924Board.org

[-nick]

I hope what I learned in this process can benefit anyone contemplating doing the swap. Here's the first part, I'll post the rear procedure soon.

Front 5-Lug Brake Swap:

Donor car:
944 ’83-’85.5
924S All
924/931 All 5 lug

Parts from donor:
Steering knuckle/spindle *
Hubs
Rotors
Calipers **

** Using 924/931 or ’83 944 5-lug front calipers:

The ’76-’79 924 uses a smaller brake booster. While the master cylinder has the right bores, the booster could be limiting. To remedy this you must use the stock 928 ’78-’83 or 931 ’81-82 master cylinder along with the larger brake booster that is stock to all 5 lug cars (i.e. all 931/944 etc).

Post ’80 924’s can use the existing MC setup. These cars already have the larger booster and the MC bores are matched to the 924/931 5 lug front calipers. Model year ’80 cars have a somewhat different MC than the others, but as far as I can tell the change is only that of using a pedal mounted brake light switch versus the pressure actuated switches of the other models. ’80 should be able to also keep its existing MC setup with 924/931 calipers.

Using ’84-‘85.5 944 or all years 924S front calipers:
These calipers use a different piston bore in the front than the 924/931 calipers. This necessitates using the 21mm/19mm stepped MC. These can be used from all post ’84 944’s or all years 924S. The 944 Turbo also uses the same bore MC. The same rules apply for the brake boosters as above, early 924’s must upgrade to the larger booster and post ’79 924’s can retain their booster.

Using the stepped MC requires re-routing the brake lines. Not as bad as it sounds. There is a T fitting that takes one of the lines from the MC and splits it to the front right caliper and one of the rear calipers. Remove this fitting and replace it with a coupling that ties the MC line directly into the right front caliper. Now screw a male-male fitting into the rear MC brake line outlet and screw the other end into the T fitting you just removed. You can now screw into the T fitting the very long line that travels from the MC to one of the rear calipers. Into the other open T outlet screw in a length of brake line to connect to the open line you have down where the T fitting once was. Use a coupling to reconnect it. This gives you a front right line off the MC, a front left line off the MC, and a rear line that you split into two using the T.

This is the best idea I had to re-route the lines. The parts you need are: two female-female couplings, one male-male coupling, and an additional ~2ft. of brake line (with the fittings attached). All these extra fittings and brake line can be removed from a donor car- except the male-male fitting, this can be replaced by a short length of line if needed.

*note the pre ’78 924’s must change to the later ball joint (924 post ’78, 931 all, 944 to ’85.5) the early ball joints are riveted in and must be drilled out. I used a good ¼” cobalt bit with a dab of light oil. The reason for the change is that 5-lug steering knuckles have a larger diameter hole for the later ball joint stud. I’m not sure what the differences are between the 4-lug and 5-lug spindles.

The arms that reach out to the tie rods seem to be shorter for the 5-lug knuckles. This results in tons of toe-in, I had to dial some of this out before I could even drive it to the alignment shop.

Some front end torque specs (in ft-lbs):
Hub to rotor bolts- 17

While you’re in there:
Replace the front wheel bearings and races, or at least clean and repack the original bearings with a good wheel bearing grease- it is a simple and cheap thing to do while you’ve got the hubs on a work bench.

MC's can be had for about $100+ shipping from this dealer (current as of 4/2002):
http://www.performancemotorcars.com
These are new without the resevoir.

regards,
-nick

[-nick]

here's the rest. the rears are pretty easy once you know where to get your parts from.

Rear Brakes:
944 ’83-‘86
5-lug 924/931 all
951 ’86

Calipers
Rotors
Parking brake cable/ shoes/ clips & springs
Hubs
Dust shields
Backing plates (what the parking brake shoes and calipers mount onto)
21mm spacers / 66mm wheel studs

These parts are all exactly the same for all the listed models. After removing the 4 lug brake drums and the plates that the shoes mount to, mount the 5 lug backing plates and hubs (the hubs will slide right on the 924 stub axle spline) then torque the castellated nut back down. The differences in the parking brake cables are only in the ends that pin into the assembly, but there is no way that I can tell of adapting the 4 lug cables.

Without the spacers a 205/55/16 tire won't rub but it's close to the inside wheel well. the spacer was stock on 5 lug 931's (and can also be found on the 944 models listed above).

924S all
944 ‘86-’89
951 ‘87+

These models all have the same components save the hubs, dust shields, and backing plates which are 951 part numbers. If you use one of these cars as a donor you will also need the aluminum rear control arms (which take the place of the backing plates) and attached dust shields, hubs and stub axles (which have more splines), half axles (which are longer) and the later type shocks. These are all the necessary components. The suspension geometry maybe better with the aluminum control arms but they can crack and are actually heavier than the early stamped steel arms. Using these parts will push the rear wheels outboard so the 21mm spacer will not be necessary and the stock 45mm studs that come with the hubs.

[gohim]

82-85/1 944s use the one-piece alloy bearing cover/caliper mount. This is not the same part used on the Series I 924/931 with cast iron/welded bearing cover, and separate caliper mount/parking brake plate. The 931/early 944 wheel hub and stub axl;e are used with the alloy rear parts, that what I have on my car now. The parts I used were from a 85/1 944 with sport suspension.

[-nick]

you're saying that the bearing cover/caliper mounts (aka backing plate, everyone seems to call it something different) are different between the 5-lug 924/931's and pre-'87 944's?

or did i make it sound like the 924 4-lug backing plates can be used with the rear discs. which they cannot.

-nick

[gohim]

The parts are different, but functionally identical. The complete assemblies can be swapped dirrectly inplace of each other without any other changes.

The five lug 924/931 have a stamp steel backing plate that has cast iron brake caliper mounts welded to it. The stamped steel splash plate is another piece welded to the assembly. This assembly has a flat flange that is trapped under the four mounting bolts that hold the wheel bearing cap onto the trailing arm.

The 944/924S part is a single alloy piece with the parking brake mounts, brake caliper mounts, and the wheel bearing cap all cast as a single piece, and a stamped aluminum splash plate bolted to it.

The alloy part is easier to install than the separate parts, is much lighter, and doesn't rust.

Both the alloy and steel/iron assaemblies use the same wheel bearing grease seals.

[ This Message was edited by: gohim on 2002-05-24 05:28 ]

[-nick]

you're talking about the alloy control arms on post '86 944's and 924S's? to use these you also need the longer axles, later shocks (the later shocks just use a larger diameter mounting bolt), and fabricate a bump stop.

931's and early 944's use a stamped steel control arm (as well as 4-bolt 924's), but the plate the parking brakes mount on is alloy, as well as the bearing keeper plate.

using the alloy control arm is slightly more involved than just swapping it on. and those longer axles are expensive! plus the alloy control arms are actually heavier than the stamped steel arms (i weighed them, and was surprised too!) and they are known to crack.

-nick

[gohim]

No, I am not talking about the alloy rear trailing arms.

I am talking about the alloy wheel bearing cap and integrated parking brake plate with caliper mount, and the asheet aluminum splash plate.

Let put it another way... What holds the brake caliper, splash plate, parking brake components, and retaining the wheel bearings in the rear trailing arms in a car with steel rear trailing arms?

The wheel bearing caps (made out of cast iron) holds the wheel bearings inside of the rear trailing arms.

A composite steel plate (cast iron, and stamped steel parts welded together) is trapped by the wheel bearing cap, and holds the parking brake parts, has the brake caliper mounts, and has the splash plate permanently attached.

[-nick]

ok, i understand what you're talking about now. i was a little confused when you lumped in the 924S. i thought all the S's had the alloy control arms, therefore not having the alloy backing plate. is this assumption wrong?

thanks for highlighting the differences.

-nick

[924RACR]

Just to clarify - the alloy or cast iron piece, depending on where the parts are from, does not hold the wheel bearings in place. It holds the seal in place. The bearings are retained by the wheel hub, which in turn is held on by the Big Nut.

_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Lizard]

any suggestions before i attemp to do this I am a very good backyard mechanic but i do like tips

[924RACR]

Plan on installing new brake hoses. Everything should bolt right up. Make sure you either have or plan to make the short brake lines for the rear that go from the hoses to the calipers, along the trailing arms.

Plan to rebuild all the calipers. $20 for the kit for each caliper, from Tweeks. Worth it, to have new brakes when you're going through all that trouble to have better than stock brakes! Get new pads too, obviously. I recommend MetalMasters for street/autox use.

To swap in the MC, put the booster in separately from the MC. IOW, remove the old MC, then the booster, then install the new (larger) booster, then install the new MC. Taken in this order, it'll be easier, since the fit around the air metering unit is tight.

The front corners are pretty easy; just bolt right in to replace the knuckle... strut and a-arm can stay. Of course, you _will_ need to re-align the front end. The rear won't need to be, since you don't have to swap the trailing arms.

_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[gohim]

Steel trailing arms (931/924/944) were used with both the steel/cast iron parts, and the alloy parts.

The mounting bolts are a different length between the alloy parts and the steel/cast iron parts. Make sure that you use the correct length and grade of bolts to mount the backing plate/caliper mounting assemblies.

The 924S and later 944s that came with alloy rear trailing arms only came from Porsche with the alloy rear brake parts. BUT there is no reason I can think of that the steel/cast iron parts could not be used if you wanted to backdate the car for some strange reason.

I recommend changing to teflon/stainless steel braind Dash-3 sized brake lines with the conversion to four wheel disc brakes for improved brake feel. The rear lines are the same length, regardless of whether you have drums or discs in the rear. Front lines are longer when you have the larger four wheel disc calipers mounted. Mount the brake lines to the hard lines before connecting to the calipers, MOUNT THE CAILPERS AFTER CONNECTING THE BRAKE LINES, and give the lines a twist in the tightening direction as you mount the calipers. DO NOT MOUNT THE CALIPERS BEFORE INSTALLING THE TEFLON BRAKE LINES. Teflon has a strong memory, and if you are not careful when installing the brake lines, when they change temperatures (get cold), the teflon lines will try to unscrew themselves, cause a brake fluid leak, and possibly brake failure.

[ This Message was edited by: gohim on 2002-05-25 14:45 ]

[Cbass]

So to clarify a point here.

If I was to replace the torsion bars on a 4 bolt NA with coilovers, and 951 brakes and hubs, I would have to get new axles? Are these the 944 axles or customs?

[gohim]

Some coilover kits are used in combination with the torsion bars, and some are designed to be used with the torsion bars removed.

Whether you have use shocks and torsion bars, or shocks, torsion bars, and coilovers, or shocks and coilovers does not change the axle length. If you replace the rear trailing arms, going from the 924/944 steel rear trailing arms, to 944/924S/944/944S alloy rear trailing arms, then you will need longer axles, and different wheel hubs.

[Cbass]

Hmm, the lowest grade of brakes I am looking at are 951 brakes, preferrable M030 brakes, or 928 GTS brakes(heavy car, lots of power, good brakes).

Yes, I would be completely replacing the torsion bars, and the trailing arms and everything. Are the axles from a 944, or do they have to be custom made for some reason?