Yeah; I was thinking this would be right up his and Rob T's alleys. I know McRomo doesn't like to talk specifics about the F3 shock stuff as much since he's never fooled with it. But the linkage and damping requirement, on the other hand. . .
So my understanding is that a shock's a shock, and it's the valving and stroke that make the difference for linkage/non. So by adjusting the valving appropriately. . .
Yeah, I'm careful on stuff I've not dealt with at all. But I'd expect that an F3 shock could be reconfigured to get it to acceptably work on a 919 if economy is major driver and it can be done cheap enough in comparison to a good aftermarket unit. (I always keep in mind what zaq did with his 919 unit some years back, stupid cheap and it sounded as though he liked the results and I'd say he's a fairly savvy and picky guy that assesses well)
Below is from your earlier post, I have interlaced some comments within, hope this helps you at least a bit.
So since I'm rebuilding this F3 shock for the 919, I'm planning on sticking on an Eibach spring (6.00" long, 2.25" I.D, 1100lbs). 1100 # IS THE LIGHTEST IíD SUGGEST FOR YOUR INTENDED PURPOSES.
I'd also like to fool around with the shim stack, but am not so sure what to do here. I suppose I'll buy the ReStackor program, but I think I'll need a little bit of an idea of what I'm shooting for before I can use that effectively. ONE DAY IíLL BUY IT AND PLAY WITH IT BUT WHEN IT COMES TO VALVING, PISTONING AND STACK BUILDS I PAY THE LOCAL WHIZ FOR WHAT HE KNOWS BETTER THAN IíLL EVER KNOW.
So question time:
Anyone got the relevant ReStackor measurements/profile for the stock or aftermarket 919 shock?
If that's a no-go, wanna help me define exactly what am I looking for? MY OPINION IS DIGRESSIVE COMPRESSION DAMPING FORCE CHARACTERISTIC CURVE SHAPE.
I figure the 919 needs a bit more low-speed compression damping (LSC) compared to the F3, but how much more? YES. LOTS MORE. F3 IS LINKED, 919 IS NOT, SO IN NOMINAL TERMS 919 SEES TWICE THE FORCES JUST BY THAT ALONE. I THINK THE F3 HAS A BETTER SWINGARM ANGLE WITH MORE FAVOURABLE SQUAT/ANTISQUAT RELATIONSHIP. AGAIN, THE 919 NEEDS MORE DAMPING FORCE. 919 HAS MORE TORQUE AND LOTS OF IT RIGHT ACROSS THE REV BAND. AGAIN, THE 919 NEEDS MORE DAMPING FORCE. 919 IS GEARED FOR A SIGNIFICANTLY LOWER AERODYNAMICALLY LIMITED TOP SPEED, IN OTHER WORDS HAS A HIGHER TORQUE MULTIPLIER. AGAIN, THE 919 NEEDS MORE DAMPING FORCE.
And how much of that necessary additional LSC will be negated with the heavier spring? THE HEAVIER SPRING HELPS BUT COMES NOWHERE NEAR DOING IT ALL AND SEE ABOVE RE THE OTHER FACTORS.
Same thing for rebound: I assume the heavy spring will require a bit more rebound damping to balance, too. Any thoughts here? REMEMBER THAT TOO MUCH REBOUND PUTS YOU ON YOUR HEAD. YOU WILL NEED MORE FOR SURE. THE REBOUND CIRUIT ON MY PENSKE WAS NEVER CHANGED, IT WAS FOR A 650 # SPRING, AND WITH A 1200 ON IT ITíS ONLY IN THE MID RANGE OF ADJUSTMENT. I CANíT COMMENT ON THE F3 BUT GUESS IT HAS MORE BUILT IN THAN YOU THINK. GET YOUR GUY TO DO A SHOCK DYNO TEST, THEY ARE CHEAP AND YIELD GOOD INFO.
I know shim stacks are a black art; I've done a lot of looking around on the web, but it seems like one would do well to have a baseline. REALLY GOOD STACK BUILDS COME FROM SMARTS/EXPERIENCE/SKILL. A GOOD PROGRAM SHOULD YIELD PREDICTABLE DAMPING FORCE CURVES SO THE QUESTION BECOMES WHAT CURVE SHAPE AND MAGNITUDES DOES ONE WANT ?
To be honest, I'm not entirely convinced I'll be able to feel the difference anyway. (I'm a regular ol' street rider; probably with a couple track days a year) YOU WILL BE ABLE TO TELL THE DIFFERENCE. ON THE ROAD AND ON THE TRACK.
So yeah, if you've got a thought or ten about stacks, I'd happily listen.
This goes for shock oil, too. I LEAVE SHOCK OIL TO THE SHOCK BUILDER. ALL I KNOW IS MINE HAS A SILKOLENE IN IT AS RECOMMENDED BY PENSKE, DONíT KNOW THE WEIGHT.