Front Spring Rate & Fork Oil

[Fudge]

As part of my Spring maintenance I wanted to setup the suspension sag on my bike today.  

For the rear I have a Penske 950lb rear shock.  I was able to get the rear setup perfectly with 40mm of rider sag and 17mm free sag (bike only, no rider).

For the front I have Traxxion 1.05kg fork springs which I always suspected were too firm for me.  I measured the rider sag at 42mm and the free sag to be 31mm.  I ran out of adjustment on the front forks so I couldn't dial in the rider sag to the goal of 50mm, but it doesn't matter because with a free sag of 31mm I can already tell the fork springs need to be softer.  

I weigh in at 180lbs full gear, so my question is what spring rate for the front forks?  .95kg, or 1.0kg?  My guess is the .95kg, but rather than guessing I thought I would ask the community for their opinions or experience, I don't want to "shotgun" the spring rate.

While I'm at it I will also replace the fork oil.  I currently have 15wt and I plan on using 10wt.  Since I'm pretty light I thought I would give the 10wt a try.  Any input hear would also be appreciated.

thx, jd

[tqmx1]

For your weight Race Tech calls for a 1.063 rate spring so I would say your 1.05 is about dead on.

[Fudge]

For your weight Race Tech calls for a 1.063 rate spring so I would say your 1.05 is about dead on.

Yes the Traxxion site also suggests a 1.05 rate spring that's why I went with them, but I cannot get the rider sag and free sag setup properly.  My goal for rider sag is 50mm and my goal for free sag is 18-22mm.  I would assume if I did get my rider sag to 50mm I would have at least 35mm of free sag which is too much.

[racerman_27410]

First thing take a deep breath and dont overthink it.

How much internal preload did you put on the springs? 15mm is recommended.

the FJ is a heavy bike and you will learn to appreciate those fork springs  i think the rate is about right...do you ever carry a passenger /luggage?

do you ride agressively?

the lightest i have ever heard of being put on a FJ were .95's  

simple rule of thumb i use is to split the fork travel into visual thirds dont worry about measuring.

first third is sag... you have the right rate springs so dont worry about rider sag just bike sag..... you should not have any problem getting this using your preload adjustment.... if you cannot get this then you may have too much internal preload.

Here is a simple spring rate test for you.....

put a ziptie around one of the fork tubes to use as a real time data aquisition device (they wouldnt be so cheap if they knew we used them for precision measuring)

Anyway go and ride the bike at least a hundred miles of your favorite hard riding roads.... check zip tie and see how much of the suspension travel you are using. you want to be using almost (if not) all the travel........that means the suspension is working .......If you are not using all the travel then you need lighter rate springs.
If you are using all the travel then you need to adress the valving inside the fork s ,fork oil weight and oil level
in order to get closer to the ride quality /performance you seek.

remember you are riding on the street and if you have the bike setup stiff for the racetrack you are not gonna be happy with the results....IMO. most published sag numbers are meant for track setup.

KOokaloo!



Frank

[Fudge]

Well after some trial and error I was able to get the front sag set right.  I ended up using Race Tech .90kg springs, set rider sag to 45mm (30% of front travel) and free sag measured 29mm (64% of rider sag).  With the 950lb spring on the Penske the suspension feels balanced.  With the 1.05kg springs the front was definitely firmer than the rear.  I'm using 10w fork oil and I'll have to see how well that works for the dampening. I'll have to try the 'zip tie' approach.  I'm heading to WV in June and will have a chance to give the new springs a true workout. 

FWIW, I weigh 180 geared up, ride solo, and have Givi E21 luggage.  For my riding style; I don't drag pegs, but I can keep a pretty decent pace going.