Thanks again to RyanS4 and others that recommended raceshopper.com for Ferodo pads...

[PSmalls::DoggieStyle]

Finally got around to ordering them, DS2500s, just now ($85 shipped).

1 question for Ryan or anyone else in the know:

RYoung's brake pad write-up says that stock pads have a coefficient of friction probably ~.35 and the DS2500s have a coefficient of friction ~.50. How much will the bias change?

[ryans4]

but if you just loaded a .5 rear and kept a .35 front, then it's a pretty good change.

If you refer to the long drawn out "brake force" calculations, you see that at the end of all the math "crap", you multiply the result by the CF of the pad.

So say for ease of sake, the front made 2000 "units" and the rear made 1000 "units".

Front pad is a .35 CF = 2000 * .35 = 700 units
Rear pad was a .35 CF = 1000 * .35 = 350 units
F/R bias using my stoopid units is 66.67% front bias

new rear pad..
Front pad is a .35 CF = 2000 * .35 = 700 units
Rear pad is a .5 CF = 1000 * .5 = 500 units
F/R bias using my stoopid units is 58.33% front bias

So you could say in my WAY over simplified example that the rear pad change had a bias affect of 8.34% to the rear.

I should have tweaked the stoopid units to mimick stock bias, but it's pretty close as is.

ok, now I welcome the math geeks to correct me.

on a side note, glad you had a good buying experience. Hope you like the DS2500's. Mine should go in an a couple weeks.

[PSmalls::DoggieStyle]

If you want more specifics, I run 332mm Stoptechs up front. I use Axxis Ultimates on the street (coefficient of friction is .35 according to RYoung's write-up) and Pagid Orange at the track (coefficient of friction on this pad is .52 according to RYoung's write-up). So basically with the Pagids up front, the bias will be almost stock-like (a touch more up front?) and with the Axxis up front, the bias will be ~10% more in the rear than stock!?

[ryans4]

...are known to shift a lot of bias to the rear (via smaller piston sizing) despite the larger then stock 332mm rotor (stock front is 321).

So for you, on the street (axis up front and DS2500 out back), it should be rear biased (more so then stoptech already rear biased you). On track (pagid orange up front and DS2500 out back) it will be damn close to waht stoptech invisioned with their kit assuming stock audi rear rotors/calipers.

Personally, i like the shift towards additional rear bias, i think it makes the car feel more stable under braking (despite the fact that it really isn't since over rear bias is what causes the oversteer or spin on rear lockup before fronts lockup). See if you notice the car take a "squat" more in heavy braking on the street.

or if you really want to see where your bias is given all the other parts of your car (suspension/tires/etc.), pull the ABS and lock them up and see what locks up first. But let me throw a caveat on that, it's not safe. I bet you'll like it, especially if you like the way your old man's P-Car brakes, it should be more like his car.

[PSmalls::DoggieStyle]

[FixedWing]

and of overheating of the pads. The result could be one end fading before the other. And that could have some very dramatic results.

I had this happen with new RS-19 pads on the back of my Porsche. With Ceramic rotors it takes a *long* time to really break them in. The result was that the rears faded but because the fronts were still operating correctly I didn't know it. I ended up getting into ABS at the front (because that end was still working well) and overheated rears. It was quite the surprise which made me realise how little margin I tend to leave on braking distance. :-/

Stephen

[ryans4]