I have some ADR Formula 5's to put on my car. The Fiero lug nuts seem to work just fine, but I'm not certain if they are OK to use. I get a slight shimmy in the steering wheel at speed. I have looked all over the net and can't find any useful information. My questions are:

Are the wheels conical or ball seat?
Are the Fiero lug nuts conical or ball seat?
Can I mix the two safely? (I'm assuming no)

Thanks!

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1986 SE Aero coupe.

3.4 DOHC swap is complete and running, now just have to finish the rest of the car...

I can't answer whether the ADR Formula wheels have conical or ball seats, but I can answer the remaining two questions. Fiero lug nuts are 60 degree conical, and no, you shouldn't mix conical lugs with spherical seats.

I do not know the rims you are speaking of but the Fiero lug nuts are conical seat. I definitely would not mix and match those types since it would seem the contact patch between a ball seat and a conical lug would be minute as opposed to full contact along the seat. Sounds fairly dangerous. I would try and track down lugs to match the wheels you have.


A quick search says they use the taper seat tuner style lugs. Fiero ones may not have the same taper so that is something to think about also.
Al

Thanks! More research and observation has brought me to the conclusion that the Fiero lug nuts will work with my wheels and all is good. I discovered that both front wheels were balanced incorrectly (one with a single large weight on the inside lip) and I believe that to be the cause of the shimmy. Balanced the wheels again and will find out if that cleared things up next time I drive it.

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1986 SE Aero coupe.

3.4 DOHC swap is complete and running, now just have to finish the rest of the car...

Something else that I discovered...

This usually doesn't apply to cars as old as ours, since most everything has been replaced, but make sure the little spring washer that holds the rotor on has been removed. There are usually 1 or 2 of them, pressed on over a stud or two. Some brands of wheels are perfectly flat on the hub side, and that little washer will interfere. Will cause odd torque readings, and a mild shimmy at speed.

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Raydar
88 Formula IMSA Fastback. 4.9, NVG T550

Praise the Lowered!