Tire weave/grab problem

95 Jog; a few months ago I put on some Pirelli SL26's (front 90/90, rear 3.50 inch). Just recently I started to experience the scooter quickly "pulling" or grabbing in either direction at any speed. Here is how I explained to to Pirelli:

"I can feel it at all speeds. It is the strongest at lower speeds, but when maintaining any riding speed (from 10-40mph) it just feels like it pulls to either direction. These are real quick pulls, its a "jerky" movement. For example, if it pulls to the left and I counter it with a slight right handlebar turn, then it will immediately start to pull to the right; counter that with a left handlebar turn, and it pulls to the left and so on back and forth. I can still keep the scooter somewhat straight, but it is actually difficult to do so. When making corners (at ~10-25mph) it feels like its harder to turn and keep that turn going. I know how to ride two wheeled vehicles and know that you have to lean into the turn, but this is different. It just feels like there is excess resistance through the turn.

Like I said before, this issue comes and goes and is not constant. It seems to vary with the weather as it is starting to get colder here now. During the summer months (85+deg days/70 deg nights) I had no issues, and now with the varying fall season temperatures (60-78deg days/40-60deg nights) this seems to be happening. Anything about these varying temperature changes that would have effects on the tire pressure to cause this problem? This problem seems to be the most apparent when the temperatures are colder or when the range of day/night temperatures is high."

Any ideas? I have the front/rear tire pressure at 35/45psi, respectively. I read the troubleshooting article and see something about motor mounts, but my problem seems to be related more to the temperature changes.

wheel bearing could be shot r u sure its the tire pirelli are quite a respected and trusted brand mate. i would say it could be bearings either stearing or wheel etc. its probabl the bike and not the tire.

Yeah I know what you mean. I'm not blaming it on Pirelli or anything, but I just feel like it has to do something with the tires such as them not being mounted correctly.

Another thought I had was that maybe the forks/handlebars/stem could be be bent there or somewhere in between???? For example, if I just sit on the bike without moving with the handle bars straight ahead it feels like the "high point". Then when I turn them either way, they drop or get pulled down. I know this might sound like what they should do, but I know that if you just move them back and forth there should be a smooth transition and this isn't. It feels like when the handle bars are in the straight ahead position there is a bump.

The bearing being bad crossed my mind as well. Its just the fact that it seems to vary with outside temperatures that makes me jump back to the tire. I should also mention that this problem seems to just be a cause from the front, not the rear. Its definitely in the steering.

Thanks for the advice

start simple... is the tyre pressure correct? as this will deffo cause this prob simple as it sounds

forks could be fucked... could be a bent frame, lots could be up with it tbh. just go through the whole bike. check bearings bushes and shocks.

The rough tyre pressures for scooters should be around 30psi..
you say you'v got 45psi in the rear?

orrrr it could be your head race bearings..you say theres a bump when the straight? are they notchy?

The rear tires cold max load is 47psi so thats why I have it at 45.

There aren't really knotches, but its just like a bump in the transition. That is the only one, the rest is smooth.

Out of all the possibly causes, which would be most likely to change with temperature?? Or if you don't want to put temperature into play, what would be more likely to just come and go?

Well the easiest thing to do would be to let the back tyre down to about 30-35 max, unless you really are big.
If you still have the trouble..then id be looking at the head race bearings..cos they sound like they've broken up.
I dont think it has anything to do with temperatures..Where abouts are you from?
If your thinking that deep into it then i'd say it was down to your driving LOL

when i 1st read this post i thought 45 psi :wtf: thats a lot of pressure...

My Runner has 19 psi in the front and 23 psi in the rear...

so i dug out the Haynes manual and had a look at Yamaha jog and low and
behold it says tyre pressure front and rear 22 psi

when putting air in the tyres you go with the manufacturers recommended
tyre pressures not whats written on the tyre wall!!

Well shit I guess I'm running way too much pressure then. I figured it depended on what tire you had on their and what the tire manufacturers amount was.

I'm still going to look into the head race bearings though.

I dropped the front down to 30psi and the rear to 32psi and it seems fixed. Even though it was warmer today (when the weaving doesn't happen) there was no weaver at all. It is suppose to get colder now so we'll see in the next few days/week if it comes back at all.

glad its sorted

yeah that was alot of pressure in the tyres.
hopefully that'll be the end of that problem eh