I'm not quite sure where people get the idea that the front tyre gets scrubbed out quicker when running DS. I got 7,500 miles on the OEM front tyre, the last 2,000 of those had a DS on the back. Since using the DS I get at a minimum 7,500 miles on the front, usually over 10,000, and as much as 17,000. How many miles do those with MC rear tyres get out of your front tyres?
A DS tyre is legal, as it is a Passenger Vehicle tyre fitted to a passenger vehicle. Many motorcycles come with them as OEM. "Motorcycles" legally include bikes & trikes - the law does not differentiate. If the tyre does not change the width more than is allowed by law then it is legal. In the USA the Magnuson-Moss Warranty Act means that you can use non OEM parts without voiding the warranty. So how can Triumph refuse warranty because of the use of a legal tyre?
I would suggest that a Carpenter exhaust system would be a much greater concern to warranty. It, according to IFT, allows for much more power. Without altering the ECU it would make the engine run very lean (if it is as efficient as claimed by IFT) and therefore cause many problems which Triumph would have the right to refuse under warranty. If the ECU has been tampered with to correct this, then Triumph could also void the warranty. If the engine is producing a lot more power and parts fail then Triumph could also void warranty. If I were to spend money at IFT's place (and there is no way in the wide world of sport that he will ever get a penny of my money), I would like to think that Carpenter Racing would put their money where IFT's mouth is and warrant what he calls "modifications for a daily rider" for the same two years that Triumph does.[/Q