jimk04

I have a moderately serious 986 S that has 997S 330mm brakes and the larger calipers. Also 997 gt3 mc. I obviously have a bit more front bias now than OE. I was thinking of fitting the larger rear calipers and discs to the rear to balance the bias out. Does this sound sensible. The larger rear calipers and discs will only give me a leverage and heat capacity advantage as they have the same piston sizes as my OE rear brakes.
Would you still run a more aggressive rear pad with the bigger rears. ?
Was initially thinking rs29 all round but now maybe 29 front and 15 rear or maybe rst3 rear..
TIA
James

stujelly

you can deal with the brake bias by using a pad with less initial bite in the rear.

Might want to play with some compounds before you go to that expense of changing rotors.

jimk04

Do you not mean more bite?

jimk04

Plus I can get discs at trade cost so aren't mega money....whereas pagid rs are expensive!

Frank 993 C4S

^^^^ This - if you want to experiment with brake bias, use different compound pads front/rear. Keep in mind that going too far from stock with your brake set-up will upset your ABS and produce unpredictable Ice Mode. BTW - just because you have bigger rotors in the front doesn't mean you have to change brake bias. Most Boxster/Cayman race cars run with stock rears brakes. You should only experiment with brake bias if the current set up negatively affects braking (ice mode, unsettled rear end, etc. ).

jdistefa

What Steve & Frank said.

Also, did you upgrade the booster as well as the MC?

Jason @ Paragon Products

Pagid RST3 rear is VERY popular teamed with RS29 front on Spec cars. RS15 is a compound that is being phased out.

http://www.paragon-products.com/U240...2407-pagid.htm
http://www.paragon-products.com/U240...2406-pagid.htm

jimk04

Thanks all.

I left the booster alone as I prefer the lower ratio of assistance.
My brother has a Cayman R with gt3 mc and rs29. I prefer my pedal...harder and less travel than his car with his 5:1 booster.....mine is 3.8:1 iirc

Do rst3 and rs29 have similar heat/torque curve shapes?

My car dives a bit too much due to the bigger front brakes...and it unsettles the rear a bit. So was looking for some added rear bias. May try 29 f and rst3 r.

Paseb

I run rs 14 front and rs 29 on my cayman

Gt3 calipers up front and cayman s front calipers in the back

Boxster booster and 997 4s master cylinder

On my f boxster, i run same pad setup , stock booster and mc

jimk04

14 front and 29 rear?

What discs with those calipers on the back?

jdistefa

Solutions to that problem:

LSD
more rear toe
higher spring rate
increase front compression
increase rear rebound
put a dead body in the trunk

....but whatever you do, do NOT increase rear pad bite/bias

jimk04

And here come the conflicting opinions....all valid no doubt.

Why are you so against increasing rear bias.?

jdistefa

^ Because it doesn't make sense.

Basic vehicle dynamics re. weight distribution: If the back end gets light you are going to have less grip for the rear tires to contribute to braking.

If you try to increase rear bias with a grippier pad all you gain is potential [earlier] activation of ABS in the rear, possibly triggering ice mode.

Frank 993 C4S

What does this have to do with unsettling the rear of your car? Is this pure feel or do you have data to look at brake and wheel speed traces? Did you vary your brake application? What is your experience level? Have you had a Pro in the car and what was his feedback? Do you have an LSD? Changing your bias too much to the rear will reduce your braking ability as the rear wheels have relatively little contact patch as your weight transfers to the front. Plus, IT WILL screw with your stock ABS causing ICE Mode. Please do a search on RL for that. Another option is to run the Bosch M4 Motorsports ABS and you can pretty much run any bias you want.

jimk04

And also bearing in mind that
I have already played with the bias by adding the larger front brakes. So I was trying to add some rear bias to compensate