Low speed instability

[sdrogue]

My bike has been acting funny at low speed. It seems unstable,  almost like it wants to weave or wander under 35 mph. I equate the feeling to riding on grooved concrete. What could be causing this? I am having a new set of tires installed this weekend which should help but wanted to get some other ideas as what to check.

13k,'99, no wrecks to my knowledge,  currently has old but OK looking tires.

[SirHansford]

possibly tires out of balance. that can cause the bike to vibrate within certain specific speed ranges.  check the pressure is correct? hardening from age might be contributing as well. new set will almost certainly fix it from your description. only other thing that i can think of is very bad bearing.  can't judge a tire by looks. 

[Sandgroper57]

Could be just worn tyres, rears can square off and fronts can get scalloped. You could also check the rear/front wheel alignment by string lining or a long straight edge. Since you are getting new tyres though, see if they will do it for you.

[Watcher]

Tire pressure is neglected by many.  Recently my bike sat for a couple weeks while I was recovering from an illness and when I hopped back on it felt "loose" in the turns.  I thought it was just me but some friendly car driver said my rear tire was low.
Got home and checked the pressures.  10 psi rear!  Like 15 front!

Got them back up to 38/36 and it rode like new.

[gsJack]

I had a similar front wheel wobble on my 85 Nighthawk 650, most noticeable coasting down from 40 mph or so.  Replaced front tire and wobble was gone only to come back a little later as the new tire started to wear.  Turned out to be steering head bearings were bad, a little notch at the straight ahead position.

I could feel the notch by putting the bike on the centerstand and grabbing the passenger handle with one hand and pushing the rear down and turning the steering back and forth slowly with the other hand.

[sdrogue]

New tires were installed today. Overall handling is improved but the low speed instability is still there. I noticed no notches in the steering today. Will check for other play in the front end then proceed to tear down and inspect the front end.

Do you need a special tool to adjust adjuster nut?