04 Dyna FXDX/I, Super Glide Sport, here goes, bear with me. On the application of the front brakes, a ‘vibration’ ensues, it’s only with the front brake, clutch in or out, and only from 52/3 mph down to stop, ALL the way to stop. Run her up to 85 or so, smooth braking, until somewhere vicinity or 52/3. It’s NOT a violent shake, just a nuisance issue, but obviously affects the tire. Looking over the side of the wheel doesn’t show any significant movement. The bike has over 70k miles, relatively trouble free, other than maintenance, and the lady rider RIDES, she’s no fair weather player. Initial inspection showed cupping around the center of the tread, ALL the way around, but not serious, it apparently has built slowly over time as she has ‘lived with’ the vibration. Serious time has been spent inspecting the frame for cracks and issues, the bike’s never been wrecked.
First step, dial indicator on the rotors, spot on, no issues, front AND rear. Also checked were the wheels while they were off, and the swing arm bearings, revealing no issues. Balance was good, tho the front had ¼ ounce too much, that was removed. No difference noticed. Front and rear bled with fresh fluid, pads inspected, one pad had ‘uneven’ (tapered) wear across the gripping surface, but appeared to be completely useable. Test ride showed no change.
Second step, neck bearings, as there was a noticeable ‘groove’ in the ‘sweet spot’ center of the bearings/races, obvious wear upon removal. Fall away performed. Test ride showed no change.
Third step, new pads and caliper pin kit, front and rear, pins showed very little wear, but changed ‘em anyway. Test ride showed no change.
Fourth step, clamped a shim in each caliper separately and mounted them outboard for testing, one at a time, neither showed issues, test ride showed no change or difference between single left, single right or dual. Same vibration.
Fifth step, on VERY close inspection of the forks, slight clearance movement between the lowers and the tubes, installed new seals, upper and lower bushings and fork fluid. The clearance movement is still present, tho it appears to be somewhat less movement. Many adjustments to the fork dampening (Sport model) and rear shocks made no differences. Test ride showed no change.
Sixth step, new rotors, just because, sigh. Test ride showed no change.
Seventh step, removed the forks/legs/wheel/tire/m/cyl, replaced with known good unit (tho NOT Sport/adjustable), and it’s a single disc set up in place of the duals. Test ride showed no change.
It was at this point that I discovered, after significant sleeplessness, that shutting the engine off while riding made the vibration disappear, at all speeds, so I decided on motor mounts, even tho they appeared to be in good shape.
Eighth step, new motor mounts, with the center hump on the front shaved for clearance. Yes, the old front showed signs of motor contact/wear on the center hump. Engine alignment procedure performed on reassembly. Test ride showed improvement but no elimination.
Seventh step, borrowed the rear shocks off my neighbors 09 Dyna (shorter) and test rode. Test ride showed no change.
So, I’ve got a 70k Dyna Sport with new neck bearings and mounts, a completely different front suspension and shocks, and the same vibration issue. Suggestions?

 

I'll admit didn't read through all that.

I didn't notice for a while, but the way the Dyna is designed, when the front brake is applied vibrations from the engine are transmitted up to the handlebar. Look at the front wheel while idling without the brake. It'll bounce around. Apply the brake. Stops bouncing, but those vibrations transmit through the frame up to the grips.

Since upgrading my motor mount to the Vibra-Technics, I can see the change, but not feel it, when I apply the brakes.

 

You say the tire tread was cupped....did you change the tire before doing all the "hard" stuff?

 

First thing I would have done is replace the tire. Since it's an obvious defect and relatively inexpensive a new one would eliminate that as a variable.

 

as noted, tire was replaced in step 7, for the reason of not wanting to introduce the same issue to a new tire, I wanted to solve what I thought originally was a brake issue before putting new rubber on, YMMV