914-6 vented rear rotor, Zimmerman or any other cross reference Options

[914Sixer]

I was looking thru the 914-6 competion parts manual to check on vented rear caliper rotors insead of using spacers on hub or washers on the caliper. The part number for those is 901.352.041.12. So I called Porsche and they said they were available from Germany at $275 each.

Does anybody have a cross refference to Zimmerman rotors? So I could see if they are available at a much lower price? 901.352.041.14 is the standard 911 rear vented rotor from 69-on so I am guessing that the .12 makes these special.

Any comments? Thanks, Mark.

[Bleyseng]

hmmmm, I was just thinking about this the other day. I bet Dave Shepard knows at GPR parts what fits.

[Bleyseng]

Yep, I called Dave at GPR and he is sending me a set of drilled vented rotors that fit. Using the spaced 914/4 rear calipers, I might have to use a spacer to perfectly center them but they should be close.

I'll see in a few days.

Oh, they are $80 sumthing and change each (IMG:http://www.914world.com/bbs2/html/emoticons/piratenanner.gif)

[Mueller]

QUOTE (914Sixer @ Nov 2 2005, 06:13 PM)

I was looking thru the 914-6 competion parts manual to check on vented rear caliper rotors insead of using spacers on hub or washers on the caliper. The part number for those is 901.352.041.12. So I called Porsche and they said they were available from Germany at $275 each. Does anybody have a cross refference to Zimmerman rotors? So I could see if they are available at a much lower price? 901.352.041.14 is the standard 911 rear vented rotor from 69-on so I am guessing that the .12 makes these special. Any comments? Thanks, Mark.

so what caliper are you going to use?

I thought the stock /6 rear is solid...so a spacer or something non-stock sounds like it'll have to be used???

[davep]

The GT rotor has a different offset that users of the 911 rear vented rotor need spacers to compensate for.

When using a 914/4 spaced caliper, the 911 rear vented rotor needs to be turned down in diameter to have clearance. ( and just because it may fit when cold it may not work when hot.) There is no benefit to the larger diameter, so you might as well lose the weight and inertia.

[flesburg]

I was always under the impression that 914-6 rear rotors were solid, and that the calipers were (?) and fitted with emergency brakes similar to or the same as 914-4's. I did not know that a vented rear rotor was ever installed on a 914-6.

I gave up the emergency brake on my car years ago.

We use 914-6 solid rear rotors, and stock 914-4 front calipers with a little home made spacer to center the caliper around the rotor.

We are running late 930 rotors and calipers in the front, and a 23mm master cylinder, and can set bias so the front brakes lock just before the rears. We do not wear rear pads out as fast as front pads. They seem to work well.

I have thought about some fancier set up for the rear, but am not convinced that it would be anything other than bling bling.

We try to spend out money on things that will make the car lighter and/or faster.

[davep]

914/6 rotors are solid
914/6 GT rotors are vented

The faster you can go, the better your brakes have to be.
I have always upgraded my brakes first, then the engine.
Emergency brakes work great if you give them the attention they deserve.
The old adage ' use em or lose em ' applies here also.

[Mueller]

QUOTE (davep @ Nov 3 2005, 02:56 PM)

914/6 rotors are solid 914/6 GT rotors are vented

so how did the factory address the vented rear rotors?

was there a direct replacement caliper?

did they lose the parking brake and install a front caliper or a 911 rear caliper?

or did they resort to spacers/adapters?

[lapuwali]

QUOTE (flesburg @ Nov 3 2005, 01:44 PM)

I was always under the impression that 914-6 rear rotors were solid, and that the calipers were (?) and fitted with emergency brakes similar to or the same as 914-4's. I did not know that a vented rear rotor was ever installed on a 914-6. I gave up the emergency brake on my car years ago. We use 914-6 solid rear rotors, and stock 914-4 front calipers with a little home made spacer to center the caliper around the rotor. We are running late 930 rotors and calipers in the front, and a 23mm master cylinder, and can set bias so the front brakes lock just before the rears. We do not wear rear pads out as fast as front pads. They seem to work well. I have thought about some fancier set up for the rear, but am not convinced that it would be anything other than bling bling. We try to spend out money on things that will make the car lighter and/or faster.

The lower a car, the less weight transfer there is under braking. Especially on a car with a fairly low CG to start with, and a static rearward weight bias, the rear brakes do a lot more on the 914 than they do on many other cars. If you're not overheating your existing solid rear rotors, then there's no need to go to vented rotors. Certainly the factory felt the need to use them even on a 1900-ish lb 914 with under 200hp.

People love fitting front calipers with bigger pistons, so they need to fit rear calipers with bigger pistons to compensate, and thus lose their e-brakes. I don't know of anyone who's actually tried to use stock front and rear calipers with widening spacers for vented rotors. You'd keep the e-brake, and you'd probably be able to actually use an adjustable prop valve rather than a T.

[davep]

QUOTE (Mueller @ Nov 3 2005, 03:38 PM)

so how did the factory address the vented rear rotors? was there a direct replacement caliper? did they lose the parking brake and install a front caliper or a 911 rear caliper? or did they resort to spacers/adapters?

The 914/6 GT used regular 914/6 rear calipers that were spaced 10mm. The same spacers as are used in the common 911 rear brake caliper; the two calipers are the same bore and share the outer casting.

The rotor used was a variation on the 911 vented rear rotor that used a different offset to center the rotor in the caliper without spacers. It may also be slightly smaller in diameter, as is the solid 914/6 rotor.

So it was a simple solution: widen the caliper with the available spacers, and a custom rotor to suit.

The front was even more simple: existing rotor with a custom caliper (borrowed from the 908) the bore was slightly bigger, and the pads slightly thicker.

A 20mm master cylinder was commonly used, borrowed from the 911S, but some people adapted the 23mm master.

[914Sixer]

I shopped around and bit the bullet for a little over $ 310 for two of them. I am going to be running 914-6 GT rear calipers. I bought them several years ago and I been setting on them until I could figure out what was the correct rotor.

When I got them the PO said the rotors were turned down 911 turbo rotors that he sent. I wasn't until I got a copy for the 1970 edition competition parts booklet did I figure out what was the correct ones to use.

My next question is to use a T or use the stock 914-6 proportioning valve? I have both. This is going to be a weekend crusier and no AX planned at present.

FYI, Porsche only has 44 of them left at the factory parts depot in Germany. I messed up on the list price, it is $225. Thanks, Mark.

[Bleyseng]

QUOTE (davep @ Nov 3 2005, 02:56 PM)

914/6 rotors are solid 914/6 GT rotors are vented The faster you can go, the better your brakes have to be. I have always upgraded my brakes first, then the engine. Emergency brakes work great if you give them the attention they deserve. The old adage ' use em or lose em ' applies here also.

Dang, that's what I am doing now since the car has been on jackstands fixing the effin motor for the last year.

I will do a detailed tech article on what I install and its not a set of rear 914/6GT Vented discs which are made of $$$$

This will be both front and rear set ups.

[914Sixer]

Well, to insult to injury I only gave $350 for the 914-6 GT calipers. So that is why I was disappointed about the cost of the rotors.

I will pass on the info how the fit .

[Oled]

If you have 6 rear calipers a vented rotor install is no problem. Get a set of spacers from M calipers and put them on the 914/6 calipers. use vented rotors from an SC. you might have to machnine a mm or so off of the rotor to stop rubbing or do what I did, just file off a smidge from the inside of the caliper arch. So there you are, M pads, vented rotor and still have an emergency brake.

ed