993 Calipers on 930

[cole930]

Guys,

I'm getting ready to upgrade brakes on my 80 930. I need to know the
mounting hole spacing on a rear 993 caliper. I know the 930 trailing arm is
3.5" but I don't know the hole spacing on the rear calipers. I'm starting to
build a fixture to redrill the rear caliper mounting holes and my calipers are
somwhere between here and East Jesus. Would appreciate any help I can
get so I can get this done this weekend.

THANKS !!!
Cole

[DUK]

The ultimate brake upgrade page.

It's in here somewhere.

[Bill Verburg]

Originally Posted by cole930

Guys,

I'm getting ready to upgrade brakes on my 80 930. I need to know the
mounting hole spacing on a rear 993 caliper. I know the 930 trailing arm is
3.5" but I don't know the hole spacing on the rear calipers

I'm very confused as to why you would do this. The 993 rear caliper can be use w/ a stock 930 rear rotor but why?, the 930 rear caliper uses the same pad and on the same rotor you get nothing but extra work to install it.

[cole930]

Bill,

First I would like to tell you how very much I appreciate the knowledge
you have been kind enough to share with all of us on the forum. You
exemplify the true spirit of the forum and the marque we all love.
Don't mean to confuse you but there is a method to my madness. I'm 65
and in the last 2 years have had 6-8 heart attacks, 3 heart operations and
then I got cancer; I've had 2 cancer operations and just finished 4 months
of Chemo. next month I have cancer operations 3,4,and 5. I'm sitting
with the insurance co pay on $740,000 in medical expenses not counting
the cost of next months fun..
I can't take committed money from the household to get the "Old One"
back together and I just want to thrash her again before this crap
kills me. So I stole a great set of 993 brakes and then sold my 930 brakes
for enough to buy the 993 brakes and finish the "Old One".
I understand your seeing no advantage to the brake swap but I promise
you when I take that ride you'll see me grinning all the way from Indiana.
By the way do you know the mounting hole spacing on 993 rear
calipers ?

THANKS !!!
Cole

[Rory Mckenna]

Good luck Cole!!!! i hope the operations are successful. I also hope you get to feel the power of a 930 again soon!

[Bill Verburg]

Originally Posted by cole930

Bill,
By the way do you know the mounting hole spacing on 993 rear
calipers ?

THANKS !!!
Cole

I wish you luck

the 993 rear caliper has ~97mm spacing. slightly more than 3", I don't believe that there is enough meat to get a 3.5" space, so you will likrly need to machine the axial mount ears and redrill the caliper to accept radial mounts


This one has been drilled for 3" mounts


you will also need to be concerned about radial placement so that the entire pads contacts the rotor.


here is one in the SC/Carrera leading mount position on a 930 rotor, yours will end up in the trailing position unless you can utilize the leading mounts.

[cole930]

Bill,

With a 993 hole spacing of 97mm we are talking 3.8218 in. the strut spacing is 3.5 in. or
88.999 mm. This means the hole centers must be moved inboard a total of .321 in. or 8.153
mm so each hole center moves inboard .1605 in. or 4.076 mm. Your pic. of the 993 caliper
with the 3.0 center to center spacing works because the hole centers are also moved up to
accomodate the larger rotor dia.which creates more flange surface to work with.
Am I looking at this correctly?

Cole

[cole930]

Rory,

Thank you that was kind of you but don't worry about the old guy I'll out last them if
nothing else and if I died in the next ten seconds I assure you I didn't miss a da-- thing while
I was here.

Cole

[Bill Verburg]

Originally Posted by cole930

Bill,

With a 993 hole spacing of 97mm we are talking 3.8218 in. the strut spacing is 3.5 in. or
88.999 mm. This means the hole centers must be moved inboard a total of .321 in. or 8.153
mm so each hole center moves inboard .1605 in. or 4.076 mm. Your pic. of the 993 caliper
with the 3.0 center to center spacing works because the hole centers are also moved up to
accomodate the larger rotor dia.which creates more flange surface to work with.
Am I looking at this correctly?

Cole

Sorrey, I should have looked it up instead of writing from memory.

I have 94mm, but will measure again today to be sure.

[930LDR]

Originally Posted by cole930

Rory,

Thank you that was kind of you but don't worry about the old guy I'll out last them if
nothing else and if I died in the next ten seconds I assure you I didn't miss a da-- thing while
I was here.

Cole

That's a great place to be... satisfied and at peace. Good luck over the coming months.

[Bill Verburg]

Just remeasured, 94mm

[cole930]

Bill,

FYI to mount a 993 rear caliper to 930 trailing arm the mounting hole
centerlines need to be moved inboard 2.588 mm. I will look at radial
positioning to see if any modification is needed.

THANKS FOR YOUR HELP !!!!!
Cole

[sc]

Cole930,

Good luck with your health issues!

For your rear caliper issue, you may want to consider selling the 993 rears and looking for a set of 965 turbo rears instead.

Not only will you need to modify the bolt spacing, but you will also need to modify the throat where the pads fit and shave the pads themselves since the 930 rotor is wider that a 993 rotor.

A 965 rotor has the same width as a 930, so the only modification would be just to the bolt holes.

I just upgraded my 911sc to turbo brakes to with 930 rotors front and rear with 993 front calipers and 965 rear calipers. I was lucky to sell my 993 rear calipers for the same price I paid for a set of 965 calipers.

FYI-965 rear calipers may be hard to find, but well worth not going through the extra effort of shaving the pads everytime you need to change them.
-sc

[Bill Verburg]

Originally Posted by cole930

Bill,

FYI to mount a 993 rear caliper to 930 trailing arm the mounting hole
centerlines need to be moved inboard 2.588 mm. I will look at radial
positioning to see if any modification is needed.

THANKS FOR YOUR HELP !!!!!
Cole

That's correct, so I guess that there is going to be enough meat. To mount them on the 3" SC arms the holes move 8.9mm each.

As you can see from the caliper modified for SC arm the holes also move radially a tad. I have no idea what the readial movement for the 3.5" 930 trailing mounts would be.

[Bill Verburg]

Originally Posted by sc

Cole930,

Good luck with your health issues!

For your rear caliper issue, you may want to consider selling the 993 rears and looking for a set of 965 turbo rears instead.

Not only will you need to modify the bolt spacing, but you will also need to modify the throat where the pads fit and shave the pads themselves since the 930 rotor is wider that a 993 rotor.

A 965 rotor has the same width as a 930, so the only modification would be just to the bolt holes.

I just upgraded my 911sc to turbo brakes to with 930 rotors front and rear with 993 front calipers and 965 rear calipers. I was lucky to sell my 993 rear calipers for the same price I paid for a set of 965 calipers.

FYI-965 rear calipers may be hard to find, but well worth not going through the extra effort of shaving the pads everytime you need to change them.
-sc

That's correct and something that I have been recommending since ~ '95. The problem is used 965 rears are just not available often enough.

[cole930]

SC,

Thanks for the input. 993 calipers on the rear is beginning to look like they
could easily become a persons life's work. The biggest problem seems to be
the 930 trailing arms. Every upgrade I find seems to be for SC's and there is
nothing out there for a 930 rear upgrades.

THANKS !!!
Cole

[JeremyD]

I've seen some people move the 930 fronts to the rear and put a 993 or S4 on the front of their 930. Not sure if that is ideal - but I have seen a few 930's set up that way.

[cole930]

Bill,

Can you give me any suggestions on alternative rear caliper upgrades that
have been done on a 930? It's time to consider a plan B.

THANKS !!!
Cole

[Bill Verburg]

Originally Posted by cole930

SC,

Thanks for the input. 993 calipers on the rear is beginning to look like they
could easily become a persons life's work. The biggest problem seems to be
the 930 trailing arms. Every upgrade I find seems to be for SC's and there is
nothing out there for a 930 rear upgrades.

THANKS !!!
Cole

that's because the oem 930s were pretty darn good to start w/

The high hp turbo guys go to 993RS or 996GT3 brakes w/ 322 to 360mm rotors

[Bill Verburg]

Originally Posted by cole930

Bill,

Can you give me any suggestions on alternative rear caliper upgrades that
have been done on a 930? It's time to consider a plan B.

THANKS !!!
Cole

I honestly think that the best thing for you to do is find some stock 930 rears.