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howworkclutch

What spring weight I need?

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howworkclutch
about 200 in full gear. i mostly bomb back-roads of questionable quality.
 

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pattonme
Consult the bike+rider vs suggest spring rate graph - http://fz07.org/post/34913
 
OEM spring was measured by me to be 0.72kg/mm despite the EU/US manuals claiming otherwise.
Traxxion puts their measurement between 0.7 and 0.75. You'll have to ask Dan@Traxxion for the precise numbers.
 
In any event 0.72 is right where I expected it to be given the behavior of the forks under weight transfer.
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bmwpowere36m3
Good stuff, glad you got it measured.  Time to make a correction in the service manual  ;)

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pattonme
Racetech's calculations vs the Traxxion graph - I consider RT's to be minimum numbers and Traxxion's to be maximums.
 
For example, a 200lb rider + 400lb bike = 0.95 (Traxxion) vs 0.9 (RT)
If racing or doing lots of track days, go with the Traxxion rate. For pure, lazy, comfy street riding go with RT or 1/2 rate higher. Personally I would recommend .9+.95=.925 for street duty with interests in canyon carving.
 
250lb rider use 0.95 for street or if you want 0.925 is workable too.

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bmwpowere36m3
Racetech's calculations vs the Traxxion graph - I consider RT's to be minimum numbers and Traxxion's to be maximums. 
For example, a 200lb rider + 400lb bike = 0.95 (Traxxion) vs 0.9 (RT)
If racing or doing lots of track days, go with the Traxxion rate. For pure, lazy, comfy street riding go with RT or 1/2 rate higher. Personally I would recommend .9+.95=.925 for street duty with interests in canyon carving.
 
250lb rider use 0.95 for street or if you want 0.925 is workable too.
 
 
RT's calculator is rider weight, no gear. Does Traxxion's charts assume gear... which I can only imagine is 10-15 lbs.

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aeisan
I just weighed myself with and without gear on. Leather jacket + RF1200 + gloves + boots = 15 lbs, almost dead on.

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howworkclutch
i think my leather jacket + leather pants might put me over the 200lb mark. i ordered 95kg springs and was regretting it, until i ran it all through a calculator and came up with a 30lb difference.
 
this bike mostly does fast switchbacks/tight chicanes. not a lot of "joy rides" but not exactly track day riding either.
 
in june i'm taking it on a week-long camping tour and will have a ton of crap tied to it. so i suspect the extra stiffness will come in handy.
 
if not, i'll sell the springs to someone (at a reduced rate of course) on the forums and go down to a 91/92.
 
i have a fully adjustable showa shock off a buell that appears like it might fit. it was a little soft for the buell (420lbs) but might be just-right for the yam. i'll find out if its a direct fit next weekend.

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gtmn
you will be happy with the 95s

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pattonme
There's an implicit +/-20lb in the figures. Actually RT asks for "in gear" values in their dialog box AFAI remember. Traxxion's is with gear, because what kind of rider goes around naked? Point being, just try to get reasonably close. If Traxxion says 0.95 for 200lb rider, then 180-220 can use that rate, no problem. For street use I just suggest sliding the Traxxion graph downward 1/2 a square, is all. So by Yamaha equipping the bike with 0.7x springs, they basically left out the rider in their calculations.
 
Now if the bike came with preload adjustable fork caps everybody's life would be less complicated.

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fflier9
hey, clutch, if you decide to sell your .95 springs let me know. :)

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howworkclutch
I installed them this weekend. I reused the stock spacer as it was close enough. I think i'd be better served with .90 springs, but I can not deny the total transformation of the bikes handling in corners. Its a complete joy to toss it around a series of tight turns.
 
But it sure does amplify the suckiness of the rear shock. I wonder if a stiffer spring would improve things, or if the shock simply needs to be reworked. Its simply too bouncy out back.

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bmwpowere36m3
@howworkclutch
Notice the same with the rear.... especially under "g-outs". Definitely needs more rebound out back.
Was the aftermarket spring the same length as the original? Reason I ask, I measured my static sag at ~19 mm up front (stock bike/springs)... which is pretty spot on, however I'd venture that my race sag will be too high.  With stiffer springs, the same length as OE, I'd think you'd need a shorter spacer to target your static/race sags.
Rear static I measured at 9.5 mm with the shock on "3".  I'm going to increase it to 4-5 and see how my sags work out.

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howworkclutch
yeah it was the same length. i followed the instructions for determining the spacer length. unless i did it backward, the static sag was about the same (but not measured).
 
i suspect you'll just get more boing-boing action by increasing the preload on the back. if you unload the spring a bit, it will be softer, but the spring wont be under pressure when you hit a bump. the oscillations will still exist but should be less violent. i think? maybe matt can chime in on this and give a little insight.

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pattonme

more preload makes the shock stiffer so it will move less given the same bump impact.(ed. Constant rate springs are the same no matter how little/much preload they have) So the piss-poor rebound circuit doesn't have to do as much. A softer spring means more travel and thus the shock will oscillate more. Set preload to get proper rider (aka race) sag. If static is way off then revisit the spring rate but you can get away with having the 'wrong' spring up to a point. Then dial in as much rebound as needed to keep the boing-boing-boyoyoyo'ing to a minimum.

Edited by pattonme

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bmwpowere36m3
Preload only makes it feel initially firmer, but the bottoming resistance and rate haven't change. Springs only store energy... for a given bump, regardless of preload, the spring will store/release the same amount of energy.
 
I think of springs as steady-state/ride height control and the damping circuits as your transient controls.

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