993 Brake Conversion Help Needed

[tahoe_snow]

Hi All. I just want to say I've learned a ton about my car from reading this forum in the last few years. The patience, skill, and willingness to help that is represented here is staggering.

On to my brakes:

I'll spare all the details, but the car had 4 piston racing calipers all around when I bought it (if to do over I would have bought a car that is stock, but c'est la vie). The rears are a pretty straight forward Bremtek configuration as shown in a recent thread. The fronts were JFZs which are a bit more obscure (some research suggests they are similar to wilwoods and used in custom stock car and hot rod configurations), and I have to say the vertical alignment over the rotor wasn't good. When one of them hung last year I decided to go to a 993 setup, and in an overzealous garage cleaning I, now regrettably, tossed the old front components.

I ordered the 993 kit from John Graber (aka North Coast Cab), and mounted the rotor on the right hub and the caliper over the rotor. I'm pretty sure I have the bearing adjustment correct, but the horizontal alignment doesn't seem right.

Here are some pictures showing the alignment:

http://www.flickr.com/photos/20243604@N00/sets/72157620884169313/show/

John mentioned that there are two different versions of the 993 caliper. The earlier calipers were the same as the S4 calipers and then were changed on later models. I'm not sure if what I have are the S4 calipers. Here's a picture of the part number on the left front caliper: http://farm3.static.flickr.com/2654/3696211383_1c2fb4235e.jpg . It is 20.4565.00.

I don't need the cooling these brakes provide, and now I'm seriously considering going to a stock Carrera setup. I've lost some mojo in continuing with this project as I still lack the 17” wheels needed to clear the calipers, and the budget is tighter now than when I started. Plus I prefer the Fuchs look on the car. But, honestly, replacing all four calipers and rotors with a stock Carrera setup isn't that cheap either.

Should I continue down the 993 route or scrap the project, sell the parts, and go to Carrera brakes? As I type this, being a serious hack (but patient) shade tree mechanic, I have to admit I'm leaning toward the simplicity of the stock setup. Plus I also have a Subaru STi which is a hell of a car with fully modern running gear. In someways it is nice to retain the vintage simplicity of the Porsche. Either way, I'll have a mechanic check over the system when it is back together.

Thanks again for the advice. I continue to feel humbled reading these threads.

[stevemfr]

I've been going through the same thing myself, so I'll put in what I've learned so far. BTW, sparing details is not a bad thing - no superfluous info - but knowing what car you're talking about is not a bad idea. I'm assuming a 74-89 narrow body.

As far as I am aware, there were only 2 993 front calipers, regular and the 'Big Reds'. They're not necessarily early or late, but big and bigger, the latter being for the 993 turbo and RS which used 330mm dia rotors vs. 322 for the regular 993. I can't help with the part #, and they are hard to tell apart if you don't have them side-by-side. I'll go out and get a measurment off mine later; the big reds are longer overall.

It's hard to see how much clearance you have from the photos, but if you've got more than a couple of mm's and the pads fit, I prob wouldn't stress. To center the calipers you'd need to mill the adapters or use different hats - much work/$.

There are 17" Fuchs style wheels available - do a search on 'Alton + wheels' or 'Rota Fox' (though I don't remember ever reading about brake clearance in conjunction with Rotas - maybe someone else can chime in here). There are also custom wheels - search Lindsey or True Design.

If you have the regular 993/S4 calipers and not the big reds, you can fit 16" wheels although you'd prob need different adapters and rotors. They fit using 930-sized rotors 304x32 front and 309x28 rear. Rears are best done with stock 930 rotors - not terribly expensive and work perfectly with the parking brake. Fronts can be done a couple of ways:
- stock, early 930 2-piece rotors - vfe, very expensive
- 993 2-piece rotors with custom hats - best method and OK budget-wise
- 993 1-piece rotor over slightly turned down 944 hubs (I still need to finish researching this - Steve Timmins/Instant-G has these available as 'custom hubs') My 993 big brake upgrade on the SC

I know what you mean by feeling humbled. Most of the above info is thanks to Bill V.

[Bill Verburg]

there were several different versions of that size caliper
all 993 used the same version(not to be confused w/ the BigRed tt/RS caliper)

964 3.3t used a version that was different in that it has raised mounting blocks but is other wise the same as the 993 front

928S4 used 2 versions of that caliper very early versions had different pistons and seals, late were the same as the 993 versions. The big difference in these was that they are set up for trailing mounts, to use them on an aircoled cars w/ leading mounts the bleeds and feeds need to be swapped.

944t/s also used the 928/S4 version.


so to answer you question the o/s issue you are running into is not the result of anything about tha calipers. The rotor and caliper must have o/s that agree w/ each other. caliper o/s won't have much lee way because of the way the adapters are designed, but the rotor can have a large displacement depending on it's design and how it's mounted. The vender of the kit should be providing parts and info to help you.

[KTL]

I had a 993 kit like is being discussed on my '87 narrowbody and it worked very well. I recall the caliper not being evenly centered over the rotor in my application too. Still, it worked fine. The only real issue is that the pistons end up being extended more on one side that the other. It doesn't appear to affect the operation because my car would brake fine on the track.

Also keep in mind that the caliper adapter can be flipped around to change the alignment of the caliper. Notice how the holes in the adapter are not centered/symmetric. So you may want to try flipping them over or switching them from one side of the car to the other. You might find you can improve the alignment by doing this.

If you don't need the cooling, then by all means get rid of them. The factory components of course fit perfectly and it's a simple bolt-on. Plus you can can avoid the hassle of bending some store-bought brake lines to fit the 993 calipers. Plus like you said, the 16" wheels are a tight fit- only the 16x9 930, 16x8 and 16x7 951 Fuchs, three-piece wheels like BBS, or some racing wheels like Forgeline RS and (no longer made) will fit over these big brakes. Stock brakes will allow most any wheels you can think of.