Rear brake upgrade (again, lol), Or,how to get a vented rotor Options

[HalfMoon]

So I know this has been talked to death thousands of times and when I do a google search there's reems of information, but rather than spend the entire evening reading through many posts that really aren't relevant, I thought I would pose the question and see what turns up.
Recently I had a four wheel alignment and corner balance done by a really great and well known shop out my way (who are very familiar with track cars for my local track-Summit Point) and when I asked the primary mechanic today what things he might suggest for my sbc Sheridan standard wide-body conversion, he said upgrading my rear brakes would be pretty important for that track.
Soooo, yes there are lots of ways to go to be sure but I was wondering about retaining the standard rear 914 brake (and e-brake) but using the vented 911 SC rotor? Do I recall Eric made/makes a spacer for this or is/was that for converting 914 fronts to rears?
A lil confused this particular application.
I like the idea of retaining the stock 914 rear calipers if I can but I really want to go to vented rotor (as opposed to drilled).
Thoughts?

[Spoke]

I added spaced 914 rear calipers and 911 rear vented rotors cut down by Eric Shea. My progress thread has some info and pics on my upgrade.

You need a spacer between the rotor and the hub to properly space the rotor in the caliper.

One thing I ran into with the spacer is when the spacer is placed between the rotor and the hub, the rotor loses it's centering capability on the hub. In this case the little screw that holds the rotor is important to setting the rotor in the center of the hub.

Also the 911 rear rotor screw placement is not in the same place as the 914 hub. I had to drill and tap a new hole in the hub.


Spoke's Progress Thread

[HalfMoon]

I added spaced 914 rear calipers and 911 rear vented rotors cut down by Eric Shea. My progress thread has some info and pics on my upgrade.

You need a spacer between the rotor and the hub to properly space the rotor in the caliper.

One thing I ran into with the spacer is when the spacer is placed between the rotor and the hub, the rotor loses it's centering capability on the hub. In this case the little screw that holds the rotor is important to setting the rotor in the center of the hub.

Also the 911 rear rotor screw placement is not in the same place as the 914 hub. I had to drill and tap a new hole in the hub.


Spoke's Progress Thread

Exactly what I was hoping for!
You wouldn't remember what year the rotors are from would you?

[Spoke]

Don't know why year the rotors are. I bought them from Eric and he cut them down to fit the 914 caliper. PM Eric about your questions.

[HalfMoon]

I added spaced 914 rear calipers and 911 rear vented rotors cut down by Eric Shea. My progress thread has some info and pics on my upgrade.

You need a spacer between the rotor and the hub to properly space the rotor in the caliper.

One thing I ran into with the spacer is when the spacer is placed between the rotor and the hub, the rotor loses it's centering capability on the hub. In this case the little screw that holds the rotor is important to setting the rotor in the center of the hub.

Also the 911 rear rotor screw placement is not in the same place as the 914 hub. I had to drill and tap a new hole in the hub.


Spoke's Progress Thread

Makes me wonder if a spacer between the caliper and the attachment point could be used to center it? This would retain the rotors "centering ability", no?

[HalfMoon]

Don't know why year the rotors are. I bought them from Eric and he cut them down to fit the 914 caliper. PM Eric about your questions.

Will do it!
Thanks again

[rgalla9146]

Certainly '69 to '73 and surely later but I can't remember when they changed.

[bdstone914]

Makes me wonder if a spacer between the caliper and the attachment point could be used to center it? This would retain the rotors "centering ability", no?
[/quote]

No. Rotors do not center themselves. The caliper can be spaced to center on the rotor if needed. You need the spacer between the caliper halves to allow the caliper to go around the rotor the thicker rotor. The caliper is in the correct position.
What is the use of the car that makes you think vented rears are needed? Doing a lot of repeated high speed braking? Or is this just something you want to do ? Does not hurt anything other then adding more unsprung weight in the rear. Or is this just something you want to do?
Yes a 69-73 911 rear rotor thatare 20mm thick will work.
What calipers and rotors are on the front ?
Or is this just something you want to do ?

[HalfMoon]

[quote name='bdstone914' date='Jun 29 2017, 11:51 PM' post='2501617']
Makes me wonder if a spacer between the caliper and the attachment point could be used to center it? This would retain the rotors "centering ability", no?
[/quote]

No. Rotors do not center themselves. The caliper can be spaced to center on the rotor if needed. You need the spacer between the caliper halves to allow the caliper to go around the rotor the thicker rotor. The caliper is in the correct position.
What is the use of the car that makes you think vented rears are needed? Doing a lot of repeated high speed braking? Or is this just something you want to do ? Does not hurt anything other then adding more unsprung weight in the rear. Or is this just something you want to do?
Yes a 69-73 911 rear rotor thatare 20mm thick will work.
What calipers and rotors are on the front ?
Or is this just something you want to do ?
[/quote]

911 SC calipers and rotors on the front.
On the advice of a local and well known mechanic that services alot of cars that use Summit Point Raceway it was suggested as an upgrade where repeated high speed braking will occur, not to mention the extra 250lbs I'm lugging around (sbc).
Good data the spacers (already using caliper spacers on the front of course) and the rotor years.
Ty

[HalfMoon]

Spec for the rest
Hankook Ventus V12 evo 225/50ZR16 front
Koni red front
Stock sway bar front
Turbo tie rods
911 SC rotors and calipers front
Stock torsion bars (soon to be changed to 21's)

Fuzion ZRi 245/45R16 rear
Koni yellow with perches
220 springs
Stock sway bar rear
Boxed trailing arms
Rear chassis stiffening kit.

Porterfield all.

[Spoke]

Here's a thread I started to ask vented rear rotor questions.

Rear Vented Rotor Questions

[HalfMoon]

Here's a thread I started to ask vented rear rotor questions.

Rear Vented Rotor Questions

Great thread! Exactly the info I needed :-)
TY

[Mark Henry]

I used spacers (flat washers) under my V-calipers it centered just fine. 2mm cut, 4mm total off the OD of the rotor. My rotors were off of a '75 911.
Only PITA is the cast rotor is hard as hell to cut, at least on lightly used rotors, but still do-able.

Eric did you ever come up with a hardware solution?
Mine came from you with no pins or pad springs.

I've made pins, but it would be nice to have springs, even if I have to modify them a bit.

[mgphoto]

I v'ed my rears about 5 years ago, I used the dust shield bracket as the spacer.
Disk needs to be cut down by 4 mm or it will hit the caliper.
See my photo on the left.
Mike

[Mikey914]

The 6 vented calipers are always an option. I'll check to see if I have a set Eric did up for me.

[Chris914n6]

911 SC calipers and rotors on the front.
On the advice of a local and well known mechanic that services alot of cars that use Summit Point Raceway it was suggested as an upgrade where repeated high speed braking will occur, not to mention the extra 250lbs I'm lugging around (sbc).
Good data the spacers (already using caliper spacers on the front of course) and the rotor years.
Ty

You might want to go the 911 rear caliper route with that setup. You lose the built in parking brake but it's a better balance.

[Dave_Darling]

Ask the mechanic why he recommends upgraded rear brakes. Is there some specific thing that he feels should be remedied on your car at that track? Does the car need more rear brake bias, more rear brake effect, more rear brake heat dissipation, or something else?

--DD

[HalfMoon]

Ask the mechanic why he recommends upgraded rear brakes. Is there some specific thing that he feels should be remedied on your car at that track? Does the car need more rear brake bias, more rear brake effect, more rear brake heat dissipation, or something else?

--DD

Good question!
The main circuit at SP has only 10 turns but many high speed straights, the secondary circuit (one that's a bit slower but better for my level) has 27 turns!
I think my mechanic was concerned that my car having a sbc and carrying more weight (2380 dry) that I may experience some significant brake fade. On the main circuit there's plenty of run off but on the secondary there's walls.
As an aside, PO removed the valve.
Oh, corner weighted at 490 front both, 700 rear both.
I think the main concern is brake fading due to heat buildup on the stock solid rear rotor. This is a mechanic well known for his tuning to this track and he reports, 914's that are well modified have experienced this problem at SP.
I guess I'm wondering if a standard vented, drilled vented, or cross drilled vented is what I want to do. I hear drilled vented rotors have been known to spider crack with alot of oscillations in heat.
As for the caliper, I'd like to keep the stock teener rears if I can. I guess that'll be a wait and see thing.

[HalfMoon]

The 6 vented calipers are always an option. I'll check to see if I have a set Eric did up for me.

I didn't see rear vented 6 rotors at PMB's site?
Confused.

[Dave_Darling]

Cross-drilled are a waste of time for almost all cars. (Rotors with cast-in holes can be OK, and drilled can be OK for a track car that gets torn down and minutely inspected every event, but very much not for a street car.)

To manage heat problems, ducting air to the rotor and caliper can help immensely. I remember Chuck Forge had clamshells around the whole rotor that were fed by an air scoop pushing high-pressure cold air onto them. You couldn't see any of the rotor.

--DD

--DD