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conversion to 4 wheels disc brakes

Discussion in 'Gen II Prius Technical Discussion' started by bsj44, Dec 22, 2007.

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  1. gazz

    gazz Member

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    Remember the drums are on the back, they add little to the braking, I think we have them in the UK because its just expected nothing to do with performance.
  2. fruzzetti

    fruzzetti Customization-Obsessed

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    Very true. How many circuits have to fail simultaneously for this to happen? One?

    ~ dan ~
  3. apriusfan

    apriusfan New Member

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    Not to sound flip, but the only circuit that needs to fail is the one that controls the corner(s) that lock up.
  4. fruzzetti

    fruzzetti Customization-Obsessed

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    That's what I'm saying; it really is conceivable.
  5. apriusfan

    apriusfan New Member

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    Well, then maybe a clarification is in order: when ABS is properly operating, it stops brake (disc or drum) lock-up. My original statement was meant to clear up any mis-understanding about the function of ABS.

    Having said that, my personal experience with over 200,000 miles on cars that were equipped with ABS, is that I have never experienced a failure of the ABS where the brakes locked up on application. There were a few times where a sensor failed, but an error message was generated and the failed sensor was replaced.
  6. fruzzetti

    fruzzetti Customization-Obsessed

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    That's the same as my experience. In ABS-equipped cars, I have only ever locked up the wheels in slippery mud.

    Or by stomping on the emergency break while driving. Don't ask.

    ~ dan ~
  7. apriusfan

    apriusfan New Member

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    That is a new one. Since the e-brake is not on the ABS circuit, that is the only way to lock up a car's brakes. And you are really not locking up the main brakes, but the e-brake. Out of curiosity, I wonder how a car with stability control would respond to the e-brake being engaged real hard.... I don't think I will try that out, though.
  8. fruzzetti

    fruzzetti Customization-Obsessed

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    From the voice of experience, please don't. This was before I got the BT stiffening plate and it was before I got the new tires, which were the reason I joined PriusChat. I'll tell you what happened:

    I was going about 60 mph down the Dublin grade with my wife in the car. A woman was tailgating me and I decided to give her a scare with a brake-check.

    When it was clear all around me (except the tailgater), I slid the car into neutral, and I hit the E-brake so the car would slow down a bit with the idea that I'd just unclick it and put the car back in drive only moments later (the idea was to startle the woman and hopefully make her think twice).

    >>> Don't ever do what I just described, ever. It was stupid, and it was the last childish thing I'll ever let myself do especially considering my wife was with me and we've been working on a baby <<<

    I was playing music in the car, and a bit loud, and it was the first time I'd tried this risky and delicate maneuver with loud music. Turns out I need to hear and feel more acutely if I'm going to not scare some sense into myself and frighten the heck out of my wife.

    >>> To this day I curse myself for such a stupid decision; imagine the possible outcomes. <<<

    The rear tires locked up and the car started sliding. It whipped the rear of the vehicle around side-to side like a pendulum, and as I was being whipped around it was markedly difficult to unlatch the E-brake. The whole time I had both hands carefully on the wheel adjusting it as I could and after about five whips side to side, I managed to unlatch it and straighten the car out. I was a full two lanes to the left of where I started (in the slow lane).

    I will say I am now certain if I lose my regular brakes for any reason I will do whatever is in my power to slow the car down, OTHER than using the E-brake.

    ~ dan ~
  9. apriusfan

    apriusfan New Member

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    I will agree - you were extremely lucky. The e-brake spin maneuver is done with hand-operated e-brakes (and with VSC disengaged).



    One thing to consider as an stopping strategy if the brakes fail is to put the shifter in B. It is not as good as having brakes, but is also not prone to spinning.
  10. kocho

    kocho Member

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    I have converted my 4 cylinder '00 Camry with rear drums to rear disk brakes myself. Used brakes from a V6 Camry. It is a straight swap with no issues whatsoever.

    Link here with downloadable PDF:

    http://www.geocities.com/kocho_chestimenski/camry.html

    Since I did this, a couple of other folks did it successfully as well so it is not impossible or too hard to do if the fit is easy.

    I am not sure if the braking distances changed in my case - they do not feel worse at least but I do not know if they are any better.

    What changed is that the shudder present at high-speed/down-hill braking is gone. Most rear drum cars I've ridden in have this since new (not due to wear), including my '02 Prius under heavy braking, and three other Camry's I've used. This is not how the Prius is supposed to be driven so most folks would never feel it. But it is there. Putting disk brakes in the back would cure this as it is due to the drums (provided front disks are straight).

    One more point: the ABS sensor works off the wheel hub which is *not part* of the drum or disk, so its reading is unaffected by the swap. In the case of the Camry I also prepared to change the front/back valve/distributor, but as it turned out the brakes balanced OK without the need to change that. What helps in my Camry is that it already is factory equipped with the V6 equivalent for the front brakes so this only makes it equivalent to the V6 brake system at all 4 corners.

    Not sure how VSC or ABS operation is affected, if at all, in the Prius though and only because it works so well in the Camry it does not mean it would in the Prius.

    Lastly, I would not be surprised if the Celica brakes work on it, but a set of UK-prius rear disk brakes would be a much safer bet. For the Camry the conversion was a snap but I had to use also the hand-brake cables, calipers and hand-brake shoes/springs etc. - not just the drums. They all mounted on the existing hub with the new rear backing plate, though one can swap the whope rear brake assembly with the plate and hub if one so desires and that would be a little easier though more expensive to buy all these parts that are perfectly fine on the receiving car...

    I would probably give it a try if I had a cheap source of Euro-spec rear disk parts but I don't in the US. The Camry conversion costed me only about $300 or so in parts so it was well worth it in my opinion as it cured the brake shudder completely, plus the car looks nicer and replacing the rear pads is now much simpler. Had them on for the last about 80K miles and no problems. Only drawback - the hand-brake on drum-based brakes is stronger but if the hand-brake on the V6 is good enough for it, than it should be good enough for me too :)
  11. JaviNOS

    JaviNOS Mod Freak

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    next time if its daylight and you want to scare someone on your tail... just turn ON your lights... some people see red and get scared and brake... That way you know you wont risk your car, your life or anyone inside your car...

    Another way is to lightly press the brake pedal just enough for the lights to go ON and then slow yourself down... your tail will change lanes if possible.



    Talking about the Topic:
    I would like to change to 4 disc brakes but I dont know if it will be too pricey so what I did is I installed slotted and drilled rotors along with sport pads to get a better cooled braking system and proper grip... however... on a prius... this is not really necessary unless you plan on using yours inside some circuit solo1 course or something like that... I dont really use much of the brakes.. I do like how it looks though!
  12. JohnP65

    JohnP65 New Member

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    The best brake upgrade to any vehicle is going to Braided Stainless Steel brake lines . You don't have the expansion of the rubber lines and loss of pressure . The S.S. lines will give a firmer pedal and shorter stopping .
  13. patsparks

    patsparks An Aussie perspective

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    But will not improve brake power, only feel.
  14. apriusfan

    apriusfan New Member

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    Some of the new brake lines (even OEM ones) use a braided kevlar construction. The braided kevlar lines are every bit as good as the braided stainless ones. Before dropping the cash on a set of braided stainless lines, you might check to see whether the OEM lines are of the braided kevlar type.
  15. apriusfan

    apriusfan New Member

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    Well, not necessarily. If the OEM lines have 'softened', meaning the woven fiberglass reinforcement has loosened, then some of the pressure from the master cylinder will be absorbed as the brake lines expand to the loosened size on application of the brakes. Braided stainless (and braided kevlar) lines do not expand and therefore, all of the master cylinder's pressure is transferred to the pads in the caliper.
  16. The Tramp

    The Tramp Italian Prius Expert

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    The EU Prius is tested 100-0 in 36 meters.

    That is 62-0 in 118 feet.

    But we also have fatter tyres!
  17. apriusfan

    apriusfan New Member

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    What is the width of the tires on the EU spec Prius?
  18. ken1784

    ken1784 SuperMID designer

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    They are same as the Turing model in the US, 195/55R16.

    Ken@Japan
  19. Flying White Dutchman

    Flying White Dutchman Senior Member

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    i dont think we think we need them
    it wil bring down the braking distance even if its just a bit IT will and therefore needed..

    i think that the us model needs to be cheaper because its going to be shipped to the us...and maybe the fuel cons. is better.



    i dont think thats nessesary
    the sensor is not inside the brake its just lookes @ the wheel and if its blocking or not.



    do the us models realy have 15inch wheels??




    I also think that the abs sensor is in the wheel and not the brake itselfs so the abs system will just detect a faster braking of the rear wheels when you have installerd disc brakes and just aks accordinggly.



    i am wundering if it is ok to put smaller tyres on it.. and when you brake and need a longer distance and therefor hit someone your faulty even when the person you hit made a mistake?
  20. Boo

    Boo Boola Boola Member

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    Yes. In the US the standard Prius has 15 inch wheels, and the Touring Edition Prius has 16 inch wheels.

    Where are you from, and what size wheels came on your Prius?
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