Thoughts and discussion on brakes: Disk vs. Drum

Links to articles to repair/upgrade your L series Suzuki

Moderator: Smuz

Post Reply
User avatar
Smuz
Resident Curmudgeon
Resident Curmudgeon
Posts: 3425
Joined: Thu Jun 05, 2003 6:53 pm
Location: Kansas City (Lenexa)

Thoughts and discussion on brakes: Disk vs. Drum

Post by Smuz » Thu Oct 05, 2006 8:56 am

Some thoughts on drum vs. disk vs. drum and disk.

Background:
1. Four wheel drum brakes use a common line pressure between front and back. Been that way since the dawn of time. (one exception is a rear proprtioning valve installed on European LJ80's to meet govt regs)

2. Front disk brakes with rear drums use a proportioning valve on the rear circuit. The reason for this is twofold. Disk brakes take a much higher line pressure to provide the same braking effect that drums provide and, during braking, 60% of the brake load is on the front. Without the proportioning valve, the rears would lock up long before the fronts provided much braking force. Power boosters are used because of the increased line pressure neccessary with disk brakes.

3. Four wheel disk brakes are now becoming standard on new vehicles and have been an upgrade to custom ORV's for years.

My thoughts and personal opinions:
1. Rear proportioning valves enhance the effectiveness and stability of any conventional vehicle braking system.
2. Rear proportioning valves are absolutely necessary with a mix of front disk and rear drum brakes.
3. Rear proportioning valves are not necessary (on ORV's) with the same configuration on all four wheels, such as 4 wheel drums or 4 wheel disk.
4. Power brake boosters are not necessary on vehicles as light as LJ's with disk brakes. Nice, but not necessary.

We (Wasp, Sancho, and myself) have 4 Suzuki vehicles that have been converted to 4 wheel disk brakes:

1. Wasp's 1989 Sidekick (Whacker) is lifted with a D44 solid front axle. It runs 15x15.50 super swampers with Sidekick disk brakes on all 4 wheels with NO proportioning valve of any kind. It has the stock booster. The vehicle stops well and lack of a proportioning valve has had no apparent adverse effects so far.

2. Sancho's 1980 LJ80V (Sancho) runs 15x10.50x31 MTR's. It was recently converted to 4 wheel Samurai disk brakes and has no proportioning valve at all. It has a Samurai master cylinder and no power booster. Initial test runs indicate that the vehicle braking perfomance is light years beyound stock. It will almost stop in it's own length at 20 mph. The rear brakes do lock up just a bit before the front, but no more so than the old drum brakes.

3. My 1987 Samurai (Henry) runs 15x15.50x33 super swampers. He has 4 wheel Samurai disk brakes. the only proportioning valve in the system is the stock one. He has the stock power booster. The braking system is stock with the exception of disk brakes replacing drums in the back. He stops well and I've noticed no adverse effects from not using an aftermarket proportioning valve.

4. My 1972 modified LJ10 (Mouser) is repowered with a G10 and runs 15x15.50x33 super swampers or 15x12.00x33 MTR's. He has a Samurai master cylinder with no power booster, 4 wheel Samurai disk brakes, and no proportioning valve of any kind. He stops straight and well, and I have no issues at all with his braking performance.

Bear in mind that none of these vehicles, in their present configuration, have been in any extreme offroad situations yet.

These are my experiences and opinions. They may change with more time and experience. Discussion is welcome.
Last edited by Smuz on Thu Oct 05, 2006 9:54 am, edited 1 time in total.
The above is my opinion. It is subject (like all my opinions) to debate, disagreement, rude gestures, and loud raspberries.
User avatar
Jimny
It's an LJ thing!
It's an LJ thing!
Posts: 4740
Joined: Wed May 28, 2003 7:02 am
Location: KANSAS
Contact:

Post by Jimny » Thu Oct 05, 2006 9:44 am

Very nice write up Smuz! You need to make it a Sticky!
I'd rather be driving my LJ!
User avatar
Smuz
Resident Curmudgeon
Resident Curmudgeon
Posts: 3425
Joined: Thu Jun 05, 2003 6:53 pm
Location: Kansas City (Lenexa)

Post by Smuz » Thu Oct 05, 2006 9:55 am

Good idea.
The above is my opinion. It is subject (like all my opinions) to debate, disagreement, rude gestures, and loud raspberries.
User avatar
stevec
The Parts Dude!
The Parts Dude!
Posts: 7546
Joined: Thu Jun 12, 2003 9:26 am
Location: Seattle WA area

Post by stevec » Thu Oct 05, 2006 10:04 am

Very nice writeup, I would have to agree on just about all points.

On a stock LJ, I think drums are fine, as long as you keep them adjusted properly. When I bought my LJ10, the brake pedal was nearly to the floor before the brakes caught - I'd usually pump it about halfway, then push down on the brake pedal. Adequate, but not enough in an emergency. When I adjusted them, it was scary! push the brake pedal down an inch, and all four wheels lock up! I backed each adjuster off one tooth, and it's perfect. Even offroad, I've had no problems with stoppong power. Those drums are plenty big enough for a stock 1300# vehicle with a top speed of 50mph.

The caveat here is that it is a stock LJ, and thus does not do any extreme offroading. The biggest problem with drum brakes is that they do not clean themselves as easily as discs when they get wet or muddy. The trails up at Liberty (the NW meet earlier this year) are about as hard as I'll take it on, and I have full confidence in those drum brakes. If I was out slogging in the mud, I'd probably go with disc brakes, but I'd also change a lot of other things as well. Incidentally, my Samurai has stock brakes (disc front, drum rear), but I wouldn't mind putting discs on the back, as long as I still have an e-brake.

Another point, my LJ81 has the exact same brakes as my LJ10, and with me and ~200# of stuff in it, it's over 2000# (close to 1000kg), and still stops on a dime. Those same brakes in my LJ10, which is around 1500#, or around 700kg, with me in it, are easily enough.

To summarize, the stock drums are more than adequate for a stock LJ - if it's not braking good enough, something is wrong. For a modified LJ, or one that sees a lot of mud, discs would be better.

As with Smuz, this is my opinion, based only on my rigs.
The only difference between an ordeal and an adventure is your attitude
User avatar
Smuz
Resident Curmudgeon
Resident Curmudgeon
Posts: 3425
Joined: Thu Jun 05, 2003 6:53 pm
Location: Kansas City (Lenexa)

Post by Smuz » Thu Oct 05, 2006 10:23 am

I agree with you 100%, Steve. The only points I would add about stock LJ brakes are:
1. The adjustment is critical to proper operation and must be checked often. There is very little tolerance for being out of adjustment.
2. The linings and the drums are very soft. Mud and abrasives eat them up in a hurry. With stock drums so rare, it is very important to inspect them frequently.
The above is my opinion. It is subject (like all my opinions) to debate, disagreement, rude gestures, and loud raspberries.
User avatar
stevec
The Parts Dude!
The Parts Dude!
Posts: 7546
Joined: Thu Jun 12, 2003 9:26 am
Location: Seattle WA area

Post by stevec » Thu Oct 05, 2006 10:41 am

Smuz wrote:2. The linings and the drums are very soft. Mud and abrasives eat them up in a hurry. With stock drums so rare, it is very important to inspect them frequently.
I don't know how soft the drums are; mine were in good shape. And drums aren't rare, just f%$@&//?# expensive!

Before adjusting your brakes for the first time, it's important to know how much lining you have left on the shoes. If you wear the linings down to the point where you have metal to metal (shoe vs. drum) contact, it'll chew your drums up in a hurry! If your shoes are already getting thin, replace them or have them relined, then adjust your brakes.

And since we're on the subject of drums, when reinstalling your front drums, be sure to properly tighten the axle nut, and use a new cotter pin. If there is any play in the drum, the force of braking will strip the splines off the drum, making it useful only as a boat anchor. This is precisely why I have no used front drums for sale, but lots of rears. BTW, a new front drum runs about $140, and that's each, not for a set!
The only difference between an ordeal and an adventure is your attitude
User avatar
stevec
The Parts Dude!
The Parts Dude!
Posts: 7546
Joined: Thu Jun 12, 2003 9:26 am
Location: Seattle WA area

Post by stevec » Thu Oct 05, 2006 10:44 am

I moved this discussion from "projects" to "how-to articles". It's not really a how to, but it is more tech related than a project. Maybe we should change this section from "how-to articles" to "Tech"?
The only difference between an ordeal and an adventure is your attitude
User avatar
Smuz
Resident Curmudgeon
Resident Curmudgeon
Posts: 3425
Joined: Thu Jun 05, 2003 6:53 pm
Location: Kansas City (Lenexa)

Post by Smuz » Thu Oct 05, 2006 10:52 am

I don't know how soft the drums are
I do and they're soft. I've cut up a few with a power band saw and it goes thru them like butter.
f%$@&//?# expensive!
I should have said "reasonably priced drums are rare".
The above is my opinion. It is subject (like all my opinions) to debate, disagreement, rude gestures, and loud raspberries.
Post Reply