Track experience with S550 6 Piston?

Discussion in 'Boss 302 and S197 Technical Forum' started by qtipconnoisseur, Mar 3, 2019.

  1. qtipconnoisseur

    qtipconnoisseur TMO Intermediate

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    Thanks for the info! Yet another testament to the cost-effectiveness of the s550 calipers. I've heard the the stock boss booster/master paired with the s550 calipers gives slightly more modulation than stock. I'm a big fan of the stock brake feel (with ss lines, good pads) so a similar feel is a positive in my book. One worry I have with the s550 calipers is the reports of knockback, which doesn't seem to be entirely cured by a 2pc rotor, which also could drive up the cost of the s550 option. I could go for those calipers and cheapo 1pc rotors if the knockback isn't too bad.

    That's hilarious and awesome that your "take-off" pads are still good. Another point for race brakes. Feels like I'm ping-ponging back and forth between these brake options.
     
  2. captdistraction

    captdistraction I am the breaker of things

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    I should state that I still have the anti rattle clips in my girodiscs. When I replace the rings I’ll remove those and that should settle the knockback some more. Also I tend to see it most on fresh Hoosiers, where the grip levels are highest and only on particular courses. There’s other options like anti-knockback springs but I’ve not been bothered enough to explore.


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  3. Coz

    Coz TMO Race

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    Is this knockback strictly caused by the 2-pc rotor or also by the caliper.

    Basically, would using solid 13/14 GT-500 rotors and the S550 Brembos still result in knockback?
     
  4. Fabman

    Fabman Project: "Frankenstang"

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    Who's taking them off?...I'm gonna run thee bitches till they're toast!
     
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  5. Fabman

    Fabman Project: "Frankenstang"

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    I have no direct experience with the S550 calipers but I've heard good things.
    Had I not come across these Brembo Race brakes I would have gone with the s550 setup.
    From a cost standpoint it's almost a no brainer.
     
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  6. JAJ

    JAJ TMO Race

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    Those pads were awesome.

    Knockback happens when you have a fixed caliper (not the base model floaters) and there's flex or wheel bearing play at the wheel hub. Movement at the hub allows the rotor to move off-centre in the caliper, pushing the pistons back into their bores. If you have floating calipers, it doesn't matter what the hub does - the calipers move with the rotor and there's no knockback.

    This is important because the base Mustangs have floating front calipers, and fixed calipers are available as an upgrade (sport packages, etc). Even though these cars have become more capable over the years, it appears that Ford hasn't stiffened up the front hubs to control knockback. At least they didn't until they started making Mustangs with high lateral G capability that were likely to actually spend time at the track.

    The GT350 has a massive forged aluminum front knuckle with a bolt-on hub borrowed from the rear axle of an SUV, rather than the simpler forged iron knuckle with a threaded spindle used on the rest of the Mustang S197 or S550 models. The GT350 brakes have the best feel of any of the Mustangs I've driven and you don't get that unless the whole assembly is super-rigid. I'm speculating here, but I think Ford changed the knuckle and bearing assembly to get knockback under control. They had other reasons too, but I'm sure that making the whole thing stiffer was a major goal.

    So, if you're trying to control knockback on a Boss 302, your best bet is to change the front wheel bearings regularly and make sure that the spindle isn't worn and that the hub nut is properly torqued.
     
  7. VoodooBoss

    VoodooBoss Rick Moderator

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    @BigTaco Those calipers look similar to the ones on the GT350 and Porsche 911's.
     
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  8. qtipconnoisseur

    qtipconnoisseur TMO Intermediate

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    Hmm I knew about how the hub affects knockback, and to treat them as consumable on our cars, but not why. I had just assumed I was learning about another wear item for all cars that see some track time. I hadn't even considered that they weren't designed to handle extended high grip levels. Thank you for that information. Now wishing we could somehow retrofit beefier hubs on the s197s!
     

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