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Discussion Starter #1
Morning Blade lovers, I had already do a post about this a few months back but i did not get much comments, I am having a issue on my 954, under hard acceleration above 8K to redline my bars start to like wobble, not like a tank slap about 10-20 mm a side. it does this 1st-3rd gear . Here is my setup stock springs Scotts Damper set half way. I have a Penske rear shock. my rear setting is pretty good, I have 1 inch of sag. I read online that the 954 have small wobble under hard accell.
 

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Mine had the same problem. Once I installed a damper, it hasn't been an issue.
If you are still having a problem with a damper installed than you need to check things like tire pressure, steering stem tightness/bearings, wheel bearings etc. as it could be a case of something else being loose or out of alignment.
 

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Discussion Starter #4
Ya but i talk toa suspension shop, they said if you put a damper and issue goes away thats not fixing the issue, thats like putting a bandage on cut . its not actually fixing issue they say. It could be bearings, or suspension geometry is not correct.
When i turn up the damper ya it goes away but thats not fixing issue.
Tire pressure i run F 34 cold setting Rear 32
 

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If it's persistent than no, you're not fixing the issue by adjusting the damper way up. Oscillations in the front wheel are not unusual though when it gets light. That's why all modern sportbikes (and race bikes) run dampers.
I would get my wobble when coming out of a corner and getting on the throttle. I never experienced any issues other than that. I run a stock setup on the front/rear.
If your tires are good, have you ever checked or replaced the bearings in the steering stem? That would be the first area I would go to, checking for looseness or play.
When you put the rear shock on did it raise/lower the ride height or have you changed it by raising/lowering the front end?
 

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Hi

The front will go light if the back is too soft. Your back tyre is too soft for a start isn't it?

If the front goes light it will be more prone to wobble.

Pete
 

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Hold on tighter. That's what I do. Jk. Petes right. Increase the compression on the rear shock and see what happens. Speed up the rebound on the fork so it can extend quicker. You are welcome.
 

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Why do you run such a low rear pressure? Would usually be 42psi at rear, reducing that will also reduce the load on the front tyre allowing it to wobble when weight shifts rearwards under acceleration
 

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Discussion Starter #9
all my friends that race , and did race run around that number 30-33 Rear. Last weekend I went on a ride w a buddy and he used to race AMA and on his RC51 he ran 18 psi on front and 30 rear cold. so he can get traction. and he has new tires. i think 42 is the MAX on the Michelin.
 

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That reduced tyre pressure would be for people who are getting some serious heat into the tyre, which heats the air inside it and causes the pressure to increase as a result.

If you're just riding around normally or predominantly in straight lines you won't be heating the tyre to a great enough degree (pun intended) to increase the pressure.

Try inflating the tyre to 42psi (this is the pressure your tyre manufacturer recommends) and you should see your problem solved. You should only reduce the tyre pressure if your riding heats the tyre to such an extent that the pressure would otherwise be too high.

Bear in mind also that if you ride in the wet with such a low tyre pressure, you will greatly reduce traction due to the fact that the treads on the tyre surface will close as the tyre concaves inwards, so they won't be clearing water in order for the tyre to grip.
 

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The higher your tire pressure the smaller your contact patch is. And the tires flexibility will be reduced to a noticeable degree. Which means you lose grip.
How many threads have we seen here where guys inflate to 42 psi and wonder why they lowsided.
And the following advice is always to reduce pressure to around 28 - 34 Rear and 30 -36 Front psi. Depending on the type of tire and riding style - commuting vs. canyon/mountain roads.
I would NEVER inflate to anything above 32 psi for the rear, unless riding two-up. even then, I'd max at maybe ~36.

There are tons of threads discussing tire pressures, and believe me - 42 psi is ridiculous.
18 psi on the front seems way to low for a normal sport/street tire as well. 30 -34 is more like it.
I've been experimenting with tire pressures on my bike for the last three years. I record the ambient temperature, and cold psi before a ride. Then I pull over during spirited riding, check tire pressures and heat (with a laser temp reader) in the tire. The Dunlops, Bridgestone, and Michelins that I've run: they are all pretty close and I run Cold pressures of about 28 Rear and 30 Front. (That's when cold temperatures are in the 60 to 80F degree range.) That's where the contact patch, flexibility, and stability is once the tire is warmed up.

I know this doesn't exactly address the headshake your experiencing, but could affect it somewhat.
 

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Not to take this off topic but in the interest of a balanced view, I've never had any loss of traction in over 20k miles of very mixed riding on a vfr800, using the whole tyre and running 36/42, which is what the bike's manual recommends
 

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I also owned and rode a VFR800 for two years. Put about 15,000 on it, and I've put about 22,000 on my current bike. Been thru about 9 or 10 sets of street/sport tires now.
 

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I also owned and rode a VFR800 for two years. Put about 15,000 on it, and I've put about 22,000 on my current bike. Been thru about 9 or 10 sets of street/sport tires now.
You've got a bit more experience than me, so please take this for the genuine question it is: why do the bike and tyre manufacturers recommend 36/42? I know this is off topic but I've an opportunity to learn something here

FWIW I still feel that the OP's low pressures could be part of his problem but I'm warming to the idea that tyre pressures are more flexible than I previously thought
 

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Discussion Starter #15
I believe thats the setting for a average weight rider about 160 pounds and all around riding , not hard acceleration and leans
 

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I have no idea why a manual would 'recommend' those tire pressures.
I was of the understanding that those were the 'maximum recommended' pressures.
Not to mince words, but to me, that just means don't go higher than this number. That's the maximum pressure this tire will handle before failure may occur. I just wrote it off to liability concerns for the tire manufacturer.

I used to run Q2's on my VFR. That bike had such soft factory suspension, and I was never happy with the adjustability. I used to run about 36 front and 34 rear. Cold. Handling was adequate for that bike.
When I got my RC51, more experienced riders kept telling me to lower my pressures. So I tried f34/r32. I noticed a little better grip on turns which gave me more confidence in the tire to hold.
Then I bought a heat reader. Got it in the bbq section at home depot. :D
That's when I learned what the real psi levels were at while riding. I was a little surprised at how much psi climbs especially in hot weather and hot pavement.
So I started running Cold psi's more in line with what track guys told me: f29-30/r26-28. I discovered that when the tires warm up to around 120-130+F degrees, I had psi's of about f34-35/r31-32.
This is the range that my bike handles the best, traction and grip feel the best, and I can lean into a turn with good confidence that the tire wont slip away. Tire wear is perfect, I average about 3,000 to 4,000/ miles per set, and always have excellent grip.



 

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That's really helpful, thanks. I'm on a bit of a learning curve here as my VFR was my first bike, so without this conversation I'd have headed straight out on the CBR with the factory pressures - now I know I need to start off a bit lower
 

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Morning Blade lovers, I had already do a post about this a few months back but i did not get much comments, I am having a issue on my 954, under hard acceleration above 8K to redline my bars start to like wobble, not like a tank slap about 10-20 mm a side. it does this 1st-3rd gear . Here is my setup stock springs Scotts Damper set half way. I have a Penske rear shock. my rear setting is pretty good, I have 1 inch of sag. I read online that the 954 have small wobble under hard accell.
Sounds like you have your sag set pretty close? But those stock springs in the forks might be to soft for your weight. How much preload do you have to set to get proper sag? I'd seriously consider springing the fork properly for your weight and putting fresh fork oil in.
Another thing that I'm thinking about is how high or low do you have the fork legs set in the clamps. Measure from the top of the top clamp to the top of the fork tube, not the nut, and compare that to the factory setting. This affects rake and trail, which comes into play when you're talking about a headshake problem.
And as already mentioned, inspect head bearings for integrity and proper torque.
Wheel bearings too.

One last thing i thought of, do you seat the forks properly when you re-install and torque the front axle?
Here's the procedure:

Front Wheel Installation

With the thick spacer in the right side of wheel, thin spacer in the left, place the wheel between the forks. Slide the axle through wheel from the left side.

Install axle bolt on right side and torque to 43 ft/lbs.

Tighten right fork axle pinch bolts to 16 ft/lbs. (192 in/lbs.)

Install brake caliper bolts and torque to 22 ft/lbs. (264 in/lbs)

Put bike on the ground, hold front brakes, pump the forks up and down to seat the axle.

Make sure index line on axle lines up with fork leg outer surface. Left side.

Tighten left fork axle inch bolts to 16 ft/lbs.
 

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Sounds like you have your sag set pretty close? But those stock springs in the forks might be to soft for your weight. How much preload do you have to set to get proper sag? I'd seriously consider springing the fork properly for your weight and putting fresh fork oil in.
Another thing that I'm thinking about is how high or low do you have the fork legs set in the clamps. Measure from the top of the top clamp to the top of the fork tube, not the nut, and compare that to the factory setting. This affects rake and trail, which comes into play when you're talking about a headshake problem.
And as already mentioned, inspect head bearings for integrity and proper torque.
Wheel bearings too.

One last thing i thought of, do you seat the forks properly when you re-install and torque the front axle?
Here's the procedure:
Front Wheel Installation

With the thick spacer in the right side of wheel, thin spacer in the left, place the wheel between the forks. Slide the axle through wheel from the left side.

Install axle bolt on right side and torque to 43 ft/lbs.

Tighten right fork axle pinch bolts to 16 ft/lbs. (192 in/lbs.)

Install brake caliper bolts and torque to 22 ft/lbs. (264 in/lbs)

Put bike on the ground, hold front brakes, pump the forks up and down to seat the axle.

Make sure index line on axle lines up with fork leg outer surface. Left side.

Tighten left fork axle inch bolts to 16 ft/lbs.
:plus1: Great info!
 
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