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Car Forum / Australian Car Forums / General Car Topics (Australian group) / May 2006Drum brakes still used?
Wonder why manufacturers still use drum-brakes on the rear of cars. Usually it only applies to smaller/lighter or lower power cars like the 4 cyl Camry. Is it because handbrakes work better? Tho that doesn't follow the weight/engine size rule. You'd think because of the extra parts, they'd be more expensive to fit. Jason > Wonder why manufacturers still use drum-brakes on the rear of cars. > Usually [quoted text clipped - 4 lines] > > You'd think because of the extra parts, they'd be more expensive to fit. Bean counters really I thought the new Nissan Tiida (f.cking awful name) comes with rear disc brakes but nope drums rear same with the Ford Fiesta irc the Hyundai Gets has discs all around. But yeah bean counters me thinks.  SignatureRegards Dan Yes I drive a V8 and I have been spoilt by HP and Torque. Don't like it? Then f.ck off and have a sook! :-)> >> Wonder why manufacturers still use drum-brakes on the rear of cars. >> Usually [quoted text clipped - 10 lines] > > But yeah bean counters me thinks. Surely disks would be cheaper? I can't imagine there being more than $50 in it. Fraser >>> Wonder why manufacturers still use drum-brakes on the rear of cars. >>> Usually [quoted text clipped - 13 lines] > Surely disks would be cheaper? I can't imagine there being more than $50 > in it. Yeah but $50 x 1 million cars is the difference between success and failure. >> Wonder why manufacturers still use drum-brakes on the rear of cars. >> Usually [quoted text clipped - 10 lines] > > But yeah bean counters me thinks. Nothing wrong with a good set of well adjusted drums on the rear , going from mechanical to hydrolics is much more important . >> Wonder why manufacturers still use drum-brakes on the rear of cars. >> Usually [quoted text clipped - 10 lines] > > But yeah bean counters me thinks. Nope - defo the Handbrake matter is the go. And I mean hand-brake. That's what they were before multi-circuit bake systems.... Not they're called park-brakes, FFS. Few and far between are truly successful rear disk handbrakes. Main design problem is the *mechanical* forces needed to get disk brakes to work. There are some cheats involving mini drums inside disk hubs, or even entirely separate systems bolted up with the disks, but they're invariably useless as emergency brakes - sorta one use only type things. And don't get me started on the warning light caper. Anyone ignoring the dull glow from one of those on a bright day can totally stuff the mini-linings on a drum-in-disk park brake in particular Incidentally, to get a decent 'handbrake' out of rear drums they need to be a leading-trailing design as well. Double leading's simply don't cut it when a handbrake is required to hold a car on an uphill grade. And then there's the transmission mounted drum brakes used on some 4WD's. Terrific idea - however they really need a locked diff to be a proper brake:-) And then there's the rear-main oil seal gag... This gag is entirely duplicated in live axle rear drums for some reason best explained by certain engineers with a truly sick sense of humour. Some interesting trivia. We have two turbo Nissans. Both have quite reasonable brakes and feature almost identical drive trains with only slightly different engines. But the 'sedan' one has an entirely different park-brake setup to the hot hatch one. The one meant to be a rally car (ok, a shopping-trolley convert) gets an absolutely magic mechanical rear disk brake system that can be used as a hand-brake - it's evidently designed to be used as an adjunct to interesting and creative driving;-) OTH, the Sedan version doesn't get quite the same level of mechanical advantage, even featuring a system with more bends (it's neater) in the actual cable, and it's not so capable of being mis-used. SignatureToby. quidquid latine dictum sit, altum viditur > There are some cheats involving mini drums inside disk hubs, or even > entirely separate systems bolted up with the disks, but they're [quoted text clipped - 8 lines] > Double leading's simply don't cut it when a handbrake is required to > hold a car on an uphill grade. and yet I have not found a hill that steep that the hand brake (drum in disc) on my 100 series doesn't hold as long as the tyres have grip and that works both ways, forward or back what I do need though is a manual that shows my how to adjust the bloody things, handbrake lever is getting too high Kev > and yet I have not found a hill that steep that the hand brake (drum in > disc) on my 100 series doesn't hold as long as the tyres have grip > > and that works both ways, forward or back I've found that "drum in disc" type handbrake mechanisms to be pretty average compared to regular drum brakes, or even handbrake operated brake callipers. The lining surface area is usually very small, and often not enough to hold the average vehicle when they are adjusted correctly, let alone something like a Landcruiser. -- Regards, Noddy. >>and yet I have not found a hill that steep that the hand brake (drum in >>disc) on my 100 series doesn't hold as long as the tyres have grip [quoted text clipped - 6 lines] > enough to hold the average vehicle when they are adjusted correctly, let > alone something like a Landcruiser. like I said I still haven't found anywhere that the handbrake won't hold maybe your experience with them is limited to crap variants and as for the brake on the drive shaft this system uses the diff for a mutiplication of the force it's very common on the 1.5T-4T light trucks(those without spring park brakes) and works extremely well hulding a total weight of 7 tonnes on a steep hill is not too shabby Kev > Wonder why manufacturers still use drum-brakes on the rear of cars. Usually > it only applies to smaller/lighter or lower power cars like the 4 cyl Camry. [quoted text clipped - 4 lines] > > Jason I suspect its a marketing exercise, if the base model has rear drums then rear discs are a selling feature for higher spec models. I doubt there is much price difference in favour of either type of brake and also very little difference in braking performance in normal street driving. Daryl >> Wonder why manufacturers still use drum-brakes on the rear of cars. Usually >> it only applies to smaller/lighter or lower power cars like the 4 cyl Camry. [quoted text clipped - 12 lines] > > Daryl I have to disagree there - that little piece of bastardry known as 'self-servo' is completely written out of the list for disk brakes. So, win some lose some. Disks and pads actually wear out even if you don't use 'em. Drums don't have that problem. SignatureToby. quidquid latine dictum sit, altum viditur > Disks and pads actually wear out even if you don't use 'em. > Drums don't have that problem. You might like to explain this ? or have the laws of physics changed ? >> Disks and pads actually wear out even if you don't use 'em. >> Drums don't have that problem. > > You might like to explain this ? > or have the laws of physics changed ? No changes. Disk pads are always in contact with the disks. The name of the game is to keep foreign material off the friction surfaces because the whole shebang is exposed to the elements in an extremely hostile environment. There are various methods for doing the business, but the most common is to use the elasticity of the seals themselves to back off the pads just enough to not cause noticeable binding. That's a function of the material clearances and actual surface area of the seals themselves. You'll also have noticed that brake pads have knife-edge leading and trailing edges. That's part of the deal to have them work as cleaners/squeeges etc. So champhering or radiusing the edges the pads is a *big* no-no unless of course you're a brake shop with a captive or over-loyal customer base:-) this begins to get interesting with older cars, where the seals still seal alright, but don't actually go on with their secondary function correctly any more. Like, we *think* disk brake seals last for a very long time. But in essence, they don't - just like the pins. You'll also heard stories about adjusting wheel bearings to be a tad loose to knock the pads away from the disks. But I suspect those stories are just that. Crazy stuff, anyway. It's possible - even advisable - to adjust drum brakes to have no contact between the friction surfaces when the brakes are 'off'. It ain't normally possible to do that with disks on a road car, and it sure as hell ain't wise to try for it either. So, there's the added bonus of economy gains from wee cars that use at least two drum brakes. But, the reel deel is that disks wear both their pads and disks just turning as you motor blithely down the road. Despite all that, I prefer disks largely due to the unpredictable results with drum brakes that aren't absolutely and completely correctly adjusted. (which blessed state lasts IMHO until the first time they are used after that super adjustment) And then there's a discussion on run-out, hot-spots alloys and symptoms looking for all the world like disk warping etc etc....for another day. I reckon electric regerative braking is THE way to get rid of most braking problems. And introduce a shitload more, probably. SignatureToby. quidquid latine dictum sit, altum viditur I got bored about 6 lines in , on usnett try to keep it short , now try again.. I doubt your right but one cant be sure... > I got bored about 6 lines in , on usnett try to keep it short , now > try again.. I doubt your right but one cant be sure... sh.t - foiled again... I set the reading age for that piece at 8. And now you want me to run it again at 5? OK, I'll send it to the subs at the Courier Mail for conversion. Be about a week or so, I guess. SignatureToby. quidquid latine dictum sit, altum viditur > sh.t - foiled again... > I set the reading age for that piece at 8. A tad too high methinks :) > And now you want me to run it again at 5? You *might* get lucky, but I wouldn't hold your breath. -- Regards, Noddy. >> I got bored about 6 lines in , on usnett try to keep it short , now >> try again.. I doubt your right but one cant be sure... [quoted text clipped - 5 lines] > > Be about a week or so, I guess. Ok so you were trying to bullshite us again and baffle with it... >> I got bored about 6 lines in , on usnett try to keep it short , now >> try again.. I doubt your right but one cant be sure... [quoted text clipped - 5 lines] > > Be about a week or so, I guess. Aim it at houseplant level Toby. Fraser > But, the reel deel is that disks wear both their pads and > disks just turning as you motor blithely down the road. That wear isn't excessive. I use engine braking mostly. My late '96 VW Transporter (4 wheel discs) is still on its original pads and discs, with plenty of pad material left, at 225,000 km. BTW, my kids tell me they fail driving tests these days if they use engine braking. I don't know what the rationale is for this bit of stupidity, but I hope it's not supposed to be safety. In my experience, engine braking is quite safe. In over 35 years and well over a million km of driving I've not been involved in any accident. It teaches you to better anticipate traffic flow. John > BTW, my kids tell me they fail driving tests these days if they > use engine braking. I don't know what the rationale is for > this bit of stupidity, but I hope it's not supposed to be > safety. Engine braking is useful to help avoid brake fade on long downhill sections so I wonder where they are coming from. I can only think it could be something to do with the puller EPA to lessen vehicle noise and if so it's too stupid. Al SignatureI don't take sides. It's more fun to insult everyone. http://kwakakid.cjb.net/insult.html > Wonder why manufacturers still use drum-brakes on the rear of cars. > Usually it only applies to smaller/lighter or lower power cars like the 4 [quoted text clipped - 4 lines] > > Jason Problem with rear discs is the handbrake - just a bit more difficult to put a handbrake on discs. Although the first family car with discs (Citroen DS) had rear drums - with the handbrake operating on the front discs. Mostly it will come down to costs, and since the design and tooling for the drum brakes (including handbrake) was probably written off decades ago, drums are still cheaper. Some models may use disc/drum to differentiate models or level of equipment or even be saving it for an upgrade in the future. The amount of braking required on the rear of most modern cars is so little (due to forward weight bias and weight transfer under braking) that there is little if any practical advantage in having discs there, particularly since they are usually self adjusting as part of the handbrake mechanism. JD > Wonder why manufacturers still use drum-brakes on the rear of cars. Usually > it only applies to smaller/lighter or lower power cars like the 4 cyl Camry. > Is it because handbrakes work better? Tho that doesn't follow the > weight/engine size rule. > > You'd think because of the extra parts, they'd be more expensive to fit. Some cars use both, disk rear with drum handbrake. Wierdest braked truck I ever saw was a small Inter with disk rear and drum front. Al SignatureI don't take sides. It's more fun to insult everyone. http://kwakakid.cjb.net/insult.html > Wonder why manufacturers still use drum-brakes on the rear of cars. Usually > it only applies to smaller/lighter or lower power cars like the 4 cyl Camry. > Is it because handbrakes work better? Tho that doesn't follow the > weight/engine size rule. I heard somewhere that on pickup trucks, like mine, drums are better due to incorporating a load sensing mechanism. Discs are of course the only thing to use on the front, and 4x4 Hilux has fairly large ones there. Signature-------------------------------------------- 4x4 Hilux Auto Service Centre, BP 106 Timbuktu, Mali (West Africa) Tel: 292 91 52 Specialising in turbo diesel and R290 aircon "Forever young, forever young, I wanna be forever young, do you really wanna live forever forever forever ..." "Feel the love generation, Yeah, yeah yeah" -------------------------------------------- >> Wonder why manufacturers still use drum-brakes on the rear of cars. Usually >> it only applies to smaller/lighter or lower power cars like the 4 cyl Camry. [quoted text clipped - 5 lines] > only thing to use on the front, and 4x4 Hilux has fairly large ones > there. That 'somewhere' you speak of was undoubtedly outa the arse of a salesjerk:-) SignatureToby. quidquid latine dictum sit, altum viditur >>>Wonder why manufacturers still use drum-brakes on the rear of cars. Usually >>>it only applies to smaller/lighter or lower power cars like the 4 cyl Camry. [quoted text clipped - 8 lines] > That 'somewhere' you speak of was undoubtedly outa the arse of a > salesjerk:-) Don't remember prezactly where however rear drums, front disc was the go. Until just now, realized have leaking seal again on 'lux on front axle :-( really gunna have to get arse in gear and fix it, before it contaminates the pads _AGAIN_, pic to follow. Oil filters on after market turbo 'luxen and any sort of mucking with axle grease requires a full length body suit, hmmm, I've got a rather unused wet suit somewhere ... Signature-------------------------------------------- 4x4 Hilux Auto Service Centre, BP 106 Timbuktu, Mali (West Africa) Tel: 292 91 52 Specialising in turbo diesel and R290 aircon "Forever young, forever young, I wanna be forever young, do you really wanna live forever forever forever ..." "Feel the love generation, Yeah, yeah yeah" -------------------------------------------- maintance on new little cars with discs we normal have to replace discs and pads at around 50k serice where as drums last for ever and still provide effective braking that is required > Wonder why manufacturers still use drum-brakes on the rear of cars. > Usually [quoted text clipped - 6 lines] > > Jason |
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