Jump to content
The MT-07 Forum

What spring weight I need?


howworkclutch

Recommended Posts

  • Premium Member
howworkclutch

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

-HowWorkClutch

Link to comment
Share on other sites

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.

bannerfans_1095431.jpg
Link to comment
Share on other sites

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.

bannerfans_1095431.jpg
Link to comment
Share on other sites

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.
Link to comment
Share on other sites

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

Life is good on 2 wheels!

Link to comment
Share on other sites

  • Premium Member
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.

-HowWorkClutch

Link to comment
Share on other sites

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.

bannerfans_1095431.jpg
Link to comment
Share on other sites

  • 2 weeks later...
  • Premium Member
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.

-HowWorkClutch

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

  • Premium Member
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.

-HowWorkClutch

Link to comment
Share on other sites

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.

bannerfans_1095431.jpg
Link to comment
Share on other sites

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.

Link to comment
Share on other sites

pantheraleo
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.
True, but they travel less. For me at 200, the factory setting of 3 was a bit too adventurous...
 
I'm planning on replacing my rear shock around the 20k mark. With preload caps on the front forks and the preload of the stock shock at 8, I find the (otherwise) stock suspension manageable. I find that if I stay on the throttle through the corners, I don't bounce.

O judgment! Thou art fled to brutish beasts,
And men have lost their reason. Bear with me.
My heart is in the coffin there with Caesar,
And I must pause...till it come back to me.

Link to comment
Share on other sites

random factoid of the day:
 
The average American is 33 pounds heavier than the average Frenchman,
40 pounds heavier than the average Japanese citizen, and a whopping
70 pounds heavier than the average citizen of Bangladesh.
 
Adjust your spring choice appropriately.

bannerfans_1095431.jpg
Link to comment
Share on other sites

  • Premium Member

I finally got a good, long, twisty mountain ride in, and I can attest to the fact that the rear shock came from a pogo stick.
I have a Matris on order, but the delivery is already behind schedule. I'm hoping it, along with spring and fluid replacement will get closer enough to good suspension that I can wait until I dismount for the season to send pattonme my forks so he can do it right. :)
 

Why can't left turners see us?

Link to comment
Share on other sites

Why is Sonic spring calculator so low? 225lb rider, 400lb bike, standard bike, & normal street riding is .80.

Link to comment
Share on other sites

  • 3 years later...

RaceTech has updated their web site: http://www.racetech.com/ProductSearch/12/Yamaha/FZ-07/2015-17

 

They now say:

"Stock Fork Spring Rate:0.88 kg/mm (stock)

Comments: First Year 2015 FZ-07/MT-07 Models may have lighter .75kg Rate Fork Springs"

 

I know can be difficult to distinguish soft springs from soft dampening. As soft as my 2015 front-end is, my static sag is only about an inch and all the spring-rate calculators I've used say I should be using 0.9 kg/mm so my stock springs are probably correct while it's just that my fork oil is way too thin (5wt should be 15wt).

I was tortured by the Japanese during the war, Jack. Not a pretty story. Strange thing is they make such bloody good cameras.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.