964 caliper adapters

[speedman]

Can anyone tell my the reason for machining off the axial mounting and installing a radial mounting adapter that mounts the caliper back to an axial mount. I see that the method used byVCI moves the caliper further out on the diameter so you can us a larger rotor, but is this the only reason

[Todd Simpson]

The VCI rotors are not any bigger than the stock 964 rotors, they are very similar in diameter and the same width as stock 964.

The reason for this is the 964 rotors will not bolt on to the early cars, so VCI adapted the 944T/Carrera rotors.

To answer your question on WHY, the other option for adapting these calipers is fill and drill and I suspect VCI doesn't want to do it that way. The 964 spacing is 3.75" front and rear while the early cars is 3.5" front and 3" rear.

[JeremyD]

993 calipers are a better option on either a wilwood or rennsport (steve weiner) machined rotor.

965 rear caliper on 930 rotors.

If you are just going for the "look" then probably the TRE adapters with boxster calipers would work better. There is a reason the 964/944turbo calipers can be picked up for a song.

[KTL]

The reason VCI does is the way they do is because they use a rotor with a different offset than the typical flat/zero offset rotor that a 911 requires. The offset of the caliper's mounting ears does not line up with the rotor, even if they simply filled and redrilled the mounting holes.

Note that VCI uses a 1986 951/944 Turbo rotor and only 1986. That's because this rotor was only used in 1986 by Porsche- later 87-up 951 rotors won't work because they have a different offset which is even higher like the aforementioned 964 rotors by Todd. This '86 951rotor has only slight additional inboard offset on it as compared to the stock SC or Carrera rotor, so they put an axle spindle spacer in place to shift hub & rotor assembly outward away from the A-arm ball joint location. W/out this spacer the rotor will rub on the ball joint location (still does a little bit even with the spacer).

Reason the 993 calipers are a better option:

All you need to fit the caliper is the proper adapter since the caliper itself is already suited to be bolted to an adapter. Whereas the 964/951 calipers have to be modified to accept an adapter ($550/pair from VCI)

They're better suited to bigger rotors. 993 is already set up to handle a larger diameter, 32mm wide rotor. 964 caliper can handle the bigger rotor but needs to be widened inside- it's designed to hold only a 28mm rotor width. That's also why VCI uses the '86 951 rotor = 28mm wide.

[speedman]

I have the calipers and I need the rotors. If the VCI rotors are not the best ones for the application can you tell me what rotor would work better

[KTL]

The Wilwood HD rotor 160-3870 and 160-3871 (they are directional, so there's a left & right part no.) will work with the small calipers. But you'll have to do some measuring to get the depth and offset of the caliper adapter correct. A simple 1/4" thick flat hat is all you need for this rotor. And again, you'll have to widen the inside of the caliper to fit the Wilwood.

There's other rotors that'll drop right in the smaller Brembo. Brembo and AP Racing make 28mm thk rotors that'll fit, you make the rotor hat. Search their catalogs to see the choices

28mm Thick

Open your wallet though...... Brembo & AP are SPENDY stuff!

Wilwood used to make a 28mm rotor but if I recall correctly, the face wasn't tall enough to span the entire pad height of the small Brembo's "345" pad size. Other companies like Coleman, Race Technologies, US Brake will make a rotor to your spec. That too is not cheap.

All that being said, that's why the '86 951 rotor is a nice choice from VCI- fits good, no custom rotor hat required, and provides some extra torque + thermal mass due to it's larger size. They're $90 each and all you need to fit them is a pair of their 5mm ring spacers for the spindle. The kicker is the $550 required to adapt the calipers...... That's really the problem, in that the small Brembos are not really cost effective to adaptation. The later calipers like the Boxster/996 monobloc or 993/928/964 Turbo are already set up to be bolted to adapters, so that's what makes them easier to implement- no major caliper modification or machining needed. So what does that tell you? If you don't like the '86 951 rotor, try the other Brembos or choose another caliper brand. Brembo isn't the only choice when it comes to calipers. Wilwood, AP, Alcon, Performance Friction.... However those last three are pretty expensive. Wilwood makes some nice calipers at a decent price point. They have mounting ears in place, all you have to do is drill them at the appropriate height for your rotor choice.

More than you asked for, but it's not as easy as it looks.......