Did you have the 2s or the originals ? The Originals had very flexible sidewalls apparently which creates too much heat on a heavy bike. They strengthened them on the 2s which made them more like the Sportsmarts so they should be better on the ST4. Not that I bought them, just bought the PR2s and they seem good.I wouldn't get too carried away about the Roadsmarts. I had a set on and the rear was gone in barely 3,500 miles but I got over 5K with Pirelli Angels. The Roadsmarts were the most expensive and shortest lasting tyres I have ever fitted. I had expected better for a new generation dual compound tyre. These were the first Dunlops I had tried for over 30 years and will almost certainly be the last.