924Board.org

[daveo]

just put 944 discs & hubs on the race car, but have got a problem

when the motor is of the pedel is nice & firm a good feel, when i start the motor the pedel can be pushed to the floor, realy soft feel, i understand the servo will take the pedel dawn one inch or something but this goes realy far down

do i need to change the servo & master silinder to the 944 one? or r they the same?

help needed as i am racing at brands on Sunday

thanks

Dave

[Martijnus]

which year is your car from?
I've read about switching pumps on some models
_________________
"Rule: Turbo's make torque, and torque makes fun." (C. Bell)

924 "50-jahre", 1981.
MSII/extra, LPG, ITB's, 5lug.
To be turbo'ed in a while.
Killed her at the Nurburgring, Porscheless at the moment

[daveo]

the hubs r pre 1985 the car is 1983

[emoore924]

I don't know the answer for sure because I don't know the diameters of the m/c bores, but if I was going to do something, I would say to change the m/c to the 944 unit.

Here's the reasoning: If the diameter of the 924 m/c is at all different (smaller) than what the 944 calipers are designed for, you won't be able to move enough fluid which would result in a difference in the throw (longer) between your 924 m/c and what the calipers are designed for.

Put another way, there's more distance for the 944 brake caliper pistons to travel to engage the rotors and your m/c isn't up to the task of moving all that fluid. That would be a very uncomfortable thing to discover at the end of the first straight.

That's my story and I'm sticking to it

Oh, and make sure you bled the heck out of them, starting from the caliper with the longest run, and tapping gently on the caliper with a ball pien hammer to dislodge any trapped bubbles....

[924RACR]

The answer is yes.

You will likely also need to change your line routing to be a front/rear split...
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[daveo]

man what a day on sunday

ok first 924 racer (change the split) how more info needed,

i have changed to the 944 master cilinder it helped a little, backs locking up befor fronts big time, racing was real fun (if fun is shiting your pants every time you try to stop) no brakes shit handeling but we come first in class sweet
its not just the brakes the motor was 2 seconds down on last year on the same track,
lots to do, camber way out tow in & out all over the place

set up info needed some one help please another race like that will kill me or make me go gray

thanks dave

[924RACR]

Yeah no shit yer locking the rears before the fronts, 'cause your plumbing is wrong.

The 924 was an X-split car. The 944 is a front/rear split, also known as an H-split or TT-split.

You need to re-route the plumbing so the rear brakes are both off the port of the master cylinder furthest from the firewall, the front brakes are both off the port closest to the firewall. This will give you proper plumbing, proportioning, etc.

Otherwise you'll keep locking a rear wheel (no, I don't remember which one).

Alignment settings vary a bit depending on chassis setup and tire selection, but something like 2.75-3 deg front camber, 2.5-2.75 in the rear, toe 1/8" out in front, 1/8" in at the rear is where you want to be. The front toe will help it turn in, the rear toe will help keep it stable on the brakes. If you fix your plumbing.

Then you need, yes, a decent motor, and good shocks.

What series are you running in, what're your prep rules?
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[daveo]

924racer
there r three ports on the master cylinder, one at the front & two side by side at the back.
so the one at the front (furthest from the bulkhead) is for the rear brakes so one line from this port splits into two & feeds the back brakes?
and the two at the back side by side feed the front brakes one left & one right? have i got that correct

i am racing in the Classic Sports Car Club Future Classics its cars from the 60, 70, 80, the class is by motor CC im am in class c 1600 up to 2000 then it it upto 3000 (944 land) and over 3000cc big jags xj6 & xjs
we beat one of the 944 and the jag xj6 in the higher cc groups

will post more later
Dave

[924RACR]

[gohim]

You didn't state exactly which 944 calipers you have. The earliest 944 calipers are 924.931 parts. Next, the 944 got 944 prefixed parts (which are in most cases the superceed parts for the 923//931).

924 and 931 have diagonal split. 944 has front and rear split.

924 and 931 use the same calipers as the early 944 with the diagonal split, and they don't have brake balance problems.

Early 944s use the same calipers as the 924 and 931, even though they are split front and rear, and they don't have brake balance problems with front and rear split with a straight internal diameter master cylinder of the same design as the 924/931. So the splits don't make any difference

924, 931, and early 944 use master cylinders with straight internal bores. The later 944s use a master cylinder with a step (different internal bore for front and rear circuits). At one time, the same calipers were used in production with both the straight and the stepped master cylinders. So there is a case for any combination you assemble being factory standard and working.

So, do you have to change from diagonal to front and rear split brake systems? No, you don't.

And, do you have to change to the 944 master cylinder? No, you don't.

Since you have an 83 924 (same as a US 81-82), you have the same sized (internally) master cylinder that came in the as the 924 and 931 with five lug brakes, no further master cylinder change is necessary for fluid capacity.

Your problem with mushy brakes is most probably due to either improper preparation before installation (did you replace the seals in the calipers?), or inadequate fluid bleeding after installing the new calipers front and rear). It takes me a minimum of one quart of brake fluid and sometimes as much as two quarts to change the fluid and get the brakes bled to where I want them.

Did you bleed the brakes with the old calipers, and wheel cylinders to remove all of the old brake fluid before you installed the new calipers? replacing the brake fluid is easier with old brake pads and shoes in place since the caliper pistons and the wheel cylinder pistons are extended out leaving more room for fluid flow within the calipers and wheel cylinders.

Did you let the master cylinder run dry at any time while you were bleeding the brakes (you would have to start bleeding process all over)?

Did you press the brake pedal HARD after you were done bleeding to set the pads and the caliper pistons?

Your brake bleeding, swaybar size, spring rates, brake pad selection, tire selection, and tire pressure can be used to change your car attitude, and are probably more important to brake balance than your choice of master cylinder.

[gohim]

I did the four wheel disc brake conversion 10 years ago to my 81 924 using 85/1 944 calipers, and I have never had any problems with fluid capacity or brake balance.

The key to a sucessful conversion is preparation.

I used new factory front and rear rotors, new factory front and rear brake pads, new caliper hardware, new braided stainless steel over teflon brake hoses, and replaced the seals in all four used calipers.

Used parts that were installed were the front spindles, splash plates, rotor hubs, wheel bearings, and brake calipers. Used rear parts that were installed included: the parking brake cables, trailing arm brake fluid hard lines, backing/splash plates, parking brake shoe assemblies, wheel hubs, wheel spacers, and brake calipers.

I reused the front wheel bearings, and one month after conversion, the wheel bearings on one side failed. This could be due to previous wear, OR the fact that when I installed the front rotors, I had to go back in a couple of weeks later, because the wheel bearing adjustment was too loose.

[Eturbo924]

I was going to say basically the same as some of the others just above me.

I converted my 1982 924 to 1983 944 discs with no issues. Never had a lock up or ballance issues and no issues with the brakes ever going to the floor. The pedal is always nice and firm.
_________________
1982 924
1992 968
2003 C4S
Parts Parts Parts and More parts.
E-mail me for parts you need!
Drive Fast!

[morghen]

i can confirm the fact that the 944 brakes will work with a late 924 brake cyl.
I have 944 brakes on my 924 and did not change the plumming from X to || nor the brake master cyl. However you need performance pads and fluid to make these brakes work properly.
I had my disks turn blue and brakes fade to next to nothing because of shit fluid and shit pads....all this in just a couple of ''laps''
_________________
Supercharger and EFI kits
https://www.the924.com

[daveo]

thanks boys
i have fixed the problem, and it was not the master cylinder, £110. down the drane.
yet another cock up by me and my trusted spaners, when changing things over from one car to the other over the two days we had striped down all the calipers to give them a good service, lots of bits Dean or Lee (they both need shot with shit but its my falt) put the back brakes on, i put the fronts on.
the front calipers on problems sweet as you like,the back calipers 924 front caliper pistons. biger than the 944 pots.
the reson for this they said 'they looked in better condition than the other ones'.
so just shows you do it your self, not only did they try to kill me with on braks but at brands dean did not tighten the wheel nuts up befor i went out, nice to have good budys
thanks all for your posts
naw need to fix the next problem
Dave