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the tape was to provide tighter grip on the bottles by decreasing internal diameter, not structurally reinforce anything. they're still going strong, problem free. £5 china carbon jobbies, and the roubaix is the only time they've faltered. once grit and water gets between bottle and cage though they do get a bit messy :/
my carbon Look ones are shit at holding bottles and they were £££, and even the fancy steel ones on the tandem chuck a bidon every now and again.
Riding the Roubaix Sportive with my club put me off carbon cages a little- 6pt's cages were producing showers of black dust over every section of Pave as his bottles vibrated up and down.
Ultimately they survived the ~130 miles, but if memory serves they had to be reinforced with electrical tape around about the halfway point.