid types (and therefore improper use of DOT 5 fluid can cause your brakes to totally fail)!

Bringing this back to FE:

If the primary safety issue is "brake fade", than lowering brake fade should increase your safety. Conversely increasing brake fade may be a safety issue for people. However, the gains from improving your brake fluid can in many cases be larger than the losses by doing something that makes sense for FE. So if (and this may depend upon how well they are adjusted and therefore how much they drag) drum brakes "fade" quicker, you can still likely more than offset this by using fresh (higher quality) brake fluid!!!

Speaking of which, many people interested in FE use smooth hubcaps. Yet, it is well know than smooth hubcaps trap heat in the brake system, and therefore would cause the brakes to fade quicker. But smooth hubcaps also improve the aerodynamic air flow around the car, and therefore should help FE! So again, if you are at all concerned about increasing the brake fade by the hubcaps, changing your brake fluid is "cheap insurance" against brake fade.

BTW: If anyone is interested, https://www.valvoline.com/pages/produ...asp?product=51 is the brake fluid I currently have in my car. I picked it because its specs are much better than the cheap/average stuff, but still a lot cheaper (only about $8/quart at the local "AutoZone" store) than some of the super brake fluids marketed to the racing community.

However, if you really want to know about what brake fluids are "good", I suggest checking out this thread ( https://theoildrop.server101.com/foru...&Number=523531 )on the BITOG forums. When reading the specs in that thread, keep in mind that the "dry" specs are what you will get when you first put the fluid in the car, and the "wet" specs are what you have when the fluid is "old" (not changed for a while). As you see, even the cheapest fluid "dry" works better than all but the most expensive racing fluids "wet". Which is why its more important to change your brake fluid "frequently" (so you are running closer to the "dry" specs) than it is to use a high quality brake fluid (which has higher wet/dry specs overall). But doing both helps even more than doing one or the other.

Thats a good post about brake fluid , and even just on a maintainance point of view its good to replace your fluid every couple of years.
Old fluid absorbs water which leads to corrosion of brake calipers , cylinders , lines and of course the master cylinder.
Water in the brake fuild lowers its boiling point too.

Unfortuantely , faded brakes are not caused by boiling fluid , its just the gas from the overheated brake pads.

Brake fuild in a normal pasenger car doesnt get to the temps required to boil it.

Race cars where you can get the discs glowing RED ,, are a totally differnt story.

Now, I'm confused. Are you talking about gas (in the wheel region) between the pads and the drums/disks making the pads grip less well, or gas in the hydraulic line (meaning you have less pressure pushing on the brakes)? If you are talking about gas in the brake lines, how would the pads have anything to do with this, as the brake lines are sealed (with the pads on the outside of that seal)?

However, if you are talking about the pads overheating and gripping less well, I can see how that could happen. And you are correct, that better brake fluid won't do anything for overall pad grip (other than let you press the brakes in harder), as the brake fluid only protects the hydraulic brake lines (not the pads). So if your pads tend to not grip well (due to heat), your best bet would be to either lower the temp (better brake cooling, or adjust for less brake drag causing heat in the first place) or replace the pads with (higher quality) better gripping (when "hot") pads.

And if you are talking about the pads giving off some type of "slippery gas" when heated/used, I can also see how that could happen (although some pad materials would naturally be more susceptible to this than others, so higher quality pads could help in this area). However, in that case, the problem isn't the brake style per se, it's failure to vent the gas outside the wheel region, so it is able to stick around to cause problems. And while I admit that many (most?) disk brake systems are naturally better "vented" (then drum brakes), I don't see this as a brake style problem per se (but rather a problem with sealing the brake system up too much from the outside world).

But, I thought a serious problem with a lot of "brake fade", was loosing hydraulic pressure due to gas in the brake lines (and thereby having trouble putting enough pressure on the pads to get the desired braking). And that problem is generally a combo of the amount of heat in the brake lines, and the quality of your brake fluid. So that portion of the "brake fade" problem really can be helped (a lot) by just using fresh (decent quality) brake fluid...

I used to be like you, because I didn't know any better. And I bet most of the population is the same as well (not changing their brake fluid, as that issue isn't even on their radar screen). And the reason why we can often get away with this, is that brake fluid will often last YEARS after it would be a good idea to change it.

But, it will work BETTER if changed (i.e. out with the old, in with the fresh). And the point is, that brake fluid (even fairly high quality brake fluid) is so CHEAP, it is silly to save a few pennies by trying to drive the fluid longer than you really should. Once I learned that fact, I went out and changed the brake fluid in all our vehicles. And even though the brakes worked before that, I was amazed how much smoother and easier the brakes worked from just changing the brake fluid all by itself (without any other brake "repairs"). Yes, it didn't solve all brake problems (I did have the mechanic lube up the springs/sliders in my brakes after that, to help even more), but just changing the brake fluid made a quite noticeable difference all by itself!

I was just dropping in to see who was still beating this drum and I see some very good posts.

I too have become a fan of replacing all the fluid every coupla years. I generally run a good DOT4 (like ATE), but I use DOT5 (silicone) for a car that doesn't see too much action and I don't want it to rot away all on its own.

Yup .thats it.

The pad material chosen for road cars is a compromise.
Pads are made of metals , fillers and resins.
The type and quantity of these parts determine the working heat range of the pad and consequently the braking system.
Choose a compound that is too cold (like suits a racing car) and it wont heat up to its rite range and stopping power will be very poor.

On the other extreme are normal road car pads.
They provide good stopping from cold (almost cold) but they have a lower top temperature limit.

When this limit is exceeded the pads start to expell gas.
This occurs of course at the frisction surface where it presses against the disc surface.
This gas (thankfully inert) has a lubricating ¨effect¨ between the pad and disc.
Discs that have holes or grooves machined into the surface allow a passage for the gas to escape - extending the effective brake system heat range.

In extreme duty applications a combination of vented discs and harder compound pads will be require to provide suitable stopping power under those expected conditions.

The signs that the pads have overheated is that you still have quite a firm pedal but it requires even harder pressure to pull the car up to a stop - and even then its stopping power wasnt impressive.

In rare cases that the fluid boils it is usually in systems with old fluid.
Brake fluid doesnt get the the same temps as the friction material or the discs but it can get hot.
Normal DOT 3 brake fluid out of the bottle has a boiling point of just over 200C , but in use this drops to about 180C.
Brake fluid is hygroscopic.
Over time brake fluid absorbs water from the atmosphere, which reduces its effectiveness by lowering the boiling point.

This can lower the boiling point to 100C , which is the same as water.
Under hard braking the water in the brake system can boil turning into steam.
Steam , unlike water or the brake fluid is compressable.

This will give an instantanious spongy pedal.

It could be so extreme that the pedal may drop to the floor and no braking effect at all.

This is of course an extreme example but possible.
The brake fluid companies would like people to belive it can happen to you at any time , but in reality , its quite rare as its from heat soak - long term high temperatures.
To get this heat-soak you would need many repeated hard braking applications.

But because the pads (in a normal raod car) will go off in 1 or 2 hard stops there is generally not enough time and heat to heat-soak the fluid to get it to boil.

Thanks for the heads up. So it seems that there are two major factors in brake fade:

1) How the pads handle heat (as you described above).

and 2) How the brake lines handle heat (which is the factor that the newer brake fluid can help with, and which I described in a previous note).

And like many things in life, it seems that the one that will "bite you" is whichever one happens to be "the weakest link" (be it the pads, or the brake lines).