What is a good mm increments to experiement with front end height?

[Speedballer347]

Just looking for coarse numbers.
1mm at a time?  5mm at a time? +5 at a time?

I added 15-clicks of hi-speed compression to my rear and the bike all of a sudden flicked around like a 250, was effortless to turn or hold a line.  But it got very unstable and started headshaking/oscilating on the gas and kinda squirly under hard braking, so I went back to original settings.
After that I realized my bike steers like a truck, stable as a freight train, but won't turn/flick or stay leaned w/out input.  I am worn out half way through a sprint race...after riding it with the backend taller, I know it is the bike's geometry, not my fat belly.

Want to get the geometry back to that 250 feel.  Raising the rear caused instability. 

Lowering the front requires less adjustment/change to get the same feel as the rear?
Less adjustment in the front compared to the rear would result in less instabilty?
What would be a good guess at mm adjustment in the front?  It is a pain in the ass to pull bodywork and move fork tubes repeatedly at the track, so I want to get it as close as possible on the first try.

Thanks

[tstruyk]

start with 6inches and see how you like that 

if your springs are right and your sag is good I would start a few mm at a time.  However you can always "play" with the preload to see if that will help you out before you move hard parts.

you really gotta pull your bodywork to move your forks???  you cant just loosen the trips and work it down without takin the whole durn thing apart?  that blows

timmay

oh yeah and re-set sag each time you move the hard parts... shouldnt be much change but always start from zero... you should be able to get it really close before lunch at a TD if you arent CR'ing

[Speedballer347]

I'm CR'ing whcih burns up most of my time...if I am not riding I am trying to recover...sprawled out like a beached whale.  I don't have really any time to work on it.

When I originally moved them when I got the bike I think I had to remove the glass to get a socket in there, I could be wrong.  Hopefully I am.
So 3mm sounds like a good starting point?  Would only 3mm possible be able to cause instability, or is that too low of a number to make the front end wobble?

My rider front sag is at 30mm front with 120mm oil height (Thermosman reccomends 140mm in my bike), anything lower and the bike easily bottoms out to the stops.  Fork springs are .925 (193lbs), and I only have one line of preload left to make them softer.  Softer springs would bottom out worse, and harder springs I wouldn't be able to get sag because not enough adjustment left.
My rear rider sag is 28mm.

[Speedballer347]

Tim, would 3mm of preload = 3mm of fork adjustment???

[Super Dave]

Why are you using so little sag up front?  30mm? 

Use preload to get a direction on what you want to do.  It's part of your operational geometry. 

If I'm shooting in the dark, I'll usually move the forks in 5mm increments.  Additionally, I'll run the fork caps below the top plane of the upper triple if I need to get the geometry sorted out.  There are plenty of bikes that need 17mm fork extensions anymore also to get the geometry right.  The extra trail that can be utilized from an effectively longer fork length can improve one's leverage, for lack of a better word to describe it, in getting a bike to do what you want without being hard to control when compressed.

You're riding a GSX1000, right?  It's never gonna turn like a 250 unless you drop a bunch of weight off, and throw away a bunch of rotating mass in half the pistons and crank.  But maybe you've never been on a 250 GP bike. 

[tstruyk]

uh... what dave said 

but thats what I was getting at by moving preload first to see if thats what is going to make it work better... I learned that from some guy that used to teach some school that rhymed with Dision Skorts  8)

I think his name was Dave also... wierd

[Super Dave]

Tim, would 3mm of preload = 3mm of fork adjustment???

No.

When you add preload, you're pushing into the spring that amount.  If you move the forks, you move the forks.  Additionally, you're moving the bike's center of gravity.  How it moves is different from bike to bike and set up to set up.  Moves around an inverted pendulum.  If you really want to think about it, a great handling bike usually has the essence of a pendulum with a long radius and its origin is directly below the bike.  Some bikes aren't that way.  Vintage bikes tend to have the origin forward of where the CG moves around.  Some new bikes are the other way with too much movement forward. 

[Super Dave]

Scotty Ryan would be a good guy to talk to at http://www.tracksidesuspension.com/

[Super Dave]

uh... what dave said 

but thats what I was getting at by moving preload first to see if thats what is going to make it work better... I learned that from some guy that used to teach some school that rhymed with Dision Skorts  8)

I think his name was Dave also... wierd

Who?

LOL!

[tstruyk]

Scotty Ryan would be a good guy to talk to at http://www.tracksidesuspension.com/

again this Dave guy with the good info... you really need to meet that other Dave guy sometime

Who?

LOL!

yeah I dont recall, havent seen him around in a bit, I think his last name had something to do with a Nose????   

[Super Dave]

Eric, if you move the forks, you'll also have to recheck your sag because of the movement of the cg.  If you really want to chase it, that's what you gotta do. 

If you just change preload, yes, it will move the cg, but it's because you're pushing into the spring and "starting" earlier.  It's similar but different. 


But, personally, I'm struggling with why you have 30mm of rider sag up front, if you're measuring it the same way I would.  Then having 20mm less air than what has been recommended thus giving you an earlier hydraulic lock up.  Then the .925 spring at your weight.  I don't think I liked the .925 on my GSXR750 at my lighter weight, not by much, but...

[Super Dave]

yeah I dont recall, havent seen him around in a bit, I think his last name had something to do with a Nose????  

Heard he might be at Road America on the 4th.  And that he won a couple of races there last weekend.  :)