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Discussion Starter #1
Does anyone know why the Prius has front disc brakes, but rear drum brakes?

I assume that disc brakes are more efficient, possibly lighter, and maybe even cheaper. They're a proven technology. My '77 Mercedes has 4 wheel disc brakes.

Duncan
 

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Disk brakes are much more expensive and usually fitted to the front only in inexpensive cars since braking is done by about 80% of the front brakes. You'll probably get close to 100.000 miles out of the drum linings in the rear and maybe 50,000 out of the front on a Prius because of re-generating braking on the car.
 

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DuncanNixon2004 said:
Does anyone know why the Prius has front disc brakes, but rear drum brakes?

I assume that disc brakes are more efficient, possibly lighter, and maybe even cheaper. They're a proven technology. My '77 Mercedes has 4 wheel disc brakes.

Duncan
I was stumped by that as well, especially since the Prius sold in Europe and Japan has 4 wheel disc brakes. And I have had some rear brake lockup/squeal when I've had to panic stop with the prius. It's just a short lockup and skid, then it seems to regain control. Never had that happen in any of my 4 wheel disc brake cars.


Maybe Toyota just thinks we're not good enough for 4 wheel disc brakes.
 

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Jonnycat26 said:
I was stumped by that as well, especially since the Prius sold in Europe and Japan has 4 wheel disc brakes.
Japanese 2004 Prius comes with rear drum brakes.

I have heard that Toyota decided to use the rear brakes because they are less friction than the discs. So, it is for fuel economy.
The European model is a differnt story.

Regards,
[email protected]
 

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nope simple economics. disc brakes are more spendy. european cars have them because its a mandated safety issue. if your brakes are dragging, then disc brakes have a much smaller surface to drag on and would create less friction, not more.
 

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DaveinOlyWA said:
if your brakes are dragging, then disc brakes have a much smaller surface to drag on and would create less friction, not more.
I don't agree this.
I believe the pad is always touching to disc to produce friction, and the drum brake can be free from the friction.
Does anyone have any comments?

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[email protected]
 

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ken1784 said:
I don't agree this.
I believe the pad is always touching to disc to produce friction, and the drum brake can be free from the friction.
Does anyone have any comments?
I think, if that were the case, people would be replacing disc brakes every few hundred miles, or the pads would be a few feet thick.
 

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Discussion Starter #9
Maybe someone who knows about brakes could post a cost/benefit analysis on disc vs drum.

The Fall 2004 Gazette from Toyota CANADA has the Yellow Cab in Vancouver, BC on the cover and a short article covering the two classic and one 2G Pri. At one point the owner, Andrew Grant, reported on PriusChat that he didn't have to replace his front pads until he hit 150,000km. I don't have info concerning rear shoes but conventionally there seems to be a 3 or 4 to 1 ratio on replacement of shoes so extrapolation puts the Prius shoes needing checking at 450,000km and replacing at 600,000km! :lol:

So while it could be an effort to maintain MSRP below a certain level I can't believe that's the whole reason. Maybe VSC is more effective with rear drum? Maybe regen braking is easier to engineer/implement? What's the percentage of regen coming from the front, if any, versus the rear? How much noxious stuff is shed when braking using pads versus shoes? Could just be me but I think there's more to it than economics. After all, in certain circles, this vehicle is touted as the most technologically advanced vehicle on the road.
 

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cmon Ken you dont really believe that do you??

in a perfect world any kind of brake system should not be dragging on the wheel. if that were the case, it would be the easiest mpg fix in the history of man.

well, it aint. disc brakes work better but cost more. sure upscale cars have 4 wheel disc brakes but they dont give a rats ass how much they spend because it all gets passed on to the consumer.

that is why the Prius doesnt have them. it costs more. drum brakes are a lot cheaper. and considering that the rears only provide 20% of stopping power in your vehicle, drums are way more than you need anyway.

if you dont think drums are cheaper than you have never done a brake job on your car then.
 

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Tis not just the econmics. Drum brakes are condiderably less expensive but combine this with "are four wheel disks necessary". They are used for lightness in weight and stopping power for high performance cars, and quite a bit of this is for advertising purposes. The Prius is an economy car and made to sell at a targeted price. They didn't add anything that wasn't necessary
 

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Prius is an economy car... haha

whose economy is that? - they cost about as much as a bmw here, and a little less than a mazda RX8

$48129.90 drive away (with i-tech pack (everything))

they are classed as semi prestige
 

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i-tech pack is all the extras you can get. Over here there is the base model which is $37,990 then with the itech pack, you get:

the curtain airbags,
sat nav,
VSC
Premium JBL audio system with 6 disc CD changer, cassette and AM/FM radio through 9 speakers
smart entry
blue tooth
the extra buttons on the steering wheel
etc.

All that is an extra $8000

remember 48,000 is equivalent to USD $35,000
 

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I don't know what they put in the beer in Australia. The Prius 2004 was made to sell for $19,900 american dollars stripped, by Toyota. Same price as 2000,2001,2002,2003 models. Fully equipped including nav pkg about $26,000 and change. Mine which is equipped with pkg #6 cost me $22,982. This price included $1084. in sales tax and $785.00 for extended warranty. They are paying considerably more than this on west coast account of local dealers and to skip normal "wait" Must be to be able to drive "something different" for a short period or maybe the expected Hov lane and discounted parking fees. You have only to look at car to see what "niche" it belongs in. Whats trhe price of gas in Australia?
 

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It's adjusted for the economy. We earn more per week than you guys. Minimum wage is around $9 per hour and national average is $45k p.a.

So luxury items cost more, but our cost of living is less than yours. - food and housing etc .(I know this from frequent trips to the usa)

Fuel is about $1 a litre right now. 6 months ago it was 70 cents per litre.

there are 3.785 litres per gallon, so we pay $3.78 per gallon. if you think that is high, the poor brits pay twice that much
 

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DaveinOlyWA said:
if you dont think drums are cheaper than you have never done a brake job on your car then.
I'm not saying discs are cheaper than drums.
I'm saying drums have less friction than discs.

I did some experiment with a neighbor. He has another Toyota with rear discs.
We jack up both cars. Turn the rear wheel by hand, then let the wheel free spin by it's inertia.
Found that wheel with drum rotated more than with disc.

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[email protected]
 

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I don't have info concerning rear shoes but conventionally there seems to be a 3 or 4 to 1 ratio on replacement of shoes so extrapolation puts the Prius shoes needing checking at 450,000km and replacing at 600,000km!
You can't extrapolate this way... see below why.
Maybe regen braking is easier to engineer/implement? What's the percentage of regen coming from the front, if any, versus the rear?
Regen braking has nothing to do with rear brakes, since it doesn't involve brakes at all but only electric motors, which are linked to the front wheels. So the answer is : 100% front, 0% rear. And that's why rear brake shoes should last approximately the same as in other cars.
 

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And what you are looking at on the "MFD" really is not what entirely is happening. It does not tell you at all times even if the "ICE" is running.
 
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