If the previously posted suggestions do not solve your problem I feel steering trail may be at fault. The Meridian was intended for pedal power & relatively sedate speeds with easy handling characteristics around town. A bike or trikes fork design along with weight distribution, tires & numerous other variables can setup the dreaded "death wobble" at higher speeds...common even on factory built motorcycles. Vendors on Ebay do a big business selling steering dampers to bikers as well as off road truck owners.
Do you recall if the road was also rough where you noticed wheel wobble occur? Often hitting a bump, not necessarily a big one, will induce the wobble at speed. I had one bike that was great on a smooth surface at most any speed, but hit a small bump at 60 plus and it went into wobble...try to hold that speed and it only got more violent shakes...slow the flack up & it would start to behave & recover.
I hope your problem is something simple, but fear it's not. Of course the dampers aren't expensive $50. or so and re-configuring the bikes neck is also easy enough; if you want to invest the time. I've had to do both in the past on dirt bikes with this really nasty flaw. In my experience not having enough steering "trail" was the most common denominator on the bikes I've witnessed the "wobble" on & the speeds they occurred at were quite a bit past 30 mph. Just a heads up it can do much more than damage a wheel so you got to figure it out or slow it down. Rick C.