Listers,

I'm wondering if someone out there can help clear up my confusion.

I've decided to swap out the Boxster caliper brakes "upgrade" on my 87 Carrera to 930 front brakes. The car in question sees about 20-25 track days a year, and I was warping rotors too easily with the Boxster setup. I bought the 930 setup from a guy I know that was building a project car, but then gave up on it and sold off the parts.

The problem is that this guy's project car was based on a 69, and didn't have power brakes, whereas my 87 does. The M/C that I got from him is a 23mm ATE M/C, but I don't know the part number. It has "23" stamped into one side, and the other side has "1 9 5 G" stamped into it. The guy I bought it from said it was a M/C for a Mercedes.

I thought all was fine until I found Bill Verburg's brakes web site. After reading that, I think I have the wrong part as that page suggests that the Mercedes part is only for non-boosted brakes. Also, if I'm reading Bill's page correctly, I can stick with the stock M/C if I'm going upgrading to a 930 caliper instead of something with larger piston. Is this correct?


Thanks
Stacy

 

I'm not really sure if the 930 set up is much better than your boxster setup grade. Your rotor warpage is from heat not the type of breaks or calipers. An easier and cheaper solution is to use frozen rotors. Check with someone else though.

 

The change to 930 brakes involves more than a caliper change. The 930 rotor is substantially larger than the Carrera rotor (304x32mm vs. 282.5x24 mm), thus it can dissipate more heat. I don't know that much about frozen rotors, but since they are the same size as the rotors I have now, I doubt they would give me much better results. Now only do my current rotors warp, but they turn blue in spots and crack. If anyone has successfully used the Boxster caliper with a frozen rotor (I also use Pagid Orange pads on the track), I would be interested in hearing about it though.

Stacy

 

Stacy is correct that converting to 930 brakes involves more than just the calipers. You are going to install 930 rears too? Otherwise you have one unbalanced braking solution. When I installed 930 brakes on my SC, I didn't have any bias valve, which your Carrera has.

If you go tech.rennlist.com, there are several articles on upgrading brakes, including the 930 upgrade, as well as some information in the 911SC FAQ that also describes the 930 upgrade. Sounds like your read the good pointers on the upgrade on Bill V's web site. VCI (www.vehiclecraft.com) talks about that upgrade too. While you can get by with your stock master cylinder, you may want to install the Turbo master cylinder. The ATE you have is, as you surmised, for a non-power installation.

 

Stacy:

First, I'd like to say that the 930 brakes (on all 4 corners) are a HUGE improvement over what you have right now. Its literally no comparison. I've installed quite a number of these Boxster front brake kits and we've removed ALL of them for the same reasons; poor performance. Its a bad design/match as the rotor cannot handle the heat no matter what you do.

As Bill said, you must install these on all four corners otherwise the bias will really be off. In fact, we will only install 930 brakes on all four corners.

Your Carrera will need the 78-89 Turbo MC to work with 930 brakes and its a bolt-on. After installing these on all 4 wheels, I would remove the brake proportioning valve you have.

The 23mm ATE MC you have is for 69-74 cars.

There is some great advice here and you can read more at; http://www.rennsportsystems.com/1-sf.html and at; http://www.rennsportsystems.com/2c.html

I hope this helps,

 

Guys, thanks for advice on the M/C. As for the brake bias, I also have a wilwood adjustable bias valve to sort out any bias problems. The setup that I bought also contained 964 rear calipers, which I was also planning on using (as opposed to 930), but I realize that since these use the stock rear rotor, I'm not gaining much there.

Aside from bias problems, is there anything else wrong with using just the 930 fronts? A friend of mine that races his SC uses 930 brakes on just the fronts (along with adjustable bias) and has had no problems, but my Carrera is about 300lbs heavier. I also have cooling ducts from the front valance to the front rotor, but no extra cooling in the rear.

I'll take a look at the articles mentioned.

Stacy

 

You absolutely need to do something w/ the rear brakes to balance 930 calipers and rotors in the front. Best is 930 rear calipers on 930 rotors. next best is 964 calipers on 930 rotors, like this


As Steve said use the '78-89 930 m/c 930 355 011 03 for best results though for temporary use and marginal results you can get away w/ the stock Carrera m/c.

The Boxster brakes on a CArrera are for posers only.

 

Thanks Bill. I didn't realize that I could use a 930 rotor with the 964 caliper. Is that the front or rear 964 caliper, or is there any difference? I already have the rears off of a RS America. I'm going to get the Turbo M/C since this is for track use, and there is no sense taking the fun out of track time with spongy brakes.

After spending a couple of years on the Boxster brakes, I'd have to agree with your opinion of them.

Stacy

 

The exterior appearance of the front and rear 964 calipers is the same. But you would want to use a 28/30 rear. The resulting bias is a little front but still good, especially for a race app.

Yes, ergonomicaly the 23 is way better.

 

Thanks Bill. The calipers I have are the 964 rears. I took a look at the calipers last night, and noticed that the 930 rotor would not fit in the caliper due to 4 small 'lobes' (for lack of a better word) that intrude into the space for the rotor. I went back to your web site on brakes and you mentioned that the calipers can either be machined or spacers added. Is it OK if I just grind these lobes off?

I do have another question regarding redrilling the caliper for the 3" bolt spacing. I haven't had this done yet, and was thinking of going the VCI route (although it's $$$, especially in Cdn $) until I saw picture of your rear caliper on your site. It looks like you just filled the existing hole and redrilled new ones. Was there enough room, or did you build up the area before drilling the new hole? I looked at my caliper and seems like a new hole for a 3" spacing would be very close to the edge.

Stacy
(Looking forward to finally having good brakes).

 

Yes, they should look like this



If you get a chance post a pic of the stock throat area to give others a chance to see what we are talking about. I gave up on the 964s after the 965s became available. This is the best I've got a 964 and a 965 side by side



No there's room. T holes will need to be ~12.5mm from the the flat of the caliper. They will look like this

 

Part I:

Here is a pic of the caliper with the 'lobes' that I talking about. As you can see by the measurement across the bottom (lower measurement is in cm), the opening is only 26.5mm, not wide enough for a the 28mm 930 rear rotor, but plenty wide for the 964 rotor.

 

Part II:

This shot shows the full width of the throat. As you can see, the throat itself is 32mm wide.

 

Part III (of III)

This pic shows the 'lobes' and the steel clip that keep the pads in. Here you can see a bolt on either side that holds the clip in place. Since the bolt head sticks out as far as the 'lobe', I guess that will have to see a little grinder action as well. Hopfully leaving enough of the bolt head to actually get it out if I ever need to.

Bill: Is the 965 caliper body, a 964 caliper body with a spacer (similar to the Carrera and SC caliper)? If so, I'm wondering if it would be easier to get the spacer for the 965 caliper and just widen the 964 caliper.

Stacy

 

The 965 rear caliper has a 2mm wider pad box that is designed for a 28mm rotor. It also has 30/34mm pistons which is too large for your needs. You will need to open up the throat w/ a grinder as pictured in my post.