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F2/F4i geometry questions

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stangmx135

F2/F4i geometry questions
« on: November 10, 2006, 09:31:20 pm »
so i was refered to this forum to get the advice of some knowledgeable racers...

im replacings the suspension on my F2 w/ an F4i front end (oh how i cant wait for real damping and better brakes) and hopefully a Fox shock on the rear.  my ultimate goal is to get back to the track, and i would never feel safe on the F2 front end anymore.  so i guess my questions are on suggestions for my final geometry.  trail, rake, swingarm angle, etc etc???  springrate shouldnt be too bad since im only 140lbs, but ya...

current trail is about 102mm just because the F2 forks are horrible and my rear shock is shot.  sag isnt even close to correct, but my forearms cant take it any other way.  i believe the F4i triple is the same offset as the F2, 36mm.. but i havent got it shipped in yet.  can anyone confirm that, and the fact that i think the F4i forks are shorter than the F2??  ill be running a 929 master; will my F2 SS lines still work??  any suggestions are much appreciated, thnx-

-robert

oh, and anyone selling a Fox shock for an F2???
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Super Dave

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Re: F2/F4i geometry questions
« Reply #1 on: November 10, 2006, 11:08:31 pm »
If the F4i forks are shorter, it's gonna have tighter trail, and that's not good.

F2 suspension was pretty darn good when we raced 'em then.  Why is it so "unsafe"?
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stangmx135

Re: F2/F4i geometry questions
« Reply #2 on: November 11, 2006, 12:40:42 pm »
well as of now, the oil has prob 35k miles on it so its sludge.  so the low speed compression is fine... forks dont dive soo much... but the high speed is ridiculous and my forearms hurt.  last time i even got close to using the front end through a corner, a nice bump almost sent the front sliding.  i cant justify putting 3-400$ into a crap damping rod suspension when i can get cartridge forks and a brake upgrade for 500$, but ya...

im sure a tighter trail wouldnt be soo bad.  should i run it about 96mm like the F4i stock?? im going to put the clip-ons below the triple, so technically i could keep it the same, but im thinking 102mm is pretty excessive.
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Super Dave

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Re: F2/F4i geometry questions
« Reply #3 on: November 11, 2006, 01:43:49 pm »
Ever put any correct springs in it?  Changing oil will only cost you a little time and some oil.

Tighter trail can cause you to loose all feel.

Stock F4i springs aren't heavy enough for 100# riders.  You're going to have to spend money on them too.

We never had brake problems with F2 when we raced them.  You have lots of options. 
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stangmx135

Re: F2/F4i geometry questions
« Reply #4 on: November 12, 2006, 02:17:47 am »
ya i resprung the front back in the day.  was actually quite disatisfied w/ the change... the F4i front end is already on its way here, so an oil change wont do me any good, hehe.  the reason y im asking about geometry is so that i dont loose all feel in the bike.  im sure if i was more confident in the suspension, id love it to drop into corners faster.  of course it will need to come out just as fast; finally found a Fox TC today.  i really jus dont want to go into this blind and end up trying to tweak a suspension that is geometrically way off.
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GSXR RACER MIKE

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Re: F2/F4i geometry questions
« Reply #5 on: November 12, 2006, 11:56:00 am »
It looks like your trying to make a 10+ year old bike handle like the late model bikes. Alot of technology has evolved in that time, I would think there's going to be limits as to what your going to be able to achieve based on how the frame and swingarm were designed and manufactured back then. Back in '95 I bought a used F2 as my 1st track bike, did my race licensing school on it, and all in all thought it was a pretty good bike on the track. But then I bought a brand new '96 GSXR750 to actually race with and was blown away at the superior handling and feel of that bike over the F2, the GSXR just went where ever I wanted it to and gave me much greater confidence than the F2 ever did. Remember that when the F2 was designed it was based on tire technology of the early '90's, tires are something that has massively changed since then providing much more grip today. Another issue is back then sportbikes were designed for the street 1st and the track 2nd, the '96 GSXR 750 was the bike that changed all that (track bike 1st based on using current race tires of the day then adapted for street use).

While I agree that having adjustable suspension is great, I seriously wonder if your going to achieve what your looking for with the F2, not saying it's a bad bike, I just think your somewhat limited. Good luck with your project!  :thumb:
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H-man

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Re: F2/F4i geometry questions
« Reply #6 on: November 13, 2006, 12:52:40 pm »
I don't recall the Thunderbike rules since it's been a year that I've raced with yous guys (y'all).  But if you can legally use forks from a 2001 bike on an F2, then more power to ya.

I've a '94 F2 and have done fine with Race Tech internals, stock rotors and Vesrah pads (they don't make the RJL or SRJL for the F2) w/ 10 wt oil (gonna try 20 wt oil).  Though I'll upgrade to either Brake Tech or EBC rotors this season.  I can understand your not wanting to spend the money on upgrading the F@ forks or settleing for F3 forks.

Like Racer Mike and SD have pointed out though, the whole bike is a package.  Upgrading one aspect may only serve to point out the deficiencies on another aspect (e.g., frame, swing arm or size of your rear wheel limiting your race rubber options).

This is a great board, though you may wish to also ask your question over in the Vintage section of the WERA BBS.
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Black Ops Racing
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stangmx135

Re: F2/F4i geometry questions
« Reply #7 on: November 13, 2006, 09:32:28 pm »
well i really have no intention of actively racing this bike.  ill be happy as long as it is stable during my occasional trackday.  im a poor college student so they dont come as often as id like.  oh and they are 2006 forks,  :biggrin: 

im just looking for some advice on set-up.  ride height, trail, sag, etc.  my goal is to have everything swapped over for my bday, the day after thanksgiving.  just waiting on shipping right now. 

ya 94' F2 forks are a million miles ahead of the 93's... honestly, if i hear one more time "riders back in the early 90s went faster on these forks than i ever will" i will just die.  im actually not unhappy w/ my 160 rear tire... Pilot Race's served me pretty well back in the day, and they were cheap too.  im going to get an F3 rear wheel soon, 1/2 inch wider.. to help out that contact patch, but ya, suspension first. 

thnx for the suggestion bout WERA too, forgot bout them.
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H-man

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Re: F2/F4i geometry questions
« Reply #8 on: November 14, 2006, 10:56:39 pm »
Just circling back here.  Here's the geometry s/u for an F2 that I've picked up from the cool kids.

top of triple to top of fork tube (not the fork cap) = 2"
center of rear axle to fixed point on subframe ~ 18.5" - 21.5"
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Black Ops Racing
WERA/Fasttrax #42 (N)

"Life has a certain flavor for those who have fought and risked all that the sheltered and protected can never experience."  - John Stuart Mill