Aaron Pfadt

Pfadt Racing Launches New Wheel Spacers



Why spend thousands of dollars on extra wheel sets when you can now equip your wheels with our light weight wheel spacers. With a stack of these in your race trailer it's easy to optimize just about any tire and wheel combination.

Made in the USA of aluminum then anodized black, these spacers are durable and functional. We have 4 unique kits available:

2 each 1/2 inch spacers. Retail $90. Please note that to properly use the 1/2 inch spacers you will need longer wheel studs. We sell a set of 5 ARP wheel studs for $25.





2 each 1/4 inch spacers. Retail $65.





2 each 1/8 inch spacers. Retail $55.





2 each 1/2, 1/4, 1/8 (6 piece kit). Retail $180.



These spacers will help your wheels fit a variety of big brake packages for maximum track day performance! All sizes are in stock and ready to ship.

A set of 1/4 inch spacers are a quick way to move the wheels on your C6 Z06 out a little and fill out the wheel wells.

Please note that certain wheels and any of our 1/2 in spacers will require longer wheel studs. ARP wheel studs are available and in stock.

-Aaron

C4TOMCAT

hi, i have a co-worker that has an 86 coupe...think the offset is 36 or 38 mm. do you have a chart that would show the necessary spacer thickness needed if 94 sawblades were to be used on his car or say 02 Z rims. I believe the 94 offset is 56mm. a chart for the vet years could help in selecting the proper thickness. thanks tom

froggy47

Look nice.

Cast, forged, billet?

CHJ In Virginia

My understanding is that C-5 wheels are hub centric with the inside of the wheel bore resting tightly on the raised portion of the hub. This takes a substantial amount of the shear load off the wheel studs. Your spacers do not have raised hubs on the outer edges and all of the shear load will be transferred to the studs. This might be OK in a light duty street application. Do you feel that this is really safe in a track application ?? I have a set of SSR wheels that would require a 1/2 " spacer due to a recent Wilwood BBK installation. I really do not want to sell them. It seems to me that a proper spacer would have the inside machined to fit tightly around the hub and a raised hub protrusion on the outside to accept the shear loading. Please advise.

wallyman424

I've been running the same style spacers (3/8") for almost 2 years now. The spacers with hub protrusion are nothing more than a convenience when putting wheels on. That protrusion is not structural.

KILR-RYD

Nice, i might be needing them. I am making my mark so I can look for this thread when i am ready.

Aaron Pfadt

You bring up a good point. The wheel bearing flange is in place for centering purposes. The strength of the studs, however, exceeds any necessary load capacity. The 1/8" ones and the 1/4" ones do allow centering on the wheel bearing flange still, but not the 1/2" ones. I, like Wally, personally race with a variety of wheel spacers depending on the wheels I am running and most other racers will tell you the same. I run 1/2' ones quite frequently because I have a set of CCW that have a funny offset in them. I also run ARP wheel studs on my race car which carry the load of the vehicle.

I'll post an FEA in the morning detailing the wheel stud's ability to carry the loads. The hubs are there primarily for concentricity (lack thereof can lead to vibration).

Oh, and these are billet, or more technically they are cut from a flat sheet.

Hope this helps,

Aaron

froggy47

I just looked at my stock rims (z16) on stock hubs. There is a small lip that certainly has a centering effect on the wheel however it does not extend even to the amount where it would be brought flush with the rim nevermind extend past the rim.

I'm not a ME, but I don't think this takes any substantial amount of load off the studs, maybe a small amount.

Someone else take a look at their STOCK setup & see if you agree.

Independent1

EvilBoffin

Nice new product, Aaron...

As it happens, SCCA Stock class autocross rules allow for exactly 1/4-inch more offset then stock per wheel, so these spacers would be a good addition to OEM-sized wheels, to reduce any chance of rubbing on the inner fender wells while also increasing the car's track to the limits of the rules.

I'm one of many SuperStock Vette autocrossers that uses stock rims because they're light, cheap and strong. I have 285/18 & 315/19 Hoosier A6's mounted on a set of '08 forged (Gumby) stockers. These wide tires fit my C6 just FINE (barely), but a 1/4-inch more clearance never hurts...

I'll probably try out a set from you soon...

Robert

Bill Dearborn

It doesn't take a big lip. All you need is enough distance for the inside of the wheel to fit tightly to the hub. Once the wheel is on the hub the wheel studs do not carry any weight. All they do is hold the wheel on the hub thus all forces applied to them are in tension. If the wheel is not riding on the hub then the wheel studs see all of the forces applied to the wheel including shear and tension. The shear force shifts as the wheel rotates so the lug is constantly bending and coupling that force to the hub flange. That may explain the hub flange failure I posted earlier this year.




Bill

John Shiels

Over 3/8" you need hub centric was what I was told by CCW and DRM where I got mine. I guess after 3/8" they are no longer hub centric without center being closed to engage the hub and rim. Wider tires equals more leverage. Banging curbs at the track is even more force.

0JoshS

Wheel Bearing Centering Flange Effect on Shear Capacity of Wheel/Bearing Interface

Introduction
There has been some question on whether the wheel bearing centering flange is necessary to cope with the shear loads seen in the Corvette.

Here is the model that I subjected to testing. The mock wheel flange is transparent in this view to show the wheel bearing flange. The centering flange can be seen in this picture.


Results
The centering flange has negligible effect on the shear capacity of the wheel-to-bearing interface. On closer inspection I found this was because the wheel studs shear capacity is so high, approximately 14,500 lbs, the maximum deflection of the studs with a shear load of 3,100 lbs is 0.007mm. Which is not enough to close the running clearance (0.085mm radially) between the wheel and the wheel bearing. So in this example the centering flange did not carry any load when the wheel was subjected to a load of 3,100 lbs because there was simply no contact.

For the centering flange of the wheel bearing to carry a significant shear load it would require that the wheel studs need to yield a significant amount. This high of a load would undoubtedly cause damage to other components, my money is on the upper control arm, before the centering flange can contact the wheel and carry a load.

Here is the Factor of Safety plot for the Wheel Stud with the lowest factor of safety.

This picture shows the FOS results for a wheel bearing without a centering flange. It can be seen from the picture that the factor of safety is 4.8 The load was 14 kN so the failure load would be 67.2 kN or 15,107 lbs.

Conclusion
If the suspension system and wheel studs do not fail before a load higher then 15,000 lbs then the centering flange may increase the load carrying capacity. At loads lower then 15,000 lbs the wheel studs alone offer the required shear strength.

I hope this short study sheds some light on this topic. Please let me know if you have any other questions!

Aaron Pfadt

Just a recap of what Josh so nicely laid out for us in the analysis above. Non-hub centric wheel spacers are not an issue because the wheel studs take all the load (not the centering flange) with realistic wheel loads. Above about 15000 lb-force, the studs will deflect enough to allow a centering, flange if it exists, to take some of the load.

At that type of load in the wheel, several other things are going to break including most likely your wheel and upper control arm.

-Aaron

snitz

Question for folks going with after market brakes(any idea?):

For racers who want to run Brembo GTs with OEM rims, what spacer is required to allow sufficient clearance?

snitz

Forgot to mention C5 application. The brembo may not fit on the fronts due to 17" rim?

CHJ In Virginia

Aaron - thanks for real world engineering information. It makes me feel a lot better about the strength of the wheel studs in a track situation with spacers.

0JoshS

Snitz,

Most brake manufactures publish a clearance guide for their calipers. Here is what I was able to find for the Brembo GT Front C5.

It looks like 46mm from the wheel mounting surface to the caliper face.

snitz

Thanks. Do you suspect the OEM wheel would clear Brembos with a spacer based on that. I know a bunch of folks have a tough time buying Brembo's because of the requirement to also get new wheels to clear. If they can use your spacers instead that would be a great option for many folks!

0JoshS

Tom,

My experience is that 14" brake packages and 17" wheels have a hard time fitting together, radial clearance is an issue. Unfortunately I don't have any stock 17" Z06 wheels here to verify fitment.

I'm sorry that I can't be of more help on this. I would suggest that someone start a wheel fitment thread at some point and people can post what wheel/brake/spacer combinations fit.

Please let me know if there is anything else I can do to help!