Dengfu R12 - has anyone experienced speed wobbles with other open molds?

[Nickk2000]

I have an r12 and i get speed wobbles at about the 40 kmph mark, which is 25 mph. its bad where i cant even stay against the shoulder, im afraid to. It wasnt terribly windy today, under 5mph MAX and i have 50mm deep wheels. Anyone know the cause of this or has anyone had a similar issue with other open molds? Im scared to ride it down anything steep because i went down maybe a 7-8% and held it at 40 kph and it scared the hell out of me. i had to keep touching the brakes. the handlebar/headset looked straight, i could realign it and see if it helps but im kind of out of options. I want to narrow down what the issue is though so my thought process in steps is

swap wheels - i have heavier box cyclocross ones so i can tell if its the wheels (why would it be the wheels, lol, ill put the deep dish on my gravel bike too.) Ill check my handlebar/headset after that.

[benando]

Could be lots of things causing it. I have not experienced speed wobs from my open mold frames.

Check your bearings for slop: headset bearings (hold front brake and rock bike forward+backward). Also check the axles for wheel bearing slop.

No noticeable asymmetry in how the tire is mounted? No noticeable frame flex or cracks visible?

I had speed wobble on another bike of mine and I solved it with bike fit. My position had my saddle too high and too far back, causing me to unweight the handlebars and generally be uncomfortable. The constant micro-adjustments between sitting in the middle of the saddle and shifting my butt to the right side of the saddle to "protect my dominant leg" (BikeFitJames insight there) and alleviate pressure would cause the bike to not track straight at low speeds, and then cause speed wobble at high speeds.

Best of luck

[carbonazza]

It is probably a resonance problem with the front wheel at a certain frequency.
Not necessarily linked to the fork.
Did you try with another wheel ?

Or try to change something, like another valve if tubeless, another tube, or another tire, as it may be deformed, etc.
Change the torque you tighten the front wheel.

[Nickk2000]

Both wheels look good, not out of true. Nothing visible. Im going to swap wheels and ill get back to you. Thanks

[Schumo]

No such issues with my R12, did 65 km/h today.

But, most downhill roads where you can reach such a tempo here aren't protected from the wind, and in combination with my 55mm wheels it can get indeed a bit scary.

[Nickk2000]

I fixed it, overhauled my fork! Thanks

[wfl3]

I fixed it, overhauled my fork! Thanks

What do you mean by overhauled fork???

Headset?

[Nickk2000]

Yeah, took most of the front end apart, built it back up, deflated and reinflated my front wheel too. Couldnt tell you what it was but by physics the headset would make the most sense. Id recommend the bike as long as you dont crash or get chaindrops. The paint job isnt durable at all, a gel coat would do wonders.

[saintrider]

any minor play in the headset bearings is enough to cause speed wooble. I had it in my boardman.