(Inexpensive) 964 front brake upgrade, would Bill V. approve?

[wjdunham]

I've read every thread on the subject of fitting larger calipers to G-body cars 10 times and I (think) I understand all the issues, of which there are many.
Here are my requirements:
Upgrade to 28mm front rotors
Keep the costs under control (this would mean no expensive machining of calipers and fancy adapters)
No brake pad overhang
Fit under a standard 911 offset 7" Fuchs 16" wheel (possibly will work under a 15")


All of the above constraints completely rule out any off-the-shelf solution as it's impossible to find a 28mm rotor with the proper dimensions that don't require caliper machining or expensive 930 calipers. One would think "Keep the costs under control" would rule out custom rotor/hat option, but no - Coleman Racing has a very reasonable 48 vane directional rotor blank that they will machine to the right dims for $152 per rotor quantity one, and Mittler Bros. will make a hat for ~$65 quantity one. So for about the price of decent 930 rotor one can get a custom solution. I haven't seen anyone using these in all of the threads I've read.

There are two other important constraints that need to be met:
1) The Coleman rotor has a minimum flange diameter of 6.1" which will effectively set the minimum rotor diameter. Things would be much simpler without this one, but that's the spec. they require.
2) While relocating the axial mounting holes on the ears of my caliper I would like to keep a minimum of 3/16" of "meat" on the ear. This effectively sets the maximum rotor diameter and the main reason why off-the-shelf rotors require conversion to a radial mount adapter.

The above two constraints make it very tight to design a rotor that will have enough clearance between the caliper and rotor hat (min. .125") and clearance between the outside of the rotor and the caliper body (min. .125") and not have any pad overhang. If my drawings are correct, it can be done though, and one can realize the larger thermal capacity of the 28mm rotor with inexpensive 964 calipers with minimal mods to the calipers, similar to what many have done on the rears using standard 930 rotors.

EDIT:
I removed the spec sheet that was on this page as it was not final and the dimensions changed. The specs. for the front custom rotors and hats can be found on page 3 of this thread now. Rear rotors are stock 930 rotors so no drawings required for those.

[Bill Verburg]

Originally Posted by wjdunham

I've read every thread on the subject of fitting larger calipers to G-body cars 10 times and I (think) I understand all the issues, of which there are many.
Here are my requirements:
Upgrade to 28mm front rotors
Keep the costs under control (this would mean no expensive machining of calipers and fancy adapters)
No brake pad overhang
Fit under a standard 911 offset 7" Fuchs 16" wheel (possibly will work under a 15")


All of the above constraints completely rule out any off-the-shelf solution as it's impossible to find a 28mm rotor with the proper dimensions that don't require caliper machining or expensive 930 calipers. One would think "Keep the costs under control" would rule out custom rotor/hat option, but no - Coleman Racing has a very reasonable 48 vane directional rotor blank that they will machine to the right dims for $152 per rotor quantity one, and Mittler Bros. will make a hat for ~$65 quantity one. So for about the price of decent 930 rotor one can get a custom solution. I haven't seen anyone using these in all of the threads I've read.

There are two other important constraints that need to be met:
1) The Coleman rotor has a minimum flange diameter of 6.1" which will effectively set the minimum rotor diameter. Things would be much simpler without this one, but that's the spec. they require.
2) While relocating the axial mounting holes on the ears of my caliper I would like to keep a minimum of 3/16" of "meat" on the ear. This effectively sets the maximum rotor diameter and the main reason why off-the-shelf rotors require conversion to a radial mount adapter.

The above two constraints make it very tight to design a rotor that will have enough clearance between the caliper and rotor hat (min. .125") and clearance between the outside of the rotor and the caliper body (min. .125") and not have any pad overhang. If my drawings are correct, it can be done though, and one can realize the larger thermal capacity of the 28mm rotor with inexpensive 964 calipers with minimal mods to the calipers, similar to what many have done on the rears using standard 930 rotors.

Below is the drawing I put together for both the hat and the rotor. Before I went ahead and spent any money, would love to hear from you guys whether I am crazy, have missed anything, or might this work.

Ist off, 965 front has a 322x32mm rotor, as does 993tt, the 965 is a 1 piece rotor and can't be used on a 911 because the o/s is all wrong, the 993tt is a 2 piece hat/annulus design and can be used, just unbolt the hat and bolt on a new flat hat.

The Colman rotor w/ a flat hat is fine as far as it goes, I'm sure that it can be made so as to bolt to a 911 hub, then the question is what caliper to use a 964 caliper is designed around a 28x299mm rotor, so the thickness is fine 290 is in the right ball park for diameter, the question then becomes does the caliper w/ stock axial mounting ears place the caliper in the right position relative to the rotor bolted to the 911 hub, I don't know. In back the 964 rear caliper can be modified to fit a 930 309x28 mm rotor by filling the stock holes and redrilling new ones to suit. Maybe this can be done maybe not.

trying to come up w/ a cheap well designed brake system that functions in all respects as well as or better than stock is a non trivial matter, you need to consider and address multiple issues

I'd start w/rotors, you need a solution for both front and rear
obvious choices are
stock 282x20 & 290x20 M, A or S front & M rear, works w/ 15, 16 17 0r 18
C3.2 282x24 & stock rear 290x20 wide M front and M rear, works w/ 15, 16, 17 or 18
C3.2 282x24 & 290x24 wide a front & wide M rear, w/ 15, 16, 17 or 18
930 304x32 & 309x28 930 f & r or modified 964 front and modified 964 rear or 993 front and modified 993 rear, w/ 15, 16, 17 or 18
993tt 322x32 front and modified 93RS r, 993RS calipers f & modified 993RS calipers rear works w/ 17 or 18

Some folks have used 996 or 996tt rotors and caliper but here the bias is too much some have used Boxster calipers but the available rotors are too thin and bias can be upset if not compensated for

If you use the above front Colman 28x290 and a 930 rear rotors w/ 964 or 993 calipers and 23.8mm m/c you will probably be ok, just not as ok as w/ 930 rotor under those calipers

[Trackrash]

Looks like the way to go, if you can pull it off. I am watching.....

Edit: how did Bill beat me to the punch?

[wjdunham]

I had a typo in my thread title - should be 964 and NOT 965 (corrected now). Thanks for all the feedback Bill. I was trying to stay as close to the 290mm x 28mm that the 964 front caliper was designed for. That caliper fits fine over the standard Carrera 282mm rotor, but without the benefit of the 28mm thickness. Can only push out radially so far before you run out of mounting ear. Definitely agree that 930 rotors are better, but also increase the cost substantially once you start having to buy adapters and machine the calipers.

I think the axial mount ears can be machined to place the caliper in the right spot with a 290mm rotor. I need to mount my caliper on the car to be sure, I've taken many measurements and it's tight but I think can be made to work.

Bill

Originally Posted by Bill Verburg

Ist off, 965 front has a 322x32mm rotor, as does 993tt, the 965 is a 1 piece rotor and can't be used on a 911 because the o/s is all wrong, the 993tt is a 2 piece hat/annulus design and can be used, just unbolt the hat and bolt on a new flat hat.

The Colman rotor w/ a flat hat is fine as far as it goes, I'm sure that it can be made so as to bolt to a 911 hub, then the question is what caliper to use a 964 caliper is designed around a 28x299mm rotor, so the thickness is fine 290 is in the right ball park for diameter, the question then becomes does the caliper w/ stock axial mounting ears place the caliper in the right position relative to the rotor bolted to the 911 hub, I don't know. In back the 964 rear caliper can be modified to fit a 930 309x28 mm rotor by filling the stock holes and redrilling new ones to suit. Maybe this can be done maybe not.

trying to come up w/ a cheap well designed brake system that functions in all respects as well as or better than stock is a non trivial matter, you need to consider and address multiple issues

I'd start w/rotors, you need a solution for both front and rear
obvious choices are
stock 282x20 & 290x20 M, A or S front & M rear, works w/ 15, 16 17 0r 18
C3.2 282x24 & stock rear 290x20 wide M front and M rear, works w/ 15, 16, 17 or 18
C3.2 282x24 & 290x24 wide a front & wide M rear, w/ 15, 16, 17 or 18
930 304x32 & 309x28 930 f & r or modified 964 front and modified 964 rear or 993 front and modified 993 rear, w/ 15, 16, 17 or 18
993tt 322x32 front and modified 93RS r, 993RS calipers f & modified 993RS calipers rear works w/ 17 or 18

Some folks have used 996 or 996tt rotors and caliper but here the bias is too much some have used Boxster calipers but the available rotors are too thin and bias can be upset if not compensated for

If you use the above front Colman 28x290 and a 930 rear rotors w/ 964 or 993 calipers and 23.8mm m/c you will probably be ok, just not as ok as w/ 930 rotor under those calipers

[JeffShoots]

Just wanted to say ...I like this Guy Bill

I’ve had so many brake questions from my race car to street car.

And Bill has always posted the best info in every search on the forum for brakes

Thank you

[wjdunham]

Originally Posted by JeffShoots

Just wanted to say ...I like this Guy Bill

I’ve had so many brake questions from my race car to street car.

And Bill has always posted the best info in every search on the forum for brakes

Thank you

Hence the title of my thread

[JeffShoots]

Originally Posted by wjdunham

Hence the title of my thread

And I’m glad you made a thread with the question.
I was told to search /read and find the answer

But the more Threads to search the newer information will be there to find

[wjdunham]

If you haven't seen this thread yet, it has a wealth of information, pointers to many other threads on the topic.

The ultimate brake upgrade page.

[chrisbalich]

Originally Posted by Bill Verburg

If you use the above front Colman 28x290 and a 930 rear rotors w/ 964 or 993 calipers and 23.8mm m/c you will probably be ok, just not as ok as w/ 930 rotor under those calipers

How would this setup compare to stock SC with regards to weight?
2pc rotors should at least break even, if not be lighter.
I know the 964 calipers are lighter.

I'm excited to see this on the car and hear feedback.

[Bill Verburg]

Originally Posted by chrisbalich

How would this setup compare to stock SC with regards to weight?
2pc rotors should at least break even, if not be lighter.
I know the 964 calipers are lighter.

I'm excited to see this on the car and hear feedback.

W/ the 290x28 front rotor and a 309x28 930 rear rotor and 964 4 pistons f/r you get a useful increase in thermal performance and an increase in brake torque, its still more front biased than I prefer(again not dangerous, just throwing thermal potential away), if you used 993 rear calipers instead you get too much rear(this is dangerous) it would be really nice to get closer to a 300mm front rotor which would allow the use of the 993 rear and give you nice balance

Weight is not the issue even if you have the giant 993RS Big Reds, the relative torque loss from these things is tiny compared to that of wheels and more so tires.

[chrisbalich]

Originally Posted by Bill Verburg

W/ the 290x28 front rotor and a 309x28 930 rear rotor and 964 4 pistons f/r you get a useful increase in thermal performance and an increase in brake torque, its still more front biased than I prefer(again not dangerous, just throwing thermal potential away), if you used 993 rear calipers instead you get too much rear(this is dangerous) it would be really nice to get closer to a 300mm front rotor which would allow the use of the 993 rear and give you nice balance

Weight is not the issue even if you have the giant 993RS Big Reds, the relative torque loss from these things is tiny compared to that of wheels and more so tires.

I give up.

[Bli8]

Doesn't Pelican's Boxster kit recommends a Mercedes master cylinder that would make the front/rear bias more correct?

How does the OP's suggested setup compare to Stop Tech's 911 kit for $2300, less what you can get from selling your current calipers and rotors, if any?

[Bill Verburg]

Originally Posted by chrisbalich

I give up.

If it was easy everyone would do it and keep in mind that you are starting w/ a pretty high bar w/ any '69-83 911.

[Bill Verburg]

Originally Posted by Bli8

Doesn't Pelican's Boxster kit recommends a Mercedes master cylinder that would make the front/rear bias more correct?

How does the OP's suggested setup compare to Stop Tech's 911 kit for $2300, less what you can get from selling your current calipers and rotors, if any?

The m/c sizes deals first w/ adequate fluid volume and second w/ pedal feel

For $2300 I think you just get the fronts then you have to do the back, The front rotor used is a 228x28mm which is a great starting point, The rear uses a 3.2 C rear rotor w/ a Stoptech 4 piston caliper depending on piston sizes this cold be a good match for their front

[kbken62]

I've been reading and reading about a good setup that is not $4K. I'm sure glad you wrote this thread. Will be watching.

[Bli8]

Originally Posted by Bill Verburg

The m/c sizes deals first w/ adequate fluid volume and second w/ pedal feel

For $2300 I think you just get the fronts then you have to do the back, The front rotor used is a 228x28mm which is a great starting point, The rear uses a 3.2 C rear rotor w/ a Stoptech 4 piston caliper depending on piston sizes this cold be a good match for their front

Yeah I mentioned the price for the front as the OP was referring to the front only. Yeah it is not cheap, but neither is a set of used 930 calipers and the rest.

[wjdunham]

Just for reference, the total cost for all four wheels of my proposed setup is:
$450 for a complete set of 964 calipers (eBay or equivalent).
$300 for custom front rotors
$120 for custom hats
$200 for rear 930 rotors
$50 hardware
$150 23mm master cylinder
$1,270 Total

I will probably spend another $150 to get my calipers powder coated and may need some additional refresh (seals etc...)

I did find an off-the-shelf AP Racing rotor that is the right dimensions but cost is more than 2x the Coleman rotors.

[Bli8]

Originally Posted by wjdunham

Just for reference, the total cost of my proposed setup is:
$450 for a complete set of 964 calipers (eBay or equivalent).
$300 for custom front rotors
$120 for custom hats
$200 for rear 930 rotors
$50 hardware
$1,120 Total

I will probably spend another $150 to get my calipers powder coated and may need some additional refresh (seals etc...)

I did find an off-the-shelf AP Racing rotor that is the right dimensions but cost is more than 2x the Coleman rotors.

I just found an outfit online selling the Stoptech fronts for $1705 and maybe you can get another 5% off with a welcome coupon. Not sure if it is kosher to post a direct link so PM me for the link. With the price difference under $500, I'd lean toward the Stoptech as everything is new with a warranty and the confident of buying from an outfit that makes lots of kits and even supply to OEMs.

Below is what I was able to put in the shopping cart...

[wjdunham]

Another update - spoke with Coleman Racing this morning and they have rotor blanks not listed on their web site with much better dimensions for this project. I will post an updated drawing later, but they have a blank that supports a 32mm x 290mm size with a much smaller flange diameter, so designing a hat which is roughly same size as the fixed 282mm Carrera rotor will be possible. It is a 32 vane directional vs. the 48 vane I first looked at, $100 per rotor vs $150 for the 48 vane.

This will get me very close to a 930 rotor thermal mass for a LOT less $$$.

Bill

[wjdunham]

Does anyone have the bolt circle radius for a 3.2 Carrera front hub. Need to double check this dimension for the hat design.

Thanks!