conversion to 4 wheels disc brakes

Wrong. The cutoff limit is 7mph. HTML, perhaps your thinking in kph?

ABS doesn't function unless the wheels are slipping while your braking. Its an ANTI-LOCK braking system.

I've verified this with my scangauge. It shows amps going INTO the battery when braking at speeds between 7-9mph.

 

Thank you...After all these years I wasn't aware of that. So what does the ABS do when one wheel happens to slide (even the slightest amount)?-release pressure, then re-apply pressure in an attempt to regain brake control. During this cycle, is it not conceivable that forward velocity will increase? Ok, now let's say that velocity does increase, when the brakes are re-applied, the car will be moving faster on the same slippery conditions as before, causing more wheel slide, more ABS, more velocity, and eventual lose of control. So as previously stated, the rear brakes primary function is to keep the car in a straight line. Does it seem feasible that 'better' rear brakes will gain better overall control? Unfortunately, I live and drive this scenario on a regular basis during the winter months, I think that lends me some small amount of insight into what is happening.

 

It is and it can and I have to say it is the most unpleasant feeling when it happens. Instinct makes you stamp that pedal so hard your leg will hurt but to no avail as the brakes do not work. It will only happen on really slippery surfaces but if it does happen then it would still be happening if you had no ABS installed so you crash knowing there was nothing you did wrong instead of wondering that if you had behaved differently could it have been avoided.

What it does give you is more control of the steering than you normally have if there is no ABS.

You should play with your ABS to see how it behaves on a loose gravel surface. I would bet all that I have that there is no way that you can stop, without the ABS cutting in, in a shorter distance than the ABS does it.

 

Disc brakes perform better than drums, it's true, but if your wheels are locking, discs won't do anything different than drums. A locked wheel indicates that there is too much braking force.

There are heavier and faster cars than the Prius sold which have drum brakes. Toyota appear to have fitted discs all round on the UK model for aesthetic and competitive reasons (i.e. competitors have all-round discs), not for braking performance.

Ford's Focus has rear drums as standard in the UK. Discs are fitted on the 2.0 litre petrol and 1.8 and 2.0 litre diesels, and on estate cars (station wagons) and the ST. The 1.6 petrol hatchback is capable of 118mph and a Gross Vehicle Weight of 1825kg (i.e. fully laden with passengers and cargo). The Prius equivalent is 106mph and 1725kg if I recall correctly. I don't recall seeing complaints about the Focus brakes. (The Focus is the top-selling car in the UK.)

 

What happens when the ABS detects one or more wheels sliding it releases some of the pressure to that brake. Velocity will not increase but the rate of slowing down will be reduced.
To get maximum braking, press the brake pedal as hard as you can and when you feel a chattering of the brake(s) arch your foot slightly. By arching, you will slightly reduce the pressure on the pedal and the ABS will stop chattering and give maximum braking.
Do not lift your foot off the brake pedal or try to reduce how hard you are pressing because if you do braking will be decreased or even cease altogether, thus the braking distance will increase.

 

The ABS will release and reapply the pressure very quickly, 5-10 times per second. You really cannot fell the brake is releasing or re-applying. You will hear the pulsing noise or feel the pulsing sensation on the brake pedal, oh no, not the pulsing sensation on the brake pedal of the Prius because the ECU is actually doing the braking, the brake pedal is only pushing a fake brake cylinder.

As you said, if you did feel the car is accelerating while braking and then decelerating with more than a second interval, then this is positively the regen braking is cutting out and the mechanical braking cutting in.

 

no conversion can occur without substantial cost of $1500. at the least with all parts, and chips for ABS system.

secondly, why convert, listen to previous post about new ceramic pads like hawk or other brands and good set of rubber. On my red 2006 Prius, I bought a nice set of rubber such as Michelins 205 55R 15. And they fit even 205 60R 15 XGT HR speed tires. Living in Tucson/Phoenix Arizona with 110 to 120 F degrees of extreme heat in the summer time, you get to see exploding tires on the road and death due to roll over and tire failure quite a bit in the deserts for 4 to 6 months.

Stopping distance is simple. Do the following. Get new tires, wider and better compound is why Formula one race cars uses them. Additionally, get cross drill rotors when available to replacement, and third get ceramic brakes pads in fronts. At over 3500 lbs of weight with 4 adult size, that is a lot of weight to stop. Most prius owners don't know that it weights as much as a regular honda accord or toyota camry.

With 2 years of ownership, and over 40,000 miles. Trust me, don't go cheap on tires, it is on worth it. think about all the eating out, beer money, and all other unnecessary expenses could have bought you as far as a set of good tires.

Don't risk your life on set of junky factory tires and save couple mpg, my mileage sustain at 42 mpg when switch, at best I was getting 44 to 46 mpg with smaller tires for the first 6 months until tires were switch out. My Expedition gets 12-14 mpg, so a slight lost of mpg on prius is worth all the peace of mind.

 

I found this .pdf file with the braking distances listed for various models.

It's hosted at an awkwardly named site http://www.4n6xprt.com/Braking_Effectiveness_at_Higher_Speeds.pdf

If I understand correctly the numbers were taken from Motor Trend and Road Track magazines.

The '06 Prius is listed as having a braking distance of 135 and 256 ft when braking from 60 and 80 mph respectively.

Hmm one reason to start thinking about throwing the stock tires away even if at 37,000 miles they easily have 10,000 miles left in them.

 

Well the prius is a family car that weighs as much as an Abrams Tank... Stopping such a mass requires more force or more distance. Not much can be done about physics.