The Porsche 944 Braking System.

The Porsche 924S/924 Turbo/944 use huge 11-inch vented disks front and rear providing more than enough braking power for your 'average' Beetle. The car that they came from produces some 160bhp and is designed to be a sports car. If you decide to go for the later 944/968 brakes which include the same disks but huge four pot Brembo callipers, then you should be able to put atleast 250 bhp through them and survive a hefty 'Slamming of the brakes' that is so common on the M25! The earlier set-up uses single pot cast iron callipers with a sliding action to keep the pad wear even. The handbrake set-up is the best on the road with the inside of the rear disk doubling as a drum for small brake shoes. Obviously on the Porsche 924/944/968 there is a Servo Assisted Master Cylinder which is bigger than the Beetle item.

The Porsche Rear Suspension.

The Porsche 924 and early 944 use an almost identical rear suspension set-up to that of the semi-auto, 1302 and 1303 beetles (Europe). This includes the A-arm starting off in life as the same part although the bolting pattern to the spring plate is different. The spring plates can be fitted to the beetle (IRS) with some machining work carried out on the chassis and enable a small amount of height and camber adjustment. The a-arms use different bushes but these can be changed for Beetle items and even the torsion bars are interchangeable. The anti-roll bar set-up can be used as well but this will be covered in greater detail later on. The 944 rear hub shafts use the same spline configuration as the beetle and run the same CV joints as a T2 meaning you can use the hub shaft and it gives you a bigger (and stronger) CV joint

The Porsche 924 Brakes.

Most of the 924 brakes can be eliminated from the "useful pile" as the standard 924 uses solid disks at the front and drums at the back, which is what you have on a bug anyway. The only useful bit from using this set-up is that the 924 uses the same PCD on the wheels as the popular Ford and Peugeot. This gives you a bigger range of wheels to look at for your bug. These parts bolt onto the Beetle apart from the front callipers. 924S and 924 Turbo brakes are exactly the same as early 944 brakes.

Rear Brakes.

The early 944 brakes are a direct bolt on feature to any* Beetle. The later four pot brakes use a different hub and handbrake cable bracket. If you are wanting to run the four pot brakes on stock steel arms then you will require the early 944 rear hubs and backing plates. The only thing that remains at that end of the car is the handbrake. This involves using parts from both Beetle and 944 cables.

Handbrake.

Use the outer from the Beetle cable and cut off the end with the bend in it (the end that goes into the backing plate). Then hold the same end of the 944 outer cable in a vice and work the cable until it comes out of the fitting. After cleaning up the end of the bug outer cable, you should be able to push the end of the outer cable into the 944 fitting. This gives you a pair of correct length outer cables. The inner cables utilise 2 N/S 944 cables. They are pinned onto the handbrake lever in the handbrake drum and are more than long enough for the Beetle. A pair of crimp-on ends completes the package. These are an M6 size bolt of 50mm long with a hole of 2.75mm in the middle for the cable. Speedy Cables can supply these. I put the crimp-on end gently in a vice so I could heat up the cable end until it was glowing red. This should give you enough room to push the cable into it and then squash it in the vice just to make sure. This should be done after you have worked out the length of cable. I did this by fitting up everything with the cables sticking up through the handbrake lever. Then pull them will some grips to make sure there's no slack and mark off on the cable where the crimp-on end should be remembering that the cable will slide into the fitting.

Front Brakes.

The conversion, which has been done my car, uses CB Performance dropped spindles. This means that while the conversion may well be possible on stock bug spindles of different years (any spindle), I can only show you what John and I have done. The early brake set-up (single pot) needs more modification than the later set-up (four pot) creating a greater cost from the machining but this is offset by the fact that the parts for the later (four pot) set-up are more expensive.

Mounting the hubs on the spindles.

As no one is offering the bearing adaptors anymore for this conversion, I thought that I would publish the measurements that I have taken from the bearing adaptors which are used in my front brakes. The inner bearing surface on my hubs has had 3mm of extra depth machined into it so that the bearing adaptor has more support for the inner bearing. These are measurements down to the nearest MM so details of interference fits will have to be carried out my your machinist. The bearing adaptors have to have an intereference fit.

A 3mm thick spacer was used inbetween the inner bearing and the spindle to push the hub back out to the correct position.

The adaptors are pressed into the hub followed by the bearings which press into the adaptors.

Seals

These seals will fit into your Porsche 944 hub and fit the seal surface which is on the CB Performance dropped spindle. Machining work to the spindles (photos to follow) There are differences in the machining work for the single pots and the 4-pot calipers. Both require spot facing the area where the caliper bolts will locate. Both require the removal of material from the spindle which intereferes with the pads sitting in the calipers.

The 4-pot calipers use the original top caliper bolt hole but it is redrilled out to M12 size. A new bottom caliper bolt hole is drilled and tapped (again to M12 size). Then there is spacing the caliper to the spindle using shims.

The single pot calipers use 2 entirely new caliper bolt holes, the removal of some of the material from the caliper itself and the usage of bolt adaptors which down size from M12 to M10 bolts. This is because the single pot calipers use a smaller diameter disk, therefore the caliper bolt holes within the caliper are situated further out than in a 4-pot caliper. The only way to have enough material around the caliper bolts is to down size from M12 to M10 bolts (giving you 1mm extra material) and machining 3mm off the O/D of the disk allowing the caliper to sit further in on the spindle. Further material is machined off the inner caliper surface creating more space for the above reason.

Once again, shims are used to mount the caliper in the correct position to the disk and spindle.

As you can see, the single pot calipers take a lot more work to fit to the standard CB Performance dropped spindles than the 4-pot calipers.

But the extra work is offset by the price of 4-pot calipers.

You need to use standard 944 disks and hubs (not turbo or later) for both of the conversion using this method.

Early versus Late. (Brakes)

In basic terms the CB Performance spindle lends itself more to the fitment of the four-pot calliper than the single pot. This means that the fitment of the single pot callipers involves extra parts such as bolt adapters (calliper bolts now M10 instead of M12), the machining down of the disks in diameter by 3mm, extra spacers used behind the calliper and the inner bearing, and machining work on the calliper itself to enable it to sit properly onto the spindle. As you can see this is quite involved. The list for the conversion of the late callipers is nowhere near as long. Both set-ups use the same bearing spacers, Beetle bearings and special seals, hub machining and spindle machining but it all comes down to cost at the end of the day. If you can afford the later brakes then go for it but beware that if you plan to run late brakes on early arms, you will need half of the early set-up as well.

Front Brakes (Early/Late) onto a 1302/1303

Fitting Porsche 944 brakes to a pre'74 1303 or 1302 necessitates the changing of all the front suspension for that of the later type of post '74 1303 suspension (if you have a late 1303 (post '74) then you're already ahead. The Kerscher balljoints are needed because of the difference between the size of balljoint between the Beetle and the Porsche 944. The Beetle balljoint has an O/D of just 15mm where as the 944 balljoint is 17mm. An anti-bump steer kit is needed to fit the spindle also but again just to make the Porsche spindle accept the Beetle trackrod end. The Porsche spindle actually lowers the car an inch or so just by the design differences between the 2 spindles. Setting the camber may involve elongating one of the hub to spindle holes.

Note, early 944 (single pot callipers) braked spindles have a hole for the speedo cable. Late 944 braked spindles (4-pot callipers) do not so you either need to have a very long hole drilled through the centre of the LH spindle or take your speedo drive from somewhere else.

List of bits for the Early (Single pot) brakes onto any Beetle

4 Disks
4 Hubs
4 Callipers (Single pot)
2 Rear backing plates/Calliper mounting brackets
2 N/S 944 handbrake cables
2 Beetle handbrake cables
2 Crimp-on ends from Speedy Cables (part #10103)
2 CB Performance dropped spindles
One set of Beetle bearings
One set of bearing adapters
2 hub seals

List of bits for the Late brakes (Four pot) onto any Beetle.

4 Disks
4 Callipers (Four pot)
2 Early or late front hubs
2 Early rear hubs
2 Early Rear backing plates/Calliper mounting brackets
2 N/S Beetle handbrake cables
2 Crimp-on ends from Speedy Cables (part #10103)
2 CB Performance dropped spindles
One set of Beetle bearings
One set of bearing adapters
2 hub seals

Porsche 944 Rear Anti-roll bar. The rear anti-roll bar set-up works on a pair of special bolts which bolt into your spring plates and A-arms. The extra hole, which seems to have no function, is where this double-ended bolt should go. Then the making of a couple of brackets is required using the original brackets (carefully removed) to bolt the anti-roll bar to. See Photos.

The fitting of 944 brakes to a pre-67 Beetle The fitting of these brakes to any early Beetle (pre-67) has it's complications but these can be got around. At the back, you have shorter shafts but you also have shorter splines. This creates a problem in that the splines are not long enough for the Porsche hub. The Porsche hub will need 15mm machined from the surface where the nut sits so that there is enough room for getting the nut onto the threads. At the front you have more problems. As I stated earlier, this conversion has only been carried out by John and I on CB Performance dropped spindles so it would seem the way to go would be to use the CB Performance dropped spindles for the Link and King pin front end which converts your brakes to late four stud disk. These spindles have the same dimensions (in the right places) as the balljoint dropped spindles therefore the conversion is the same.

Wheels

I have not found it possible to run 15-inch wheels on either of these brake conversions*. The reason for this on the early set-up (single steel callipers) is that with 15X6 Porsche wheels on dropped spindles, the bottom balljoint sits on the inside of the rim! On the later brakes the four pot callipers are so big that 15-inch wheels simply will not fit over them. The offset also comes into play a lot. If you want to get the wheels under stock wings then you have to run an offset of atleast 52mm. This limits you to the later Porsche wheels. All the early Porsche wheels such as Fusch, Cookies, Mahle Gas Burners, Telephone Dials etc come in a smaller offset and therefore sit outside the wing. They are also too small in diameter. There would be ways of fitting earlier Porsche wheels like narrowing the beam plus spacers on the front wheels and running a narrow swing axle back end.

*If you were to fit the brakes to a 1302/1303 then the use of the late offset wheels from a 924S would be possible. These are a Telephone dial design and come in a 52mm offset. Also if you were to narrow the front beam by 3 inches and run 15 inch wheels with and offset of 0-36mm, it would be possible. The rear axle would also need to be narrowed by at least 2 inches, this would necessitate the use of pre '66 rear axles which are an inch shorter per side.

Prices - These are just advisory.

Early set-up of 944 brakes £250
Late set-up of 944 brakes £500-£600
Porsche 968 brakes £500-£600
CB Performance Dropped Spindles £200 ish