I've just been scrubbing at my car almost all weekend as it was filthy (hasn't seen a hose pipe for months).

I pulled off the wheel centre caps as I've lost one, another is hardly attached, so I've ordered four new plain grey ones from ebay. I've found that the hub ends look very different on the two front wheels. See photos.

Am I right in thinking that what's missing from the right wheel is a "grease cap"? If so then I'll try ordering a Vectra one (after checking the diameter).

I've googled for discussions, but there's limited info about them. Am I right in thinking that despite the name, you don't fill them with grease? Is a wipe of grease a good idea or would that just encourage it to fall off?

Is it just hammer on? With a lump of wood on top, after taking the wheel off.

I don't know whether a garage has taken it off in the past or it's just fallen off. It's possible that it fell off and took the wheel centre cap with it.

I learn new things every week thanks to my Croma falling apart.

Thats normal i think, i have never come across a car that has them on the front. Im sure they only put them on the back.

i had none on the front, but new front hub came with one so i now have 1 on one side

Most of the cars I have had have them on . In the old days we would put grease in them to lube the bearings, but now with sealed bearings all i can see them doing is keeping out the c*ap . A lot of the sealed bearings I have seen have a plastic cover on each side to "seal" the bearing and keep the grease in. If you lose the plastic cover and you dont have the outer cover then the bearing is open to the elements

Yes you are missing a cover / "grease cap" although there is no grease behind it.

You should have two at the front, P/N:51704626 @ £7.66 (June 2012) each.

Thanks very much to all. I'll give ebay item no 310681573863 a go. The woman selling them looks like she's very helpful anyway, and I get a free tape measure. No dimensions are mentioned, but Vauxhall/SAAB suggests it's a Vectra C type of thing.

I'll report back on whether it works for future reference, and for all you lot with them missing.

s130 is right. I have both of them and their role is to protect the driveshaft nut from water and crap.

people who have them, did your car come from factory with steel or alloy wheels?

Mine came with 17" alloy. I think Doofer "lost" the cap at the service where he repaired/replaced the driveshaft. The only way you can lose the cap is forgetting to put it back . You can't lose that with wheel mounted and even when you take it off, you need to apply some good amount of force, so someone forgot to put it back.

my car did have a new gearbox before i got it, i suppose mine could have been lost then

Not arrived yet (only ordered yesterday). Is a wipe of grease a good idea, to prevent it rusting on?

Am I right in thinking a lump of wood and a hammer is the official method?

only tap from the edge as they dent easy, i just used old screw driver no wood

Doofer said:

Not arrived yet (only ordered yesterday). Is a wipe of grease a good idea, to prevent it rusting on?

Am I right in thinking a lump of wood and a hammer is the official method?

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To mount it on, yes, use wood or just a plastic head hammer, but if its all clean there, the cap should go in easier only with some taps. Before you mount your new cap, degrease with some WD40 if you have signs of rust or if its dirty use some compressed air. In my opinion, the only grease that you could use there is the copper or ceramic grease, both are anti seize lubricants, but more anti seize than lubricant.