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I went to install my diffuser after my last oil change on my 2005 Lotus Elise and 2 of my bolts wouldn't tighten up, they would tighten until they contacted my diffuser and then would simply spin freely. I thought the threads were stripped but the bolt easily came out and went back in with almost no pressure on the wrench and the threads looked good.
I jumped on LotusTalk and after a quick search I found that several others had ran into this same problem, the posts I found said that the threads that the bolt went into were actually a rivnut. They gave a part number to order new rivnuts from Mcmaster Carr and the correct bolt size needed for the new rivnuts. I ordered these parts up and have now received them. After doing some more research I have read that 2005 Elise's have nuts welded to the subframe instead of rivnuts like later models, it seems that if they were indeed nuts the welds would have broken and the nut would be loose and would rattle/move around but it stays intact but spins, the threads seem to be in good shape as well so now I am unsure if they are nuts or rivnuts...

I have been driving without both rear diffusers on my car for some time now so I was anxious to finally get the new rivnuts and install them. I got underneath my Elise and cant figure out the best method to remove the old rivnuts so I can install the new ones.
The spinning rivnuts are located in a square channel that only has access at the ends so reaching the rivnuts is not an easy job. Do I need to remove the old rivnuts from the end of the square channel or can I pull them through the hole that they are installed in?? From what I have read the rivnut should be expanded so it would prevent it from coming back through the hole it was installed in, meaning the only method to remove it would be through the end of the channel, is this correct?

If anyone could give me some advice on the removal and installation of the new rivnuts it would be greatly appreciated, I am ready to get my diffuser back on. I have read that I need to drill the lip off of the rivnut and push it through the hole into the square channel and then remove it from the side but I do not see a lip that I can drill, the rivnut seems to be flush mounted to my subframe... I will try to take pictures later today and get them posted.

Thanks for any advice!
 

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You should be able to drill them out. If you're replacing the rivnuts with new ones of the same size, be sure not to open the hole up too much with too big of a bit.

V2subFIX Installation - YouTube

We're using a 5/8" drill bit in this video to fit the V2subfix, but size your bit to whatever the rivnut calls for.
 

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I'll be doing this exact same issue this weekend. I was hoping for a better solution though. :-/
 

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Older but getting faster
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The subframe is galvanized.

Contact between the aluminum rivet and raw carbon steel may allow electrolysis to occur, as well as exposure of the raw steel to the elements.

I'd spray the drilled holes with galvanizing repair paint ("cold galvanizing") to avoid a rusting problem down the road.

Overkill? :shrug:

Cheap insurance / peace of mind? :up:

King Metals Catalog - Master 2013 - page 644
 

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Closer than you think
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Pictures are worth 1000 words. Maybe you can post some...

I just did a DIY side skirt project and installed my aluminum skirts very successfully with Rivnuts. If I could better visualize your issue I might be able to help.
 

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The subframe is galvanized.

Contact between the aluminum rivet and raw carbon steel may allow electrolysis to occur, as well as exposure of the raw steel to the elements.

I'd spray the drilled holes with galvanizing repair paint ("cold galvanizing") to avoid a rusting problem down the road.

Overkill? :shrug:

Cheap insurance / peace of mind? :up:

King Metals Catalog - Master 2013 - page 644
What about packing axle grease in the hole instead of the galvanizing paint?
I just ordered the V2subFIX because my diffuser bolts are spinning as well.
Thanks Lotus!
 

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Yep. Ordering one next week.
 
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