I’m running 25mm GP5K tires on my bikes, either with latex or tubeless. The actual measured width of the tires is 27mm. Based on that, what size butyl tire should I carry for spares?

I’ve been carrying spares marked 20/25c, but I’m concerned those may be too small based on the actual size of the tires. On my group ride yesterday, one of the guys kept getting flats, but turns out he was running tubes marked 20/23c in his 25mm tires. So this has me doing a sanity check on the size of spares I carry.

Vittoria has a butyl tire that’s rated for 25-28c. I’m thinking about swapping my spares out for this model, but wanted to get a sanity check.