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Thread: Brake rotor and caliper advice please.

  1. #1
    Retired dsm2002's Avatar
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    Brake rotor and caliper advice please.

    Looking at 300x32mm rotors on the front and 294x19 on the rear of a E30 with M3 struts and rear arms. A search of suitable calipers to match are R32 GTR fronts (29632 rotors) and R32 GTR/R33 GTST rears (29718). I have a 25mm master cylinder.

    I gather the R32 has 40.4mm 4 pistons and 38.182 and a 25.4 master cylinder stadard.

    With rotors more or less the same size, matched calipers and same size master, will this combo work?

  2. #2
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    Yup will work fine
    Depending on your pedal ratio
    And what master your using
    You might be able to tailor the 'feel' of the pedal by using a smaller master to feel less 'woody' or a larger one for more firmness
    Location Perth Western Australia

  3. #3
    Retired dsm2002's Avatar
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    BMW M/C options range from 22mm to 25mm. The stock pedal ratio is 4:1 I think or else I use the wilwood pedal box I've got which would be better anyway

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    Are going to be using a booster with this setup?

    A booster acts like a pedal ratio increaser.
    Quote Originally Posted by Lord_fahrquhar View Post
    The au put the fucking tunnel in with the bullbar. Even Chuck Norris respects the ability of the au coon.

  5. #5
    Retired dsm2002's Avatar
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    Okey dokey, fitting the front GTR calipers is causing problems. I original thought it an option because Jason Broadhurst used the GTST calipers on an E30 but the M3 spindles are clearly different. Bolting up one hole, the GTR caliper is too far out. It needs to be be moved in at least 20mm possibly more. Rotating the caliper, the mounting 'ears' fouls the caliper.

    I don't want to cut up the M3 struts at all. They are too rare.

    What other calipers suit 300x32 are there? Porsche Brembos for the 944 Turbo S, 928 S4, 968 M030 or 993 C2/C4 apparently. Anyone have a set?

    AP Racing Link in the US have one with 41.3/38.1mm pistons although they are on back order or Wilwood forged narrow Superlite 6R 6 piston with 1.62/1.12/1.12" pistons. APs will be at least $1800 and the Wilwoods about $1000-ish

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    I think all 928's had a 322x32 fronts?

    E38 750 334x32 front and 328x20 rear
    Evo 5-9?

    Other thing to look at is what pads are available for each. Caliper designed for 30mm rotor but with a 16mm pad thickness instead of 18mm on the thicker caliper.

    If looking at Radial mount new calipers;
    Alcon CRB332/32 4 Piston
    Stoptech ST42 Sport / ST43 Sport / STR43 Sport

    Whats the radial depth / annulus of the current rotors?

  7. #7
    Retired dsm2002's Avatar
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    Thanks I'll look at those. The rotors are 298.5mm OD with a 213.7mm ID.

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    Ok the GTR calipers wouldnt have worked, the Annulus on those was 61mm, those dimension will give you 42.4mm - Most of the other will be the same I'm guessing.

    If going new, Stoptech ST42 Sport - Their product listings say accommodates a 32mm, but part listing only gives part numbers to 28mm (#372.V25.6054 is trailing 4 piston front with 38mm and 40mm leading and trailing pistons) The 43 pad is 43mm so a bit over

    I'll try and source a 32mm part number

  9. #9
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    Stoptech ST42 #372.V35.7171/2 38mm leading 40mm trailing pistons , forged. on 120mm centre radial mount. Apporx $790 per caliper landed

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