Jerry Feather

Not so quick. Greg's post lacks some important details, such as when exactly was the "hay day" for the 951 in racing mode and which model years of the 951 were involved then. I did a little research online about the 944 hubs and can find very little, but one site I found about the offset involved describe in some detail that the 86 944 hubs are "very much lighter" than the 87 hubs. I kind of take that to mean 86 and before and 87 and later. The 87 and later hubs look very much like the 928 hubs in terms of heft, although there is a very slight difference in favor of the 928, as viewed in the pictures I previously posted. I can find almost nothing online about 944 hub failures except a site selling the billet hubs for nearly $700 each for racers. In the sales pitch there they only make reference to the "problem Porsche left us with."

So, my intuition is telling me that the 87 and later 944/968 hubs that look so much like the 928 hubs have most likely solved the problem that Greg has brought to our attention. I hope he has much more to contribute about it because I would not like to see that look on his face.

It is also interesting to note in the offset discussion I found that the later hubs also involved what they are calling "Big Black" brakes and those are apparently derived from the 928 S4. That suggests that the 944 big black brake rotors may very well be the ones to utilize with the 944 hubs (billet or otherwise) in adapting them to the 928 for the intended offset purpose this thread is about.

icsamerica

I get all that and I appreciate it.

Bottom line... this something that carefully needs to be considered. A billet hub is an off the shelf option, and a good one if this works out. That option makes the solution even more viable albeit at a price and that's OK. Costs can be dealt with, they offer a choice.

I understand as manufactures progress their processes get better. Case in point I built a "high Hp" Jaguar long ago. At that time it was about 350 HP and the rear hub cracked. Some one on the Internets told me I should go check them and that's a wonderful thing.
The solution was to use a hub from a later model but was dimensionaly the same. Eventually the car progressed to the track with 500 HP and much higher stresses with the brutalness of quick manual shifts. So far so good but I check things more often and never ignore a noise or click. A 600 HP turbo Inline six is in process and slated for next years track work.

dr bob

Circling back to post #6, where it looks like we need a new hub with the same bearing spacing as the 928 has now. That should eliminate the concerns about the 951 hub bearings too close together and working at the wrong angles. The actual wheel mounting face needs to move 10-15mm towards the large bearing end to help with the offset offset we want.

Then the issue of caliper mounting gets ugly. I haven't found any offset bolts that would let us install 4-piston calipers to clear a wheel that's 10-15mm inboard of original. I think the clearance I have now is enough to allow a little wheel and bearing flex without hitting the caliper, but not much more. I'd need to clay the caliper to verify actual clearance, by a mark-VII eyeball makes that about 1/4" (6.3mm) now. A few years ago, a creative user here came up with an offset spacer for the calipers to move them back, and out from the center to allow bigger rotors with stock calipers. MK did his initially with washers for a bigger rotor, but that's weak and doesn't do anything for the lateral position change needed.

The outer bearing end of the new hub won't come close to allowing the wheel centers we use now, as the nose of the hub will be well past the wheel face at least with the Porsche wheels I know.

To work with that inboard mounting and the new caliper position, we'll need to use something very close to the rotors and hats we have now, and that means there's a clearance problem inboard of the rotor itself. Decide how far you can move the rotor in without hitting stuff. The rotor shield will need to be removed and a new mounting figured out. The same mark-VII eyeballs say that the rotors will still have an issue with the spindle frame that's just inboard of the stock shield.


As we are mocking up pieces, it's probably a good idea to actually mount them on a car and make sure we get the biggest head-slap moments out of the way early.



Do we need to look hard at Panamera spindles?

Gary Knox

Jerry,

You referred to 'Big Black calipers'. I'm pretty sure these are the same as the 'Big Red calipers', just painted a different color. The Big Blacks were the front caliper on the 928 GTS, and the Big Red were the rear caliper on the 993 Turbo. When I bought front pads for my GTS, they were the same part number as those for the rear of the 993 Turbo.

Yes, Bob, as you note. There's a lot of stuff between the inside of the wheel spokes and the Crossbar. Most of it is important as I recall (over 6 years since I did a close-up and personal examination).

Gary

GregBBRD

I'm pretty sure that you could get one of the people that make adapters for high performance, aftermarket rotors (like Alcon) to make a custom hat to get the rotor back where it belongs.

My thinking is:
By the time you buy a billet spindle, an aftermarket rotor, and a custom hat for the rotor, you could buy a custom wheel built to the specifications you desire.

worf928

Sooo... lemme get this straight:

Billet hubs, different brake disks, something to space the calipers, and I don’t see how any of this works without extensive machine work in the steering knuckle. Or maybe it’s just custom knuckle, custom hub, bespoke disc, different bearings.

And the labor cost to do the swap and alignment.

All this so I can run some wheels I find cheap on ebay?

Instead of $x,xxxx in custom parts and the labor to R&R the front end, I’ll call Augment, or any of the other half-a-zillion companies that will make a wheel with any offset, and then use the money I save for gas and the time I save to drive.

Seriously. What am I missing?

GregBBRD

Glad to see you are back.
Missed your expertise!

And logic....

drooman

I knew if we floated out enough crazy concepts he would not be able to resist indefinitely

worf928

This... —^

Adamant1971

It would likely be cheaper to buy a custom set of wheels from Augment, and a hell of a lot safer. Just my 1.55 cents

dr bob

Come on guys-- We might be able to do it with custom balljoints with offset stems. The stems would have to index in the spindle. Or maybe better, redo the tapered holes in the spindle with an offset reamer. Think outside the box a bit!

Gage

Good idea, you'd need a negative offset reamer though... I think.

icsamerica

All good points to consider.

Have you priced a set of custom wheels Lately? A good set can approach 5 figures and look garish or out of place on a 928. Quite frankly lots of newer Porsche wheel look 'right' on a 928.

Everyone has different needs and my calculous is a bit different than the scenario your questions lead to. The following points also factor in to my situation.

1. Here in the north east wheel and tires are disposable, I'm over custom wheels. You can hit a pot hole and wham, ya gonna need a new wheel, tire or both. I've been down this road with a BMW I owned many years back, I cracked a wheel in a custom set and after a few years replacements were no longer available. Same thing happened to me with a GTO I bought recently that came with a set of semi-custom VMR wheels. Now I need a replacement, VMR no longer makes that specific wheel. There's a whole industry for wheel repair here in the North East too. Some wheel damage cant be repaired and sometimes the end results of a wheel repair aren't that great. Often you just need a new wheel or two. A few years back I hit a pot hole so big I blew out both tires and bent both wheels on one side with my Escalade ESV (family hauler). That was a $2000 day.

2. I'd need 3 sets of wheels with custom offsets. Track, Summer UHP and Winter AS. This may not be the case for most but it is for me so it makes sense not to rely on a custom one off wheel. Ultimately, I may need a custom set of wheels for the track and thats OK too. I'll have more choices and lower costs when specifying a more common configuration found on other P cars.

3. I see the brake disc issue as an opportunity to fit larger brakes for track duty.

4. The price of the wheel and whether its "cheap on ebay" isn't the only consideration, availability of a replacement is a major factor.
I considered getting a wheel widened, which fixes the offset problem but welded wheels are 1 off's that are time consuming and expensive to replace when need be and they cant be used on track. Ultimately I may need a custom set for the track and that Ok too.

5. My labor costs for installation and alignment are Zero, Like others here, I do my own work and I do full, custom and detailed alignments in my garage. Perhaps the cost is even less than zero as I find this kind of work relaxing and almost therapeutic. Moreover, the success I had with the rack on the street and the partial success on the tack was quite motivational and confidence building which for me leads to better results at my paying job.

I dont know if this is all going to work but it might and I have to try, that's just how I'm wired. I have to try and if I fail, at least I tried. My last re-engineering project was a complete re-do of the of rack for greater precision and lighter feel. After a few revisions, it worked out far better than I anticipated. In the beginning of that project, there were doubts too. Some well founded but in the end, the lighter and more precision steering transformed the car but it still drives like a 928 and perhaps more like the designers original intent. I say this becasue the early 928's with their lower curb weight and skinny tires may have felt more direct than the heavier and later 928's with wider tires. The rack results were so good it motivated me to keep going and re-develop and improve the 928 in ways that I can appreciate. I recently let a friend drive my 928, he's a track friend and high strung guy into moto GP bikes, unprompted he said "the steering in that car is amazing", I feel the same way and that success has motivated me to keep going.

This endeavor may not work out, I have no illusions and it wouldn't be my first fail by a long ways. There's lots of aspects yet to be considered, tested and developed. So far I appreciate the feedback. I've learned somethings I didnt know (billet hubs) and had my mind cleared and focused on why I'm dong this. Had a few laughs too at some of the snide comments. Nothing bad about that. Stay tuned.

icsamerica

Cheaper? I dont think so by a factor of 4. Have you priced a set of custom wheels lately?

worf928

Yes.

If you're looking at three sets of wheels, aren't paying anyone else to futz around with your 928 and you want this extra challenge then go for it.

If you've done the cost/labor/stress/fun trade off and that makes sense to you, then it's all good.