I've just bought a trailer which i think may have series/defender wheels on it. Tyre is a Michelin 650R16
What do you think?

Thanks. Common sense isn't very common.
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2007 Land Rover Freelander2 I6 hse Auto

Measure diameter across studs, measure diameter across hub, and you will have your answer.

Defender/Series wheels were 5x165mm (5 x 6.5" in old money) with a 114.3mm (4.5inch) hub. M16 x 1.5 thread on the lugs.

To add to this, if they are the above size then LR Series/Defende/Disco/RRClassic were pretty much the only vehicle produced with that size, so by definition it would be a "defender" wheel, although could be an aftermarket one of some kind. Current driveway contents:
2021 V60 Cross Country B5
2009 FL2 dog bus and shooting wagon

On Order: 2023 Fisker Ocean Ultra - deposit paid.

Any idea on make of trailer? I think most Rice trailers for starters had LR size wheels and of course Sankey etc

And LR studs started as BSF - definitely not metric  2014 Freelander 2 TD4 Manual Dynamic
1956/7 88" Series One Land Rover
1956/7 88" Series One Land Rover - undergoing restoration