Running tire pressures that are too high certainly can make for a rough ride and that bouncing around you mention - they'll also contribute to a lack of traction on cornering, darting &/or erratic steering, an increased tendency to wear oddly, a higher risk of punctures, and a whole lot more. So maybe dropping your tire pressures will help...
However, be warned, the OEM Kendas and any of their clones or copies are really just lightly constructed car tires, often with little in the way of quality control or quality construction, and they are nowhere near as capable of safely running under a Spyder at pressures anything much lower than about 2 psi below
THEIR recommended pressures. 'Normal' car tires (as opposed to the lightweight OEM car tires like the Kendas etc) are made a
LOT stronger than the Kendas etc, and generally, they're made with better quality materials and to a
LOT better standards too, and they are more than capable of carrying a full sized car, ie much higher loads than a Spyder, at those higher pressures, so they don't
need as much air pressure in them to safely carry the load and operation of a lightweight Spyder; but due to their lesser construction, the Kendas et al
DO need those pressures just to do the job, as best they can anyway!
So even if they are brand new, if you are still running OEM tires &/or any of their clones and your Spyder's tire placard &/or manual calls for 23 psi or similar in those tires, then you really shouldn't run just 15 psi in them!! After all this, you might be beginning to grasp why so many Spyder owners scrap the OEM tires &/or any of their clones and run 'real' car tires instead - the improvements the 'real' car tires bring in ride, handling, traction, safety, tire wear, and more when run at an appropriate (lower) pressure for the lighter load of a Spyder vs that of a full sized car are often more than enough to overcome any extra effort involved in changing your Spyder's tires yourself, or finding someone who's not a dealer to do it for you.
Ps: If your dealer has fitted non-OEM tires for you, please don't 'out' them here on the public pages of the Forum, or even hint at it - doing that may well see them change their minds about doing it for anyone else, maybe castigated, &/or possibly worse... It's happened before, so just don't 'out' them!
