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Buy a second foam piece, swap the stock one back when you take it in?

 

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I personally wouldn't bother, I'm just saying if they're that worried about it then it should be cheap peace of mind.

 

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increased heat exposure (or even worse, UV if tire isn't enclosed)

As opposed to the other 4 tires that are also outside? The cabin A/C isn't going to be doing much for something under the trunk floor. When the car is parked, which is most of the time, it's just going to be the same temp or higher.

 

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You're arguing that the tires on the car, partially covered and perpendicular (roughly speaking) to the sun get the same UV exposure as one mounted flat on a roof? Beyond that the 4 tires get UV exposure via being used as their tread wears down. The spare tire would just receive unnecessary UV exposure while not being used, drastically shortening it's life. Driven regularly, and enthusiastically, average life of the driven tires will be in the 2-3 year range. Spare tires are usually kept 8+ years.

Just seems like a pretty obvious negative to me. Especially in addition to the other items mentioned. 🤷‍♂️

I'm saying that a tire on the roof isn't going to receive "increased heat exposure" compared to one stored in the cabin, and definitely not when compared to the other tires that are on the road.

If you're worried about UV exposure throw a cover on it, though I'd doubt that will be an issue either. Most people aren't killing tires that quickly and they're fine, and every Wrangler is sold with the spare tire sitting on the back in the elements and it's fine. You'd probably have more problems from water pooling on the rim and rusting it, especially near the bead.

 

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I believe all of the older Rav4s that are likely to be at junkyards all have full sized spares. At least the 3rd gen does and I think that's probably the earliest that would have an 18 available.