Brake upgrade questions

[The Turk]

I'm getting ready to upgrade the brakes on my 1975 911 wide body.
I've searched and read everything I could find but I still have a few questions.
The car has 16" wheels and I have front & rear 1995 993 calipers, a machinist buddy will make adapters for the front and do the mounting hole and throat modification (to allow 28mm) on the rears.

Here are the questions:

1. Will the 1 piece 81-89 Turbo/930 front rotors (Pelican part #'s 930-351-047-02-M259 & 930-351-048-02-M259) bolt up to my hubs ?

2. Are the 78-89 Turbo/930 rear rotors (Pelican part #'s 930-352-045-01-M259 & 930-352-046-01-M259 the correct ones for this upgrade ?

3. Since the car doesn't have vacuum assist brakes, what master cylinder do I use ?

All advice and/or comments will be appreciated.

[The Turk]

I know Bill Verburg can answer these questions...

[Bill Verburg]

Will the 1 piece 81-89 Turbo/930 front rotors (Pelican part #'s 930-351-047-02-M259 & 930-351-048-02-M259) bolt up to my hubs ?

As long as you have the late 930 hubs which have built in o/s, yes

Are the 78-89 Turbo/930 rear rotors (Pelican part #'s 930-352-045-01-M259 & 930-352-046-01-M259 the correct ones for this upgrade ?

Yes

Since the car doesn't have vacuum assist brakes, what master cylinder do I use ?

ATE (ports face left) # 03-2123-3402.3, best to buy a kit w/ the elbow, fill extension, extended rod, plug and copper seals. Wayne ought to have it if he doesn't, SRP and Steve Weiner certainly do.

[The Turk]

Bill,
Thanks for responding back.
Since my car started as a narrow body I'm guessing it doesn't have the 930 hubs, I currently run a 1 inch spacer in the front.
I want drilled rotors to match the 930 rears, what are my rotor options without changing to the late model 930 hubs ?
What do you think of using the 993 rotors and turning a little
(.12 I think) off the OD off the hub ?
Thanks again, I really appreciate the advice.

[Bill Verburg]

My choice would be the '78 - early '80 930 floaters, keep your stock hubs and spacer. This is expensive but is also best.

You can also get drilled rotors and a flat hat from VCI, but the drilling won't visually match the rears and the rotors weren't cast that way anyhow.

Steve Weiner cuts down 993tt 2 piece rotors and supplies the correct flat hat, drilling will match rears. I am somewhat uncomfortable w/ the proximity of the outer holes to the edge. But Steve and users haven't reported any problems even w/ very severe track usage which quickly destroyed the VCI rotor

[The Turk]

The floaters are probably out of my league, it looks like the rotors alone are around $800 and I'd still need the hats and hardware.

This is a street car that will see no track time but I do tend to drive it fairly aggressively.

Any thoughts on using the 1 piece 993 rotors and turning a little (.12 I think) off the OD off the hub ?

I think Instant G sells a modified (turned down) hub for this purpose

[KTL]

Keep wheel fitment in mind. If you're using Fuchs, you'll want to make sure you've got the appropriate wheels or the necessary spacers.

If you use the factory 993 front rotors over a machined hub, there are a few things to keep in mind.

1. The 993 rotor and the hub should be drilled to index the rotor onto the hub with screws, just like your current rear rotor attaches to the hub.

2. The use of the 993 rotor over a machined hub pushes the wheel outboard and also requires longer wheel studs for your front hubs.

Here's a great topic that covers the install done by Jeff/Slider79SC

993 brake upgrade with 993 front rotors

If it's going to be street only, you honestly could get away with a Boxster brake upgrade like TRE does (http://www.tremotorsports.com/Brakes.htm) or do what I did and use Wilwood 309x32 HD front rotors with appropriate flat hat adapters & caliper adapters. Rear rotors can be 84-89 Carrera rear rotors. Saves you alot of money and the rotors visually match (no cross-drilling though, unless you have that done- but why bother).

Bill will scold me for recommending the Carrera rear rotors that induce pad overhang. I don't like it either, but Chris Streit's 3 years of full-on racing with this setup in the rear and no ill effects leads me to believe that a bit of pad overhang for street use is not the worst thing. Again, i'm not too fond of the idea either, but it works.

I really think a cool setup would be the 993 fronts with TRE's Boxster rears. The TRE rear appeals to me because of their adapter bracket makes for easy installation of the caliper and no modifications are necessary to the calipers. I think this rear arrangement is pretty slick.



Just bolt it on. Plus you can use the Carrera rotor- with no pad overhang! Granted the bias is a little more front, but for street use (or even DE track use) you'd hardly notice? Okay, the calipers wont match and you've got to order front and rear pads for two different OEM applications (993 front, Boxster rear). I'd trade non-matching calipers for ease of installation without a doubt.

Also make sure to have your friend redrill the rear 993 calipers so it sits high enough over the rotor (only applies to 930 rotor) to avoid interior radial clearance. I tried to snuggle my calipers down as far as I could to help with wheel clearance on my 16x8 Fuchs. All that accomplished was more grinding inside the caliper and they still don't clear my 16x8 Fuchs.......

[Bill Verburg]

For street use the 993 rotors over machined hubs will probably be fine. At least no one has reported any issues in that use. For track use the hubs take a beating, even the much beefier 930 hubs need regular replacemet when used heavily on track.

[Bill Verburg]

P.S. When using the 993 one piece rotors you are giving up one of the big advantages of the two piece, i.e. lighter weight w/ improved heat handling

[The Turk]

Kevin,
I already have the 993 calipers and I'm committed to that upgrade path, I'm currently using 16X10 (rear-no spacer) 16x9 (front-1" spacer) BBS style 3 piece wheels, if I end up going the
993 front rotor I'll reduce the thickness of the spacer by whatever amount the rotor adds.

I hope the wheels clear...

I checked out the picture on the link you attached to Slider79SC, it looks like the two screw holes used for indexing the rotor sit over the recessed area where the bolts that normally hold the rotor go.

Do spacers get made and go between the hub and the rotor for the indexing screws ?

It doesn't look like Slider79SC used the indexing screws, what
is the purpose for them ?

I really appreciate the info, thanks a lot.


Bill,
I'm going to make a few calls on Monday or Tuesday to see what the exact total cost for front floaters will be but it looks like for starters I'll have go with the 993 front rotors and the 930 rotors on the rear.

Thanks again for all your advice.

[KTL]

Gary,

No spacers are made for indexing. The setup that Jeff uses with the 993 rotors is a slight press fit onto the hub. That sort of accomplishes the same thing. Dave Bouzaglou @ TRE recommends the indexing with screws to prevent pad knockback. I've never dealt with this setup myself and i'm just passing along what Dave recommends. He mentioned the 993 rotor use is not necessarily worth the effort, as there's other alternatives.

Your BBS 3 piece wheels will clear the brakes no problem. I have a set of BBS RSII 16x8, 16x9 wheels for track use. They have more than adequate clearance on both the front and rear of my car. I temporarily have the front 16x8's on the rear with 930 factory spacers until I get my 16x9's squared away (one is damaged). Otherwise no spacers would be necessary with these wheels.

Same goes for the Forgeline wheels that Jeff/Slider79SC has on his car. A friend of mine has a set of those and there's more than enough clearance with those too. Fuchs are a tight fit because of the taper on the barrel inside the wheel. The fuchs with deep hubs (951 16x7, 16x8 and 930 16x9) have better fit and can get by without spacers.

[The Turk]

The saga continues....

REARS - 930 rotors / 993 calipers with plugged & redrilled mounting holes.

I finally finished the rears they turned out exactly as expected, Perfect !!

FRONTS - 993 rotors on turned down hubs / 993 calipers with adapters for the 3.5" struts.

Now the problem, I decided to do a little test fitting before machining the adapters. take a look at the attached pictures, it doesn't appear the standard square caliper adapter is going to work.

Does this combo require a different adapter ?

Any info or pictures of the adapter from anyone that has done the 993 rotor and caliper upgrade with 3.5" struts would be greatly appreciated.

Bill V,
Please no " I told you so's"

[Bill Verburg]

Never tried this so it's new to me too, Can the rotor be set up w/ less o/s? Or will that cause interference at the steering knuckle or ball joint?

[The Turk]

Unfortunately the offset can't be adjusted because of the one piece rotor.

[img]http://forums.pelicanparts.com/uploads7/IMG_53001146

I know other guys have done this (993 rotor on a turned hub) , there's nothing unusual about what I'm doing, I'm hopeing some of the guys that have done it or are working on it will pipe in...

Pictures of the adapters that work is what I need...

SliderSC , KTL (Kevin), Duke Zink and a few others that I've forgotten their names, are you guys out there ??

[The Turk]

Here's the picture that I tried to attach of the hub / rotor.

[The Turk]

bumpola

[JeremyD]

Looks like the hub is not turned down enough. The rotor should be much closer to the spindle.

1. I don't like this mod because I don't think the hubs are over engineered enough to take material off.

2. I think with the extended "hats" of the rotors you are more likely to transfer heat into the hub.

[The Turk]

Hi Jeremy,
When you machine down the hub you only take a little off of the circumference, you don't take any off of the front side which is what stops the rotor from going on the hub any farther, as you can see from the picture this rotor is all the way on the hub.

I agree with both of your other points, this is not the best method but most people agree that it should pose no problems on a street only car.

[TRE Cup]

gary
we have the adaptors for the front only to install the 993 calipers exactly how you have yours set up. 993 front calipers, turned hubs to support and center the discs, and stock 993 rotors. contact me at info@tremotorsports.com for price
thanks
dave

[Slider79SC]

Gary,

I used a hub from Steve Timmons that I belive to be a 944 hub. This hub and the standard Racers Group adapter worked perfect.

I am not sure that I can help more than this..... Sorry.

The hubs were about 450 including new bearings.