Upgrading rear brakes - ditch the drums!

I'm not really sure... but I think I remember seeing somewhere that the rear drums were part of the regenerative system? I too had this thought when I first bought my Prius, like Wth!? why didn't they use superior disk brakes for all 4 wheels? I just accepted it, and now I really don't care, the car stops when I need it too. so I don't think about it too much now.

 

The rear drum brakes are not part of the regenerative system; neither are the disk brakes.

There really isn't much need for disk brakes on a Prius. Much of the routine braking is done regeneratively by MG2, so you don't have the usual issues of fade.

In a panic stop, drum brakes can stop the wheels just as well as disks. The big advantage of disks is heat dissipation, so they can provide longer continuous braking before exhibiting fade. While this can be an issue with the Prius, it isn't very likely.

The Gen III Prius has rear disks. Mostly this is a marketing tool, since most prospective owners think it an advantage.

Tom

 

This article points out how much harder it is to use a disc brake as a parking brake.

Besides price, I think that is the major reason for rear drums.

What's the difference between drum and disc brakes?

 

In Europe, the Gen II Prius came with rear disc brakes, so presumably it should be possible to convert using all OEM parts.

What you need to do is to find a parts diagram of the rear axle for a European car and compare to the US car... then figure out where to get the parts.

 

Others have answered. But I am curious. Why do you need disk brakes? In all of the posts on PC, I have yet to read of any situation where a Gen II Prius had inadequate brakes.

Tom

 

How long have you owned your Prius? You don't seem to know a whole lot about how the brake system works. I have never seen ANYONE complain about drum fade here. Regen braking does most of the work. If you are coming down a long, steep grade, then you should have the car in B mode i.e. the jake brake.

The brake ECU controls line pressures to caliper pistons and wheel cylinders individually. You will need to investigate whether or not the ECU is the same in North America vs. Europe. Otherwise you could go to a ton of work and cost, only to find that the rears either lock up, or are completely ineffective.

 

The swap isn't too hard at all and I have done it on a couple of other cars like a civic. It's just about getting the parts: rear hubs, rotors, calipers, parking brake cables, brake lines, brake pads

 

Actually the European version of the gen2 Prius has disc and drum rear brakes, disc for the foot brake and drum for the parking brake to give the best of both systems.

 

Maybe he's racing his Prius at his local race track? If that was the case than drum brakes would certainly be inadequate.

please elaborate, or better yet open er up and give us a picture!!

 

In the business this is known as a "drum in hat" rotor.

With respect to the ABS, the question will be whether the current rear hub units can be used (which probably incorporate the rear wheel speed sensors).

 

There is a risk that the brake system is "tuned" differently in the cars with rear drums. Less likely but still possible is that there are different master cylinders and reservoirs used due to the drum brakes requiring slightly more fluid volume on application while there is more fluid drop with wear.

Google "electronic brake distribution" regarding the earlier mention of individual electronic brake control.

 

I would think that it would be cheaper and safer to add brakes to your trailer, that trailer seems to be putting a lot of stress on your rear suspension. I would actually keep the axle currently on the trailer and try to buy or build another axle with brakes in front of the current axle.

 

You can have your drum brake shoes relined with semi-metalic linings. I used to get mine religned with Velve-Touch linings on cars and motorcycles back in the pre disc brake era. They had vastly improved fade resistance. Velve-Touch had almost none of the drawbacks of some brands and acted pretty much like normal brakes except they didn't fade when they got hot.

Here is one source of semi-metalic rear brake shoes for a Prius.
Premium Brake Shoes
I have no experience with this company. If I were doing it, I would find a good performance brake shop and have them reline my shoes with
Velve-Touch material

 

Disc brakes became practical only when "power boosters" became available.

Without a "power booster," the disc brakes required a lot of leg strength to apply.

Drum brakes, however are known as "dual servo self actuating." That means the front and rear shoes are "locked" as a unit by springs, the hydraulic wheel cylinder and thed pivot pin. When the hydraulic cylinder expands the unit, the friction of the front shoe "twists" the entire assembly, forcing the rear se against the drum.

I remember this from Smokey Yunick who advocated the old tried and true drum brakes vs. Jan Norbye preference for the newer disc brakes in an article that was published in Popular Science in the early 1960's.

 

The genIII has disk brakes because of the skit/traction control. The gen 3 will apply braking pressure to the rear brakes (i think indipenedntly left/right) to help steer the vehicle in slide/cornering. It's the only vehicle on the market with larger rear disk than front disk.

If you get this mod functional with miles tested, I'll be curious of the same upgrade for towing reasons.