Low speed shimmy
 

I have a 2011 Cube Hyde Team. Had an accident 4 years ago so had the front wheel was replaced (kept stock hub/rotor). Fast forward to today and out of nowhere I'm noticing significant wobble at low speeds most apparent as I'm leaving my neighbourhood < 10mph. If I let go the handlebar you can visibly see a wobble once per revolution. Once I get going > 10mph it is much less noticeable but I can still feel it through the grips.

So the 4yo wheel was poor quality, spokes rusty and some loose compared to the 9yo stock rear wheel which I think is fine. I brought it into the shop and they replaced the rim//spokes keeping hub/disc brake rotor. Took it for a spin today on the new wheel and the wobble is still there.

So I'm trying to figure out what else it could be if not the wheel? I can prop the bike up and give the front wheel a spin and it looks true and I don't see any wobble. Maybe it needs weight on it to become apparent? Should I replace the tyres? Could it be the headset? Could it deceptively be the rear wheel even though everything points to the front? Any tips much appreciated. I'll put it on the rack for a proper look before taking it back to the shop but want to get some ideas of what to mention them to check.

On a tour I once heard the accompanying mechanic tell a friend "I don't need to know what you think might be the cause, just what the symptoms are." He said it in a nice way but it was a "duh" moment.

Since you kept the stock front hub and rotor, which was on the bike when the accident happened, those would be the first things I would check. Maybe there was damage that didn't immediately show up. Then I'd starting looking at the "normal suspects". Check all tubing joints for any signs of damage. Check headset, fork, frame alignment, and go over the rear wheel, also.

Is the wheel still true, or is it possible one or more spokes have loosened and/or broke?

Bent QR or fork? Tire not seated correctly, axle seated in fork? Lots of things to check.

If it wobbles ONCE per revolution that pretty much points to the wheel/tire.
Have you looked at the tire for a bulge of poor bead seating in that area?
Squeezed adjacent pairs of spokes together, looking for some exceptionally loose ones?
What area? Look down and see where the valve stem position is re the "problem spot". Look where the rubber meets the road at that position.

It turned out is was the rear tyre. I noticed the stick on reflector was detached over an area. On the rack it was easy to see the bulge. Sidewall blown out. Threw on a replacement schwalbe supreme, good as new! Guess I rebuilt my front wheel on a lazy hunch but it was in such bad shape it needed doing anyhow. Funny how it really seemed to come from the front perhaps because you feel it thru your grips.