Originally Posted by nhluhr

the DT RR440, being a Tubeless Ready rim bed, does in fact create a bit more effort for tire mounting. If anything, your old gumwalls were loose or stretched-loose. I've found that yellow Veloplugs work well in my DT RR440 and RR440Asymmetric rims, giving a hair more slack than a normal rim strip leaves. You absolutely have to install the tire correctly that that means the final bit of bead you seat is at the valve and that you keep the bead centered in the rim channel all the way around before you attempt to finish seating it.