http://www.barrystiretech.com/speedratings.html
In speed rating tests, failures are almost always belt area separations - and in particular "belt leaving belt" separations. In other words, tire construction, not tread compound, seems to be the limiting factor.
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To get a tire to pass an H speed rating almost requires the tire to have an overlay - commonly called a "cap ply" and nylon is a commonly used material.
This overlay restricts the growth of the tire due to centrifugal forces as well as the movement caused by the standing wave. Not only does this result in reduced stresses in the tire, it also reduces heat generation.
Adding further overlay layers results in higher speed capability. That is, you achieve higher speed capability with just changes in construction. Rubber compound changes are almost incidental.