Very Odd Wheel/Cap Problem

[Poobah]

Every used car has its foibles. One of my car's quirks is that each wheel has a different center cap. I figured I'd just get a set of matching O.E.M. caps and change them out - should be no problem. I bought a set of matching caps but soon discovered that changing them out isn't all that simple!

The car has four chromed alloy wheels all of which look exactly alike, that is until you take off the center caps. All four wheels take the same diameter caps, they all have a GM stamp in the casting, but there are two distinctly different center cap mounting profiles.

One of the wheels is a Type A (see photos). My new caps fit this wheel perfectly. Notice in the close-up that there are two grooves between the outer face of the wheel and the ridge that holds the tangs on the cap.

The other three wheels are Type B (see photos). My new caps won't fit these wheels. There is a ridge cast into the backs of my new caps which fits into the second groove of the Type A wheel. They just won't sit flush on the Type B's. I carefully cut the ridge off one of the caps in an effort to get around this. Now the cap fits the Type B wheel perfectly except that it is loose. It turns out the ridge that holds the mounting tangs on the Type B is about 1/8 of an inch closer to the face of the wheel than it is in the Type A.

I can't believe that GM would make two different wheels that look exactly alike and yet require two different caps!

Be that as it may, I need to work this out. Does anybody know if GM makes identical looking caps that fit the different mounting in the identical looking wheel? If so, how would I identify it so I could order the proper cap? Option #2 would be to glue some plastic on the tangs to pad them out to where the fit snuggly in the Type B wheels (after I cut the ridges off so they fit flush).

My third question is how in the world am I goung to explain to the guys that rotate and change my tires whats going on so they don't bust my center caps trying to put them on the wrong wheels?

Any ideas?

Thanks in advance.

P.S. It just occured to me that it was Cadillac that first achieved interchangeable parts. They won a major engineering award in the early 1900's when, at a world's fair, they completely disassembled three Cadillacs, mixed up all the pieces, and then put three functioning cars together from the pile of parts. I think we've lost something along the way!

[GreenMachine]

Could be that some of the wheels were from a differant model.

For example, 2 might be from a cadillac, but the other 2 from a buick.

Or 2 might be from a Deville, 2 from a seville. They had differant options and in some cases differant center caps (STS stamped, ETC stamped if eldorado etc)

Ot they might be when cadillac changed from the old crest to the new crest design. They also change to a better holding cap design from my understanding. I gathering these are not the stock wheels.

[cardio-doc]

Thanks to Ted TCB for pointing me to this post. Yes, you've got some 'different' wheels and no - they aren't GM's fault. You've got something of a 'mixed-up' set going on....

Type "A" are truly OEM/Factory-chrome Cadillac wheels. However, ALOT of dealers chrome-plated the base-finish wheels - they took OEM/Factory GM/Cadillac wheels that came from the factory with a base/painted finish - and then chrome-plated them. Now, usually wheels stay together in 'sets'. But it can happen that somebody put together a set and they are mixed up....as here.

While the wheels may look the same - the problem (as you've found out) is with the center cap situation. The only chrome caps that readily fit those aftermarket-plated wheels - are aftermarket caps which don't have the little 'ridge' like the OEM/Factory-chrome caps do. I sold a set of aftermarket-plated wheels to Dave in Canada awhile back, and I'd been planning on shipping them with aftermarket caps (which fit the OEM-chrome wheels just fine, BTW) but he wouldn't have it. He HAD to have the OEM/Factory-chrome caps on all those wheels. So....I told him what he needed to do. Take a Dremel (or similar small handy grinding tool) and ground down the offending ridge so the cap sits flat. We're talking about a 1/8" ridge running around the back, at the very closest to the edge. Ground that ridge down, and OEM/Factory-chrome wheels will fit aftermarket-plated wheels.

I hope I'm clearing all this up.

cheers,

~Doc

[Poobah]

Doc,

Thanks for helping clear this up (I was hoping you could shed some light on it). It didn't take me too long to realize that the ridge had to come off the back. I cut them off of one cap using a fine toothed hack saw blade. Problem is (and I could see this when comparing an aftermarket cap to an O.E.M. cap) the tangs on the O.E.M. cap are about 1/8" longer than the tangs on the aftermarket cap. As I said, the cap with the ridge removed fits but it's loose. I'm afraid if I got a matching set of aftermarket caps, the one on the O.E.M. (Type A) wheel would pop off easily because the tangs would be 1/8" short of reaching beyond the ridge on the wheel.

I think my best out (short of buying new wheels) would be to glue some thin ABS sheet material on the tangs to effectively move the point of engagement outward 1/8". Hopefully, this fix will stand up to the riggors of brake heat and the weather. I'll just have to remember to take the caps off before I ever take the car to a tire shop!

Thanks for your help.

[adallak]

Poobah,

Regarding your third question...Do not even try to explain anything to tire guys. Just remove the caps before taking the car for a tire job.