Re: Boxster brakes for 4KQ to be done....

[Gary Erickson <erickson@teleport.com>]

Glen_Powell@ne.3com.com wrote:
 
> I must select a suitable rotor for this project. I guess an 11" rotor is as
> big as can be fitted, so this is a starting point.

What needs to be looked at are twofold:

a) will the Boxter caliper suitably mate up with a 279mm (11") rotor? 
It was designed for use with an approx. 310mm (12.25") rotor.  Hence the
reason that John Karasaki used the A8 rotor (which I believe was 308mm)
when he installed these brakes on his V8.

b) will the caliper _fit_ under a 15" wheel?  before this is taken too
far, somebody should do a dry fitting with a rotor and a caliper to see
if there's any chance in hell of this combo fitting inside a 15" wheel,
or if it's limited to those running 16" or larger wheels.

> If this is wrong and a
> larger rotor that is obtainable and will work please provide details on
> same.

I wouldn't expect to be able to use anything larger than a 11" rotor
under a 15" wheel.  Those people who have done the G60 conversion say
that there's just barely enough space for the rotor and caliper under a
15" wheel.  (And this jives with how the G60 brakes look under the 15"
wheels that are currently on my 200q.)

Follow the relationship between rotor, calipers, and wheel diameter:

The larger the rotor, the further out from center the caliper needs to
be mounted, and the larger the wheel diameter needs to be in order to
fit over the whole mess.

> Now I need help and advice to identify a rotor that has:
> 
> 1) the correct hub diamater for the 4KQ hubs for guaranteed perfect
> concentricity
> 2) the correct thickness to work with the Boxster calipers and available
> race pads for said calipers
> 3) the correct offset/hat
> 4) available as both an OEM piece (cheap) and also in high-performance
> versions, cross-drilled, etc. (OEM optional but
>      nice)
> 5) a 5-lug rotor that meets all of the above requirements is acceptable, it
> can the re-drilled for 4-lug and concentricity will be
>      guaranteed by virture of the correct hub diamater

I've been down this path once before, without much success.  The obvious
choice, the 11" rotor used on the 20V cars with the G60 brakes, has too
deep a hat and actually contacts the strut upright before it sits flat
on the hub.

I was unable to find any other rotors that might fit the bill and have
the 4x108 bolt pattern.  However, something may have become available
since I did my looking about this time last year.  I corresponded with
John Nelson of Novatechnik about his G60 kit for the 4kq/GT and he
informed me that he did have an 11" Ate Power Stop rotor (the funky
atom-grooved ones) with the 4x108 bolt pattern that fit, but (and I
quote) "The rotors used are proprietary and took me some time to come up
with, so forgive me if I dont give out any further info on them."

He was willing to tell me that his rotors had a different hat size then
the 5ktq rotors.  (Actually, I extrapolated this from his statement that
5ktq rotors redrilled for 4x108 wouldn't work with his kit.)  Which
leads me to believe that somewhere there might be an application that
would cross over since custom brackets will have to be made anyways. 
(Unless he's gone to the expense of having Ate produce custom rotors for
him, which I can't see them doing on such a small scale.)

Does anybody have any contacts to Ate or a distributor that might be
able to do a little research?

But, based on past experience, using a redrilled 5ktq rotor might be the
easiest and most economical way to go.  The rotors are cheap and known
to be available, and they should be the same width as the A8 rotors (I
think that's what I remember John K. telling me) so that would take care
of the rotor thickness issue mentioned in #2 above.

HTH!

-Gary

'84 4kq
'85 turbo GT coupe
'89 200q