Regarding first, yes, the F would do more work because of weight shift, that’s why I asked about maybe the rears doing more to help with that
Regarding second, doesn’t bigger in F mean more braking in F and so more nose diving and faster wear in F? This doesn’t seem to be saying any more than the first point.
And could more even wear between F and R described by some be a function of the rear brakes being smaller and so wear faster to be similar to the fronts?
IOW, the observation of F wearing faster is because R brakes are big enough to not wear as fast.
It’s an interesting idea, but if the brakes are proportioned too aggressively towards the rear (presumably to reduce wear on the front pads), that could cause the rear wheels to lock up in hard braking and start the rear wheels skidding. Not a safe thing. I imagine the engineers who design the brake system determine by test-track experiment which proportion of front/brake force causes the quickest and safest braking, and dial that into the proportioning valve.
I don’t have the benefit of years of engineering schooling, as some of you guys do, but I believe the reason is so that the vehicle does not nose-dive when applying the brakes. I believe when the brake force is more evenly distributed, the vehicle weight is distributed more equally on all 4 tires, braking efficiency is greater, the vehicle is more stable, and perhaps the overall braking distance can be decreased. Naturally, electronic stability control also plays a role in this, in the typical newer vehicle
I believe it’s all about safety, not about having the front brake pads last longer
Which scenario is more desirable?
And which scenario would likely produce shorter braking distances?
You apply the brakes, the vehicle nosedives, the rear tires have poor traction, and you just about hit your head on the steering wheel
You apply the brakes, the vehicle remains level, all tires have good traction, and you don’t hit your head on the steering wheel
I wish I stated it as well as you. I suspect that balancing the work on all 4 wheels is best for overall safety/control/wear.
But yet it seems that fronts wear faster than rears on many cars (despite some comments to the contrary).
This is what got me wondering.
By NHTSA specification (FMVSS135) all brake systems must be designed under all conditions for the front brakes to lock first. Rear skidding is unstable and tends to spin the car. Fronts locking means the car slides straight. So this happens on ice AND on dry pavement, the systems used to be designed so that the front brake does nearly all the braking (especially on FWD cars). The systems were designed with fixed mechanical ratios so that right at skid, the fronts locked first.
Now we don’t brake right to the edge of skids on all stops but something much, much less. That means the rear could work much harder but can’t because the fixed mechanical ratios won’t allow it. Enter ABS. Design the system so that the rear does much more of the work during normal braking BUT the rear brakes go into ABS to prevent rear lock when you brake harder. Voila! More even brake wear front to rear.
Ultimately that’s the entire point of the braking system. To stop your vehicle as effectively as possible while still maintaining traction, steering, and stability. How long the brake pads last is irrelevant. Who cares? Brakes are cheap, wrecks are expensive.
It’s impossible to design a brake system where all the pads wear evenly because no one knows how the car or truck will be driven, loaded, or used.
That is interesting, now at maybe 20k all my pads are 8mm, and as stated previusly at 85k miles I do all 4 wheels, 2 times with 188k, but I feel on my 03 Trailblazer abs is on the front wheels only, is that the case with my car and newer cars?
No, ABS has never been offered as front-only. Some GM and Ford trucks got rear-only ABS and it was awful. Some older ABS units are 3 channel (2 front single rear) but nearly all (can’t say all 'cause someone will find a 3 channel somewhere) are 4 channel systems.
Wear, as others have stated, is highly dependent on where and how you drive.
I still have an old 89 Chevy 1/2 ton. It may sit for 3 months at a time until I need to make a dump run, haul some yard stuff, etc. Occasionally in the rain I’ll lock up the rear brakes, and when the ABS kicks in I can feel the rear brakes pulse as much as 3 or 4 times per second!
My original comment wasn’t intended to focus on how long the pads last as the goal.
It was intended to use wear as an indicator of how much work was being done by F versus R.
Larger brake pads mean that there will actually be less wear of the friction material.
Additionally, anti-dive suspension geometry has been in use for a few decades, and the amount of nose-dive when braking is truly minimal with modern vehicles.
My opinion - nose diving has little to do with front-rear brake balance. Instead, it is caused by weight transfer (which happens regardless of which axle is doing the braking), and is increased by worn shocks and affected greatly by the front suspension geometry. Google “anti-dive suspension geometry” for lots more info.
Nose dive is a reaction to how hard the car is braking and the suspension geometry (anti-dive, as @VDCdriver correctly states). The rear can affect this as well because “rear anti-lift” geometry can come into play. Actually anti-dive in the front is set very low because it hurts the ride but lots of anti-lift at the rear doesn’t hurt ride at all so manufacturers like to put in lots. Consider many cars actually “squat” under braking because the front dives and the rear squats from loads of rear anti-lift.
If you want a demo of rear anti-lift, pull your parking brake at 3-5 mph and note how much the rear squats when you do this. Imagine how much you’d get with the actual brakes.
Nose dive is also a function of the front suspension. It’s why a popular modification for some motorcycles is the installation of progressive springs in the front forks.
Front brakes wear faster because as you brake the weight of the vehicle transfers to the front of the vehicle. Thus they end up doing most of the work. This is especially true for hard braking. Lighter braking the brakes wear more evenly because there isn’t as much weight shifting (although there is some).
The wheels stop, but inertia causes the body to want to keep going forward; i.e. there’s a forward pointing force on the body. That itself wouldn’t cause the nose to dip, if everything in the car was solidly connected together. . But the body of a car is attached to the wheels by springs. So the configuration it is sort of like a kid’s rocking horse. If you pushed forward on the head of a rocking horse, the horse’s head would go forward & down and the tail end would come up.
Check out the anti-dive, anti-lift discussions. You’re right for a hobby horse, wrong for a car with certain design parameters in the suspension. But most cars do dive to some degree.