Toyota RAV4 Forums banner

1 - 9 of 9 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter #1 (Edited)
'06 RAV4 V6 third row seats (long wheelbase). US-Spec, living in Germany.

BLUF (bottom line up front): What can cause uneven brake pad wear on single wheel?

Background: Right rear wheel had scraping noise. Removed the wheel to discover thick inner brake pad (fine, bottom pad in picture) and completely worn-out outer brake pad (super bad, top pad in picture). After google-searching, I assumed I had a stuck caliper. Took it to a local German repair shop to confirm and start the process of ordering parts (parts for US-spec models in Europe can be challenging).

Problem: Mechanic ("Meister" or "Master" in accordance with German apprenticeship laws, so definitely a pro) said that caliper was not the problem. But he did say that the brake was "too tight." His English and my German (specifically for automotive subject matters) are not the greatest. Entirely possible there is a translation error. He said he was extremely busy and didn't have time to explain further (not an unexpected remark here in Germany).

Question: If not a stuck caliper, what could cause such uneven wear of a single (of 8) brake pad? On a 2006 RAV4, could the parking brake system have caused it? For instance if the cable was set too tightly? Does the parking brake go to both rear wheels, or just one? It uses a separate cable but applies pressure to the same pad/disc as the normal brake, correct?
(Googling to find the answer as well, but thought this forum might be a good source of model-specific experience.)

Remarks: I have not removed the left rear wheel yet. The outer brake pad is visible through the wheel and is thick. It is possible that the left rear inner pad is also almost worn away, but it has not started making any odd noise yet.

Plan: I have already ordered new rotors and pads for all 4 wheels from the US, which are currently somewhere in the shipping process. I plan to replace all of them just to start fresh on all 4 wheels. However, I don't want the current uneven-wear problem to immediately start happening to the rear wheel again.


Thank you for your time and wisdom, and have a great day!



153941
 

·
Registered
Joined
·
4 Posts
Discussion Starter #2
Looking at the Toyota assembly diagram (normally used for ordering OEM parts) for the rear brakes, it looks like the parking brake system uses a (separate) Shoe on the rear wheels to brake the wheels. So I think that means that the parking brake cannot be a culprit for the brake pad wear. Is that an accurate assumption? Thanks!
 

·
Registered
Joined
·
580 Posts
There are a couple of moving systems in a disc brake setup. First of course is the piston in the caliper. Since your inner pad is shot, that’s working. Next is the slider pins between the caliper and the bracket - these allow the caliper to float and lets the piston pull the outer pad into contact with the rotor when the piston activates. Last is the pads in contact with the stainless steel clips which sit on the caliper bracket. These are very susceptible to corrosion, not from the clips themselves but from the metal backing of the pads. When getting the brakes serviced, the slider pins are lubed and the contact points of the pads in the stainless clips are refreshed and lubed with anti-seize. Given the year of your RAV, you’ve definitely had the rear pads replaced once already. I’ve found that some brands of rear pads have a backing plate that’s just a smidgen too long compared to the factory pads, which can cause binding and sticking between the pads and clips. The parking brake doesn’t activate the pads, instead there is a small drum brake setup inside the rotor (called drum in hat).

Do you get the brakes serviced from time to time? If not (and I suspect you don’t, like most people) corrosion will cause the pads to stick and seize. When this happens the force from the piston is enough to overcome the sticking on the inner pad but not the outer. I suspect that a lot of people in the southern states wouldn’t need to concern themselves with annual brake services as salt isn’t used on the roads, but anyone in a salting or rust-prone area should absolutely be doing annual brake services. Here’s the rub: the labour cost is very close to replacing the brake pads, so nobody wants to pay for that every year; instead most people who don’t do their own work will ride it out until replacement parts are needed, typically 1-2 years earlier than for someone who services the brakes regularly. In Canada, it’s just something we’ve come to accept, and I do mine twice a year on each car, when I change from snow to summer tires, and back again in the fall (RAV is in the air anyway with the wheel off...). Since you’re in Germany and need to use snow tires, if you’re changing the tires, you might as well get familiar with doing the brake service yourself (14mm socket and a big C clamp are your friends, along with a file and anti-seize.)
 

·
Registered
Joined
·
4 Posts
Discussion Starter #4
Perfect, thank you!!
I may have poorly phrased my original post (since edited): the outer one is the one that's completely worn away.

A more mechanically-inclined friend and I have been discussing, and we think (he thinks) it could be frozen, stuck, or sticking guide-pins. From what you wrote above, I think you're saying something similar.

I'll ask the mechanic to clean/lube the brake systems when he installs the new rotors and pads. I'll also ask him to keep an eye out for extremely tight fits when installing them. I found Centric parts Rockauto (4 rotors, 4 sets pads).
If that's one of the too-tight-fit culprits in your experiences, please let me know.

My '06 is a bit of an anomaly. I was stationed in Japan for 5 years and left the vehicle with my parents during that time, which they only drove a few miles a year to keep the battery charged (eventually that too failed and it just sat there in their driveway, in New England so definitely salt/corrosion prone area).
I'd estimate that it had about 80k miles on it when I departed for Japan. I had it inspected/serviced at the dealer when I came back to the US, but other than noting the pad thickness on the inspection form (8mm at the time), I don't think they cleaned or serviced the brakes at all. At least, they didn't charge me for that specifically...which, at a dealership, means they likely didn't do it.
I just passed the 100k miles mark a couple months ago, just before Corona and the car began sitting for extended periods of time. It's entirely possibly that the brakes haven't been serviced in a very long time. Years more than miles ago.

Follow-on question. The worn-away outer brake pad is much more worn at the outside edge, where there are scratches indicating that the bare metal has been scraping against the rotor. Towards the inside edge (near the center of rotation and the hub) there is less evidence of wear (still a tiny bit of pad left).
Is this uneven wear based on distance from the center of the hub important information to have to help diagnose and troubleshoot the problem?

Thanks again, and have a great day!
 

·
Super Moderator
Joined
·
9,888 Posts
A more mechanically-inclined friend and I have been discussing, and we think (he thinks) it could be frozen, stuck, or sticking guide-pins. From what you wrote above, I think you're saying something similar.

I'll ask the mechanic to clean/lube the brake systems when he installs the new rotors and pads. I'll also ask him to keep an eye out for extremely tight fits when installing them. I found Centric parts Rockauto (4 rotors, 4 sets pads).
If that's one of the too-tight-fit culprits in your experiences, please let me know.

Follow-on question. The worn-away outer brake pad is much more worn at the outside edge, where there are scratches indicating that the bare metal has been scraping against the rotor. Towards the inside edge (near the center of rotation and the hub) there is less evidence of wear (still a tiny bit of pad left).
Is this uneven wear based on distance from the center of the hub important information to have to help diagnose and troubleshoot the problem?
Frozen slide pins ARE a primary culprit when the inner and outer pads wear significantly differently. If they aren't freed up, which is often a difficult job, sometimes impossible enough to require replacing the caliper, the new pads will wear unevenly again.

I wouldn't be concerned with the inner/outer wear differences on the outer pads since that will most likely fix itself with new pads, rotors and good slide pins.

Also, sometimes I've had to grind just a little off the "ears" of new pads to make them fit. It's not uncommon.

Also want to apologize for the nearly one day delay in getting your post "released."
The forum seems to have a hiccup the does that randomly and it's above the moderator/administrators' pay grades to fix.
 

·
Registered
Joined
·
580 Posts
Totally agree with Doc. And sorry, may have transposed my own rear pad situation in replying to your note. Best that they make sure everything moves right when it goes back together. I actually have the Centric pads on the back right now and they have been ok, but they are the exact ones I meant about being too tight of a fit in the pad mounts on the caliper bracket. Just make sure the clips are put back (or new ones added) as the clearance is so tight it’s tempting to leave the stainless clips out. Not a good idea.
 

·
Registered
Joined
·
270 Posts
I agree with it not being a stuck caliper. Its rare to see the outer pad wear more than the inner. I haven't seen that yet in the hundreds of brakes I've changed.

It has to be your slider pins were seized and the brake pads weren't sliding in their grooves.

When ever you change your brake pads, you should use the proper type of brake lube and lubricate the pad ears where they slide in the clips. Then, once you put the pads in, if you cant easily move them in and out, you should grind the ears a little ,until they slide easily. This will help them last a long time.
You should always lubricate the slider pins also. If you can't slide your caliper in and out (once the piston is compressed) then the pins aren't free for the caliper to slide on. That's a problem.

If the pads don't "relax" once you release your brake pedal, what happened to your outer pad will continue to happen to both pads. This creates unnecessary heat and will kill the brake pad and rotor life.

My yearly brake duty is similar to Foryota. I live in Canada also and change my tires/rims twice a year on three vehicles. Every time the tires come off, (spring/fall) the brake components get cleaned and re-lubed.
My 2017 Camry has 97,000 kms and the brake pads still look new. Toyota pads do last a long time though. I got 123,000 kms with my 2006 Corolla.

Good luck
 

·
Super Moderator
Joined
·
9,888 Posts
I agree with it not being a stuck caliper. Its rare to see the outer pad wear more than the inner. I haven't seen that yet in the hundreds of brakes I've changed.

It has to be your slider pins were seized and the brake pads weren't sliding in their grooves.
I've seen slider pins frozen so tight I had to use heat to get them loose. With the sliders seized but the piston caliper free, wear on the outer pad is exactly what happens. The caliper pulls its frame and thus the outer pad in but then the stuck slider keeps it from releasing.
 
  • Like
Reactions: kevcules46

·
Registered
Joined
·
3,485 Posts
I agree with it not being a stuck caliper. Its rare to see the outer pad wear more than the inner. I haven't seen that yet in the hundreds of brakes I've changed.

It has to be your slider pins were seized and the brake pads weren't sliding in their grooves.

When ever you change your brake pads, you should use the proper type of brake lube and lubricate the pad ears where they slide in the clips. Then, once you put the pads in, if you cant easily move them in and out, you should grind the ears a little ,until they slide easily. This will help them last a long time.
You should always lubricate the slider pins also. If you can't slide your caliper in and out (once the piston is compressed) then the pins aren't free for the caliper to slide on. That's a problem.

If the pads don't "relax" once you release your brake pedal, what happened to your outer pad will continue to happen to both pads. This creates unnecessary heat and will kill the brake pad and rotor life.

My yearly brake duty is similar to Foryota. I live in Canada also and change my tires/rims twice a year on three vehicles. Every time the tires come off, (spring/fall) the brake components get cleaned and re-lubed.
My 2017 Camry has 97,000 kms and the brake pads still look new. Toyota pads do last a long time though. I got 123,000 kms with my 2006 Corolla.

Good luck
I lube mine every year when I swap my snow tires to all season in the Spring. I use 3M silicone paste. Most people I bet don't even know that the slide pins needs to be lubricated. Doing this every year will greatly increase brake life and performance.
 
1 - 9 of 9 Posts
Top