99 S70 T5 Why are the rear disks bigger than the fronts?

c70_lindsay · Post by **c70_lindsay** » 30 May 2014, 16:47

I recently bought a 99 S70 t5, to replace my dearly beloved C70. I was changing the winter tires over to summers yesterday and noticed that the rear disks are actually bigger then the fronts!! What the hell that makes no sense. I didn't actually measure them, and they all look stock. Could someone please shed some light on this~ Thanks, Tim

Post by **BEJinFbk** » 30 May 2014, 22:27

Where are your emergency brakes...?

difflock54 · Post by **difflock54** » 30 May 2014, 23:15

Are you referring to the outside diameter of the disk or the width of the rotor unit itself?
The rear rotors have an e-brake drum incorporated as implied above.

c70_lindsay · Post by **c70_lindsay** » 31 May 2014, 00:15

Ummmm ya, I am talking about the outside diameter of the rear break disks. I'm not a moron. I am well aware the e-brake drum.

Post by **BEJinFbk** » 31 May 2014, 11:43

So, what's not obvious here?
Front has a hub, rear has a hub and E brake.
Am I missing something in your question?

difflock54 · Post by **difflock54** » 31 May 2014, 22:00

No one impied that you were a 'moron'.

Your question is not actually that specifically clear as you merely say bigger.
Other member responses posted also indicate uncertainty about the direction of your question.

Post by **precopster** » 02 Jun 2014, 14:40

Do the rear brakes have the small DB2 pads like these: http://www.sunburybrakes.com.au/prod1702.htm

If not they're definitely NOT standard though if anyone is intent enough to run a tiny pad on larger discs it COULD be done.

wjhandy850 · Post by **wjhandy850** » 05 Jun 2014, 08:52

May this be the case because the way the brake system is designed to prevent the nose dive on hard braking. It was a horrible problem with the heavier cars of the of the past.

Post by **j-dawg** » 05 Jun 2014, 10:15

dive and weight transfer on braking are actually a function of deceleration, center of gravity, and suspension geometry, not of front/rear brake balance. biasing brakes towards the rear is a no-no - you end up actuating the ABS very early to avoid spinning, or on cars with no ABS, you just end up spinning.

Post by **QuirkySwede** » 05 Jun 2014, 10:59

Even if the disc has a larger diameter, if the pads and caliper piston(s) is smaller than less braking power is developed. Imagine pinching a wagon wheel with your fingers versus a 12" disc with a hydraulic caliper. Same goes for when a different proportioning is used at the MC end.