75 280Z -Front and rear hub sizing for rear rotors and aftermarket wheels

[HusseinHolland]

Searching has not brought me any definitive answers. It appears the front and rear hubs are not uniform size?

I'm asking for two reasons -

1)  because I'm converting the rear brakes to disc, and the Milkfab kit uses 300ZX Turbo rotors which have a  67mm bore.

2) I bought Konig Rewind 15x7 4x114.3, 73.1 bore 0 offset - So now I'm assuming I will need hub centric spacers for the rear wheels, but not for the fronts?

Can anyone advise?

[Zed Head]

What do you mean by "uniform size"?

Here's Milkfab.

https://milkfab-engineering.com/

[HusseinHolland]

Andrew from Milkfab got back to me with some info:

"The factory hub diameter on the rear is ~67mm. Most aftermarket rotors and factory drums have a center bore ID between 67mm and 68mm to center the rotor to the hub. 

The wheel itself centers on the studs in the rear so the 73mm inside diameter is for clearing the front hub only."

 

Having wheels not hubcentric seems like such a bad idea, especially when increasing the rotating mass with larger wheels / tires. I'm going to get hubcentric spacers for the rear - 67.1 - 73.1.  Anyone have experience with this?

[HusseinHolland]

3 minutes ago, Zed Head said:

What do you mean by "uniform size"?

Here's Milkfab.

https://milkfab-engineering.com/

Not the same OD F & R

Edited April 19, 2023 by HusseinHolland

[Zed Head]

Looks like you answered your own question.  Center is center, not clear why one method would be better than another, besides perception.  Since Nissan did not use the hub as a surface meant to fit another surface then there would be no reason to have a tight tolerance on the machining process.  So you might find that each of your adapter/spacers will have to be custom-fit.  Don't forget the longer lugs or longer lug nuts.  Don't know what type of nut the Konig's use, tapered seat or shanked.  15mm is substantial.  Or maybe it's 25mm.  Nissan either made a typo or can't do math.  Probably supposed tobe 0.59.

[HusseinHolland]

 

 

There is a significant difference between lug-centricity & hub centricity, I'm sure you understand. Relying solely on lug centricity brings in greater likelihood of wobble or out-of-round. I guess I'll have to figure it out. I'm just surprised that no one has either encountered this or commented on it using aftermarket wheels.

22 minutes ago, Zed Head said:

Looks like you answered your own question.  Center is center, not clear why one method would be better than another, besides perception.  Since Nissan did not use the hub as a surface meant to fit another surface then there would be no reason to have a tight tolerance on the machining process.  So you might find that each of your adapter/spacers will have to be custom-fit.  Don't forget the longer lugs or longer lug nuts.  Don't know what type of nut the Konig's use, tapered seat or shanked.  15mm is substantial.  Or maybe it's 25mm.  Nissan either made a typo or can't do math.  Probably supposed tobe 0.59.

 

Edited April 19, 2023 by HusseinHolland

[Zed Head]

29 minutes ago, HusseinHolland said:

Relying solely on lug centricity brings in greater likelihood of wobble or out-of-round.

I don't think so.  If the wheel is properly designed for a lug centric application it should have the same likelihood of misbalance as a hub centric wheel.  I think that the problems come out when people use a hub-centric wheel on a lug-centric hub or vice-versa.  Which looks like what you're thinking about doing.  If Rota designed the wheel as a lug-centric wheel then they most likely would have balanced/centered it around the lugs.  The hub hole would be low tolerance.  Plus, the lug holes will be tight tolerance and if your adapter is not centered between the lugs you could find a tolerance mismatch.  You might even end up putting a bending load on the lugs when you force the lug nuts in to the holes or down on their tapered seats.  And, you'll need to match the center of the wheel to the center of the hub in your adapter/spacer since it's not just a gap filler.  It is a spacer that has to fit two centers.  Neither the hub or the wheel was designed to be the centering mechanism.  It's more complex than it seems if you want the actual mass to be centered and supported.

Apparently, hub centric can be stronger than lug centric.  But, it still comes back to the engineering group that designed the system.  

Here's a simple review.  The guy covers some of what you're considering.  Things to be aware of.

https://www.machinedesign.com/fastening-joining/article/21832042/whats-the-difference-between-lugcentric-and-hubcentric-wheels

Edited April 19, 2023 by Zed Head
yoru > your

[Racer X]

27 minutes ago, HusseinHolland said:

 

 

There is a significant difference between lug-centricity & hub centricity, I'm sure you understand. Relying solely on lug centricity brings in greater likelihood of wobble or out-of-round. I guess I'll have to figure it out. I'm just surprised that no one has either encountered this or commented on it using aftermarket wheels.

 

Lug centric and hub centric are two distinctly different methods for centering wheels on the hub of a vehicle. I can’t recall at the moment which is the method used on the early Z cars, but it will only be one, or the other, as no vehicle will have a combination of the two methods.

So if the Z hubs are lug centric, then the wheels must be of the lug centric design, and if they are hub centric, then wheels of hub centric design must be used. Using a lug centric wheel on a hub centric design will result in improper fitment, and rotational vibrations. Using a hub centric wheel on a lug centric hub design may result in the wheel not seating fully on the hub, again with resulting excessive runout.

I believe the Konig wheels come with a plastic piece inserted in the center, to compensate for the difference in hub diameter, and the end user is cautioned to be sure it isn’t removed when installed on the early Z hub.

 

 

[HusseinHolland]

I guess I'm just used to cars (such as Volvo)  that utilize wheels that are (obviously) lug-centric with cone-seated nuts or lugs to ensure proper seating, that also combine hub-centricity in their design. All the hubs on the cars have a wheel centering lip. I may just be assuming that wheels I've bought are lug & hub centric. 

The only aftermarket wheels I ever bought that were only lug centric were those American Standard wheels of the 70-80's that were in many cases slotted to allow fitment to a couple of close bolt patterns. Those do not use a cone seat. I had definite balance issues with that style - one had to torque the lugs with the wheel unloaded to avoid vibration.

I'll take a read of the article.

 

[Zed Head]

I have a truck with hub centric wheels that uses flat faced nuts to hold the wheels on.  Torque spec is 150 ft-lbs.  It's an interesting topic.  One of the first of my many cars had a set of mag wheels with replaceable adapters for different patterns that fit in a recess in the wheel surface.  Very sketchy.  Most of my cars back then had numerous vibration problems so I never noticed if the wheels were one of them.

Found a picture of a similar wheel.

https://inthegaragemedia.com/rolling-stock/

 

Here's a Ford hub centric lug nut.  The hub centers and helps out but the nut and lugs do most of the work.

This is aftermarket, the Ford nuts have a spinning seat with some grip texture on the face.  Still flat.

 

 

Edited April 19, 2023 by Zed Head
+ first my

[HusseinHolland]

I'll get a better sense of what I'm facing with the wheel/hub concern once I pull all the suspension apart. 

In the meantime, I did get the 300ZX T rear rotors redrilled to 4x114.3 using the Milkfab template. I had to redraw the center to 67mm, as the printed version they send was only 66mm ID. I used an xacto to carefully cut out one locating hole so that it is a snug fit on a stud, then center-punched the other 3. I also used the steel wheel center I cut off the spare wheel to test fit the rotor. 

as provided:

laminated the template to make it rigid enough to be useful

Checked the spacing & offset on each relative to each other and the inner & outer hub lips before drilling

All done

Edited April 24, 2023 by HusseinHolland

[Zed Head]

The rotors are interesting because they can be off center and still work just fine.  The pads will not know., they'll just create a new circle.  There could be a very slight weight imbalance.