In the process of converting to 5 lug and also rear vented rotors, there appears to be two ways to go about it. Both have been explored and written about by Eric Shea over the years. (Ya, I've done a lot of searching and reading)

One is the usage of a late model 914 rear caliper with spacers placed in the body, to get the needed clearance for the vented rotor. (as I read it; a late model ATE caliper is used and not a rare 914/6 caliper) A spacer is required between the brake rotor and hub (moving the rotor and wheel outward). The rotor (911SC) has to have it's diameter shaved down 4mm) The parking brake cable just hooks up as stock.

The other option is to use the "M" caliper from a 911 and also the parking brake assembly. Mounting the parking brake assembly requires grinding and welding on the housing. Hooking up the parking brake cable requires fabrication, but is possible (and can be found by searching this site).

Now I can think of plus and minus points for both, but I'd like to hear from others.

Wes Vann

Eric is on vacation....

A third option is to install a second small caliper like the Carrera GT.....%^B.....

Wilwood has nice units for a good price.

Wilwood

Or simply put it in gear and/or use a wheel chock. I did that for years....I still find myself reaching behind my seat out of habit looking for that collapsible chock...

other vendors are Marty at MSDS and Renegade...

I use V caliper because Martys was not available at the time. The 911 ebrake is good but will add a "little" weight if that matters as will the spot calipers.

Dang, who said he could go??

Mikez; The question doesn't really have anything to do with the parking brake aspect, due to the fact it can be solved using either caliper.

My guess (and that's all it is at this point) is that the "M" caliper would have a larger bore, resulting in better braking (Ya, I know you have to balance it with what you have in the front).

With the "V", all you are getting is ease of installation and vented rotors (which until heat becomes an issue, doesn't add in braking). (plus the negative that adding a spacer in the caliper will increase it's flex, basic physics)

Wes

OK...braking not parking brake is the issue....unless you are racing and need huge brakes with heat dissipation, the non-vented rotor is fine...you can slot them for more grabbing power....but due to the brake bias....most of your braking comes from your front brakes.

Shaving an SC rotor down is easy the first time, a PITA the next.....you booger up one because a pad takes a dump...you don't have a rotor sitting around to throw on collectiong dust and you need to wait for the machine shop to open up....BTDT.

Mike;

What are you running, and why that particular combination?

(and I agree that vented rear rotors are not really "needed", but since I'm doing the 5 lug conversion, would "like" to do them)

Wes

On which car???

I'm using my experience based on shaving rotors on more than a few combinations....they always tend to take a shit when a replacement is needed and I have no access to a machine shop.....having one already done then means it will never happen and I have a rotor that only fits that application and I keep tripping over it until I toss it then need it that next weekend....

I have an SC front end and my take is the same as you.
The "spaced" solution is relatively easy, but no real gain. The rear M calipers are better.
I bought the calipers and rotors (cheap) and am looking for the parking brake setup. Meanwhile, I'm running stock rear, no proportioning valve, trying to determine if I realy need it. I'm not convinced yet for a street application.
Hopefully someone will make an easy parking brake solution - I live on a hill.

I don't know who developed it first, but I have been selling kits for V-calipers for over twenty years. I've got one set ready to go on a friends car as soon as he brings it to me. It certainly adds a little extra weight, and takes a bit more power to spin up. However, most 911's came with vented rotors front and rear, so if you have more than 120 HP, it probably is a good idea to think about the extra cooling the vented rotor provides. I don't think that an emergency brake is optional, and I believe that most motor vehicle authorities and insurance companies agree. It is nice to have bigger pistons and bigger pads in the rear to complement the vented rotors, however 914/6 calipers are very pricey, and the 911 calipers require an emergency brake solution. Most people find that the 914/4 caliper is adequate in moderate HP vehicles, especially if the proportioning valve is replaced or readjusted.

Notice I refer to the emergency brake, it doubles as a parking brake but that is just a bonus.

Here is a link to a page showing various solutions to the parking brake hook-up when using the "M" caliper;

link to 911 parking brake hook-up

I personally like what Larry Hubby did, as shown in page two.

Wes

Other road (high)


Use the stock 914 calipers with whatever V spacer kit you desire in 14mm

Use Carrera rotors and late Carrera hubs with a bearing spacer while retaining the stock 914 bearing.

Use Carrera axles (100mm)

Bulletproof! No turning rotors needed.

Bump, since Eric's back from vacation.

Wes

I feel the Carrera rotors are heavy and overkill for this application. The Carrera axle shafts will be about 19mm short unless you are using PMS adapters. Also 14mm spacers are huge and require about $3,713.00 worth of custom 12.9 fasteners (rough guess)

The simple advantage to a V-Caliper is, it allows you to use a (milled) 911 vented rear rotor on your car without any custom handbrake solutions. These solutions can get expensive quick. With a V-Caliper or a V-kit you'll be in it for the calipers/kit and the cost of the rotors. You use your very same handbrake cables and bolt them up. Your rear rotors should last quite a long time in this configuration as well.

I don't know of any flex issues with these. Rear M-Calipers have the 10mm spacers, rear Carrera calipers have 14mm spacers. From M-Calipers have 7mm spacers...

Basically, this is probably the cleanest and most cost effective ways to add a vented rotor.

Eric;

OK, I want to do the rear "M" caliper swap. Could you please outline (or verify) what year 911's I need to source the parts from.

It seems like the parking brake assembly has to come from a 69-71 911 (which would have a steel trailing arm) if I want it to be a direct bolt-up to the 914 arm (after grinding for clearance). I can use 72 and latter (which would come off of an aluminum trailing arm) if I was willing to open up the spacing of the attaching bolts.

It seems like everybody is talking about 911SC rotors, but from what years?

What year rear "M" calipers do I want to use?

In one of your posts, you talk about longer bolts to attach the calipers and also 5mm washers (spacers). Is this something you have in stock?

Wes Vann

You're on a roll so far.



74 and later had the larger bearings and AL arms.



Simple 911 rear rotors from 1970 through 1983 which included all the SC years (probably why people call them SC rotors)



The later the better as they did away with the knock-back mechanism and they had the cupped pistons for better cooling (more surface area at least). Make sure they're rear M-Calipers BTW. They're all fine but, if you're looking look for 76 and later (up to 83).



Lowe's item. Get the wavey-washers there as well. Get a handful of washers for spacers as well.

Son of a...! That's gonna leave a mark.

Jeff, I think he was talking about your custom ARP bolts.

Wes

Are there any tricks to ID'ing 76-83 rear M calipers? (I know that the 3" bolt spacing is a given)

That's assuming I can't take them apart to verify the shape of the piston.

If somebody has an "M" caliper, is the thickness of the spacer between the two halves a quick give-away as to if it was a front or rear caliper. (rear having a 10mm spacer, front having a 7mm spacer, per earlier quote)

Is there any advantage (or is it even possible) to use a front M caliper on the rear, after swapping spacers.

Wes

Maybe Jon Von Bovey can weigh in with a picture of his. I saw them in a thread here recently somewhere?? You don't have to take them apart to verify the shape of the piston, you can see it by simply looking at the piston. It is cupped or dished out in the center. One other thing you'll notice about the later calipers is the 10mm cast spacer has sharp corners that better follow the profile of the caliper. Early models were machined and rounded on the corners (see the #11 restoration thread in the Classics forum)

(found the picture)





Yes however; why they are both called M-Calipers is beside me. They are two different animals. Fronts have 48mm pistons. Rears have 38mm pistons. Fronts have 7mm spacers. Rears have 10mm spacers. Fronts have M8 fasteners with 13mm nuts and R8 Ribe heads. Rears have M7 fasteners with R6 heads and 11mm nuts. Fronts have a side fluid inlet. Rears have an end fluid inlet. The casting molds and the overall shape and size are totally different. The rear M-Caliper is almost identical to the early 914 front caliper. Same "basic" casting mold with a different fluid inlet and a smaller bore for the pistons.



Well...48mm pistons in the rear? Huge bias issue. The front M-Caliper nose would have to be shaved as well. The hat of the rear rotor gets in the way and rubs on the caliper. Can it be done? Yes. I know of a -6 that has them on there now but... wow, what a bad match of calipers.