Underbody washers - LotusTalk - The Lotus Cars Community
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post #1 of 4 (permalink) Old 02-26-2018, 03:05 AM Thread Starter
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Underbody washers

The M8x25 bolts under my 2006 Federal Elise have unusual washers. They appear to be about a 35mm OD, with an inner step that's thicker. The Lotus parts diagram says this should be a 25mm OD washer.

(Mine are rather messy, and I'm planning on upgrading all the underbody bolts/washers to stainless steel.)

Any thoughts?
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post #2 of 4 (permalink) Old 02-26-2018, 08:02 AM
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Somewhere I posted a question about them. They are called out for the diffuser but not necessarily the aero tray.So you can get them from lotus but order the diffuser washers or you will get expensive 10mm washers
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post #3 of 4 (permalink) Old 02-26-2018, 03:13 PM
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That step is designed to keep the under tray centered and in position. If you use a flat washer just ensure it is in position before you torque it down.

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post #4 of 4 (permalink) Old 02-26-2018, 04:25 PM
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I never really understood the purpose of that stepped washer.
I had the problem that with that step facing the undertray, the bolt would not clamp the undertray tightly, causing it to rattle.
So I started installing those washers with the step facing the bolt head and I never had an issue (that was about 10 years ago).
I might as well just use flat washers if I ever need to replace the original ones.
Just make sure you hand start all the bolts first to get everything aligned before tightening them down

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