I have a 1999 toyota 4runner and I was just wondering why toyota used disc brakes in the front and drum brakes in the rear? This always puzzled me. Can someone please explain to me why this is the case or what kinds of benefits arise by using disc in the front and drum in the back? Thanks.
Rear brakes handle a small fraction of the braking job, so drum brakes are actually good enough for many applications. Four-wheel disc braks are nice, but often not necessary.
Drum brakes are much easier to accommodate the parking brake and the manufacturing process was amortized long ago. And they are quite reliable.
Lower cost. My 1991 Isuzu Trooper had disks all around – a bit unusual for inexpensive SUVs of that era.
Twotone
Drum brakes have some advantages over disk brakes that serve on the rear where the braking is less severe. Though drums are capable of supporting abs, disc brakes lend them selves to this function better (as well as traction control etc.) that it ultimately becomes more cost effective to use disc brakes all round in later models. Off road only vehicles could often be better served with drums all around where cooling may be less of an issue and protection greater. 4Runners though have become primarily on road. Your car is in the “tweener” stage where both are used for each’s own set of advantages…protection, PB use for the back vs. cooling for the front where braking demand is greatest.
This doesn’t have much to do with Toyota or your 4runner. It is an incredibly common set up for all car makers for the reasons already listed. (Everything I have ever owned except for a '64 Ford pickup has been disc front & drum rear. The '64 was drum all around).
This is a very very common setup. From the 70’s through the 90’s it was very unusual to see a vehicle with 4 disc brakes. Almost ALL were disc front and drum in the rear.
Now my 05 4-Runner has both disc AND drum in the rear. Disc for stopping…and drum for the parking/emergency brake.
In truth I think we’re all speculatng on the reason. Truth is, drums are as capable of stoping a vehiclel as discs, except thet the frictional surfaces are enclosed and thus do not disspate heat as well, leaving them more susceptable to fading, and if water gets into a disc brake it can be hard to dry out. The water stays inside the disc, kept by the centrifugal force as a thin lubricating film against the inside of the drums. In the old days we used to lose uor brakes immediately after going through puddles.
Drum brakes have only two advantages. (1) they can be designed such that the friction from the applied brakes assists in creating the pressure of the pads against the drum, and (2) they can more easily be used as parking brakes as well as main brakes. Most cars today with 4-wheel discs also have little drums included in the cenetr of the discs for use as parking brakes.
Item (2) above is, I’d guess, probably the real reason they use drums in the rear. It’s cheaper to simply just use drums in the rear than to use discs and add the tiny drums systems for parking brakes.
For SERIOUS off-road work especially in mud, drum brakes perform better. Disc brakes can get packed so full of mud they become useless…
If you own a paid-for factory that is tooled up to produce drum brakes and your disc brake factory is operating at its production limit, you continue to use the output from the drum-brake factory in order to maintain overall production…