Brake balance for staggered setup?
 

For those with staggered wheel setup, do you run proportioning valve in the front to weaken it at all? My front locks up way before the rear and I'm thinking of doing fender flare in the rear for 305+ width tires which would only worsen the problem. I can also do custom 4 pot in the back and weaken the rear with proportioning valve, but I know the stock valve has some nonlinear split, which makes things tricky.

I would be curious to know from those that have done this and how the balance felt afterwards. Love to copy some proven setup rather than trying things on my own again. Otherwise, I would have to run 285 in all corners which I don't want to do... they feel too twitchy at high speeds with wider fronts.

It's usually called ABS ;) Is your ABS inoperative?

If its twitchy the issue isn't the tires. It seems like you might not be going about it the right way.

There is a company in England that sells a bolt in a dual brake cylinder with adjustable balance bar assembly for the RX8 if you really want to go about doing it that way though. :dunno:

I am staggered and I can stomp on the brakes from 70-0MPH without even the slightest tire chirp or wiggle really. I have a BBK with more aggressive pads but even with the stock brakes and Hawk HPS pads it was the same.

Cool. I didn't know they made one. I'll get it ordered.

Maybe twitchy wasn't the best word. It just feels like it takes more effort to drive at high speeds with wide fronts. I have 245 front and 285 rear now and they ride much more comfortably than 285's all around especially over 100mph. Turn-in is lot better with 285's all around, but it doesn't want to go perfectly straight with wide fronts. I don't know how to describe it well. My alignment is good btw.

RX8 stock brake balance was designed for equal width on all 4 tires, so if you increase your rear tire width, your front will lock up first. My ABS does works which only accentuates the problem. Once ABS does it thing with the front, it starts to slide, and rear tires don't get used much. I can notice drastic difference in braking and balance when I brake with 285's all around vs. 245/285 setup. I bet 245 all around will brake much better than 245/285 stagger.

I don't think the issue you are having has anything to do with brake bias though. The front tires on staggered setups have way less surface area...and under braking the weight transfer to the front will result in overstressing your traction and understeer.

If you decrease braking on the front enough to compensate for reduced tire contact patch from using smaller tires...where do you think the braking is going to come from? You would be very surprised how little the rears brakes do

Modification of your braking behavior will likely do a lot more than altering your brake bias

Its all just patching a flawed setup, but another option is to leave the fronts alone and get a higher torque rear pad.

Are you experiencing these problems on the street or on the track?

I'm staggered 245/275 with stock brakes and I have no brake bias problems on street twisties at 80mph.

I have not put this car on a road course, so I can't say much for speeds higher than that.

Have you ruled out suspension problems? Are your wheel and tire widths properly matched?

Find yourself in a situation where you're going 150+mph with a curve coming up with a $200k+ car just a couple seconds ahead of you, then you start asking these questions. Frankly, for me anyway, these things weren't really a problem until I went 3 rotor. It takes the car just a short stretch to go into 150mph+ range and when you start to get over jealous with the last minute braking, you really start to think more about braking than anything else for the time being.. just mho.

As I implied in my response, I can't speak for those kinds of speeds. :)

What sre you running for a rear wing?

just the oem mazda one.

I find that braking softer initially until the car sets and then threshold braking keeps the car a lot more stable than slamming on the brakes at the last minute and hoping for the best. It doesn't take a lot to make it much less twitchy

Remember that slow in fast out is better

dan, do you have progressive springs? I have linear rate springs now and that took care of the set-in problem. I used to deal with the same thing.

btw, you can only do slow in and fast out with the 20b lol. i'm still getting used to the car. took it out to tracks just a few times over the past 3-4 years. the car's down right now because I decided to relocate the fuse box and run a cold air intake. itching to get back into it.

There you go ...

You need downforce if you want to just drop anchor at 150+ MPH.

yea I guess that would help traction at high speeds... although not sure if that would help with my braking problem. My problem is that my front tires lock up, abs kicks in, and once abs kicks in, the car starts sliding almost like I'm hydroplaning. even when abs doesn't kick in, I know there is more I can use from the rear tires with appropriate proportioning before the front locks up. I probably get that product from england you recommended earlier. thanks!

Probably not as much as you think... all of the weight shifts to the front of the car under braking. With the proportioning valve in my Miata I can go from 90% front brake bias to about 55% front brake bias and it doesn't make a massive difference in how fast I can slow the car down. If you want to increase braking power, then you need better and wider front tires. 245's are tiny. And if you want better braking at 150+ MPH then you need to reduce lift and increase downforce.

If you went to 245's all around I doubt your braking performance would change much at all.

I'd really suggest looking into other options before you get that dual master setup and delete your power brakes.

that's helpful insight. it's true weight shifts to front... well, sucks. I'm not trying to shave fraction of second here. if it's not going to be a big difference, probably won't be worth the effort. thanks man.

Don't RX-8s also have electronic brakeforce distribution?

Care you elaborate on what "good" is?

A non 0 degree thrust angle will cause the car to move off track during hard braking.

Also not enough negative toe in the rear could cause the rear end to lose grip under braking.

I would suggest moving the fronts to 265's.....since it worked pretty well for the 20B powered Rolex GT cars. They ran a 265 front and 285 rear setup IIRC.

I don't think anything setup wise on a Riley Chassis (tube frame) Rolex RX-8 is comparable to a stock chassis RX-8.

Shhhhhhhhh.......just trying to get the OP on some wider fronts.

And get him to get an alignment to spec ;)...not an "It's Good" alignment

Which BBK do you have and what pads are you running? I'm interested in going bigger purely from a cooling standpoint. I am nearing what heat the stock brakes can handle on the track and am beginning to research the options. Can you give or point me to a prior review?