Hi Jason,That is an great question. A little research show that indeed, Hutchinson does not recommend roughing the surface of the tire. Even though Hutchinson's web site's product page for Rep'Air is predictably short on the this information, Universal Cycles web page for Rep'Air has the goods, "[Rep'Air] Superglue does not require degreasing or roughing the surface which saves the tire casing threads from damage"
I've not yet converted to road tubeless, but am running tubeless on my MTB and have had to patch one big cut.
In your review you say "Rough the surface up" but I've seen advice that the inside of tyres should not be sanded, as the threads are much closer to the inner surface and risk being damaged by abrasion. I've seen advice to use specialist tyre cleaning chemicals, as used in auto shops, but in the end I just rubbed the inside clean, put normal superglue in the cut, and applied a normal inner tube patch to the inside. Seems OK so far!
Does the Hutchinson kit come with sandpaper? I'd be interested to know, to work out what to do with future cuts.
That said, I don't see the point. The purpose of roughing the surface up is to provide greater surface area and better adhesion between the patch and the tire or tube. After my first attempt to patch a tubeless tire failed due to lack of adhesion, I felt that I needed to do whatever I could to save my $50 tire on the next attempt.
While I did clean the Stan's sealant off with a rag, I didn't use any automotive grade tire cleaner. I do like that idea however, and I might pick some up for next time. I think the key here is that the Rep'Air product apparently uses a "superglue" i.e. Cyanoacrylate, rather than the typical rubber cement that is traditionally found in bicycle tube patch kits. It is conceivable that superglue type adhesives do not require the surface treatment that other glues do.
Realistically, I have a hart time imagining how rubbing sandpaper on the inside of my thick, tubeless tire is going to damage the threads. When you consider the large gash in my tire that I was repairing, the last thing I was worried about is a little abrasion to the threads, not that any threads or thread damage was visible.
You will find that that there is a lot of new and evolving techniques out there when it comes to the care and maintenance of road tubeless tires. From uncertainty flows different approaches that might deviate from manufacturer's recommendations. As in other area's of cycling, you have to go with the technique that works best for you, without compromising safety of course. For me, roughing the interior surface seemed a natural way to seal the gash and save the tire, regardless of Hutchinson's recommendations.