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GT350 front brakes on Boss/S197 - who has done it?

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675
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Full Tilt Boogie sells a kit to upgrade to the GT350 rotors and calipers. Who has done it? Any feedback? Obviously, stopping power should be vastly improved but I am also curious about pedal feel.
 
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Good point, steveespo! Has anyone weighed Boss 4 piston caliper/rotor, S550 6 piston caliper/rotor, and GT350 6 piston caliper/rotor combo?

But . . . I have a lead on some used 350 front brakes and my new 23lb 20x10.5 Signature Wheels are hungry for more brakes!

Boss caliper clearance.jpg
 
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Talk to me about the softer pedal feel with the PP1 15" brakes, please! I have stainless lines, RBF600 fluid, and Ferodo 2500s currently (along with 2013 GT500 rear rotors) and pedal feel is pretty good but not as firm as my Focus RS was. I don't want mushy. I have driven a stock S550 PP1 and that pedal was way too touchy at the top of travel, making heel-n-toeing very jerky.
 

JDee

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My '16 PP1 has stainless lines, RBF600 and has never been touchy with any brakes I've used (OEM PP pads (which are Ferodos), StopTech TrackDay and now Hawk DTC50/30). Might be unique to your car? Binding in the pedal travel or something like that?
 
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Yeah who knows. It was a stock, low mileage 2016 PP1. Honestly, the brakes on my Focus RS were similarly touchy at the top of the pedal travel, too, making it awkward to brake smoothly unless you were ON IT (which was when that car was happiest, anyway).
 

captdistraction

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Oddly, the GT350 uses a master cylinder diameter more similar to the S197 and has a very firm pedal; but the brakes use a 38/36/34 piston arrangement (compared to the 36/36/36 on the GTPP caliper). The GTPP uses a larger master cylinder bore than the 350.

So the brakes have very slightly more area on the pistons (which could mean imperceptibly softer/longer pedal), but maybe the 38/36/34 arrangement helps the pedal feel (and this doesn't include any calculations of rear area and bias). I can say the pedal feel on my 350 is by far the best I've had out of any car I've ever driven (which is a very exhaustive list)
 

captdistraction

GrumpyRacer
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Talk to me about the softer pedal feel with the PP1 15" brakes, please! I have stainless lines, RBF600 fluid, and Ferodo 2500s currently (along with 2013 GT500 rear rotors) and pedal feel is pretty good but not as firm as my Focus RS was. I don't want mushy. I have driven a stock S550 PP1 and that pedal was way too touchy at the top of travel, making heel-n-toeing very jerky.

The PP1/2 brakes on S197 result in a longer and softer pedal through. There's more ability to modulate, but ultimately it doesn't have that touchy/tight feel that the S197 systems have to start. That said, they work phenomenally. I just had to do a number of things to be able to heel-toe appropriately (as the pedal throw gets real long as pads wear down (ultimately I bought an auto-blip because it let me shift and focus more on braking and the release of brakes than the janky pedal rearrangements I tried)
 
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Excellent info, cap'n! I remember reading about the travails of your braking issues now the you mention it. By your estimation and experience, what sort of pedal feel would you anticipate with 350 calipers and Boss master? I'm a big believer in more brakes is always better even though my car is 100% street driven (but sometimes at a very fast pace on back roads).
 

captdistraction

GrumpyRacer
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I have no idea. Its something I've thought about myself.

In the 350, the brakes are bliss: work great, incredible stopping power (helps having 295/305 wide tires too). It supposedly shares a master cylinder diameter with the boss. The booster/rod/pedal ratios are unknown along with the ABS programming and overall bias.

Per caliper, the surface areas are:
GTPP - 6108mm^2
GT350 - 6120mm^2


Its certainly worth a shot, if there were kits to use an 18" 380x36 rotor with it that cleared apex wheels, I'd likely consider running that caliper on my racecar. That said, I'm at the point where I have no real complaints outside a little knockback on the GTPP caliper, but I'm addressing that through anti-knockback springs and that's a function of racing tires + curb use more than anything else.
 
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Awesome, thank you. I am going to try to talk to FTBR for their impressions. I have spoken to a guy on another forum who says pedal feel is better than before but I want as much feedback as possible before biting the bullet.
 
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I am more than willing to be the guinea pig if you will pay for all of the parts! Hah I'll email FTBR tonight. I have a 2020 350R on order so I will get to sample GT350 brakes soon one way or another!
 
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From Bruce at FTBR:


The difference in the brake pedal feel will be negligible. You will notice the difference in the braking capacity a LOT more.



We hope that helps.



The FTBR Team
 
Honestly waste of money and weight. The 15" PP1 S550 setup does the job as well, lighter, for less money and fits 18" wheels for better track tire selection.
Steve do they fit all 18s or only certain offsets? I havent found a template i could try an measure with. I have an alcon front caliper so it kinda throws comparing the regular brembos to it out the door for me.
 

steveespo

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Steve do they fit all 18s or only certain offsets? I havent found a template i could try an measure with. I have an alcon front caliper so it kinda throws comparing the regular brembos to it out the door for me.
I know they fit 18" Apex wheels all sizes, Team Dynamics Wheels in ET +43 18 x10. Forgestar F14s and any Forgeline wheel for Mustang fitment. There may be others.
Steve
 

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