How do you compensate for the front bias on Subies with your BBKs?
This is a very generalized and broad question and we will try to explain as follows:
Brake bias adjustment can usually be achieved by a variety of changes,
1. The rotor size (torque arm)
2. Brake pad compound (coefficient of friction)
3. Caliper piston size or installing proportioning valve (brake pressure)
There are pros and cons for different modifications to obtain optimum brake balance but based on our observation and extensive experience in brake design
, we believe #1 and #2 are the most effective way.
To adjust bias, the entire front-rear system must be looked at as a whole. For example to reduce front bias, the most common practice is to increase the rear braking power. RB offers several front and rear upgrade options to allow customers to adjust any bias for optimal balanced system.
There is hardly one setup that is optimally balanced for all. Even each driver's braking condition (e.g. how sharp of the turn and how you tap the pedal) can generate different biases with the same setup.
Our rotors kits were designed to make up the deficiencies of Subaru stock set ups. To better understand this, here is an example.
Rotor sizes of the early Forester model (98-2/02):
Front: 277x24 mm (10.9"x0.94")
Rear: 266x10 mm (10.5"x0.4")
The brake bias in this setup was balanced, but Subaru likely felt that there was not enough overall braking power
, so they increased the front brake rotor size for the late model Foresters:
Rotor sizes of the late Forester model (3/02-08):
Front: 294x24 mm (11.6" - Increase from 10.9")
Rear: 266x10 mm (10.5" - No change)
Although Subaru increased braking power in the front, they kept the rear brake rotor size unchanged
! This likely led to the increase of front brake bias, so Subaru recently changed their brakes again for the 2009 Forester, enlarging the rear rotors
Rotor sizes of the 2009 Forester:
Front: 294x24 mm (11.6" - No Change)
Rear: 290x10 mm (11.4" - Increase from 10.5")
Long before the 2009 Forester was released, RB had offered this rear 290x10 mm BBK upgrade kit
. Many Forester owners have installed this kit to make up for the rear braking deficiency and to catch up to the latest design for a more balanced brake system.
In the future, for '09+ models, if Subaru decides to upgrade the brakes further, RB will have already been providing BBK upgrades for a long time, with our soon-to-be released 322x25 (front) and 316x18 (rear) big brake kits.
A better balanced brake system is definitely a wise investment for any car owner, not only for driving safety but also to lower maintenance costs. RB is proud to serve the Subaru community with effective yet affordable brake upgrades.