924Board.org

[-nick]

who has done this using the 931 MC? Vaughan, in your tech section it says if you use the 931 MC then you can just plug in the brake lines where they fall. however, looking at the pictures, i'm finding that may not be the case.

my disc/drum MC has the LF line positioned on the left front part of the MC, the RF on the right front part, and the rear single line on the right side center part.

the 931 MC has one line opening on the top front, and two in the middle on the left and right sides.

these don't seem to match up! am i not looking at a M-471 MC? or?

here's the 931 MC:


can anyone who's done the swap help clarify. any info will be greatly appreciated.

regards,
-nick

[Chaz]

When I did this conversion on my '77, I used the complete setup out of a 931, including the front brake lines that run from the MC down to the splitter under the passenger footwell. I did have to coil up some of the extra line behind the engine, but other than that, it was totally bolt up.

[924 turbo]

If you check the part numbers, the '80 924 and '80 924 turbo share master cylinders, regardless of whether or not they are M471 or not. I did the brake swap on my '80 924, and just kept the stock master cylinder. Works fine.

Part number is 477 611 017.

[-nick]

thanks Jon,

that clears up a little with the MC's. apparently the '79 had a different MC for 5 bolt and 4 bolt. '80+ cars have the same MC for both 4 and 5 bolt (for NA's). this is something i didn't know.

so i'm going to guess that the brake line layout changed with the '80 cars too?

anyone ever bend the stock lines using a brake line bender? that's really all i need to do, just to get the steel lines to match up with the MC holes. getting the later steel lines maybe a bit of a pita.

thanks for the info,
-nick

[924 turbo]

The '80-'82 maintain the diagonal split, so you shouldn't have to bend the lines at all.

[-nick]

ahh, now i'm realizing (insert lightbulb)- the 944/924S calipers have differet internal biasing (presumably due to piston diameter) than 5-bolt 924/931's. thus requiring different MC's. i can't believe it's taken me this long to realize this...

my parts are off a 924S, so i really will have to use a 944/924S MC and reroute the lines. what a pita!

anyone know what the configuration should be? how many lines are off the 944/924S 2, 3, 4?

-nick

[ This Message was edited by: -nick on 2002-03-01 05:01 ]

[-nick]

well, looking at the parts listing here, i see that the front calipers are different between the 944 and 931 systems. this makes sense if 924 MC are 19mm and 944 MC's are 23/19mm. the 19mm is for the rear on both systems and the 944 fronts require 23mm while the 931 fronts require 19mm to get the biasing.

maybe i'll just look for some 931 front calipers then to avoid this big mess with the lines.

i'm going to assume that i can just keep my stock 4 lug MC in if i use 931 front calipers. since they're all 19mm.

are the 924/931 brake boosters all the same?

it pays to check...

-nick

[ This Message was edited by: -nick on 2002-03-01 05:40 ]

[Pat]

The size is the same after '79 I think, they switched to the larger brake booster in both the N/A and the turbo. The part numbers are different for the 944/924S brake boosters though.

[John H]

Early 944 / and the Euro 931’s all had the same brake systems with the exception of the master cylinder.
The 944 and the 924 Carrera GT both run the stepped master cylinder which has 19 mm for the front and 23 mm dia cylinder for the rears.
If you want to run the stepped master cylinder on the 931 then you need to do the following.

From the rear of the cylinder (closest to the booster) run a line to each of the front brakes. You can use the existing lines. However on the line running to the right front brake (looking forward) you will need to disconnect the line running to the left rear brake. This connection is located on the underside of the floor passengers side foot well. It’s fairly easy to locate. Remove the line and cap the tee piece. You can at this point either re use the line going to the rear or run a new line. When I did my car I capped the existing line and ran a new line to the left rear. Fittings are a normal metric which are easy to obtain in New Zealand but possibly harder in the USA.

At the master cylinder I ran a single line out of the front outlet and used a T piece of aVW (obtained from a breakers yard along with the new unions for the new left hand rear line. The only hard part was putting the flare on the end of the steel tube for the brake line. Once I had the length right I just took it to the local brake shop and got them to put the ends on and then flare the tube.

All told it took about 3 hours to do the whole job.

[-nick]

thanks John,

if the front calipers are the same, then the biasing must be different for the 944's and 931's. is this true?

does the stepped MC provide better biasing? just when i thought i had it figured out...

-nick

[John H]

[-nick]

thanks all,

what i've found is that there was a change in front caliper biasing beginning with the second model year 944's and up through all 924S and 944na's. i'm not sure what the 944S' and S2's used in the front.

anyway, you can only use the 924/931 5-bolt non-stepped MC with the early 924/931 (first year 944) front calipers. otherwise you've got too much bias in the rear.

i just picked up a 924S booster and MC and i'm going to replace mine with those. the change in the hard lines seems straightforward.

btw- Jason@Paragon has very nice SS brake lines for $65. they are DOT and the braided part is encased in plastic to keep any gunk from working its way between the metal and the teflon.

i'll keep posting on this topic as i get further along in the process.

regards,
-nick

[bacook]

Thanks for the footwork, Nick. My donor was an '83 944 so my '81 MC should be properly biased.

[Cbass]

A good site for 924/944 brake and supsension swap info is

http://www.944s2.com

You can put 928 GTS or S4 brakes on a 5 bolt 924 without too much trouble.

[John H]

You can but you need to change the wheels to get clearance for the calipers.