1948 front end shimmy

[jn1972]

My 48 chief front end has a shimmy at 45 mph plus ,I put new firestone tires from croaker on and set the pressure at 20 psi in the front ,it is especially noticeable when you back off on the throttle any ideas thanks

[exeric]

You can play with tire pressure, but I would look at your neck bearings, and wheel bearings very carefully. I had that problem with my '40 Chief and it was all in the bottom neck bearing. . . Just saying.

[tfburke3]

did the shimmy happen after the new Coker was installed or before?If after then does the wheel and tire spin true?did you have tire balanced?Lowering the pressure may help if the problem is radial run out but not so much for lateral wobble.
If you get the wheel off the ground you can spin and see if there is a wobble and if the wheel always stops in the same spot thats not good.
While you have it up you check the neck bearing play as Eric mentioned,although I like to do this with the wheel removed.
Tom

[jn1972]

The original tires were from the 60,s are were very worn when I bought the bike,I took it for short rides but I did not trust the tires ,the front end felt a little loose then but I thought it was the tires ,I will have the front tire rebalanced ,how do I check the neck bearing when the tire is off ? Thanks

[tfburke3]

If you grab the bottom of the fork lift up and back and forth check there is no play.Also check for smooth turning.Good time to look at shackle shaft adjustment also.
I would also check the wheel runout before you remove to balance.At those speeds I doubt its balancing,unless it severly out,which you may notice in the wheels stopping position.
Tom

[DEEBS47Chief1991]

I have to periodically lubricate (46 & 47 no grease zerk) and tighten up my front shackles. Changed the needle bearings to bushings 30 years ago. When the shackles get a little loose you can really feel the instability when you lean the bike way over in a slow turn like taking a left hand turn after stopping at a stop sign. The axles are tapered and a tap of a brass or nylon hammer frees them for adjustment. When properly tightened you should just barely be able to turn the washers that reside between the shackles.