Author Topic: Wobble (not deadly but could have been)  (Read 633 times)

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Offline Jerdurr

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Wobble (not deadly but could have been)
« on: March 25, 2020, 11:41:48 pm »
So this happened to me just now; went for the second ride of the season (Toronto, 5 degrees celsius, so fairly cold). When I got out I realized my tires were under inflated, but I figured that for a 15km ride each way, it should hold alright. Pressure was:

Front: 38 PSI
Rear: 40 PSI.

I am aware that pressure should be 42 PSI cold, yes.

I have Pirelli Angel GT A Specs, they were installed last season, and do not appear to be overly worn or badly worn (will add pictures soon). Other than that and aside from Ivan's flash, the bike is stock.

Today, while on the highway, and under acceleration, around 140 km/h, I could feel the bike starting to fishtail and wobble. I let go of the throttle, she would re align and all was good. Then I pushed the throttle again to see if I could replicate it, and it did.

The bike used to ride straight as an arrow. This is the first time it ever happened. Of course I will properly inflate the tires and re-test, but is it possible that just having low pressure on the tires to cause this dangerous issue?

TIA
Best,

JD

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Offline Phil

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Re: Wobble (not deadly but could have been)
« Reply #1 on: March 26, 2020, 02:17:43 am »
Tires cold and too hard of acceleration? I hated the Angels in the cold. They were great when warm, but not cold, in my experience anyway.  Fishtailing to me isn't a wobble, it's generally right wrist induced wheel spinning. Just a thought.

Offline Jerdurr

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Re: Wobble (not deadly but could have been)
« Reply #2 on: March 26, 2020, 04:37:50 am »
But that’s my point... it was fishtailing and I felt the wobble at the front. Do you think the tire pressure had something to do with it?
Best,

JD

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Offline Jorge

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Re: Wobble (not deadly but could have been)
« Reply #3 on: March 26, 2020, 10:42:10 am »
FWIW... I run a Pirelli Angel GT in the front, and normally run 38/42; can't remember having anything like that happen.

Offline EZ

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Re: Wobble (not deadly but could have been)
« Reply #4 on: March 26, 2020, 11:42:17 am »
FWIW... I run a Pirelli Angel GT in the front, and normally run 38/42; can't remember having anything like that happen.

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Offline gsun

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Re: Wobble (not deadly but could have been)
« Reply #5 on: March 26, 2020, 01:08:16 pm »
I've had lower tire pressure than that with no issues. I run the same tires with no issues. I've been in temperatures that low and lower with no issues.  Steering stem bearings?

Offline connie_rider

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Re: Wobble (not deadly but could have been)
« Reply #6 on: March 26, 2020, 01:15:56 pm »
When we did the Track Days, Doug had us lower the tire pressure to approx. 28-30 lbs. Didn't have the wobble your describing.
Your initial report sounds sorta like ice or something slick on the road.. {??}

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Offline Daytona_Mike

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Re: Wobble (not deadly but could have been)
« Reply #7 on: March 26, 2020, 01:36:58 pm »
  No way it was tire pressure. I run 38 - 38.     He was only doing 86 mph at 41 degrees F  when it happened.      What if anything was done recently to the bike?  What was the bike carrying, anything unusual like a big trunk? How many miles on the bike?    I would think something mechanical is loose.. Stem bearings, pinch bolts. axle shaft..uni-trac.. something like that
I doubt it is the tires but I would still inspect then for a broken belt..
« Last Edit: March 26, 2020, 01:43:52 pm by Daytona_Mike »
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Offline gpd323

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Re: Wobble (not deadly but could have been)
« Reply #8 on: March 26, 2020, 06:07:13 pm »
Mechanically, I would look the entire bike suspension over. I would also nut and bolt the bike, especially the suspensions and wheels. I have never experienced that before.
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Offline Jerdurr

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Re: Wobble (not deadly but could have been)
« Reply #9 on: March 27, 2020, 04:50:12 am »
The bike was only carrying myself, no too case or nothing. I’m 185 lbs.
nothing has been done to the bike lately (no brake change, tires or otherwise). I changed my front rotors last year around may, but used it plenty since and never had an issue. These have been the first 2 times it happened. How do I check the stem bearing tightness?

Suspension hasn’t been played with at all either.

Appreciate all of your inputs!
Best,

JD

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Offline Jerdurr

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Re: Wobble (not deadly but could have been)
« Reply #10 on: March 27, 2020, 07:16:49 am »
I've had lower tire pressure than that with no issues. I run the same tires with no issues. I've been in temperatures that low and lower with no issues.  Steering stem bearings?

I’m leaning towards that initially as well, or worn tires. I’m still at work (I work nights) but I will take pictures when I’m done, maybe you guys can tell better than I can.
Best,

JD

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Offline Jerdurr

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Re: Wobble (not deadly but could have been)
« Reply #11 on: March 27, 2020, 10:36:37 am »
Photos of the tires attached. They don’t seem to be overly worn.
Tried the forks, no play. Same with rear tire. I’m at odds here :o
Best,

JD

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Offline Jerdurr

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Re: Wobble (not deadly but could have been)
« Reply #12 on: March 27, 2020, 12:33:06 pm »
  No way it was tire pressure. I run 38 - 38.     He was only doing 86 mph at 41 degrees F  when it happened.      What if anything was done recently to the bike?  What was the bike carrying, anything unusual like a big trunk? How many miles on the bike?    I would think something mechanical is loose.. Stem bearings, pinch bolts. axle shaft..uni-trac.. something like that
I doubt it is the tires but I would still inspect then for a broken belt..
[/quote

30000 miles on it. No big trunk. I'll have to try and adjust the pinch bolts. How can you tell if you have a broken belt?
Best,

JD

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Offline HeavyRotation

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Re: Wobble (not deadly but could have been)
« Reply #13 on: March 27, 2020, 01:25:39 pm »
I do a lot of high speed riding on light bikes, they wobble frequently, generally it's a crosswind under heavy throttle that does it. Was it a bit blustery? Did it happen when traveling in both directions?
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Offline gpd323

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Re: Wobble (not deadly but could have been)
« Reply #14 on: March 27, 2020, 03:17:37 pm »
Probably hit a slick patch, I would not worry anymore about it. You already checked for loose items. Tires look fine.
Greg Downing
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Offline Douglas

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Re: Wobble (not deadly but could have been)
« Reply #15 on: March 28, 2020, 02:22:51 am »
I can only make assumptions without seeing the bike..... But.... Most common things that cause that Are a

1 rear shock that is fully extended or rebound damping set waaay too slow
2 bike pitched forward,
3 worn swing arm bearings

#2 can have the following causes: rear tire tall, front tire low profile, fork tubes pushed up lowering front of bike, rear shock preload cranked up waaaaay toooo much.

You need someone to look at this one.
PLEASE report back on the findings/causation
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Offline Jerdurr

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Re: Wobble (not deadly but could have been)
« Reply #16 on: March 28, 2020, 04:44:49 am »
I can only make assumptions without seeing the bike..... But.... Most common things that cause that Are a

1 rear shock that is fully extended or rebound damping set waaay too slow
2 bike pitched forward,
3 worn swing arm bearings

#2 can have the following causes: rear tire tall, front tire low profile, fork tubes pushed up lowering front of bike, rear shock preload cranked up waaaaay toooo much.

You need someone to look at this one.
PLEASE report back on the findings/causation

I agree.

Anybody knows of any good mechanics for suspension tuning in or around Toronto, Richmond hill or the surroundings in Ontario?
Best,

JD

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Offline connie_rider

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Re: Wobble (not deadly but could have been)
« Reply #17 on: March 28, 2020, 02:16:13 pm »
JD, can you tell us of how your suspension is set.
Have you made any adjustment's/additions or know if a prior owner did?

Have you rode the bike again to see if it reoccurs?

I was involved in a discussion awhile back about cracks developing in early C-14's and ZX-14's frame or swingarm.
I'll try to find that discussion for you. I don't think that is the problem but it's a thought.

Ride safe, Ted
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Offline Daytona_Mike

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Re: Wobble (not deadly but could have been)
« Reply #18 on: March 28, 2020, 02:26:56 pm »
Ted,
  that is a good point you brought up.  Also loose motor mounts could do the same thing.. it is rare on C14's but a possibility and something to easily check
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Offline Jerdurr

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Re: Wobble (not deadly but could have been)
« Reply #19 on: March 28, 2020, 08:00:33 pm »
JD, can you tell us of how your suspension is set.
Have you made any adjustment's/additions or know if a prior owner did?

Have you rode the bike again to see if it reoccurs?

I was involved in a discussion awhile back about cracks developing in early C-14's and ZX-14's frame or swingarm.
I'll try to find that discussion for you. I don't think that is the problem but it's a thought.

Ride safe, Ted

Hey Ted my friend! Long time no speak.

In half hr I’m gonna put the right pressure on those tires and take her out for a spin, see if I can replicate the issue. It’s about to rain here, so it might have to wait until tomorrow.

The weird thing is that the bike has been sitting in the garage for the winter, so a crack in the frame ir swingarm wouldn’t develop out of nowhere no?

The last time I adjusted the suspension was about 2 years ago, where I stiffened the bolt at the bottom of the rear shock, and counted the clicks on the front fork adjusters to make em a tad stiffer because I like sportier riding. Again, over TWO years ago. It would be weird that all of a sudden an issue develops with that no?
Best,

JD

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Offline Douglas

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Re: Wobble (not deadly but could have been)
« Reply #20 on: March 28, 2020, 10:56:04 pm »
Why was that bolt loose? Trust me, tire pressure is not it and you're gonna need help here... Who is near you...
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Offline Douglas

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Re: Wobble (not deadly but could have been)
« Reply #21 on: March 28, 2020, 11:38:41 pm »
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Offline Douglas

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Re: Wobble (not deadly but could have been)
« Reply #22 on: March 28, 2020, 11:48:56 pm »
The first two bikes shown here would definitely wobble like hell. It's hilarious how people crank down on the preload and suddenly the back end feels stiff at slow speeds. Everything feels good until right before the crash lol
https://youtu.be/3FeZJRiAXRk
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Offline Nickrides

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Re: Wobble (not deadly but could have been)
« Reply #23 on: March 30, 2020, 02:21:42 am »
IMHO I would install 2 new tires, no matter what they look like.
I've had several front end wobbles on my BMW's and replacing the front tire Always fixed it.
its the beginning of riding season, put 'em on, I bet it will fix your problem.

Offline Jerdurr

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Re: Wobble (not deadly but could have been)
« Reply #24 on: March 30, 2020, 09:12:46 am »
Alright guys, I inflated my tires properly, so I went for a quick loop on the highway north and back...
Hit hard both directions... heading north I did 220, coming back 240... straight as an arrow. I tried upsetting the chassis 7 or 8 times by downshifting and getting hard on the throttle... even though the rear slipped a bit (it was 6 degrees there), nothing out of the ordinary... so I guess nothing major! 👍🏻 😎

I would still like to get the suspension properly tuned to my riding and weight. I guess at some point I will have to change the fork’s oil as well. I already got the number of a guy here in Toronto that does such job.

I must say though, may be a good idea to change those tires; they are angels gt a spec right now... but I think I liked the PR4 better. My pockets are a bit strained now so that might have to wait a bit.
Best,

JD

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