Late 930 Hubs on a 911

[Roamer]

I have been searching for the answer and have not found one here or on Rennlist. What parts exactly are needed to change a narrow bodied carrera front hubs to a late turbo front hub? I would like to use late-front-930 rotors on my brake upgrade instead of the floating style from the 78-mid 80's 930. Also, where can I find the parts, other than through a Porsche dealer ($)?

Thanks in advance!

[Bill Verburg]

It's been posted numerous times.

The late '80-89 front 930 rotors are a 1 piece design which incorporates a 21mm spacer which was a separate/removeable piece on the '78-79 930.

As such they can only be used w/ a widebody car like Thom Fitzpatricks.

IFF you have a widebody car then the late rotors are a bolt on

[Roamer]

Bill, I thought both the hubs and the rotors on the 930 were different from the 911. If not, can the late-930 rotors be bolted to a 911 hub? I am building custom wheels so the offset can be compensated for on the rim.

Thanks.

[Bill Verburg]

Brake disks are mounted on hubs w/ M8bolts and nuts as for the type 911SC cars. They will bolt on. Thom Fitzpatrick has a web site somewhere showing the work he did on his SC widebody 930 brake conversion.

[Roamer]

Thanks Bill, I will try and track it down!

[Wil Ferch]

Bill:
I think Roamer is asking a more specific question.
If the brake discs are bolted to the hub....and if he wants to stay with his narrow body configuration...isn't there a shallow height hub ( factory or otherwise) that can bolt up to a early or late rotor ( again, either factory or or aftermarket) that works "in combination" ?

It sounds like the later hubs won't fit a narrow body car ( because the spacer is "built-in" the hub...leaving the early rotor ( factory or aftermarket) as his only choice. Is this correct? If so, then he's saying can a 930 late rotor ( minus hub) be bolted to a 911 ( type) hub? Is the pattern/size the same? I believe he's saying not to worry about wheel offset and fitments for the moment as he may have a separate solution for *that* part of the interference issue. Roamer...is that paraphrasing correct...as I got confused over yours and Bill's replies ( and previous posts) too !

---Wil Ferch

[Bill Verburg]

Originally posted by Wil Ferch
Bill:
I think Roamer is asking a more specific question.
If the brake discs are bolted to the hub....and if he wants to stay with his narrow body configuration...isn't there a shallow height hub ( factory or otherwise) that can bolt up to a early or late rotor ( again, either factory or or aftermarket) that works "in combination" ?

NO!

Originally posted by Wil Ferch
It sounds like the later hubs won't fit a narrow body car ( because the spacer is "built-in" the hub...leaving the early rotor ( factory or aftermarket) as his only choice. Is this correct? If so, then he's saying can a 930 late rotor ( minus hub) be bolted to a 911 ( type) hub? Is the pattern/size the same? I believe he's saying not to worry about wheel offset and fitments for the moment as he may have a separate solution for *that* part of the interference issue. Roamer...is that paraphrasing correct...as I got confused over yours and Bill's replies ( and previous posts) too !

---Wil Ferch

The '80 on 911 and 930 hubs are not same, but are close enough that the late 930 rotor w/ the integral o/s for widebody use can be bolted on to either one.

The '78-79 930 hub is different and specificly set up for use w/ the floating rotors but can also be adapted for use w/ the later 1 piece 930 rotors.

The biggest difference in the various hubs is the grease cap attachment method and hub centric mechanism.

Just call Doug A. @ VCI or Steve Weiner @ Rennsport Systems. Either can set you up w/ all the pieces that you need @a resonable price w/ no headaches.

[Bill Verburg]

Here is the best pic I can find, it shows the same 911 hubs 1 w/ 911 rotor and 1 w/ a late 930 rotor. This is from Thom Fitzpatrick's website

note the planes(i/o) of the hub mounting faces, 21mm difference

Here is the link.

[Roamer]

So bill, what you are saying is that from 78-89 the hubs in the 911 are different from the 930 preventing a simple bolt-on of ANY 930 rotor onto a 911 hub. The difference in the 78-80 and 80.5- 930 hubs is that space between the rotor and the strut.

However, I am confused as to where the extra 21mm of offset is coming from on the later 930s. From what I understood, the early 930 offset was the same as Carreras, meaning that swapping hubs should allow the use of the early 930 floating rotors on a narrow-bodied car without having too much positive offset. So why is there also added offset in the late-930 rotors? Did they need more than 21mm extra? If so, how much extra was incorporated into the rotor?

It appears that the space is in the hub design, but you also said that there is internal positive offset in the late-930 rotors. It looks to me from Thom's pictures that the hub alone would provide 21mm of positive offset.

Unfortunately Thom was able to absorb the added offset on his widebody conversion that I might not be able to even with custom wheels.

I know I am beating a dead horse, but I am just trying to get this all straight in my mind.

[Bill Verburg]

I am running out of different ways to express the same thing

So bill, what you are saying is that from 78-89 the hubs in the 911 are different from the 930 preventing a simple bolt-on of ANY 930 rotor onto a 911 hub. The difference in the 78-80 and 80.5- 930 hubs is that space between the rotor and the strut.

The hubs are slightly different, yes, they prevent the use of late 930 rotorsNO!!

Some '78-79 930 304x32 rotors w/ floating hats, notice how flat they are?


Some 993 fronts also 304x32 notice the additional o/s. They won't work on a 911


A 2 piece 993 front rotor, just detach the o/s hat and replace w/ a flat one. Perfect for 911


Some Al. metal matrix r304x32 rotors w/ flat SC hats


Some 322x32 993tt w/ stock o/s hats bolted on and separate flat 911 hats ready to bolt on


The engineering drawings for a Brembo 911 rotor it has a small o/s because it is thinner than the 930 part


In Thoms pics you see 2 identical 911 hubs 1 w/ a 911 rotor and 1 w/ a late 930 rotor. That is the only difference. The inner mounting face is fixed to exactly the same spot on the axle by the hub seal.

the outer wheel mounting face when the late 930 rotor is mounted is 21mm further outboard than when the 911 rotor is mounted

[Roamer]

Bill, the pictures are worth a thousand words, now I understand what you were trying to tell me.

What I have gathered from your discussion and a discussion I had with Doug from VCI is that the hub issue boils down to this. The early 930 hub and the 911 hub are the same (as per Doug). However, the 930 rotor hat had additional positive offset (or a built in "spacer") to push the wheel outward. In 1980.5, Porsche changed the 930 set up by using hubs with additional positive offset but used a rotor with a taller hat (more negative offset) to allow the rotor to line up with the calipers which had not moved further outward from the spindle.

Yet another option, Steve at Instant-G makes 993 hubs adaptable to 911s, the only limitation being that the extra positive offset effects wheel offset so you need to have a wheel with greater positive offset to allow it to tuck into the wheel well.

Basically my options boil down to this:
1. Factory hubs with early 930 front rotors and new, longer wheel studs, new wheels with additional positive offset to compensate for the 21mm spacer on the rotor hats;
2. Late-930 factory hubs and rotors, new wheels with additional positive offset as compensation;
3. Instant-G's 993 hubs/adapters and 993 front rotors, new wheels with additional positive offset as compensation; or
4. Custom rotors and hats to fit to stock 911 hubs, spacer to provide caliper clearance if using 6" fuch centers.

Bill, your patience and perseverence are appreciated!

Thanks.

[Bill Verburg]

The early 930 hub and the 911 hub are the same

YES!

However, the 930 rotor hat had additional positive offset (or a built in "spacer") to push the wheel outward

No! the '78-79 930 used a separate 21mm spacer. The rotor and hat have zero o/s. For use w/ a narrow car the additional spacer is left off, for use w/ a widebody it is added on to the hub to push the wheel 21mm outboard.

In 1980.5, Porsche changed the 930 set up by using hubs with additional positive offset but used a rotor with a taller hat

NO! The additional o/s is in the rotor. Which can bolt to either the 911 or 930 hub. In either case the rotor stays in the same position relative to the caliper/strut but the wheel mounting face is now moved outboard 21mm by the ROTOR.

but used a rotor with a taller hat (more negative offset) to allow the rotor to line up with the calipers which had not moved further outward from the spindle

Yes, the '80 on rotor has the 21mm o/s built in, but the only change that there ever was in rotor placement was to accomodate the additional width of the rotors. All of the movement outboard was to the wheel.

Steve at Instant-G makes 993 hubs adaptable to 911s, the only limitation being that the extra positive offset effects wheel offset so you need to have a wheel with greater positive offset to allow it to tuck into the wheel well

Yes, In addition he is using 322mm rotors, he takes a hub from another Porsche model and has it machined to accept the stock 2 piece 993tt 322x32 rotor & hat. This has the same unfortunate effect as the '80 on 930 rotor in pushing the wheel outboard by ~28mm so he recommends an additional 19mm spacer and late o/s wheels. You can do the same thing by using your 911 hubs, '80 on 1 piece 930 304x32 rotors, and then make your wheel o/s +44mm or so.

The best front setup is still your hub, a VCI or Rennsport zero o/s hat and either floating or non floating 304x32 Brembo or Alcon rotor annulus bolted to the hat. If you want more brake use the 322x32mm annulus, but that is overkill for most cars. You will want ~23-25mm o/s 8" wide wheels 16" for the 304mm rotor and 17" for the 322mm rotor

[Roamer]

Got it!

[David]

I'd like to resurrect this thread for one more question that's probably answered above, but I can't find it.

Bill, what is required to run the later 930 front disks on the 78-79 930's? Thanks.

[Bill Verburg]

Originally posted by 125shifter
I'd like to resurrect this thread for one more question that's probably answered above, but I can't find it.

Bill, what is required to run the later 930 front disks on the 78-79 930's? Thanks.

2x 930.341.065.01 hubs
2x 930.341.066.01 caps
1x 930.351.047.02 930 l/f disk
1x 930.351.048.02 930 r/f disk

[David]

I was afraid of that. There's probably a lot of used hubs to be found though.

[palle7688]

wrong, 930 hubs are rarer seen than 930 calibers.
I see you have a widebody car so can probably use them with the onepiece rotors and your calipers. Narrow cars will want the 911 hubs with twopiece rotor with flat hat.

[roadsterswap]

it is late and I have read this about 5 times. I may have missed the answer already posted and sorry if I repeat it....
can i use my 911 hubs with the early 930 flat rotor, with spacer removed and get the same offset as my regular 911 offset? Will the calipers clear the center of the fuchs?
What was the purpose of the spacer? to move the wheel out to fill in the wheel well? Not for brake clearance?

I want the 930 brakes but do not want the extra offset. So my understanding is that I need the flat rotors. I can use my 911 hubs. All is well........

or run the VCI-3510 flat brake rotor kit. my hubs. 930 calipers. This all me to have the 930 brakes and not gain any width at the hub.

[cdrik915]

My brakes , first 930 models .(front )

[palle7688]

"cdrik915"
Your picture shows a 911 hub with '78-'81 two-piece rotor (or smilar)
This is what we want for narrow cars. Use this setup without spacer.
For widebody cars you need the 21 mm spacer with this setup. (Or use the late 930 hubs with one-piece rotors with the bigger o/s, without spacer)