Last year I installed RaceTech springs and used a mixture of 10 and 15wt fork oil. [becasue I didn't have enough of either on hand] I've since noticed at times, especially earlier in a ride, that the bike will "wallow" during high speed sweepers. I.e. 75-80+ MPH. If I hit a bump mid corner, the whole bike momentarily becomes destablized and wallows, not unlike HD's death wobble, but as soon as I lift off the throttle the bike settles down and all is good again.

As you can imagine this can be a bit disconcerting and take some of the fun out of a ride. ...Now here's the interesting part; this issue seems to lessen as the day wears on, so my only thought is that as the fork oil heats up and becomes less viscous the problem resolves itself; allowing for more rebound and less dampening.

Could this be resolved by adding some more washers to increase preload or do I need to drain the forks and replace the fork oil with straight 10 wt?

Thanks.

Doc_V

Preload is not what i would be looking at. I would check the neck bearings and tire pressures first and then play around with oil level be it add or subract oil

I noticed the same problem when i left work my bike did the same thing thought it was sand when it kept doing the little jiggle on the third day i checked my air pressure found the front down 2 PSI and i was told that as little as 1-2 PSI can make a difference on your handling, that is why if you watch the races dropping a 1/2 psi can make a heck a car turn better or worse in the curve same theory on our bikes just a smaller scale Just my $.02

RSOkie wrote:
I noticed the same problem when i left work my bike did the same thing thought it was sand when it kept doing the little jiggle on the third day i checked my air pressure found the front down 2 PSI and i was told that as little as 1-2 PSI can make a difference on your handling, that is why if you watch the races dropping a 1/2 psi can make a heck a car turn better or worse in the curve same theory on our bikes just a smaller scale Just my $.02Precisely !!!

What’s your rear shock situation?

I had that same "wallow" that you describe. It always happened in the same corner with a bump in the middle, except it was a 45mph flat corner and running it at about 60. I went to the road wing shock and seamed to solve it, but it very well could have been tire pressure. I would check neck bearings and swingarm. Unfortunately I didn't change just one thing at a time and try it. I made several changes over the winter and in the spring it was better. I think what I changed that winter was, I packed and adjusted my neck bearings, checked my swingarm for cracks and added the road wing shock, always adjusting tire pressure, so any of those could have been it. And I may have gone from Dunlop tires to Continental tires that winter.

The part that made me think it may be fork oil is it does seem to lessen as the day wears on and everything on the bike "heats up". I can definitely feel the difference when my tires are warm vs. cold; it's like night and day. They're not bad when they're cold, but the 777s are just *so* good when they're warmed up.

I'm running a Roadwing and keep the preload between half and three quarters when riding solo. I do check my tire pressure often an run 38 psi front and 40 psi rear, maybe I should try 40 psi front and 42 psi rear? After all I am a big guy and do have a lot of gear on my bike. I'm just concerned about premature tire wear and squaring off the profile; which only makes it worse.

I tightened the neck bearings last year, but maybe it's time to check them again? It's just such a pain to get it right; the service manual procedure is too lose and I'm concerned about over doing it if I just "go by feel"... And after my fiasco with replacing the neck bearings on my 99, I DO NOT want to go through that again any time soon. ...Anyway, was hoping it was more simple.

BTW -Does JD come around anymore?

The neck bearing does not make sense to me, why would (minimal) heat play a factor there?

The fork oil or tire air pressure seems more reasonable.

I'm thinking that air pressure is easier to check first,
but I don't remember anyone else here reporting ride changes as their tires heated up.

MidwestMike wrote:
...I don't remember anyone else here reporting ride changes as their tires heated up.

You won't really notice tires heating up unless you have semi sticky tires and you ride aggressively on twisty roads. So the stock Bridgestones and Dunlops on freeways won't do it. But it does make a difference when they warm up; it's why race teams use tire-warmers. They're essentially industrial electric blankets that keep the tires warm and therefore sticky.



BTW - I came across these two great illustrations. The first one demonstrates steering head shake; which is what you'd experience with loose head bearings. It's often referred to as a "tank slapper" and is more likely to occur at high speeds in a straight line; usually under hard throttle. It's why you see a lot of sport bikes with steering dampers.



And this is what I'm referring to as "wallow"; which is a little more difficult to diagnose. It's more of a full-bike oscillation that occurs during high speed sweepers.

Your text descriptions are spot on but the graphics help too.
The wobble is not as violent as a front end shake but still un-nerving.
I think I run my neck bearings a little on the loose side per descriptions I have seen on here. But they may be a little tighter now then when I had the wobble. The reason I did the neck bearings was due to front end shake on deceleration. But the wobble didn't feel like neck bearings, it felt like it was coming from the back of the bike and shivering forward.
And it has been awhile since seeing JD on here, he's probably just been busy. I don't know him personally.