69911

Is there any solution for decreasing the front/rear brake bias ratio for street/AutoX use?
The common track PFC11/08 compound is common sufficiently successful, but I am looking for a solution without squeaking and maintains consistent, corrected Ratio at low and medium temps.
Either a component change or pads change suggestions would be great.

I currently have the stock brakes on the car. I have considered going to larger 350mm front rotors for track, but this would only worsen the brake bias problem for non-track use when not using pads with differing friction coefficients.

(Please keep this post related to the topic and refrain from posting opinions that are not specific to the question of < F/R ratio. Please do not change the post to "why do you want it or need it". There are people on this forum that feel the need to post replies to virtually all post and muddy post in a counterproductive manner.)

s65e90

Add a proportioning valve.

powdrhound

Add 997TT/GT3 rear calipers. They have much bigger pistons and will add significant rear bias. You could also simply add 350 rear brake rotors and leave the fronts at 330. This will have a smaller effect than adding the 997 rear calipers.

69911

powdrhound: Great suggestion (as usual). I will look into that further.
Thanks!

69911

Are there any rear calipers that would fit with similar piston area besides 997TT/GT3 rear calipers?
The 997tt/GT3 appear to be hard to find and quite expensive.

powdrhound

Negative...

sub-zero

1500 full set that needs rebuilt you pay shipping and fees !

Mtrboatvr6

I just went through the upgrade. The parts are currently unavailable anywhere. Took me 8 months to source everything I needed. If you can find them even used good luck! Very nice upgrade and well worth the wait though.

theprf

I overpaid for a complete set of F/R 997 Turbo calipers last winter, just for this reason - none available anywhere. I do like them.

Mtrboatvr6

I found both fronts for $1400 that were newly rebuilt. The rears I got at retail, one was super easy to get, the other is when the supply chain went away and it took me literally 6 months to find just that one. Ended up punting, and ordered it from eBay via Latvia and crossed my fingers it showed up. Not just the calipers are an issue, the brake lines and other ancillary parts like the front pad retaining springs were NLA too (they seem to be back now though). I also did the GT3 master with proportioning valve so the PSM doesn't freak out when street driving. Rear brake lines we converted to steel flex likes with dry breaks. it makes pad and rotor changes a 5 min job, no joke. Its incredible. I had one of the springs in the rear ebrake assembly fail (of course) the day after we finished the project, so the ROI for the dry breaks was immediate LOL!
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69911

Thanks for all of the information. I found some rear calipers and will have to wait until spring to try things out.

RennPart

If you need help with rotors let us know. We have Sebro and Girodisc available as well as PFC etc.

--Aaron

Bernard IV

Anyone do some sort of valve? This would be ideal.

Mtrboatvr6

Exactly, Here is mine with the GT3 master. We 3D printed a mount for it that attaches to one of the other lines to give it a little more support as well. This valve is to keep the PSM happy, not rear bias though.

69911

Brake bias (reduction) valves should only be fitted to the rear circuit, so that would only make the rear bias worse.

As far as the valve to keep PSM happy, I have PSM electrically disconnected as it is way too sensitive. In my opinion, it is dangerous for the car to "decide" before the apex to apply brakes on one side. This would cause you to miss the apex and run out of pavement on corner exit. I have heard the Motorsport version is safe to use on track, but computer chassis control in general begs the question of why do we drive on the track.