Maybe these brakes aren’t getting broken in properly, or an issue cleaning the new rotors.
That seems very odd indeed. Usually the rear brakes sustain much less wear that the front. I suppose the manufacturer – to produce desirable performance and mpg number for the sales force – may be going to extreme lengths to reduce the weight of the vehicle, and the weight of the wheel assembly’s rotating parts.
hmmmm … ok, let’s do a comparison. From what I see the rear brake rotor is spec’d at a nominal 10 mm thickness, the wear limit at 8.5 mm for the solid version on the 2018 Forester. For a 2018 Toyota 4-runner, I’m seeing 18 mm nominal, and 16 mm wear limit. The rear rotors for the 4-runner are considerably thicker, but there’s not that much difference in the amount of wear allowed, 1.5 mm for the Forester vs 2 mm for the 4-runner. Not sure how to interpret that.
The Forester apparently has two versions of rear rotors, solid vs ventilated. Which are you using?
oops, OP mentioned a Forester above. ok, let’s look at the 2018 Cherokee. For the rear rotor I’m seeing 14 mm nominal, and 12.5 mm wear limit for the base version. There’s apparently a premium version also, 22 mm nominal, 20.5 mm wear limit. OP, do you have the base or premium rear rotors?
Right now I don’t think the alignment is the issue, something is broken or severely worn.
First I’d start with the brake problem. When brake pads wear down quickly, my first thought is the caliper pins. If they get stuck, they will wear the pads very very quickly. They can also cause a dynamic alignment issue that won’t show up on a static alignment rack.
Next, do your steering joints have zerk (grease) fittings? And if they do, are you getting them lubed at least twice a year. If you ignore the lube jobs, the some of the grease will squeeze out allowing a little play in the joint. It won’t be enough play to be out of tolerance, but the combined play of all the joints could add up to an out of tolerance situation and it would be aggravated by dragging brakes causing the front tires to toe out at speed.
Another thing I would look hard at are the front hubs. Wheel bearings inside the hub could be worn enough to cause the caster to change while in motion, but that could also show up on the alignment rack. But because it is constantly varying, it could look good on one trip to the rack.
One test I like to do for this situation is to (do you really trust your wife?) have someone in the drivers seat with the engine running and turning the steering wheel sharply right and left, only a few inches but fairly rapidly, while lying on the ground in front of the vehicle observing any movement between the two halves of each joint, including the upper and lower ball joints. Also observe if the front tires are in sync. You will have to move further away to watch the front tires.
Usually a bad joint will be easily spotted. Also watch the idler arm for any up and down movement. It will move up and down a little but anything over about an 1/8" would be suspect.
Lastly, with the Jeep off, jack up the front so that the tires are just barely clear of the ground. Then have someone stick a shovel under the tire and rock it so that the tire moves up and down. Observe the ball joints for any vertical movement between the two halves of each ball joint.
BTW, worn wheel bearings can cause excessive wear of the brake pads. Also in these newer vehicles, if the pads are replaced without new hardware installed, the new pads will wear faster.
Edit: once the worn/broken part(s) are replaced or repaired, then the alignment must be checked and if needed, set to spec.
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