Vibration when braking

[Clamminfrank]

Driving 2025 Forester with 7,000 miles and experiencing significant vibration when braking, usually at 50 mph. Any advice?

 

[bmart]

Brakes...

 

[Matt42]

One or more brake discs have deformed a little. Do you also feel it in the steering wheel? If yes, it'll be one of the front discs.

Have you recently had to make several really hard stops, followed by waiting at a traffic light for an annoyingly long time? That can cause the brake discs to form hard spots that can also cause vibration. They can be machined to get rid of the hard spots, particularly if the car is low mileage. Sometimes the only cure is new discs.

Sometimes the brake discs are defective from the beginning, but that's rare.

 

[Clamminfrank]

Matt42 thanks for your reply. Sounds logical. I have a service appointment with the dealer on 9/23, let’s hope they find the problem and correct it under warranty.

 

[Matt42]

Let us all know the outcome, good or bad.

 

[chasfish]

I had same issue couple years ago on my 2018 forester. I had private mechanic use Napa discs and pads as replacement parts. Napa parts no good any more. I had previous good experience. My Subaru dealer turned rotors as they were found to be slightly out of spec. Dealer replaced pads with Subaru pads. Good as new. No more vibration. Always will use Subaru parts from now on.

 

[Clamminfrank]

Let us all know the outcome, good or bad.

Repaired satisfactorily.
Here’s what invoice stated:
Run out is out of spec, 0.0 8MM run out on left rotor. 0.707 MM on rough rotor. Rotors need resurfaced. Cut and resurface rotors road test good.
Thanks for your interest.

 

[Train Dan]

It's been my experience that modern cars, in an effort to shed weight, often are significantly underbraked. That is to say, the discs are smaller/lighter than necessary. This is done to help fuel mileage (not only the weight penalty to the car, but the inertial drag of spinning up heavier wheel assemblies...and there's the unsprung weight issue. That affects ride and handling)
More than I used to, I'll downshift on a long downhill, rather than riding the brakes all the way.
It's something we'll all have to notice.
Dan

 

[chasfish]

It's been my experience that modern cars, in an effort to shed weight, often are significantly underbraked. That is to say, the discs are smaller/lighter than necessary. This is done to help fuel mileage (not only the weight penalty to the car, but the inertial drag of spinning up heavier wheel assemblies...and there's the unsprung weight issue. That affects ride and handling)
More than I used to, I'll downshift on a long downhill, rather than riding the brakes all the way.
It's something we'll all have to notice.
Dan

Now I know why brake rotors can’t be ‘turned’ anymore (because so thin) and maybe why brake parts are more cheaply made.

 

[bmart]

It is a partial truth. You can turn them, generally, but it is cheaper to replace them..and MUCH faster.

 

[Train Dan]

Now I know why brake rotors can’t be ‘turned’ anymore (because so thin) and maybe why brake parts are more cheaply made.

Often, they can still be turned (they turned them on our daughter's 'roo), but you're right, there's not much metal there to cut away. There are exceptions; the rotors in my M340 fill up the wheels.
Dan