I use inserts in gravel tyres, don't see why you couldn't in road (assuming they're tubeless). I just use 'backer rod' off eBay. Can probably get it in small enough diameter for road tyres.
This is excellent insight
@PhilDAS started
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I use inserts in gravel tyres, don't see why you couldn't in road (assuming they're tubeless). I just use 'backer rod' off eBay. Can probably get it in small enough diameter for road tyres.