josesantigo57

iTrader: (4)

I have an 05 Base 350z.

Front brakes are Wilwood 6pot. I run Polymatrix E-compound pads on the front.
Rear are stock brakes, and I run Hawk HPS pads in the rear.

My problem is that under hard braking, my rear tends to turn a little loose.

Should upgrading to more aggressive rear pads such as HP+ fix my problem, or am i going to need more rear downforce?

Thanks in advance!

Spork

iTrader: (6)

Doesn't only a front BBK upset the brake bias?

Billhyco

iTrader: (14)

i would put about 250lbs of blocks in the trunk, that should help

just think about what Spork asked.

nismo53E

iTrader: (1)

under really hard braking, that is something that is difficult to over come. most of your stopping power is in the front brakes anyways...because of weight transfer. so under hard braking, the rear end of the car gets a little light = less traction on the rear tires = the rear end can get a little bit wobbly. although yes, your set up may put too much bias to the front brakes and upset the rear of the car even more. try more aggressive pads in the rear and see if that helps.

also, were you trying to say that under hard braking, the rear end TURNS loose? you shouldn't even be turning a whole lot if still under hard braking. if you meant the rear get gets a little loose, that would make more sense...remember, slow in...fast out.

josesantigo57

iTrader: (4)

Thanks for the input guys!

I don't think a BBK upsets the bias, a BBK will help you brake hard consistently, without fade, not harder, that's the work of the pads. I think. Right? But i may have upset my bias from my combination in pads.

Yea, I didn't mean turn loose, more like get loose. Haha. That was me thinking in Spanish and typing in English. Ill try more aggressive pads in the rear and see where that takes me.

Thanks again guys!

WXSigns

iTrader: (15)

Yeah, pretty normal. On the track the car only should know throttle and brake. Never lift or coast.

Hard braking transfers or loads the suspension moving forward. You probably don't feel it as much braking hard up a hill on the track, if your track has an area like that.

Practice hard braking them threshold braking.

betamotorsports

iTrader: (1)

Adding just a front BBK (larger OD rotors, larger pad size, more pistons) increases front bias by design, usually by a lot. Your just seeing the results of your more unbalanced braking system. I bet if you did some threshold braking distance measurements you'll find that your braking distances have increased.

terrasmak

iTrader: (8)

Same setup i had for a while, getting the matching rear kit will be nice.

josesantigo57

iTrader: (4)

Interesting, would it be the same also if with stock brakes you get aggressive pads in the front while keeping stocks in the rear? That would upset bias? However i doubt braking distances have increased given my pad choice and sticky tires.

I remember tracking the car with stock brakes, those where scary moments.

Yea I was looking at either that or stock Brembo for the rear. For now im just gonna go with better pads.

mhoward1

not exactly true. But for those just starting straightline braking is the prefered method.

scotts300

iTrader: (46)

I wouldn't mix pad types. That's like running a winter tire in the rear and a Hoosier in the front.

akomsr1

iTrader: (1)

If your rear end is getting twitchy under braking, adding a more aggressive compound in the rear is only going to make things worse.

Are you running Rcompounds? And what's your alignment?

betamotorsports

iTrader: (1)

Yes. Increasing pad compound friction increases the torque that the front brakes can generate (up to tire breakaway). This increases front bias.

sno

iTrader: (4)

Sounds like you're braking too late.

thinking

iTrader: (4)

To the OP:
When this occurs, does it feel like the rear end is wiggling ever so slightly for just a fraction of a second or maybe one second?

laze1

iTrader: (17)

You can also run a little negative rear wheel toe-in to help some...but that may ne to do anything due to your brake bias issue.

1cockyZ

iTrader: (46)

More front spring to reduce dive? If you have a model with ebd and you are doing something dumb the car will feel "funny".

akomsr1

iTrader: (1)

This is why I don't believe its his brake bias that's causing him problems. He should be locking up the front tires before the rears with his brake setup (theoretically) unless he's running Rcompounds and has a ton of weight transfer off the rears.

betamotorsports

iTrader: (1)

IMHO, I don't think brake bias has anything to do with the "problem." On an ABS equipped car its hard to get the rear end really loose under braking. It should be moving around a little bit if you're getting full use of the rear brakes and I think the OP needs to just get used to that feeling.

mhoward1

in truth, none of us really know the issue. We just don't know enough about the situation. It could be the car, the compunds, the set up, or the driver. Unless someone is there watching and feeling the issue only the driver can tell.

This is why an instructor at a track day, or friend on an Autox dry run can be very helpful.