1" Hubcentric wheel spacers

[L92 OLDS]

Can anyone recommend a 1" hubcentric wheel spacer for a G body that is safe and well engineered?
I'm looking at some 8" wide SSIII rims for the rear with a 4.5" backspace but need 3.5" to make them fit without a frame notch. Thanks in advance.

 

[UNGN]

How long are your wheel studs? If the wheel has a flat face without pockets between the holes, you might need a 1.25" adapter. If they have pockets, 1" is fine.

Factory G-body wheels are generally not hubcentric. You can get a hubcentric spacer to match your wheels, but the adapter will ride where the adapter rides.

 

[L92 OLDS]

How long are your wheel studs? If the wheel has a flat face without pockets between the holes, you might need a 1.25" adapter. If they have pockets, 1" is fine.

Factory G-body wheels are generally not hubcentric. You can get a hubcentric spacer to match your wheels, but the adapter will ride where the adapter rides.

The wheel studs have already been replaced in the rear with longer to accommodate disk brakes. I can change the studs again if needed. The Olds rallye wheels are hubcentric. The center of the wheel nets out on the raised section of the axles that would normally protrude through the brake drum. With 400 plus RWHP I don't want to take any chances. Any leads on a good supplier / design are appreciated!

 

[L92 OLDS]

Check out this video. This guy makes some good points.

 

[pontiacgp]

I would not run a 1" space with a 7.5 rear with stock axles. The weight of the car rests on the axle bearings so with the added leverage with the wheel sitting further out that puts more stress on the axle. We have broken right side axles on our circle track cars and so many cars also sheared off the right axle at the edge of the bearing the track changed the rules after a wheel ended up in the stands so we had to run an after market axles that were stronger than the stock axle on the right side.

and as far as hubcentric rims wheel studs are designed to resist lateral forces that are experienced when the vehicle is cornering. They are not designed to carry the weight of the vehicle. All wheels that manufacturers put on their cars are all hubcentric
http://www.croberts.com/Automotive-wheel-detachment.htm

 

[oldsmobile joe]

where did you find SSlll rims that are 8" wide? are they new?
joe

 

[81cutlass]

https://www.amazon.com/dp/B01FDAY0DE/?tag=gbody-20

I have some cheapo hubcentric ones off amazon or ebay or whatever on the front of my 2+2. Was to fit c5 17" wheels, 2" spacers. They had to be trimmed to clear the spindle but overall fine with them.

Adding a spacer on a 4.5" BS wheel isn't any difference than just buying a 3.5" wheel (minus unsprung weight). The true wheel centerline is still in the same spot on the wheel. If you slide into a curb having a spacer on isn't going to help or hurt your side load strength.

Also, a lot of 14" wheels aren't hubcentric from the factory anyways. Anything aluminum wheel or post 1990 or truck is sure, but normal pre 90 GM car had a lot of stamped steel lug centric.

Fun fact too, the studs don't actually hold the wheel vertically to the axle. Clamp load of friction between the brake rotor/drum and wheel is what holds the wheel to the car. The hubcentric ring just locates the wheel axially concentric to the axle so there is no runout between the axle and car. It certainly helps, but not the main support function.

Page a-5 on this document goes into clamp load. 7/16-20 bolt has a clamp load of ~10,000 lbs at 80ish ftlbs depending on the friction of the nut and stud. So you have 50,000 lbs of force sandwiching the wheel on.

https://www.fastenal.com/content/documents/FastenalTechnicalReferenceGuide.pdf

And friction between cast iron and steel is .25-.5 (.6 with alum wheels)
https://www.engineeringtoolbox.com/friction-coefficients-d_778.html

So you end up with high of 25,000 lbs to low of 12,500lbs of force holding the wheel to the brake rotor with zero thrust load on the studs itself.

Yay math/engineering!

Think about that, the bolts don't hold the wheel on the car (in an up down force), friction does! If you really want a mind bender, think about a world without friction!

So actual shear stress required to break the bolts off (assuming a non hubcentric, non friction world)

Root diameter of a 7/16-20 screw is ~.375, area of .11 square inches. Shear strength is some % of ultimate tensile, so lets say ~%50 on the conservative side. Grade 8 bolt is 120ksi, so you have 60,000 pounds per square inch (60 ksi), times that .11 square inch. Again, that is about ~6000 lbs of shear stress per bolt. Total of 30k lbs in a frictionless world.

There is fatigue in the picture, but the wheel is going to fail well before.

 

[pontiacgp]

The wheel bore of the G body OEM rims is 70.3 mm but the bore of my AR rims is 83.06 so I got hubcentric rings to fill in the void.

 

[L92 OLDS]

Fun fact too, the studs don't actually hold the wheel vertically to the axle. Clamp load of friction between the brake rotor/drum and wheel is what holds the wheel to the car. The hubcentric ring just locates the wheel axially concentric to the axle so there is no runout between the axle and car. It certainly helps, but not the main support function.
Page a-5 on this document goes into clamp load. 7/16-20 bolt has a clamp load of ~10,000 lbs at 80ish ftlbs depending on the friction of the nut and stud. So you have 50,000 lbs of force sandwiching the wheel on.

https://www.fastenal.com/content/documents/FastenalTechnicalReferenceGuide.pdf

And friction between cast iron and steel is .25-.5 (.6 with alum wheels)
https://www.engineeringtoolbox.com/friction-coefficients-d_778.html

So you end up with high of 25,000 lbs to low of 12,500lbs of force holding the wheel to the brake rotor with zero thrust load on the studs itself.
Yay math/engineering!

Dude! Thanks for that summary with data. As noted in video there is a lot of misinformation and negativity out there regarding spacers. If done properly it is safe even with high power levels. Another fun fact or application regarding frictional clamp load is in the tooling industry. We clamp 40 ton tools in equipment with mechanical clamps. The clamps don't support the load, they just provide the friction between the platen and mold which holds it in place.

 

[L92 OLDS]

where did you find SSlll rims that are 8" wide? are they new?
joe

I called Wheel Vintiques today ready to make an order. Turns out all the Olds rallye rims they sell are discontinued. Their web site needs to be updated.

https://www.wheelvintiques.com/catalogsearch/result/?q=oldsmobile