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> Lug-centric to Hub-centric?
gord
post Jun 29 2020, 09:44 PM
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I'm in the process of getting a 1972 safety certified (for registration in Ontario), and the inspecting mechanic has raised the issue of the lug-centric rear wheel design. While I'm pretty sure he's going to issue the certificate based on the fact that this is the way Porsche sold the vehicle in 1972, he has opined that changing a flat tire at the side of the road would be difficult or even impossible with this design...

I understand Porsche did change the hub/wheel at some point, so I guess I'm wondering if there's an option of "upgrading" from a 1972 rear hub to a later model year that would provide an easier way of centring a wheel on the hub? Or did the rear wheel design remain unchanged throughout the entire production period?

Any insight here would be appreciated!
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Mueller
post Jun 29 2020, 10:24 PM
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QUOTE(gord @ Jun 29 2020, 08:44 PM) *

I'm in the process of getting a 1972 safety certified (for registration in Ontario), and the inspecting mechanic has raised the issue of the lug-centric rear wheel design. While I'm pretty sure he's going to issue the certificate based on the fact that this is the way Porsche sold the vehicle in 1972, he has opined that changing a flat tire at the side of the road would be difficult or even impossible with this design...

I understand Porsche did change the hub/wheel at some point, so I guess I'm wondering if there's an option of "upgrading" from a 1972 rear hub to a later model year that would provide an easier way of centring a wheel on the hub? Or did the rear wheel design remain unchanged throughout the entire production period?

Any insight here would be appreciated!


One could use a temporary screw-in stud to locate the wheel. Insert 3 bolts, replace screw-in stud with 4th bolt.

google "14mm wheel stud pilot pin" , and feel free to share with the inspector.
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davep
post Jun 30 2020, 06:43 AM
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Time for a new mechanic. (IMG:style_emoticons/default/wink.gif)
It is not difficult, and certainly not impossible to change a wheel.
The easiest way is to jack the car up so that the wheel is in the correct position with perhaps a quarter inch clearance to the ground. Install all the bolts loosely until all are nearly in place; start at 3 o'clock, then 9, 12 & 6. Tighten one up, but do not torque it, until it seats; wiggle the wheel to be sure it has seated. Tighten the diagonal bolt, then the final two. I find it best to make sure they are tight again, then lower the car down and torque in two steps with a criss-cross pattern to final torque. Check torque again after a 100 miles or so.
I do not recall any hub-centric parts for the rear of the 914, and only hub-centric rotors for the very late 1972 and later model. Not all rims are hub-centric either.
While a hub-centric system aids getting the rim in place, it is ultimately the cone on the bolt mating with the cone on the rim bolt hole that will locate the wheel on the hub.
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wndsrfr
post Jun 30 2020, 06:45 AM
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QUOTE(Mueller @ Jun 29 2020, 08:24 PM) *

QUOTE(gord @ Jun 29 2020, 08:44 PM) *

I'm in the process of getting a 1972 safety certified (for registration in Ontario), and the inspecting mechanic has raised the issue of the lug-centric rear wheel design. While I'm pretty sure he's going to issue the certificate based on the fact that this is the way Porsche sold the vehicle in 1972, he has opined that changing a flat tire at the side of the road would be difficult or even impossible with this design...

I understand Porsche did change the hub/wheel at some point, so I guess I'm wondering if there's an option of "upgrading" from a 1972 rear hub to a later model year that would provide an easier way of centring a wheel on the hub? Or did the rear wheel design remain unchanged throughout the entire production period?

Any insight here would be appreciated!


One could use a temporary screw-in stud to locate the wheel. Insert 3 bolts, replace screw-in stud with 4th bolt.

google "14mm wheel stud pilot pin" , and feel free to share with the inspector.


It's actually quite easy but most of us are trying the wrong way...... just lean the wheel against the hub and start any lug bolt that lines up... then rotate that one to the top and presto, all the others line right up... much more like dance than wrestling....
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914Sixer
post Jun 30 2020, 06:52 AM
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Go see our friend a Tangerine Racing and buy the rear hub centering kit. Make it easy on everyone.


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73-914
post Jun 30 2020, 06:54 AM
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I always start with the top hole at 12 o'clock . Makes it the easiest to start
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mepstein
post Jun 30 2020, 07:02 AM
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Prop the wheel on my foot and start screwing in bolts. Just did all four a week ago. Took 10 minutes. 914-4 wheels and tires are pretty light.
I use a dab of anti seize on the threads.
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GregAmy
post Jun 30 2020, 07:14 AM
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QUOTE(914Sixer @ Jun 30 2020, 08:52 AM) *

Go see our friend a Tangerine Racing and buy the rear hub centering kit. Make it easy on everyone.

+1. I bought these last month and not only did it stop a slight vibration it makes getting the rear wheels on and off SOOOOOOOOOOOOOO much betterer.
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barefoot
post Jun 30 2020, 07:51 AM
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QUOTE
I understand Porsche did change the hub/wheel at some point, so I guess I'm wondering if there's an option of "upgrading" from a 1972 rear hub to a later model year that would provide an easier way of centring a wheel on the hub? Or did the rear wheel design remain unchanged throughout the entire production period?

Any insight here would be appreciated!


My 76 rear hubs do not have hub centering ring.
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ChrisFoley
post Jun 30 2020, 08:38 AM
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QUOTE(barefoot @ Jun 30 2020, 09:51 AM) *

"I understand Porsche did change the hub/wheel at some point, so I guess I'm wondering if there's an option of "upgrading" from a 1972 rear hub to a later model year that would provide an easier way of centring a wheel on the hub? Or did the rear wheel design remain unchanged throughout the entire production period?

Any insight here would be appreciated!"

My 76 rear hubs do not have hub centering ring.

The rear hubs/rotors never changed throughout production. Early alloy wheels did not have the hub-centric bore, making them unusable on later cars at the front only.
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bdstone914
post Jun 30 2020, 08:42 AM
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All 914 rear hubs are lug centric. The front rotors changed in 72 at VIN 019033 to hub centric.
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gord
post Jun 30 2020, 01:52 PM
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I hadn't seen this before — but it would completely resolve the issue.

Thanks!
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gord
post Jun 30 2020, 02:03 PM
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Oh, he's not "my" mechanic, just the closest who's qualified to issue safety certificates for the Ministry... but his point wasn't about changing the wheel per se, but changing it in the context of a roadside puncture, on the highway, in less than ideal conditions, etc...

As I said, I'm pretty sure he's going to issue the certificate, but he wanted to research the car first to verify that this is, in fact, how it was sold from the factory — and what do I know, maybe he wants to cover his butt by verifying with the Ministry or his insurance company that there isn't a liability issue with him signing off on it as such...

Gord

QUOTE(davep @ Jun 30 2020, 06:43 AM) *

Time for a new mechanic. (IMG:style_emoticons/default/wink.gif)
It is not difficult, and certainly not impossible to change a wheel.
The easiest way is to jack the car up so that the wheel is in the correct position with perhaps a quarter inch clearance to the ground. Install all the bolts loosely until all are nearly in place; start at 3 o'clock, then 9, 12 & 6. Tighten one up, but do not torque it, until it seats; wiggle the wheel to be sure it has seated. Tighten the diagonal bolt, then the final two. I find it best to make sure they are tight again, then lower the car down and torque in two steps with a criss-cross pattern to final torque. Check torque again after a 100 miles or so.
I do not recall any hub-centric parts for the rear of the 914, and only hub-centric rotors for the very late 1972 and later model. Not all rims are hub-centric either.
While a hub-centric system aids getting the rim in place, it is ultimately the cone on the bolt mating with the cone on the rim bolt hole that will locate the wheel on the hub.

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