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-   -   Disc vs. Drum Brakes (http://www.saturnfans.com/forums/showthread.php?t=17169)

DualCamCoupe 03-12-2003 10:22 PM

Disc vs. Drum Brakes
 
So why exactly are disc brakes better than drum brakes?

Phil 03-12-2003 11:24 PM

Discs shed heat better, so you get less fade. Brake fade is where, in repeated stops, the brakes gradually lose power. Discs are also more powerful. And they are much easier to maintain (drum brake springs were invented by Satan). And they look better through the spokes of a wheel.

But apparently drums are cheaper, so guess which ones Saturn uses in the rear?

silverplum 03-12-2003 11:30 PM

Check out this link.

[url]http://www.edmunds.com/ownership/techcenter/articles/43857/article.html[/url]

Jeff P 03-13-2003 08:43 AM

The Edmunds take is interesting. For the most part, rear drums stop the car as or nearly as effectively as rear discs. From a purely objective, feet-to-stop standard. But I'd rather my car stop in 120 feet than 125 feet. Those last five feet could be the difference between hitting something and not! It's also funny because Edmunds, like all the auto reviewers, discuss braking feel a lot in their reviews. Disc brakes are far superior to drums in this respect. They engage smoothly and react to the pedal in a linear manner. They're just plain nicer from a driving standpoint. And I'd love to see the numbers as to how much it would cost to have them standard on a car. I can't imagine it would be more than $100-200 bucks.

btw my mountain bike even has disc brakes. They're awesome!

jeff

ProDarwin 03-13-2003 06:08 PM

Phil is right, working on drums will make you want to kill whoever invented them. Discs are a whole lot easier to work on, and are very cheap to maintain. (I just did all 4 discs and pads for less than $110). And drum fade is horrible. It takes forever for them to cool back down.

Qlara 03-13-2003 06:52 PM

Ha! I found this is ever-asking question in here. :D

On later Saturn cars: S-series, ION, L and even VUE they are all Drum brakes at the rear as standard.

As we all agree on Disc brake is superior (also looks better) than Drum, but it's not cost-wise for Saturn Corp. For regular commuter driving, drums work OK, so are the standard Firestone tires...... :rolleyes:

amazinghl 03-13-2003 07:18 PM

Like me.. i have all wheel disc.

Phil 03-13-2003 08:12 PM

I still wonder just how much more discs cost over drums. Assuming a full conversion (so economies of scale carry over), I doubt it is over $100, if that. An amount I would gladly pay to have rear discs. It would also be a nice point to use when making a sale.

Saturnmeister 03-13-2003 08:45 PM

Disc brakes are inherently better because as they wear, the pads and rotors may get thinner, [B][I]but the entire pad surface remains in contact with the disc when braking; [/I][/B] with drums, the [I]circumference of the drums increases, and that of the brake shoes decreases as they wear, so as they wear, [B]you have a smaller portion of the brake shoe in contact with the drum.[/B] [/I] In addition, the drums wear out of round, so your brake shoe contact is intermittent in force as the shoe rides from "high spots" on the drum to "low spots" on the drum. In addition, drum brake "automatic adjusting" features are prone to malfunction; disc brakes are self adjusting by design and require no mechanical adjustment mechanism.

Basically, drum brakes are something that should be a conversation piece in an automotive museum by now, but because the rear wheels don't bear a lot of the braking load auto manufacturers continue to use them to lower costs by a few bucks per car. It's amazing to me how they'll sink god knows how much into side curtain airbags, airbags that pop out of seat cushions, etc and then give you brakes that should have seen their last new car installations a decade or two ago. If you compare the cost of the Saturn ABS option from the model years where ABS included 4 wheel discs to those where you get front disc/rear drum with ABS, the difference is about $200. That's what [B]they charge you, not what it costs them,[/B] so you can bet the actual cost per unit is even less. Plus, if they standardized the rear brakes as discs, they could reduce the cost even further. Over a 5 year car loan, you're talking about $3.33 plus interest per car payment. Who wouldn't pay that for better brakes when people are so bombarded with and aware of vehicle safety information?! What's $200 on a vehicle you're paying [B][I]tens of thousands of dollars[/I][/B] to buy?! It's nothing. For those who think you're getting that cost difference as a price cut, as many who defend the use of drum brakes assert, you're kidding yourselves. The price isn't being reduced, they're just decreasing their cost.

wolfman 03-13-2003 09:03 PM

I'll add that disks are WAY easier to service , have far fewer moving parts, and are essentially "self cleaning"...

eRic 02sc2 03-14-2003 11:47 AM

Re: Disc vs. Drum Brakes
 
[QUOTE][i]Originally posted by wbarnum [/i]
[B]So why exactly are disc brakes better than drum brakes? [/B][/QUOTE]

discs dissipate heat better. you have the pads and spinning disc exposed to the air for better cooling. shoes inside a drum cannot cool off as well and will fade faster. discs are easier to inspect and service since you only need a mirror and a flashlight or simply crank the wheel and peek to see how much pad is left and you can measure the rotor thickness without taking anything apart. drums need to come off before you can look inside to measure and/or replace linings. replacing disc pads on a saturn is an easy remove one or two bolts and flip or remove the caliper job. replacing saturn rear drum linings involve springs and things. i did rear discos on my old 92 sc and now 96 sc2 both w/o abs.

Qlara 03-14-2003 03:49 PM

Will drums last longer between replacement, esp on the rear?

eRic 02sc2 03-14-2003 04:35 PM

dunno. my drums lasted until i had the time and $ for the rear disco then the drums went promptly into the trash can. i've never needed to replace rear lining on my old 92 sc or 96 sc2 drum (pre-disco) in the time that i'd burned through 3 or 4 sets of front pads, if that's what you mean.

ssicarman 03-14-2003 09:25 PM

Re: Disc vs. Drum Brakes
 
[QUOTE][i]Originally posted by wbarnum [/i]
[B]So why exactly are disc brakes better than drum brakes? [/B][/QUOTE]

Disc brakes provide more consistant braking as the brakes heat up or go past heat up into way to hot. Disc brakes have everything in a sandwhich between the calipers, as everything gets hots it all expands into the calipers. Drum brakes have the drum around the brake shoes. As the drums get hot they expand away from the brake shoes, the shoes will expand out as well but not as much as the heat goes into the metal drum more than the shoe material and metal part of the shoe. The drum moves away from the shoes and now you use much more of the brake pedal travel to push the shoes out to the drums before any of that movement can tranlate into braking. Also in most/many/all systems the hydralic preesure in the system has to hit a point before the valving in the system will allow pressure to the front discs. The system won't get this pressure point until the rear shoes are out against the drums. Four wheel disc you don't have this problem.

cloud819 03-18-2003 03:47 PM

Disc are cheaper then drums. The reason they are offered as options is that they know people will pay for the cheaper brakes; and they will ma

cloud819 03-18-2003 03:47 PM

Disc are cheaper then drums. The reason they are offered as options is that they know people will pay for the cheaper brakes; and they will make more money. It doesn't make sense that they dropped disc from the S series.

They parts and labor needed to install disc brakes is quite a bit less then discs.

eRic 02sc2 03-18-2003 05:15 PM

[QUOTE][i]Originally posted by Qlara [/i]
[B]Ha!

As we all agree on Disc brake is superior (also looks better) than Drum, but it's not cost-wise for Saturn Corp. For regular commuter driving, drums work OK, so are the standard Firestone tires...... :rolleyes: [/B][/QUOTE]

in other words saturn corp are cheapskates. drum brakes stink, firestone tires stink more. saturn could have commonized the rear discs instead of dropping them and drop the rear drums instead. they could have saved money on the ion by carrying over the s-series in-front-of-the-driver-where-it-belongs ip instead of developing that center mounted eyestrain.

McSaturn 03-18-2003 10:24 PM

On the lighter side of the subject...
If you are anal about keeping you car as clean as possible ( I resemble that remark) you will be partial to drum brakes as the rear rims are always so much easier to clean and stay that way longer.

muzikmann 03-19-2003 05:18 AM

Try these sites:

[url]http://auto.howstuffworks.com/brake.htm[/url]
[url]http://auto.howstuffworks.com/drum-brake.htm[/url]
[url]http://auto.howstuffworks.com/disc-brake.htm[/url]

Jeff

100KSW2 03-19-2003 03:23 PM

This question of disc vs. drum brakes is very important to me. My whole family was almost killed by drum brakes when I was a kid and I don't want them on any car I drive.

I was ready to order a new SW2 in 1996 but cancelled my plans when I found out the rear disc option was gone from the S series wagons. I like the brakes (and ABS and Traction Control) on my wagon a lot. On long trips or in huge traffic jams or in rotten weather I want their maximum stopping power. Like Jeff said, +5 feet can be all the difference (and I have had a number of close calls that were just that close). If drum brakes were "just as good" then every luxury car maker in the world would be using them and not discs on all corners.

Carmakers agonize over saving nickels and dimes, so +$100 IS a LOT. Saturn isn't the only one deleting the rear discs, but Saturn is supposed to be different. I plan to hold onto my car for as long as it is repairable - or until things change on the rear disc issue. I have made this clear to sales and service and the CAC, but so far I don't see any hope of change. The only (new) Saturn available with 4-wheel disc brakes right now is the Lx300 sedan and wagon, and I don't want the steel 1/4 panels, high maintenance engine, lesser gas mileage, and questionable quality of those models.

It will be interesting to see what kind of brakes show up on the rear of the 200HP+ ION Turbo Quadcoupe.

I think in 2003 we should all be talking about why there is no stability control available on any Saturn (even though it has been available on the Focus for a couple years). The rear disc issue should have been settled years ago. The parts were already there, the development money spent, etc. :no:


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