Rear brake bias?

[Lightbringer]

So I took my CR-Z in for its first maintenance today and discovered an interesting data point. The rear brakes have worn 2mm more than the front brakes. While this is a small difference, it is still notable and got me wondering if this is just an anomaly or if the default configuration of the CR-Z from the factory is a slight bias to the rear.

So, any thoughts?

[Gitano]

I have a 2006 Infiniti FX35 that wears the same (i.e., rear pads go quicker than the front). According to the dealer (if you trust them!), this is by design so that the car's front doesn't nose dive when stomping on the brakes. I guess they've tried to balance out braking in the Z as well?

[lexicon]

I'd say the dealer comments are, as usual, BS. Even if the bias was set slightly rearward for the reason they say, the front brakes still do about 80% of the work. Physics says weight transfer goes forwards.
In my experience this happens precisely because the rears do less work and they get more corrosion on the faces - then they wear away faster due to the roughness.
This might not be such an issue if you don't live near Manchester, England where it rains (seemingly) all the time

[lldsandsll]

Beats the 8th gen accord. Honda did a stupid thing, which they seemed to be remedying a bit since 2008 (8G accord). What they did was put more power to the rear brake so that the car breaks more evenly. If the power to front and rear was equal, the car would dip hard forward, which feels funny and is also less safe. In the 8th gen Accord they beefed up the power to the rear, but put the crappiest, smallest pads. The result was that we had to change our rear brakes about 3-4 times for each front brake change. There was a class action and they recalled and gave out one free set of pads for this. Kinda lame.

[Ksport]

Judging by the position of the rear caliper this would make sense and possibly because of the compound used in the rear also.

With the position of the rear caliper it would be "pulling" the car to a stop rather than if it were towards the front of vehicle.

[Koala Yummies]

Originally Posted by lexicon

I'd say the dealer comments are, as usual, BS. Even if the bias was set slightly rearward for the reason they say, the front brakes still do about 80% of the work. Physics says weight transfer goes forwards.
In my experience this happens precisely because the rears do less work and they get more corrosion on the faces - then they wear away faster due to the roughness.
This might not be such an issue if you don't live near Manchester, England where it rains (seemingly) all the time

I agree completely. The front brakes are doing the large majority of all deceleration/stopping work. The corrosion is a good point as well, along with the rear discs being solid (and much thinner), the fronts discs are vented and thicker overall.

I've never known of a production car that had a rear brake bias. The proportioning valve controls the amount of pressure applied to the pistons in the calipers, they're typically 70/30 60/40 etc. Along with that the piston size, pad size, caliper size, and pad compound determine the amount of braking force/torque is capable from each brake. The fronts have much more power than the rear (from the factory).

If you want to know what a rear bias would do, yank on the handbrake above 30mph, and be ready to call insurance. A rear bias will kick the rear out during threshold braking, and generally make the car very unstable during hard or emergency braking.

[lldsandsll]

My front discs aren't vented. Is this a Euro feature? Yes the front discs do most the work, they always will, but to increase braking stability (called dynamic braking system by Honda), they increase the bite in the rear. I'm not saying the rear necessarily bites harder than the front, just more so than other cars. The braking distribution may be tied to sensors that detect the car dipping forward, and increase power to the rear slightly to counter that.

[Koala Yummies]

Originally Posted by lldsandsll

My front discs aren't vented. Is this a Euro feature?

The front rotors on all the CR-Zs, are vented. The rears are solid.

This is what they look like:



Not talking cross-drilled or slotted.

[hujo580]

Yep agree Euro and therefore assume all CRZs vented front and solid rears. Agree any bias to the rear will make for at the very least dodgy handling under hard braking; had this on a car in the eighties (Chrysler). Had rear discs corroded and replaced in the nineties, the English complaint, (Citroen) and in the noughties front discs replaced due to wear/bad scoring (Toyota). So I suppose all makes different, I would not expect rears to show more wear than the fronts under normal circumstances especially given a) front brakes take 70-80% of the braking force & b) the newness of the Zs although appreciate the points made by other posts on this thread

[TCroly]

There are some good points made in this thread. But I think the basis for the question is flawed. It assumes that it would be "normal" for front and rear brake pads to wear evenly and I do not think that at this is necessarily the case. As has been already pointed out these are different braking components in size and in what they are being asked to do. I also think that the wear rates would be different based on different driving styles and different driving conditions.

For example if someone is a very hard braker, they would probably see greater wear on the fronts because with greater braking effort more weight is shifted forward. Conversely if someone if is a brake dragger, who applies light pressure constantly, the rear brakes will probably wear faster. My point being that one should not expect front and rear brakes to wear at the same rate under different conditions.