Hand-tightening is your friend

 

Pete, noticed you bought new wheels...keeping your TSWs? Anyways, you can also PM ss04 and tunerplayground your question...I know both of them have or had the PF01 wheel.

 

The 17x9 PF01 are for the Miata. Keeping the TSWs for now. Thanks for the heads up. Might as well post it here too:

Track guys, does this look right?


I just ordered a set of Enkie PF01 from TireRack. They arrived a day later (fast service) but look odd where the wheel makes contact with the rotor hat. Manufacturing defect?

Basically, if you look at the pictures you will see a line that can bee seen about halfway through where the lugnut holes are. That line is where ~2mm of material has been milled away from the wheel. The missing, milled material starts at the hub bore and continues out till about halfway past the lugnut holes.

So when the wheel is mounted, it will only make contact with the rotor hat on the car at the very ends. Most of the wheel will not be touching the rotor at all. Also when the lugnuts are torqued down, they will only be make contact with half of the stud/lugnut combo. Seems very odd and not safe. I have never seen a wheel like this in the past and i have owned many sets of Enkies. All 4 of the Enkie RP01 wheels are like this. Safe? Normal? Looks funky to me. I just sent these pictures to TireRack to see what they think.

 

Pete, you can also try going straight to manufacturer and calling Enkeis dedicated U.S. office 817-490-5600

Other than this issue, how is the weight on these things?

 

They are reasonably light but not super light. Just slightly lighter than the TSWs.

Interestingly enough, I am talking to Enkie on the phone (as I type this) and they seem to think this is normal (and unique to the PF01). The guy I talked with at Enkie is going to call me back on this.

 

I'd think that this is normal....different, but still safe.

 

Olie, what possible reason is there to mill out that material? The wheel will no only make contact with the rotor hat at a few select points. When the lugnut is tightened, the area under the lugnut will only partially be in touch with the rotor hat.

I can't think of a single good reason to do this?



Edit: the only reason I can think of to do this is if people have dirty rotor hats (rusted) then perhaps this will allow the wheel to make better contact on the periphery (where it is needed)?

 

If you really think about it, there is no reason for perfect contact with the rotor hat.
As long as there enough material to keep stresses down so that metal don't plastically deform the wheel is ok.
You shouldn't worry about it "slipping" as well. Wheel studs are there to keep it in place, they will even be able to support the wheel if it is not tightened.
When the wheel is tight there is enough static friction to keep it in place.

I'm trying to think of an analogy.....but can't really think of anything....

 

I understand. You mentioned my main concern, there will be very little contact area so the possibility of the metal deforming is what I would fear.

Once the lugnuts are torqued, the wheel is not going anywhere.

 

Knowing Torque on the lug nut, calculate the normal force F per lug nut/stud given all the parameters.



5 studs, therefore total normal force is 5 X F

Measure the contact area between the rim and the rotor (improvise and approximate)

Calculate applied stress S[Pa]= F[N]/A[m2] * C; C is stress intensification factor (~2.5)

Compare to Yield strength of Aluminum (200 MPa to 600 MPa)

The value you get should be well below the yield strength, indicating that you are safe.

(There is also a question about dynamic loading during driving, as well as some shear stresses, but I don't think that they are too significant to be accounted for.