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2006 Forester X 5 spd
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29 Posts
Discussion Starter · #1 ·
I just recently went to the dealership for my 60,000 km (~37,000 miles) service and I had been noticeing a brake shudder previous to the service so I asked them to check it out.

It turns out my front rotors were warped!

Thankfully they were still under warranty (just) so it wasn't a cost to me but I was wondering if anyone else has had that problem and what would cause that. I hope it is not normal to replace rotors that frequently.

I haven't had the vehicle loaded while braking down a long hill and I've never towed anything. It just seems odd to me but that's why I'm asking you guys and (gals)!

Let me hear any thoughts on this one.
 

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2010 Forester 2.5X Base Model
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305 Posts
Well there are a couple of scenarios:
1. You could have just hit a puddle while your brakes were warm. (That Ruined a set of mine)
2. If you had the brakes replaced previously, and the rotors were only tuned, they are more susceptible to fail.
 

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2020 Forester 2.5 Touring CVT
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186 Posts
I'm surprised they replaced them under warranty -- rotors are explicitly not covered under their best extended warranty in the US.
 

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2010 Forester Diesel
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62 Posts
I just recently went to the dealership for my 60,000 km (~37,000 miles) service and I had been noticeing a brake shudder previous to the service so I asked them to check it out.

It turns out my front rotors were warped!

I haven't had the vehicle loaded while braking down a long hill and I've never towed anything. It just seems odd to me but that's why I'm asking you guys and (gals)!
Same thing happened to me, on a new Forester with 15.000 km on the clock.
My rotors were also replaced, since there was no time to have them turned.

I discussed it with Subaru and got the following information: Brake rotors do not "keep" under storage. Something in the material change over time, if they are not used. Rotors mounted on a car stuck in a showroom for a longer period of time, or rotors left on the shelf, are more likely to warp than rotors in regular use.

A set of newer, turned rotors are no more likely to warp again, than a set of rotors off the shelf.

Furthermore, hard braking is not likely to cause warping. Careful braking or "feathering" is more likely to cause warped rotors.

The combination of hot rotors and rain/snow/water is merely a theoretical cause of warped rotors.

Some manufacturers save money and weight by spec´ing rotors with less mass, compared to quality brands. Thin / low grade material in a rotor, of course, also contribute to warped rotors.


So - you should be allright :-D


M
 

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2006 Forester X 5 spd
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29 Posts
Discussion Starter · #5 ·
Thanks for the input.

I've wondered about the hot rotors coming in contact with cold water - specifically in a situation off off road driving and water crossings. Is that a real issue?
 

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The Modfather
2019 Impreza 5dr Sport - Manual
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8,070 Posts
We've had that issue on two outbacks it also happened to my Forester. Not an uncommon issue with Subaru's front rotors unfortunately. I think it's not really warping though but this:

StopTech : Balanced Brake Upgrades
 

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2010 Forester Diesel
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62 Posts
Thanks for the input.

I've wondered about the hot rotors coming in contact with cold water - specifically in a situation off off road driving and water crossings. Is that a real issue?

From my competition experience (rally) and adventure travel (Land Rover), I have never experienced brake disc problems, due to water crossings or contact with snow/ice/water.

Since what is typically refered to as a "warped disc" isn´t really warped – I doubt contact with water is an issue.

M
 

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2000 2 Outbacks 1Man , 1 Auto
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312 Posts
Main cause of warped discs is sustained heavy braking where the discs become red hot and then subsequently sitting with your foot on the brake pedal once you have come to a stop.
 

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2004 fxt A/T
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2,567 Posts
Main cause of warped discs is sustained heavy braking where the discs become red hot and then subsequently sitting with your foot on the brake pedal once you have come to a stop.
That causes deposits in one spot and the pulsing effect not warped rotors.:icon_wink:
 

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2004 fxt A/T
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2,567 Posts
Causes different parts of the disc to cool down at different rates and hence subsequent distortion
Didn't read this above did you?

Cliff's notes version
The term "warped brake disc" has been in common use in motor racing for decades. When a driver reports a vibration under hard braking, inexperienced crews, after checking for (and not finding) cracks often attribute the vibration to "warped discs". They then measure the disc thickness in various places, find significant variation and the diagnosis is cast in stone.
In fact every case of "warped brake disc" that I have investigated, whether on a racing car or a street car, has turned out to be friction pad material transferred unevenly to the surface of the disc. This uneven deposition results in thickness variation (TV) or run-out due to hot spotting that occurred at elevated temperatures.
:icon_cool:
 

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2000 2 Outbacks 1Man , 1 Auto
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312 Posts
Quote "Didn't read this above did you? ". No I didn't. Came across the same comment years ago. At the end of the day for Joe Public 'Warped Rotors' whether for DTV or true runout amounts to the same thing and both rightly or wrongly are acknowledged as "warped Discs".
 

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2000 Forester GLS
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39 Posts
I've just had my rotors changed and the mechanic, a subaru specialist says they go wrong so often he keeps a large inventory of them in stock. He measured thickness and run out and couldn't find much wrong with mine, but boy did they vibrate under heavy braking.

He said that what tends to happen is that a brake piston doesn't retract, and the pad is still being pushed against the rotor as the car drives causing the rotor to heat up. He didn't say what happens after that but I guess you can add your own variety of cold water, pad deposition, warp, or other contributory factor to the mix.
 

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2006 Forrester X 2.5
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11 Posts
We have had the same problem with our 2006 Forester. The dealer turned the rotors under the warranty at about 10000 miles. They are doing the same now at about 21000 miles. Anyone know a permanent fix?
 

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none none
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8,844 Posts
We have had the same problem with our 2006 Forester. The dealer turned the rotors under the warranty at about 10000 miles. They are doing the same now at about 21000 miles. Anyone know a permanent fix?
I'd throw on new rotors like the centric premiums (since oem is $$$) and a pad that can hold up to heat better. You're likely overheating the pads and then holding the brake while the rotor is still hot. You can often even see the silhouette of the pads on the rotor from where the pad has been left in contact with a hot rotor.

Also its possibly getting hot due to poorly serviced brakes. If the slide pins aren't lubed up properly and the edges of the pad, then they can stick or drag on the rotor, also a boot on the caliper could have torn (often when replacing pads) allowing the piston to rust or seize in the caliper.

I personally don't like to get my brakes turned. I lightly sand them down when I put new pads on, and then replace the rotors every other pad change.
 

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19 19 Touring, 17TrgXT CVT
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632 Posts
I know this is an old thread I am resurrecting, so Admin if there is a more recent thread on the same topic please move this post. We have a 2017 XT Touring, 33,500 miles with 4 months left on the warranty. Noticed a pulsating feel while braking. Took it in to the Dealership and was told the rotors were warped. They replaced both the rotors and front brake pads under warranty!

No real hard braking or unusual conditions other than we have had a lot of sudden thunderstorms with pretty deep water accumuating here in the area. I am speculating that I must have been doing some hard braking when dry and then suddenly hit a large puddle rapidly quenching really hot rotors.

I asked the mechanic if this failure was normal, he said no, but that they have occasionally seen bad rotors from the factory that are more prone to warping then normal. He said with my model year and type I should see on average 40K - 50K miles before rotors/pads are replaced.
 
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