Here's the idea: Take the front brake assemblies from a wrecked xA/xB, and replace the rear drums. Question is: Would this be a relatively simple procedure? Could we call it a 'bolt-on' replacement? What would it take to make it work?

 

If you do so, say goodbye to your near perfect OEM brake bias, and good luck trying to stop in a straight line.

Rear brake upgrades are best saved until you've already upgraded your front set up. Even then, great care has to be taken that you do not upset your brake bias in a negative fashion.

Oh, and your parking brake is operated by your rear drums. Most cars with rear disc brakes have a "drum in disc" parking brake. If you were to use the front brake assembly off an xA/xB, it would be difficult to rig this up.

 

rear disc brakes aren't as effective as rear drum brakes.

 

Why do virtually all high-performance cars come with rear disc brakes then? Your statement is incorrect. Perhaps you meant rear drum brakes arent as effective as rear disc brakes.

Heck, even some economy cars come standard with rear discs. Kia Rio5 has rear discs ...

 

no statment is correct i learned about it brakes class. rear disc are more just for looks than function. a drum brake has more surface area to displace engergy. even with most rear disc brakes the parking brake is still drum design. look at the design of rear disc brakes there is nothing too special about them solid rotor which doesn't transfer heat well at all. even though it shouldn't be producing that much anyway since it doesn't do that much in braking. do some research and see what you find. alot of it is just manufactures making them look pretty and ease of service not always function.

 

So, do tell why all modern racecars use disc brakes vs. drums in the rear? It certainly wouldn't be for apperence purposes. If drums were superior, why aren't F1, WRC, IRL and others using drums? Also, why aren't they on the fronts of cars anymore?

I'm not meaning to be insulting, but you are incorrect. The one thing I agree with you on is that drum brakes are usually more than adequate for most situations, as the majority of the braking is done with the front brarkes. However, by your logic, drums provide more surface area. If this were the case, we'd see cars with front drums still.

May I suggest an article?

http://www.edmunds.com/ownership/tec...7/article.html

 

ok i read your article i think i was a little misunderstood. i'm not trying to broad the example to all cars. high end cars use a completly different brake fluid which has a higher boiling point all together. drums in most modern cars are adequate. your statement is focusing on performance cars not so much commonly street driven vehicles. some manufactures are required to make there race cars a production car of so many before they can even race it.

aslo note that rear disc are much smaller than front disc making less surface area for contact. drums allow for a more conential force in how the shoes contact the drum. disc require more force from the booster and pedal in the rear than a drum does.

i thinks its safe to say we have the same to similar idea of what is going on in a braking system.

 

I honestly don't see the benifit of upgrading the rear brakes at all. The brakes on my car work perfectly, and if I was to go and auto-x the car, I would upgrade the front pads to something that wouldn't fade as much; Other than that they are fine. Remember, the xA weighs less than a Miata, there is not a lot of car to stop!

 

I wouldn't upgrade the rears, either. I have thought about upgrading the fronts. I plan to throw my xB around the local auto-x course at the end of the month, so I'll really get a good idea how the brakes hold up.

I did some hot laps at Road America last month during lunch (They call it "touring" where you get to drive around the track for an hour). The brakes did begin to fade a bit, although every car I've ever done a touring session with has had some amount of brake fade. This indcludes Civics, Sentras and Preludes.

 

Yes they are and last just as long as the rear shoes. Rear drums need adjustments over time, where as calipers never need them. There is a grand difference to disc drum braking and I would take disc brakes over drums anyday. In fact my last car was a corolla with drum brakes, converted it to disc and the braking power was more effective.


As far as bringing the front calipers to the rear, the fluid transfer is NOT an issue. The issue is the wheels that you have and the hub mounting for the caliper. Willwood make a rear disc brake conversion but never released it to the public. In this kit was the complete rear disc convertion assembly and no modification was needed to the master cylinder. Of course there was also no Emergancy brake cable connection. This is one of the reasons why we they didn't release it to the public. Was not complete and was really not needed for a vehicle with only 94hp to the wheels.

 

Good point about the braking bias. I can certainly see where balance would be affected, and tuning that could prove exceedingly difficult.

What I was going for in this question was just to see if it can be done. I'd very much like to upgrade the entire braking system, without going to a big brake kit because I want to be able to run snow tires on the stock 15"alloys. Part of this would be to replace front solid rotors with slotted, along with a corresponding improvement in brake pad selection. Calipers would come later, if necessary. The rear disc option comes in primarily because better-performing shoes are not available, at least that I've been able to find, so going to discs would give more options.

Thanks for the input, and please keep it coming!

 

There is already a topic where someone replaced the rear drums with the disc set-up from a 1988 toyota corolla GT-S coupe. Here is a pic of the car.


I know the car because thats the one I did the conversion I did on mine as well. You do have to modify the rotor inside cut out and of course you have to make a bracket that is strong enough to hold the caliper.

 

Besides the usual upgrades: pads, rotors, etc, you may want to consider disabling ABS (NOT RECOMMENDED FOR AMATEURS).

In almost ALL comprehensive tests, cars without ABS outperformed cars WITH ABS. This is, of course, assuming that you have enough driving/track experience to know how to feel for your traction limits. Relative to other cars I have owned, the ABS is rather sensitive on Scion's, and you'll probably increase braking quite a bit by disabling ABS.

Just remember, this applies to ideal (track) conditions. Don't go driving into the snow with the ABS off (unless you want to slide around).

 

My suggestion is to leave the rear brakes alone. I regularly race my scion with OEM brakes and it brakes perfectly, no fade, good bite, obviously not a racing brake, but its VERY decent for being OEM. I now changed to slotted rotors, braided lines, pads and motul fluid and the change is really noticeable, but for everyday driving the brakes are PERFECT!!

The only problem with our cars is the ABS for racing it really kills the perfecformance of the braking, I HATE IT when i have to miss the apex because the ABS made me loose my brakes. I know how to control the brakes when they lock up so i wish the computer would let me do my thing, but i guess i just have to deal with it.

By the way, does anybody know how to remove the ABS, without F-ing up the computer.

 

I'd imagine that you could kill the ABS by removing the fuse, but I'm not sure since I havn't experimented. I know that it is more difficult for xB's and RS1.0 xA's, since VSC adds to the problem.

The handling characteristics of this car are great. Oversteer is near impossible to induce (and you have to try REALLY hard to oversteer on purpose), and the car understeers in a predictable manner. With the right tire setup, this thing is perfect for the autox. The balance is perfect, IMO, and I wouldn't want to upset it. There is a tad too much dive, but that is a suspension issue, not a braking issue.

Fade is the main enemy, and it's best to deal with that by upgrades to the front.

 

If you have ever had to stop a car with front drum brakes in the rain, you would understand why they started putting discs up front. For almost any purpose, rear drums are at least adequate.

 

There is one topic around here somewhere that shows how to disable the ABS without causing the VSC light to come on. One of the RS xA owners here in norcal did it. He races the track and figured out how to do it. As far as disabling the ABS for regular driving I would NOT do it. Your car is fine with the ABS on and the disc brakes installed on the rear. If you really want a project , then do it. If you just want better braking, I recomend tightening up the rear brakes a little and just enjoy your scion.

 

I replaced the rear drums on mine with rear disc brakes from a 99 Honda Civic SI. Worked great! just had to swap alot of parts. I also used the proportioning valve out of the Civic, had to rebend the brake line to make it work!!