Porsche 930 rear brakes

[Sandeep]

Has anyone done this brake upgrade to an IRS rear ? I'm in the process of gathering parts for the rear conversion on my '74 standard. I'll be using this car on the track as well so thats why I'm going with something of this nature in the rear.

FYI, the 930 rears are 309mm x 28mm, crossdrilled/vented. If no one has done this then it looks like I'm going to have to go to a dealer and try and find out what parts work ! I'll be using 944 Turbo front calipers on the rear.

Jim A....do you have pics of the 322mm x 28mm 993TT rear upgrade that you did a while back ?

Thanks for any info that anyone might have.

Here's a link I found on adapting these to a 911 rear...
http://www.vintagebus.com/howto/brakes/rear/index.html

Looking at the ebrake setup...does anyone know if the 930 rotor will fit over the 944 ebrake setup ?


Sandeep

[Sandeep]

All,

I just fitted the rear 944 ebrake setup with the aluminum backing plates to the stock beetle trailing arms and here's what I found.

This setup increases the width per side by 7/8" (22.25mm). I can't believe how easy the setup was ! I literally unbolted the beetle drum brake backing plate and then bolted on the 944 rear. It was that simple...took me about 10 minutes !

I am missing the wheel studs that press into the rear 944 hubs but will get them this next week. I will then take pictures and write a tech article. I am also going to test fit the 930 rear rotor (309mm x 28mm) and will be using the 944 Turbo front caliper on the back to fit the width of the rotor.

If everything goes well and the 930 rear rotor bolts up, as well as the caliper, then thats another bolt on rear setup that you can use using stock Porsche parts !!

All I have to do now is figure out the handbrake cable setup...doesn't look tough though...

This is cool and I will keep you posted. I love it when things come together this easy !

Sandeep

[Sandeep]

I took some measurements last week of Alex's pan with the early alu arms and I can CONFIRM that the width increase per side is the SAME as the alu arms with the 944 backing plate method on stock beetle arms. The advantage of the alu arms is weight savings.

I just fitted my rear 18x10 (47mm offset) with 265/35 PZero. You need a 10mm spacer to clear the upper bump stop and get the wheel off of one of the spring plate bolts. The wheel fits very nice.

I haven't got the 930 rotor yet so I am using a boxster rear rotor (299x24mm) that I borrowed from Alex. Unfortunately I didn't bring the digital camera home from work.

With this setup, If a 2.25" wider rear fender existed, it would fit over these rear wheels...but the clearance will be very close. With a 2.5" wider fender (if it existed) , the fender would clear the wheel enough for some lowering...but it will be close. With a 3" wider fender, you could fit an 11" wide wheel...I have measured it and it WILL fit, even with lowering.

Sandeep

[Jim Andritsakos]

Sandeep,

911 rotors has a different offset than any other Porsche.
As per the caliper mounting holes has the same distance.
I have done this a long time ago and IF I was remember RIGHT
you need to machine the inner mounting surface of the 930 caliper for about 5mm to fit correctly to it's own rotor...

I was have some pictures from my rears but no scanner here!

Rgds,
Jim

[Sandeep]

I have mounted the 930 rear rotor to the 944 ebrake assembly !

At first attempt the rotor bottomed out on the backing plate (I had to find 13mm more clearance)...so I added another spacer (the steel spacer that slides over the axle from the splined side, it just happens to be 13mm thick !) and it sits fine now....the 944 ebrake engages in the proper area on the 930 rotor....

The axle nut also JUST fits...you can tighten it up and still JUST BARELY get the cotter pin in...this increases the track per side by another 13mm....good for my application because I needed a 10mm spacer to get the 18x10 wheel off of the spring plate...so Killed 2 birds with one stone !

Now, all thats left is to get the 944T front calipers to mount on the rear, and figure out the ebrake cable setup.

Sandeep

[Alex]

Question:

Do the front and rear 944 Turbo caliper have the same bolt hole spacing for the mounting points?

Alex

[Sandeep]

Yesaaa .... they do.

Sandeep

[Sandeep]

I thought I'd change focus this weekend because it was to cold in the garage to work on the oil cooling system. I did some work on my 944 T/930 hybrid brake setup.

I had the rotors mounted but had to do some minor machining to the calipers to get them to fit. I had to elongate the mounting holes 1/4" so the 944T front calipers would fit the 309x28mm 930 rear rotors.

Here's the pics...







Now I just have to figure the ebrake out and then powdercoat the rears red to match my fronts (322x32mm Big Reds), Then I'm ready for the track !! (oh yeah ... still need the RAT 2270 )

Tech article to come !

Sandeep

[Andy White]

Hi Sandeep,

Did you check the calipers with the brake pads in place? You might find that the pads overhang the disc now that you've elongated the mounting holes.

I used the 944T front calipers at the rear and found that with the standard 944 discs the pads were overhanging. I upgraded to the larger Turbo discs and everything just bolted together perfectly.

Looks sweet, keep up the good work!

Regards,

andy.

[Andy White]

Another quick suggestion for taking the baked on crud off of the calipers the easy way... Oven cleaner... Mr. Muscle takes it off in about 5 minutes flat!

Andy.

[Sandeep]

Thanks Andy,

I did check the brake pads and they look like they fit fine.

Sandeep

[Michael Ghia]

Man, that castle nut looks like it's about to fall off! Are you really gonna run it like that?
If it's for the cross-drilled disk that you've pushed everything out, grab some 993 rear disks and bolt them on instead. You don't need a spacer then.
You may find that you'll have too much of a rear brakes bias with the 951 front calipers on the rear. It depends on what you will be counter balancing them with up front.
I have fitted 951 fronts on the rear of my 951 but I've fitted 928S4 calipers up front and will be running a bias control.
The only calipers I can think of which would balance out the 951 fronts would be 993 TT front calipers.
Looks sweet though.
MG

[Sandeep]

Mike,

Read my post again. I did it this way so I wouldn't have to use a spacer. I've got 18x10 rears and needed a 13mm spacer to get the wheel off of the spring plate. I've got 993TT fronts already.

I've already machined 5mm off of the front face of the rear hub to allow the castle nut to fit perfectly. There was a small lip there that I took off.

Sandeep

[Michael Ghia]

Sandeep,
I couldn't see anywhere about 993TT calipers... but fair enough they should work, I'd be using a bias control on the rears just for dialing it in though.

I have a customer who is fitting 18X10's with 65mm offset on the back of his Bug but he's using 944 late ally arms for the correct fitting.

Looks good, keep us updated.

MG

[Sandeep]

Mike,

A while back I took an 18x10 wheel et47mm (265/35) and test fitted it on Alex's rear setup (early al arms) and the wheel fit fine as well. There was about 7mm of clearance between the inside of the wheel and the bump stop.

Sandeep