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Suspension Musings


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I've had some interesting experience with the suspension on the FJ and thought it worth posting, it may well help those looking for cost effective improvement, I'm 220 / 230 lbs.
When I first bought the FJ, great bike but unsettled when pushed hard (for me) over rough roads, too much brake dive and hard to hold a line or change line mid corner, great bike just not quite right.
First thing I did was change the shock, a lot of people I know default to this I think because it's easy, I bought a Wilbers that turned out to be set up badly, too hard a spring and too much compression damping, it's a work in progress.
I then really bit the bullet and bought Intermediate cartridges from Pattonme / Forks by Matt. Installed those, huge improvement but due to the shock the bike still wasn't right. Matt provided .9 springs, originals are apparently .7.
Here's where it gets interesting, 
I put the stock shock back on to get the Wilbers sorted, I wound the preload up to full and closed the rebound adjuster fully then backed it off by half a turn expecting it to be too soft and under damped, well I was wrong, I had to back the preload off to position 5 from 7. That gave me close enough to the right sag and the shock worked much better than I was expecting.
Looking at raw numbers the bike as standard seems unbalanced, .7 front to .9 is roughly a 30% increase and arguably I could need .95, the rear spring at 100 nm is close to correct, I've gone to 110 nm but I think either would be ok, so correct to possibly 10% light.
The guts of the story is, if I'd done the forks first I doubt that I'd have bothered upgrading the shock, with forks sprung correctly and actually having effective damping and the stock shock set up the bike is hugely improved.
I realise that this won't necessarily be correct for others, but, if I had my time again, at my weight, I would do the forks first then re-assess.  
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Maybe I mis-read, but how did you set the fronts? I see that the rears are at 5, but where are the fronts? I am super concerned about messing with the suspension without knowing the details. 
No you didn't mis-read, forks have been upgraded with Pattonme intermediate cartridges and heavier springs, unless you have the same setup my settings are irrelevant to your bike. 
This may help,
when the bike was stock there was nothing I could do with the settings available to get the bike to work as it should, the springs are simply too soft and there was too little damping.
Once I got the front right though, the rear, for me, is actually pretty good. So good that a friend is going to try it on his FZ 09 before spending up on an aftermarket shock.
The point I'm trying to make is that I think most of us swap out the shock first because it's easy and obviously a bling factor, then maybe do the front when my experience tells me I should have upgraded the front first and I wouldn't have needed to upgrade the shock.
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I'm larger than you by nearly 2x, but found the stock stock was not that bad compared to the FZ09 that was TERRIBLE. (Waaay too soft front and rear.)
I have my preload at max on the shock. But have it mid range on the fork preload.
On the FZ09, had to crank the shock and fork preloads to max, but still was way too soft.
Some guys are now saying that going to to right forks on the FJ 09 is a good upgrade. Just run thin fluid in both tubes, and buy a used tube from someone who's up graded to something else.. And don't need the right fork guts anymore.. Run 5wt oil in both, fill by an extra 20cc's and call it good.
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It's called front to rear coupling. If the forks are too stiff, they cannot compress over a bump in the road. Since the forks cannot compress, the force of the bump pushes up the front of the bike, which transmits the force back down the shocks. This preloads the shocks, making them feel even stiffer when the rear tire hits the same bump.
If the forks are too stiff, and the shock is about right, fix the forks first. However, if neither forks or shocks are close to where they should be, you will still have to fix both.
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  • 2 weeks later...
+1 on smifff's analysis! I'm not sure the science behind what I did but after riding for 2 seasons I have hit on a functioning set up with stock suspension. I'must 220 with gear. I had been getting my sag set on the front end, at
least I thought I was. Last ride out I just went for it and cranked the preload full in, right to the top of the cap and tightened up the rebound 3 clicks out from fully seated. The front is the best I have felt it since I got the bike. Improving the front end even to this extent ha prompted me to see that the shock now feels very acceptable.
It was funny smifff, after I got home from my last ride just yesterday, I flopped down on the coach and came to the website and ended up reading your musings. Thanks for you ideas.
Now someone please explain to me how fully loading front spring and chocking down its rebound tamed my front end down.
It still nosedives under heavy braking but seems very much under control the rest of the time.
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Setting rider sag and rebound is only the first steps of suspension adjustment.  Rider sag sets ride height and chassis pitch, rebound helps stabilize the wheel over bumps / dips, and reduce topping out to keep fork travel in the middle of range of travel. 
220  lbs is probably on the heavy side for the stock spring.  Adding extra preload to reduce excessive rider sag, increasing compressing and rebound damping settings, and increasing oil viscosity and oil height are all settings that can be stiffened up to compensate for a weak spring, to some extent.  Based on your report, next step it to increase compression damping to reduce fork dive, then increase oil height, then get heavier spring if needed
Rider experience and expectations is another important consideration.  You did improve your suspension by making very basic changes.  It may be as good as you can get it with the components you have, but it is only half as good as top of the line components properly set up.
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I fully agree xlxr. Got up early and took a ride this morning. Soon realized that even though ride was improved as realized yesterday, when hitting small sharp bumps at speed, too much compression damping was still jolting front forks and heavy braking still overwhelms light springs. On nice smooth road all's good. Put rebound at only 2 clicks out from full hard on fork. As soon as pattonme gets caught up I'm pulling the ECU and fork legs and getting this thing dialed in for the rest of the summer.
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