And now my wheel cap is lost

[ParknVibe]

As most of you may know, new owners of the 2009 Vibe with the Aluminum wheel are losing the center Pontiac cap. Well now I am one of them. Only 370 miles on the car. I lost the rear driver side. I just took the last three off with a screw driver. My are made in Italy. I noticed on the inside that each cap has its own number 2, 3, and 4. I lost #1. I went looking for it before, because I think it just happened on a local trip. I have a theory that the cap pops off by hot air pressure building up in the cavity. One of you said that the cap was found next to the wheel in the driveway.

[ToolGuy]

Sorry to hear about this...My theory on any of these caps that fall off on any vehicle is from vibration such as hitting a pot hole or just uneven pavement will cause it.

[ParknVibe]

Yes, I would agree in most cases. However, in the Vibe's wheel hole, it is a dome shape (bell shape) sealed air pocket. The cap fits tight in the circle and is just pushed into place. clip tabs whole it in place. The brake friction has to heat the metal mass up raising the air temperature in the dome...so the pressure pops it like a bottle cap.Also the aluminum must expand as well. Some owners said that the cap was found near the parked car. Another point to make is that the cap has a metal cover over a plastic base cap. they are heating up or expanding at different rates.

[SeattleJeremy]

Sounds like you need to drill a small hole in each of them to let the gases escape.

[Baltovibe]

Quote, originally posted by Ivibe »I have a theory that the cap pops off by hot air pressure building up in the cavity. One of you said that the cap was found next to the wheel in the driveway.That might be a cause. I have a boat with the "Bearing Buddies" installed. This kit seals the bearings and has a tight cap that fits over the hub to keep out the elements. Every so often, I find the cap popped off and laying next to the wheel undisturbed, and when pushing it back on creates quite a backpressure. I am assuming also that the cap gets pushed off gradually by expanding gases.

[ToolGuy]

OK I see and respect your theory...I suppose you could conduct a test where you drive around for a few and than pop one of the caps off to see if you can hear or measure the amount of pressure.I guess I am a little skeptical since these caps have been around for years on cars and my vibe may no have a dome shape in the rim but I think the center cap is probably similar and that it is not an air tight seal but a friction seal inside the bore. Plus the brake heat should not be traveling up that far with that intensity, if so then it could also be cooking wheel bearing and things. I also do not see gases building much with disk brakes because of their well ventilation.If the tabs are bent out more and the cap does not pop off then I suppose that would be enough to counter act this. As far as it being near a parked car, it could be that the centrifugal force holds it in place until the wheel has stopped. Not saying what you state is not true, and not trying to argue with you, I just find this one intriguing and anything is possible.

[nygiantzz1]

Quote, originally posted by ToolGuy »As far as it being near a parked car, it could be that the centrifugal force holds it in place until the wheel has stopped. The same as a boat propeller when the shear pin breaks, the prop will stay on until you cut the motor, then it falls off. That is probably why I found my missing center cap in front of my house, it didn't fall off until I pulled in my driveway. It's just a cheap, soft plastic cap. I think heat plays into it a little, it probably expands the plastic a little when warm and shrinks it a little when cold. I was able to spin the center caps last night when it was cool, this morning after warming up, they feel tight.

[ParknVibe]

The steel (iron)disk rotor is what is getting hot then the heat is being transfered to the Aluminum wheel like a heat sink. I am also thinking that the center hole is enlarging do to the aluminum expanding. However the plastic cap is not expanding but maybe the thin metal cover is and is pushing against the hole making it tight. Then the hot air is trapped in the cavity. So at just the right thermal conditions and mechanical stresses as well, it will pop. The only thing wrong, is that the plastic clips (teeth) just don't "lock in on the lip (groove) on the back side of the hole. If you looked at the clips you can see that it can easly slide out when you pry it from the edge. This cap should only have been design to be removed from back side...after removing the wheel. I don't know, but maybe they must be able to remove it for wheel alignment or balancing on the car. In my case, that rear tire is always facing the sun and heating up all day, I then drove the car at about 2:00 pm. I only went two miles after which I notice it was gone. I have been eye balling them since I got the car... I just know I did not look at them that last time before I went. I was not able to find it by retracing my trip a few times as well as taking a slow bike ride. I have a second theory to add to the physics... a vortex effect like a horizontally spinning tornado (caused by the blades of the wheel) and then the cap is suck out of the hole as well being helped by the hot air pressure behind it.

[DarkVibe]

i lost one, but the dealer replaced it for me, i just hit 2000 miles

[ToolGuy]

Quote, originally posted by Ivibe »The steel (iron)disk rotor is what is getting hot then the heat is being transfered to the Aluminum wheel like a heat sink. I am also thinking that the center hole is enlarging do to the aluminum expanding. However the plastic cap is not expanding but maybe the thin metal cover is and is pushing against the hole making it tight. Then the hot air is trapped in the cavity. So at just the right thermal conditions and mechanical stresses as well, it will pop. I see but this is no different then my 2003 Vibe center caps. They are plastic with a thin metal cap over the plastic. I just do not see any gases getting trapped since it is not an air tight seal between the caps teeth and the rims bore. Again, not trying to argue just logically figure this out. My Jeep Compass has plastic caps that the recessed into the bore more like the Vibe and also has disk brakes at all four wheels. No caps have poped or fallen off on it but the cap is probably designed differently. I would say it is just an issue with the caps mounting tab design in general. Once the cap is pushed into the bore the tabs flex a little and sound like the tabs need to be a few mm wider/longer or whatever to stop this. The design needs to be improved to prevent all of this on the 09 Vibes with them IMO.

[ParknVibe]

Quote, originally posted by ToolGuy »I would say it is just an issue with the caps mounting tab design in general. Once the cap is pushed into the bore the tabs flex a little and sound like the tabs need to be a few mm wider/longer or whatever to stop this. The design needs to be improved to prevent all of this on the 09 Vibes with them IMO. Yes, I agree it is a design flaw. The wedge shape tab just will not lock in place. I just feel that road forces could not make it come out, if so, the hole would have to radically deform. Its plastic tab design clearly shows that it can be PUSH or pulled out. I simple think the only thing that can do it in this case is air pressure and heat. In other words, all the tabs would have to be press equally and evenly for it to come out. Suction or compressed air pressure can do that.Think of a cork in a bottle. Solutions??? Add silicone to glue it in. Or. fill the gaps between the taps with silicone to make the plastic ring more rigid but still be able to remove it. Some said to add tape to the ring. I also thought of drilling a hole but better to make a slit on the edge (break off some metal tabs to give it air outlets.) Maybe they don't water or dirt to get in. Thanks for your opinions... enough said, right? I just will get a new one and try one of the solutions.

[ToolGuy]

Just posting to your theory from the first post and have a friendly discussion to other theories that is all. I have some engineering background so I thought I would make some comments originally... If it moves in and out of the hole in the rim, to me it is not air tight like a cork in a bottle...I gave my suggestions for solutions in the first member that posted on the site about a lost cap, good luck!

[ParknVibe]

Thanks for the service report. Where did you get it? I have been trying searches without any results online. We have to give Pontiac /GM/ Toyota a copy of this discussion for their review. What is a PI? or PIC number?

[ParknVibe]

When I lost the one cap, I took remaining three off the car. Today, I try to see how it will fit back in the hole. (just never though of do this, it seemed to be a good fit when removing them) Anyway, I gently placed one partially into the hole only to note that the plastic clip diameter is less or equal to the wheel's center hole inside diameter.I then got my Caliper tool. and did a accurate measurement of the circles. The plastic cap at the "clip teeth" (widest ring) = 1.835 inches. The inside ring of the wheel measures 1.83 inches. What this shows is that NOTHING holds the cap in... not even the wedge teeth. The wedge teeth don't even get pressed in to snap in. I can't believe what I am seeing!!!!Clearly they were not meant for each other. The only thing holding that cap in is the metal cover (bearly). It was hard to catch it on the edge with a flat screwdriver. I did nick and mark one of them. They will all fall out in short order....silicone them in ASAP or tell the dealer service shop manager. My Vibe was made in late May. maybe on the 22nd. Maybe they changed the cap part by now...who knows.

[ou.grizzly]

A quick and easy solution for these center caps that keep on falling out is to secure them down with magnets I would think.Epoxy one (1) thin round magnet to the underside of the center cap and get one (1) taller round magnet, place it on the hub as it should be attracted to it and then call it a day. The two (2) magnets being drawn to one another should keep the center caps from coming loose.

[ParknVibe]

You have a good idea. This may work on the front wheels because the axle (rod) sticks out almost into the center hole. So the magnet just has to be glued to the cap. However the rear wheel/ rotor has a deep cavity maybe three inch depth. Like I said, an air pocket that can hold a lot of hot air.

[ou.grizzly]

Quote, originally posted by Ivibe »You have a good idea. This may work on the front wheels because the axle (rod) sticks out almost into the center hole. So the magnet just has to be glued to the cap. However the rear wheel/ rotor has a deep cavity maybe three inch depth. Like I said, an air pocket that can hold a lot of hot air. Put a depth gauge into the rear hole and see how deep it actually is; there is one thing to remember, those magnets can be placed on top of each other to make up the difference.

[ParknVibe]

Quote, originally posted by ou.grizzly »Put a depth gauge into the rear hole and see how deep it actually is; there is one thing to remember, those magnets can be placed on top of each other to make up the difference. Using my caplier (but a ruler will fit in there) It measures about 2.5 inches to the deepest part from the outside edge of wheel hole. Note that the rotor part has a inverted dome cavity. Maybe two inch long magnet would fit. I would think however, that a stack of round magnets would spin out of control while the wheel is turning fast unless they were taped together. I also think that it can throw the wheel balance off. What will the tire dealer think when he sees magnets in there? When I get around to it, I will go to the dealer and asked if there will have a new replacement for these bad ones. I just can not believe that at the factory, or the engineers did not see how easy it is for them to come out. I suspect that they had to rush the new Vibes out a year early and could not get this part to pair with the new wheel designs....so they used a standard Pontiac cap from another model. I will keep my caps off until I show them to the dealer's parts dept. If I glue them on now, it will be hard to remove them if and when an improved one becomes available. However I wish they were on now.How about Velcro tape in the inside ring and the outside of the plastic ring. I have a lot of velcro tape. I think I'll try that now!! Even with just a strip of Velcro in the wheel hole ring will help lock in the teeth better. I will still be able to remove it when needed without cutting out the glue or silicone. Then again.... how long will the tape stick in a wheel that will always be exposed to the elements???

[ou.grizzly]

Quote, originally posted by Ivibe »Using my caplier (but a ruler will fit in there) It measures about 2.5 inches to the deepest part from the outside edge of wheel hole. Note that the rotor part has a inverted dome cavity. Maybe two inch long magnet would fit. I would think however, that a stack of round magnets would spin out of control while the wheel is turning fast unless they were taped together. I also think that it can throw the wheel balance off. What will the tire dealer think when he sees magnets in there? Only one way to find out is to try it out. Magnets can be purchased relatively cheap, do the rear of the vehicle on both sides (tape a magnet onto the center cap) and see if it throws the tire off balance on the highway. For under $10.00 USD you could find out. Edit:After re-thinking this in the shower, one could also find a very high density foam, epoxy it to the center cap and wedge it in and or round thin round magnet - epoxy another thin round magnet to foam - then epoxy the foam to the center cap. As for the Tire Shop, notify them before you have the vehicle serviced.

[ToolGuy]

Yeah it is hard to believe this was not caught before production...In the mean time I am sure the dealers do not have the replacements yet due to the above notice. Like you said, I would also pull all of them off the car or if you or anyone has bought a new one at the $22 price, save the receipt and possible pull all of them off the car too. I know this is not a good look for the car but unless someone wants to fab up their own fasteners and wait for the new part that would be the only option. I am sure once the replacement as been developed then the supplier will have to make them all and at four per car, this could take awhile before parts reach all dealers everywhere in the Country. That is amazing what you found as far as dimensions with your micrometer!

[ToolGuy]

Quote, originally posted by ToolGuy »I can IM you about it...Did you get my IM?

[Sublimewind]

I can see the theory of rising heat causeing pressure to build enough to pop the caps, EXCEPT, that it couldn't possibly rise fast enough to pop anything... I CAN see the metal expansion to be a slight problem.. Like mentioned, they are tight when cold, and losen up when hot... But as far as building enough pressure to pop them... Not happening, it's just not tight enough of fit (even at .005 measured difference) it's still not sealed well enoough and heated quick enough to creat any amount of positive pressure.. Cool theory though...

[ParknVibe]

As an update about what I did. I have Velcro fastener tape. 3/4" wide. I used the soft felt part and I cut it to 3/8" wide. Made a length to fit the circumference of the Wheel inner circle. when place carefully around the ring, this will give smaller diameter as well as a cushion for the tabs slip thru. I did NOT add the Hooks of the Velcro to the plastic cap. Make sure the Velcro is even or flush or behind the inner edge of the hole so that the cover will fit tight into its seat. The cap snapped firmly into the hole.I just tried this on one cap for now.