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Solving a Hub and Spindle Mystery: Part 1
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ideola  



Joined: 01 Oct 2004
Posts: 15500
Location: Woodstock IL

PostPosted: Sun Nov 02, 2008 8:48 am    Post subject: Reply with quote

OK, this should be revealing (and Dave, you were partly correctly, but partly not):
  • 1987-88 924S: spindle=31.72mm diameter; caliper holes=76mm center to center
  • 198x 944: spindle=31.72mm diameter; caliper holes=76mm
  • 1986 944S: spindle=31.72mm diameter; caliper holes=76mm
  • 1986 951: spindle=31.72mm diameter; caliper holes=94mm (this is the one my Brembo calipers came from)
  • Myster car: spindle=31.72mm diameter; caliper holes=89mm
  • 198x 951: spindle=35.00mm; caliper holes=76mm
  • 1987 944S: spindle=35.00mm; caliper holes=76mm
  • 1989 944S w/ABS: spindle=35.00mm; caliper holes=76mm
All measurements are somewhat approximate, could be a few 100ths off one way or the other.

So from this somewhat scientific survey, it appears to me that 1987 was the switchover to the larger diameter spindle, which means that the hubs of the variety on the left and in the middle will work on the early spindle. I confirmed this by fitting them up to the 924S spindle. And by the way, Vaughan Scott is running hubs from a 1986 944 with early spindles on his race car, so I know this combo works.

The interesting piece is the mystery spindle. It comes with inserts for adjustable tie rod end links, and the calipers are NOT like the standard iron lumps. They are slightly larger pistons, a different-looking housing, and the mounting points are 89mm apart center-to-center vs. the standard 76mm for the stock iron floating calipers and the 94mm for the fixed Brembo style. An in-betweener if you will. I'm wondering if these might be from a CGT...
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15 981 GTS | 88 924S SE | 82 931 Holbert | 82 931 Rallye | 81 937 | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 80 US 931 | 80 931 GTR | 79 Sebring | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition | 77 Martini
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ic932  



Joined: 11 Feb 2005
Posts: 1104
Location: UK

PostPosted: Sun Nov 02, 2008 10:18 pm    Post subject: Reply with quote

Dan, interesting fact to know that the 86' 951 had the thinner 31.72mm spindles. i too can confirm that the 86' 944 hubs/spindles are interchangable with the preceeding models inc the 931. they are identical apart from having no hole drilled through them for the speedo cable.

it would be an interesting exercise to compare the weights of the various model year spindle/hub/disc/caliper assemblies. any chance you could weigh the 86'951 assembly? it would be nice to compare it with my 90' 944S2. i'm pretty sure those later style discs must add considerable unwanted unsprung weight...
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ideola  



Joined: 01 Oct 2004
Posts: 15500
Location: Woodstock IL

PostPosted: Sun Nov 02, 2008 11:21 pm    Post subject: Reply with quote

Yes, that's a good idea...the only thing I can't weigh though is the later style rotor cuz I don't have one of those. Since they're all disassembled, I'll weigh each piece individually, then we can add it up.
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15 981 GTS | 88 924S SE | 82 931 Holbert | 82 931 Rallye | 81 937 | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 80 US 931 | 80 931 GTR | 79 Sebring | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition | 77 Martini
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ic932  



Joined: 11 Feb 2005
Posts: 1104
Location: UK

PostPosted: Mon Nov 03, 2008 3:00 am    Post subject: Reply with quote

cheers, no problem i can weigh the later 944N/A set-up aswell.
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ideola  



Joined: 01 Oct 2004
Posts: 15500
Location: Woodstock IL

PostPosted: Wed Nov 05, 2008 4:39 am    Post subject: Reply with quote

OK, I'll be posting photos and stuff over in the definitive 5-lug conversion thread. Here is a diagram to show what it was that I measured:

A = diameter of the spindle where the hub bearing sits
B = diameter of the spindle at it's largest point
C = center-to-center bolt pattern for caliper
D = center-to-center bolt pattern for strut housing
E = width of strut mounting flange

Here are the measurements I took last night, indicating that there are at least four different variations on the spindles (differences highlighted in bold red italics). All measurements are approximate. Center-to-center numbers were calculated by measuring the furthest distance between the bolt holes, and then subtracting the diameter of one bolt hole from the total distance.

Early 924 5-lug (a.k.a. M471 option) / 86-88 924S / 83-86 944 NA
Part numbers 477.407.311 and 477.407.312
These should all have the mechanical speedo cable hole
A = 31.7mm
B = 45mm
C = 76.5mm
D = 58mm
E = 20mm

Mystery spindle with adjustable tie rod ends (possibly 924 GTx or D-Prod variant???)
A = 31.7mm
B = 45mm
C = 89mm
D = 58mm
E = 20mm

1986 951 (with Brembo 4-pot fixed caliper upgrade)
A = 31.7mm
B = 45mm
C = 94mm
D = 63mm
E = 18mm

1987 and beyond 944
A = 35mm
B = 45mm
C = 76.5mm
D = 63mm
E = 18mm

What I'm missing is a post-87 951 setup, but according to PET, it's the same as the NA; I'm also missing the so-called M030/758 option, which I suspect is the same as the NA except for the caliper bolting arrangement, which I suspect is the 94mm arrangement to accommodate the Brembos. However, I can't be certain of this because I do not have an example spindle nor do I have an example Brembo, and PET shows a different part number suffix for the post 87 Brembo caliper than the 86 Brembos. So, until we get one of these setups in somebody's hands that can measure, the jury is out on the M030 stuff.

I also did some approximate weighing. I do not have a sufficient scale to do this with any precision, so these figures are strictly estimates, but interesting nonetheless. I forgot to weigh the calipers, which will make this info complete, but I can do that tonight and post an update later.
Code:
             spindles   hubs      discs    calipers   total
-1986 NA       13       9.5       17.5        ?       40
1986 951       13       9.5       27          ?       49.5
1987-          13       7.5        ?          ?       20.5
M030/758       ?         ?         ?          ?

Everything was weighed in PAIRS, so individual pieces will be approximately half of what is listed above. The hubs were weighed with studs, locking nuts, and bearings intact.

It occurred to me this morning that I might want to go back and verify the dimensions of the tie rod connector on the spindle, as well as the ball joint attachment geometry, as these could be different as well. I'll do that this evening. Some observations and conclusions to follow.
_________________
15 981 GTS | 88 924S SE | 82 931 Holbert | 82 931 Rallye | 81 937 | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 80 US 931 | 80 931 GTR | 79 Sebring | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition | 77 Martini


Last edited by ideola on Fri Mar 27, 2009 11:30 pm; edited 1 time in total
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ideola  



Joined: 01 Oct 2004
Posts: 15500
Location: Woodstock IL

PostPosted: Wed Nov 05, 2008 6:25 am    Post subject: Reply with quote

Notes and observations:
  1. Based on the part numbers, I believe anyone doing a five lug conversion that wishes to retain the mechanical speedometer arrangement MUST source from one of the following platforms: any early 924 with the M471 4-wheel disc option (introduced as an option on 931's in 1979, available as options on NAs beginning in 1981, standard on 1981 and later 931's); any 1986-1988 924S; and any 1983-1985.5 944. The 1986 NA appears to have the same part number, but it's not clear if it came with the speedo cable hole. I have at least two examples of 944 spindles from unknown years that match all of the measurements listed for the early 944's, but do NOT have the speedo cable hole.
  2. With the introduction of the 951 in 1986, there appears to be a spindle and hub combination that is unique to that year. According to what I can see in PET, the Brembo 4-pot fixed calipers were standard on the 1986 951 (i.e. not an option). This required a spindle that is essentially identical to the NA version except for the caliper bolt pattern. Furthermore, the hub for the 1986 951 appears to be unique to that year. As depicted earlier in the thread, the depth of the backside of the hub is approximately .5" or 12mm shorter than the NA hub, even though the rest of the geometry is essentially identical. This was to accommodate a much larger brake disc, which not only has a deeper hat, but a larger overall diameter. For now, and until I can confirm this conclusively, I think it is best to assume that the 1986 951 hub is not compatible with the early style cast iron calipers due to a much thicker disc surface and a much larger diameter. Consequently, the 1986 951 spindle and hub arrangement is not an ideal conversion IF you wish to maintain a mechanical speedo and stock 924 strut housing.
  3. From what I can tell, all non-M030/758 cars from 1987 onward (or at least thru 1990...I haven't done exhaustive research on the post-1990 cars) have the same spindles whether NA or Turbo. This includes cars with the ABS option.


More to follow, but will need to finish up later....
_________________
15 981 GTS | 88 924S SE | 82 931 Holbert | 82 931 Rallye | 81 937 | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 80 US 931 | 80 931 GTR | 79 Sebring | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition | 77 Martini


Last edited by ideola on Fri Mar 27, 2009 11:30 pm; edited 1 time in total
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ideola  



Joined: 01 Oct 2004
Posts: 15500
Location: Woodstock IL

PostPosted: Tue Nov 11, 2008 4:17 am    Post subject: Reply with quote

Still need to finish the above, but I think I have solved the mystery of the spindles and brake calipers, with the help of a friend in the VW community.

I believe the spindle and drop link components are bonafide D-Prod parts:
933 099 341 17 : Spindle - left
933 099 341 18 : Spindle - right
933 099 341 19 : Standoff - Conical spacer for steering arm (lowers tie rod)
As listed on this pretty obscure page on our own 924.org: http://www.924.org/models/924Dpartslist.htm

Now, the interesting thing is that the calipers I photographed are two pot steel calipers, and my VW friend said they appeared to be early 911 calipers which are known to have the 89mm spacing that I identified on these spindles and matching calipers, sent me some pix of some he'd converted to run on a VW, and they look very similar (although not identical). However, reading more carefully on the D-Prod history page, it indicates that the D-Prods ran 930 brakes. So, I am surmising that these bits are D-Prod. Hubs are standard early 5-lug.

{EDIT}
Clip from PET (911_USA_78_83_KATALOG.pdf, illustration 602-00) compared to photo:

9) 911.351.425.02 (L) & 911.351.426.02 (R)
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15 981 GTS | 88 924S SE | 82 931 Holbert | 82 931 Rallye | 81 937 | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 80 US 931 | 80 931 GTR | 79 Sebring | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition | 77 Martini
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ideola  



Joined: 01 Oct 2004
Posts: 15500
Location: Woodstock IL

PostPosted: Sat Dec 06, 2008 12:12 am    Post subject: Reply with quote

Still need to weigh the calipers, but here are the metrics in a public Google docs spreadsheet:
http://spreadsheets.google.com/ccc?key=po7Rlxw3vnMloMgxNGvEIKg
_________________
15 981 GTS | 88 924S SE | 82 931 Holbert | 82 931 Rallye | 81 937 | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 80 US 931 | 80 931 GTR | 79 Sebring | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition | 77 Martini
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huckster  



Joined: 22 Dec 2006
Posts: 115
Location: Burnaby B.C.

PostPosted: Sat Dec 06, 2008 6:32 am    Post subject: Reply with quote

Very interesting Thanks for sharing. You have endless energy!!
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