strange wandering/swaying/wobbling

[tylerc]

Today coming back to my place I was riding around and took a few corners relatively fast (well for me anyways ) a little after this i noticed that the bike felt like it was wandering a little. it would sway back and forth. I realized that I hadn't checked the air in the tires this season (i know, i know, but i have only had it running and licensed for a few days) so i went and filled them up to 35 psi (is this right?) from about 10 anyways the bike felt totaly different with the air in it and i thought the wobble was gone however i instantly went off and went blasting around some corners again. kept undershooting where i intended to apex like it was falling into the turn. after i stopped cornering the wandering was either back or still there. the bike just kind of sways left to right when i am going in a straight line. i don't think it is as bad under acceleration, however i can still detect it.

a little background on me and the bike. my bike hasn't run very wel, or much, since i got it because of the carb issues it has when i bought it. I rode it around maybe a cumulative of 30 mins last season before i tore it apart. now its runningly decently but this wandering is very discontenting and i would like to get it fixed quickly

it is about 10-15 degrees colder today (probably unrelated) i looked at the tires and they look pretty new (lots of tread, no whether cracks.

so whats the prognosis doctors?

-Tyler

[BraadaJim]

Guessing........

Tires distorted internally from running dangerously low pressure.

Head bearing loose

Rear wheel out of allignment.

Rider not sitting centered on bike.

[BISQ]

I don't know much about you or your riding style... :dunno

But:

Falling into the corner is a good thing--but it sounds like you're target-fixating on either the apex or the inside of the corner, and therefore turning in too fast.

...that's beside the point.

My #1 guess is that you are too tense on the bars and gripping to tightly, as well as giving uncertain (and therefore multiple corrections) inputs to your bike. You'll transmit every bump and hump in the road directly to your suspension and upset the bike if you're holding on too tightly, and you'll do the same as you fight from correction to correction.

#2 Tire pressure and cupping--as well as what Jim said about the bearings. Check for that--do the bars wobble back and forth when you take your hands off of them while going in a straight line?

#3 Suspension issues. I had similar problems with my Kat, but I only experienced them when transitioning from knee down on one side to knee down on the other at places like Marion and the Gap. It was a wobble at the peak as the suspension tried to manage the transition forces. It was annoying, but manageable. Again, I don't know your riding level or style...

[tylerc]

I have been riding since i was about 16-17 and i am 22 now so about 5-6 years. had a 79 kawasaki kz and a 87 vfr and never had these problems. before this started happening when i took my hands off of the bars it wanted to pull to the left somewhat, I will try after i post.

i was wonderirng about the low tire pressure. since it got so much colder today i am guessing it dropped it a few psi from what it was. the tires sidewalls wern't sagging at all, but i hope i didn't ruin them.

how do you check for cupping and what is it?

i will also double check the rear wheel and make sure it is alighned in the swing arm, although i checked quickly and it looked straight

[Anonymous]

Well, I think yours (stock) is 36 in the rear, 33 front cold...

[tylerc]

Thanks for the pressure info! i will adjust that, although with such a small difference i don't know how much it will change.

Little more info, checked out the bike and front fork seals are both wet, definately leaking. could this cause it?

when i take my hands off it pulls to the left still, not vibration. also the tighter i clamp the bars the better the swaying gets, and I was as centered as i could get

condition seems to get better on card cornering, no swaying. light cornering(coming from a stop sign) and straight line are most prevalent. rear wheel is centered in the swing arm. light application of rear brake worsens it, hard application of either brake makes it go away (perhaps because this forces so much of my weight to the front )

so now what do you guys think, tell me its not fatal

[ThAzKat]

It is very possible to have tore up the interior on the tire by running such a low pressure. I also wonder if you threw the balance of due to the low pressure, if you were riding at a slightly hot pace you could have moved the tire on the rim(that is a possibility because the tire is not bolted to the rim). Also with a bike of that age it can be bearings too. there are just so many things it can be. Put the bike on the centerstand or a race stand and see if there is any movement left to right. you have wheel bearings and swingarm bearingson the rear and wheel bearings and steering head bearings in the front that need to be checked.

[The CyberPoet]

What to know:

At speed (30 mph +), if the sway is at or under 4 times a second, it's usually in the rear. If it oscillates faster than that, its in the front. My best guess is that your rear wheel is out of alignment (to the swingarm) and the low tire pressure masked that, but in the process wore the tire unevenly as well.

I'd recommend having the tires looked at by a pro and the wheels rebalanced at minimum.

Tire pressure needs to be checked at least once a week (I check it every time I go riding -- foot-operated bicycle pump from walmart with integrated pressure dial: $11.87). Running it at 10 psi is tantemont to asking it to delaminate on the insides, and as others have stated, you may have ruined the tires that way. Since your life rides on your tires, don't take chances -- have them checked out and replace them if you are unsure.

Cheers
=-= The CyberPoet

[tylerc]

Point taken, i will have them checked out. it is definately under 4 'sways' per second. the strange thing about tires being that low is that they wern't deformed hardly at all considering the low pressure, i will definately be more vigilant now however.

as for the pulling left w/no hands (has always done that) and leaky front forks do you guys think that may be related? front forks bent perhaps?

i will get back everyone whenever i get any news on tires. i suppose this may be an opportune time to upgrade to 98+ wheels and a nice fat rear tire

[The CyberPoet]

Point taken, i will have them checked out. it is definately under 4 'sways' per second. the strange thing about tires being that low is that they wern't deformed hardly at all considering the low pressure, i will definately be more vigilant now however.

Because of the strength and shape of the steel belts in most modern radial motorcycle tires, most radial tires can hold their shape even with virtually no pressure (ambient). While this is a major safety issue -- imagine getting a puncture in a high-speed banked turn -- it means that you can't just eyeball them for pressure readings. You may want to invest in tire pressure monitoring valve caps (get ones rated at 3 to 4 psi over what your pressure should be -- so when they drop below the right level, the warning starts showing, instead of having to be 4 psi low to warn you).

as for the pulling left w/no hands (has always done that) and leaky front forks do you guys think that may be related? front forks bent perhaps?

i will get back everyone whenever i get any news on tires. i suppose this may be an opportune time to upgrade to 98+ wheels and a nice fat rear tire

Used tires often pull left in countries where you drive on the right side of the road, because the road is crowned for drainage, and after thousands of miles, the tires have worn more on the left side than the right side (the exact opposite happens in countries with drive-on-left rules, like the UK and Japan).
Leaky front forks may be a cause of a harder pull to the left, and is a safety issue that needs to be addressed as soon as possible -- right after the tires or at the same time.

Good Luck!
=-= The CyberPoet