I have asked about this recurring (never really been gone) issue with my wife's CT Road.
When I ride it, there are no issues. I have taken it to the Depot up off the Comet which is the local retailer and service center for a check out. The guy that checked and rode it also didn't have the issue. His comment was that he hadn't ridden one that drive so good....so...
To refresh. On flat land at slow speed she has no problem unless she hits a bump, which will result in a quick oscillating vibration on the front, back and forth. Any time she gets the bike going downhill above around 15mph it does so and gets more pronounced the faster you go. Take one hand off the steering and it will do it as well.
I have checked the hubs, brakes, both headsets seem to be fine. I have adjusted the toe from about 1/4" toed out, to neutral, to 1/4" toed in and various settings inbetween on best guess. I don't have the "tool", just eyeballing with a yard stick jig I made. I took off the wheel reflectors thinking that was the issue and it did seem to help but it showed itself again when we went to the mountains last week. Basically unridable like this and seriously unsafe.
I am at a loss here. The shop that knows them sees nothing wrong. I have asked and tried many of not all of the relevant solutions. What am I missing?