FZRSupport: the FZROnline Archive

Does someone here have a Fork stabilizer / Fork brace on theirs FZR-600 ?

Can someone explain the meaning of tire cupping ?







Quote :
"Fork flex is the main reason why a rider incurs speed wobbles, unstable handling, road sensitivity problems and tire cupping.
Fork brace eliminates fork flex and allows the fork assembly to cycle in a straight line.


The fork brace provides better stability.
Reduces low and high speed wobbles.
Improves stability in tight cornering.
Improves tire life and reduces tire cupping.
Decreases sensitivity to rough road surfaces and rain grooves."

http://www.superbrace.com/simulation.html


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modking makes a wickedly sick fork brace. Significanly more substantial than the flattened beer can that Yamaha put on there from the factory. I've got pics I can throw up tonight when I get home. Tire cupping is from poor suspensions. The tire if examined will actually have cups, or deprssions worn out of it. Something else to consider are new fork springs as the .45kg progrssives that came fitted from the factory are normally not adequate for ridres in excessive of 120 lbs.

I bought one from this guy, but it looks as though he raised his prices: http://cgi.ebay.com/ebaymotors/Yamaha-F ... enameZWDVW

I'm sure ModKing can / does make something similar.

M in KC wrote:
I've got pics I can throw up tonight when I get home.

It would be nice with some pictures.

thatkid also has fork braces he will be producing. Link here -->viewtopic.php?f=53&t=586

Try this site. http://www.rattlebars.com/valkfaq/tirewear/

http://w6rec.com/duane/bmw/cupping/
This explains it some also. Fork flex or the tire being out of balance will exacerbate (make worse) tire cupping. Most regular street riding will only experience this after 50% of the tire is used up anyway. Unless they ride full throttle - leaned over and hard braking all the time, or have maladjusted forks / tires etc.

It's best to throw the tire away and get a new one if it gets bad enough to throw off your steering / balance. Only problem is most the time it happens slowly, so you may not notice it all at once. That's why you need to visually inspect the tires often and keep the air pressure correct.

M in KC wrote: http://www.rattlebars.com/valkfaq/tirewear/

YAM93 wrote: http://w6rec.com/duane/bmw/cupping/

THANX guys, for this superb links !!


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Lasse wrote:Does someone here have a Fork stabilizer / Fork brace on theirs FZR-600 ?

Can someone explain the meaning of tire cupping ?







Quote :
"Fork flex is the main reason why a rider incurs speed wobbles, unstable handling, road sensitivity problems and tire cupping.
Fork brace eliminates fork flex and allows the fork assembly to cycle in a straight line.


The fork brace provides better stability.
Reduces low and high speed wobbles.
Improves stability in tight cornering.
Improves tire life and reduces tire cupping.
Decreases sensitivity to rough road surfaces and rain grooves."

http://www.superbrace.com/simulation.html


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Guys,
Sorry to rain on your parade BUT fork braces DO NOT cure the hassle of poor suspension performance.

Tyre cupping is when the front wheel patters and skids momentarily and wears "dents" in the tyre .

As pointed out else where any one over about 120 pounds will find the front suspension very soft at 0.46Kg/mm. I have just had springs made to 0.85Kg/mm to work with PD valves (you might know them as cartridge emulators ) http://www.saltmine.org.uk/kgb/catalogue.html

Once i have those installed I will be able to tell just how much fork flex i am getting.

Now the half ass method is to bolt a big F*** off plate half way up the fork which is pretty silly as this is where it shows up but is NOT the cause of the flexing.

The flexing originates from the fact that the 2 fork legs are NOT working in unison on a parallel framework but against each other in the worst case, the root cause being that bit of wet string that yamaha gave us as an axle that is actually flexing under load.


If you look at the likes of Moto GP , & knock offs as street "race bikes" like ducati they have massive diameter axles (hollow to save weight and because the forces we are concerned with are acting thro skin effect rather than thro the core of the material.

If any of you care to look up Eric Buell's ( now owns the second largest US made motor cycle company ) white paper on axial loads he wrote back in the '80.

I read it way back then and all my race machines (drag, street,MX have massive axles usually 25mm or as big as I can go with the wheels I have to use the smallest being 20mm )

The difference is doing what was 80 MPH sweepers at 120 +like the bike was afright train on rails not the hint of a wobble

yamaha_george wrote:
Now the half ass method is to bolt a big F*** off plate half way up the fork which is pretty silly as this is where it shows up but is NOT the cause of the flexing.

The flexing originates from the fact that the 2 fork legs are NOT working in unison on a parallel framework but against each other in the worst case, the root cause being that bit of wet string that yamaha gave us as an axle that is actually flexing under load.


If you look at the likes of Moto GP , & knock offs as street "race bikes" like ducati they have massive diameter axles (hollow to save weight and because the forces we are concerned with are acting thro skin effect rather than thro the core of the material.

If any of you care to look up Eric Buell's white paper on axial loads he wrote back in the '80.

I read it way back then and all my race machines (drag, street,MX have massive axles usually 25mm or as big as I can go with the wheels I have to use the smallest being 20mm )

OK, so if I understand you right, you are saying that the front Wheel Axle is made way to thin and/or of a cheap shit material.... , Or have I miss understood you ?

How thick is the front wheel axle on the FZR-600 ?

Any suggestion of an alternative steel quality to make a front wheel axle of ?


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Any input about this fork brace ?

http://www.tarozzipaolo.it/inglese/home.htm

( for Yamaha FZR-600 1989-1999 , Part # 25-0042 )


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Lasse wrote:
a} OK, so if I understand you right, you are saying that the front Wheel Axle is made way to thin and/or of a cheap sh*t material.... , Or have I miss understood you ?

B} How thick is the front wheel axle on the FZR-600 ?

c} Any suggestion of an alternative steel quality to make a front wheel axle of ?


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Lasse
a} Yup spot on

B] when I get the suspension set up then I can address the axle problem

C}I will know that after I have taken the axle out tested it for hardness and seen what bearings are available to us and wether the whole thing is do able in a meaningful way


Stay tuned <BG> Nerd

i feel an off-season front-end rebuild coming.

Lasse wrote:Any input about this fork brace ?

http://www.tarozzipaolo.it/inglese/home.htm

( for Yamaha FZR-600 1989-1999 , Part # 25-0042 )


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looks cool but thats it

any amount of extra bolting together adds flex to it.

it is not as strong having that middle part separate.

haunter wrote:

Lasse wrote:Any input about this fork brace ?

http://www.tarozzipaolo.it/inglese/home.htm

( for Yamaha FZR-600 1989-1999 , Part # 25-0042 )


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looks cool but thats it

any amount of extra bolting together adds flex to it.

it is not as strong having that middle part separate.

Lasse ,
Fork braces by armani are just fork braces the answer to a non -question.

Fork braces do NOT cure the source of crap front ends PERIOD.

I was as sceptical as you all when I read Eric's paper.
BUT being an engineer I decided to try it out on my street drag racer (I am sure you are all familiar with illegal friday / saturday night drag races for money )

I checked the wheels and they could take the same size oputer diam bearings BUT with 25mm inside instead of 15 mm (?) memory is iffy on that figure but it was way thin. I made the axle from a 1" construction bolt 14" long and turned & ground to suit the new bearings. I bored the stantions to take the new diam fitted it up on the saturday morning. Told my riding buddy I was gonna take it out for a trial.


Pictures at:- http://www.saltmine.org.uk/kgb/gallery.html

The trial was simple we had a piece of hiway with 6 sweepers over about 2 miles that connect 2 hiways at each end there were roundabouts.
The max on the bike was 80 ish mph thro those sweepers and you had better be good to do that.
over the next 3 hours I got that top speed upto 120 + and ran out of bottle (traffic was getting exciting at that speed ) without a wobble , twitch or any other oddity.
I lined the bar end up with the white line & RODE.

when I got back my buddy was glad to see me in one piece he thought I had got into a wreck I was gone so long. I told him ride the bike , that alone signified that something was definitely odd, you could probably ask my wife for sex and get a better odds than asking to ride any of my bikes. He went out and I swear he had trouble getting his helmet off afterwards due to that stupid grin.

He decide then and there that hid bike had better have one and bought the bearings then at the store and by SSunday we both had fat axles. Neither of us have ever had skinny axles since.

The FZR I have not done YET due to the fact that I want the suspension done first because no amount of axle will stop those dead springs from diving,and wriggling under braking.