[KSagal]

A couple things come to mind... All of them guesses.

1. Perhaps the tires have developed a flat spot, or are out of round. This can happen during storage or shipping. (Of course, first check air pressure, and be sure both tires have the same)

I might deflate the tires a bit, and then inspect the bead seat, then re inflate them. Take it for a glide.

If your symptoms change, even that the same feeling comes as a different speed, then you are onto the solution, and need to try again, and find a combo that will work.

Also, if there is a flat spot, the best solution is to glide for a bunch of long trips. That will re-round the tires. (especially if warm, or on warm pavement)

2. At some point in the past, a wheel may have gone out of flat, or is not flat, or is warped, whatever you want to call it. (1 above was about the rubber tire, this one is about the plastic wheel)

This is pretty easy to see, just look down at the wheels as you glide. they should stay in the same plane.

IF your wheels are wobbling, and the bolts are not loose, then you may want to remove the nuts, and rotate the wheel on the wobbly side one third. Again, there are threads on this kind of a repair. I use a sharpie, and mark all bolts a,b,and c. I also mark the holes in the wheel a, b, and c. Then when i put the wheel back on, I make it a point to put hole a on bolt b.

Then take it for a glide or two or ten. If I like the glide better, then I am done. IF not so much, then I do it again, but put the hole a onto bolt c. Glide some more. Do the other wheel, and glide some more. you get the idea.

3. Elastomers may be starting to go. These can be replaced pretty easily, and there are lots of threads on it.

Good luck. Keep us posted.