OK, from everything I've read so far, increasing the size of your front brake rotors (with a BBK or upgrading from 2.5i to wrx rotors in my case) will cause the brake bias to change. I'm told that this increase in front rotor size will shift bias to the rear brakes, in fact the stoptech BBK is designed to work with stock rear brakes to do just that. My question is how does increasing rotor size shift the brake bias to the back? And furthermore, if I increase the size of the rear rotor (like in the classic H6 upgrade) would that shift brake bias forward? I have read a lot on sticky forums, faqs, and howstuff works etc.. And I still am confused as to how this counter-intuitive physics works. Thanks! -Matt
That's a good fucking question. Pardone my Francias To be honest I never really thought about changing brake bias by simply upgrading the hardware. And come to think about it one could probably alter the brake bias by simply using different pads, although I'm sure someone will chime in saying that is a horrible idea. I believe the bias to be a lot like understeer, more (front bias) is safer while less (rear brake bias) is more aggressive and intened more towards the performance side. Could be wrong though. Sorry I couldn't help with the backwards thinking delima. I say upgrade to the WRX setup and you can't go wrong but I'm no expert.
i'm using some intuition so this is not necessarily correct: going with a larger rotor in the front and keeping everything else unchanged: peak grip between the rotor and the pad shouldn't change... however, now there is more rotating inertia in the front (assuming the larger rotor has more inertia) which will cause your front brakes to lose stopping power... hence brake bias is moved backwards going with better pads in the front and keeping everything else unchanged: now peak grip between the rotor and the pad will increase... hence improved stopping ability in the front and brake bias will move forward anyone have a more correct explanation, please chime in...
This is a great question.... Hopefully we can get some good answers. Here's a good site on this. http://www.stoptech.com/tech_info/wp_brakebiasandperformance.shtml If you look down the page about half-way, it shows what factors increase bias front & rear. It looks like if you increase your braking force up front only, then your rear brakes/tires are less useful because you're moving more of the weight up front and not reaching the maximum grip factor of the rear tires, which you want.
That is a new concept on me pEd. I was trying to think of how I brake on my bike. I use a lot more of the rear brake when I'm riding aggresively whereas the fronts are more for casual situations and moments when slipping the front tire isn't a concern. Obviously it's really different on a car where you can be so choosey.
Actually matt you've got it reversed. If you increase to a wrx brake in the front it will become more front biased. The rear jdm brakes I gave you will increase the rear bias somewhat evening it out.
From reading the article, it seems fairly intuitive what increases brake bias one way or another. The real question seems to be how far can you go one way or the other without actually increasing your stopping distance. It seems you also need to consider the rear brakes carefully, as too much rear bias will make the car's rear end lock up too soon, which would be even worse on my wagon. For those of you who don't know, I am working on a brake upgrade for my 2.5i that consists of sti v6 rear calipers & vented rotors and wrx rotors and brackets on the front. Rotors and pads will be bigger in the front. Pads will be bigger in the back while rotors stay the same diameter (but now they will be vented!). From what I have read these are the issues that I am dealing with as I am not lowering or redistributing any weight in the car. Factors that will increase front bias: 1. Increased front rotor diameter 2. Increased front brake pad coefficient of friction 3. Increased front caliper piston diameter(s) Factors that will increase rear bias: 1. Increased rear rotor diameter 2. Increased rear brake pad coefficient of friction 3. Increased rear caliper piston diameter(s) The article does not mention anything about pad size, but I would assume that a larger contact area despite actual caliper piston diameter would result in an increase in bias. Please correct me on this though, too many holes in this logic
I've actually got an excel spreadsheet of different brake setups for an RS/2.5i that'll help you figure out what you want. I'll get it to you next week. My main computer is down and out for the count at the moment. PCI-E graphics card is dead and I have a stack of agp cards. Soon as I get it back up I'll show it to you. But the setup you have is pretty much going to put it where you want. It's almost a perfect match as far as brake bias and front and rear being vented.
Awesome! I only ask these questions because I assume that Subaru would design to brake bias as close to optimal balance as they could within their capabilities of producing a car for the average american driver. But the brakes on an 18K car could be better I'm sure!