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Thread: Aftermarket calipers and rotor size

  1. #21

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    I will be very interested to hear what the solution is when you get it fixed

  2. #22
    Need Input Cozzm0's Avatar
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    I went with A32 rears because the park brake on the N15 SSS Sucks balls and the A32 has a longer lever to get more leverage so it works better with the same effort.

  3. #23
    Ruddigger's Avatar
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    Quote Originally Posted by Cozzm0 View Post
    I went with A32 rears because the park brake on the N15 SSS Sucks balls and the A32 has a longer lever to get more leverage so it works better with the same effort.

    Yer yer that what i was going to say

  4. #24

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    If you where going to go the two pots how would you solve the hand brake issue?

  5. #25
    Need Input Cozzm0's Avatar
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    Quote Originally Posted by cav21 View Post
    If you where going to go the two pots how would you solve the hand brake issue?
    Drum handbrake retrofit.

  6. #26
    Administrator Spectrix's Avatar
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    Quote Originally Posted by Cozzm0 View Post
    I went with A32 rears because the park brake on the N15 SSS Sucks balls and the A32 has a longer lever to get more leverage so it works better with the same effort.
    I used the A32 rear caliper bracket & handbrake arm along with redrilled A32 278mm rotors. I didn't swap the caliper body itself as it's identical and my originals are in good condition.
    The handbrake is better, but I'd still call it mediocre compared to most drum/disc combos like the 2 pots. I've learnt to just compress the foot brake hard as I'm pulling the handbrake on.



    Quote Originally Posted by Boosted VLAD View Post
    Spectrix,

    I have an N14 with:
    N16 front hubs
    310mm R34GTT brakes machined down to 302mm
    Gti-r rear brakes
    Gti-r master cylinder

    ...the main thing I'm trying it get at is that this setup is very unbalanced...

    Hey Vlad, something worth checking on your setup is that those rear brakes are functioning properly.
    Pistons in good condition,
    Rubber seal intact
    Rear lines properly bled
    Slider pins well greased and not binding, etc.

    I would check that before spending a lot of money changing components.

  7. #27
    Boosted VLAD's Avatar
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    Everything is spot on Spectrix

    We ran the numbers through a brake force calculator and what we found was shocking,
    Stock brake force distribution is around 60% front, 40% rear

    With the multiple pistons on the front and larger diameter the brake bias is 80/20 !!!!! Yes 80% front, 20% rear

    In my opinion anything over a 5% shift reduces braking efficiency significantly, this is a lot more than that

    Now you combine that with a car that has next to no suspension travel and is stiff as a rock and no wonder it has issues,

    I'll be upgrading the rears soon, a friend of mine with a race car just had the exact same issue and he was only using 288mm fronts and he fixed his by upgrading the back brakes to skyline twin pots
    Last edited by Boosted VLAD; 29-12-2015 at 11:50 PM.

  8. #28

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    Not sure what's been covered or not as I was reading on my phone and probably missed stuff, but here goes:

    1) Vlad definitely fades up the mountain; first time it happened he was running with me. Rotors turned blue and I told him they'd been overheated.

    2) stock brake bias for an N15 setup is ~61/39. Rough calculations on Vlad's setup puts it at over 80/20, probably closer to 85/15. When he brakes he's experiencing rear end lift which is eliminating traction and forcing the bias even more toward the front than it is statically. This is why the rear gets so happy under braking, especially in corners.

    Normally I would agree with lift-off oversteer as his main problem in corners, and it likely contributes somewhat; however, he experiences the same thing to a lesser extent even braking in a straight line. This is because of the rear end lift under braking due to the massive imbalance in brake bias.

    3) gas between pad and rotor is fade, and the pedal should go soft during fade, not hard (in my experience).

    4) it's not just Vlad's opinion that any shift in bias greater than 5% is detrimental to braking performance. That's shared by most sources I've come across in regards to this topic. Normally I'd provide references but I don't have the luxury to do so at the moment.

    I'm sure there was more I wanted to add but I forgot.

    Fun!
    Last edited by Bengineering; 03-12-2015 at 04:23 PM. Reason: Added #4

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  10. #29
    SSS_Hoon's Avatar
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    Spectrix, so u used the stock n14 rear calipers with a32 rotors?

    Hrmm interesting.

  11. #30
    Need Input Cozzm0's Avatar
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    Quote Originally Posted by SSS_Hoon View Post
    Spectrix, so u used the stock n14 rear calipers with a32 rotors?

    Hrmm interesting.
    Spectrix has an N15.

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    SSS_Hoon (03-12-2015)

  13. #31
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    ^ ok nevermind

  14. #32
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    SSS_Hoon,
    On the rear brake upgrade thread I've explained how you can do the maxima rear brake upgrade on an N14

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