GenII Brake Upgrade w/o breaking the bank?

You been to the rodeo, eh? As the clown or or the cowboy? There's quite a difference between sprung and unsprung weight...

 

and extra rotational weight makes an even larger difference from what i understand.
polite is always good. lets all try to be polite...

 

Awesome, glad it's manageable and brake bias can be adjusted. I was looking at summit racing and see that they offer a remote brake bias adjuster that can be changed from inside the car... but I'm sure your aware of such things... and since this isn't the first brake swap Justdidit has done, I'm sure he's got it under control.

 

We're putting this same one in our track car, as we may be running some races in the wet. Being able to adjust the front/rear bias on the fly will keep the car from getting tail-happy under hard braking. Not really an issue for cars with traction control, but we don't even have ABS in our sh*tbox

 

what kind of track car? LeMons? some of my friends and coworkers are big into the lemons racing. seems like fun, but alot of work.

 

Yep! We're building a Dodge Neon ACR into the Popemobile. The work hasn't been too grueling yet, but the car has been full of surprises. There's usually several reasons why you find such a car for under $1k on Craigslist... crumpled fenders, scored rotors, oil leaks, bad radiator, several torn boots, etc., etc., etc.

 

The biggest downside I see to going with larger discs/calipers is the transition from regen braking to normal brakes (friction).

Toyota must have gone to great lengths to get a balance when the transition takes place. If you improve the friction braking, when slowing down with regen brakes you are going to get a sudden increase in braking at the transition to friction brakes, in slippery condition this could result in wheel lockup.

I do not see a problem with going the UK route with the rears, but going to larger discs good as they may look could be problematic.

 

I really hope that this thread doesn't end here. I'm looking upgrade a gen 2 prius purely for safety. The only thing I care about is not hitting some dumb kid that jumps out of nowhere. Also, I will be adding LPG and possibly plug in upgrades at some point so that extra weight needs to be considered (e.g. wider tyres for extra grip, stiffer suspension, bigger brakes, rear sway bar)



Once again, I see these as safety upgrades, not performance. A performance car driven hard will make use of its performance features all the time. With safety upgrades, you may only need to rely on them a few times a year. This is an important distinction as high performance tyres and brakes are hopeless if not warm enough.

So going back to the beginning, is there a brakes upgrade that doesn't require custom made brackets? I don't know anyone who can do that for me.

 

The biggest upgrade that I believe to be worth while on the Prius is wider tyres to improve grip and stability.

Going to disc brakes on the rear as UK spec "may" give some extra braking power when carrying weight, but under normal use "not emergency stops" the rear brakes are only used below 7mph no matter what load you are carrying.

If you live in a mountainous region where the HV battery is often fully charged and the car defaults to the normal brakes the rear disc set up would have better cooling and be less prone to fade.

If you put in your avatar what country and region you are in this helps us to give you better advice.

 

I'm in the UK so all standard models here have larger unvented discs on the rear compared to the front. I've read loads of stories about the rear disc/pads wearing out much sooner than the fronts. This is because regen kicks in first, then the rear brakes engage and the fronts are only used to completely stop the car or under heavy braking.

I think wider tyres is the first thing I'm going to get but I can't find any specific advise (just the usual "make sure there's no rubbing"). Can you fit wider rubber on the stock 16" rims? I'm planning on keeping the stock wheels with standard size winter tyres and get another set of rims for wider summer tyres. I can't do these things until I find out what brakes I'm going to get as the rims might not fit.

 

Hello Semo, welcome to PC. I am afraid you are misinformed about the rear brakes on the Prius. They typically last 200,000 miles +.

The rear brakes do not come into use during regen "normal braking" only the front wheels slow the car in this mode. The rear brakes are used with the front brakes below 7mph and in an emergency stop or if the ABS system detects a wheel slip.

I have just changed the rear discs on my car at 85,000 miles because of severe rust the pads were less than 2mm worn from new and were refitted after machining them flat, I estimate they will be good till at least 250,000 miles.

There is a taxi driver on here "Grumpy Cabby" who runs a Prius as a taxi and even with that use all low speed town work he gets 60,000 + miles on the pads.

I run oversize tyres (205/55/16) with a great improvement in grip and stability, you can run 215/50/16 or 225/45/16 without problems but you will take a hit in MPG if you go to the larger sizes. If you go with 205/55/16 provided you go with (B) rated tyres for economy "and I only know of two" you will not loose MPG. There are no clearance problems. There are no (A) rated tyres that fit your car.

Hope this helps.
John (Britprius)

 

Hi Britprius,

Are you saying that 225/45/16 tyres will fit on stock 16" Prius rims? That would be great. I don't mind the MPG reduction as grip and stopping power are my main priorities.

If the rear brakes do so little, why are they larger than the front ones. I know that the rears are solid and not vented but still a bit baffling.

I hope to be able to get away with upgrading the fronts only. Something like a larger disc and 4 pot calipers. Would this be possible with the stock 16" wheels?

 

The rear discs are larger in diameter than the fronts because they have drum brakes in the center for the parking brake. Yes 225/45/16 will fit ok.

 

Nice to know that 225s will fit but I wonder if this stretching will affect the contact patch and actual grip.

Sorry for hijacking your thread Justdidit but I think that my points are also relevant as you need pay attention to rim sizes when upgrading brakes.

It will be interesting to find out if there is a straight forward brake upgrade for cars with stock 16" rims.

 

The biggest problem your going to face if you "upgrade" the brakes is in the transition from regen braking to normal braking.

If the brakes you fit are more powerful for a given pedal pressure you could end up with wheels locking when for arguments sake the system sees a front wheel slowing more than it should under regen braking or you slow down passed 7mph the system will then change to disc brakes and lock the wheels even more.

Remember also the car is fitted with vehicle stability control "that cannot be turned off" this takes input from a yaw sensor, the steering angle, and the speed of each wheel. If it detects that the car is beginning to spin it will apply braking "hydraulics" to the wheels that it needs to to bring the car under control. This is without you touching the brake pedal.

If the brakes are more powerful "greater stopping power" than the system it is calibrated for it could actually get you into more trouble.

 

So this has never been done by anyone yet? Does it mean that it can't be done on a reasonable budget?

 

You can "up grade" the disc brakes to larger discs/calipers but whether it will balance with the regen brakes is another question. Not using regen will destroy the economy and performance of the Prius, no power in the battery little power to the wheels as the engine will not only have to power the car but will be directly needed to charge the battery since the battery will not have been charged by braking with regen.

No one as yet as far as I know has cracked the ECU program that controls the brakes and VSC. There is no way to turn off the VSC unless you enter service mode and this resets every time you turn the car off, it also turns off traction control and runs the risk of destroying the transmission.

The question I would be asking is why do this at all when under normal circumstances are not used to anywhere near there full potential.

Do a run and then check the temperature of the brakes my bet is they will be just warm on the front and cold on the rears. Because they are so little used rust particularly on the rears is a problem needing most users to run the car in neutral to force use of the discs to clean them up.

 

so, rather than mess w/ toyota's brake design, i bought these drilled zinc plated rotors from ebay. they came w/ centric pads, which i think suck, but you could buy just the rotors. they look cool, work fine, and the zinc will keep em shiny for a while.