question about fork bushes

[sheltiedave]

From the racetech instructions

Step 1: Extend the fork completely and measure from the wiper (the dust seal atop the slider) to the bottom of the triple clamp (or lower fork casting on inverted forks; Figure 2). This measurement is L1.

I got 134mm


Step 2: Take the bike off the sidestand, and put the rider on board in riding position. Get and assistant to balance the bike from the rear, then push down on the front end and let it extend very slowly. Where it stops, measure the distance between the wiper and the bottom of the triple clamp again. Do not bounce. This measurement is L2.

I got 86mm


Step 3: Lift up on the front end and let it drop very slowly. Where it stops, measure again. Don't bounce. This measurement is L3.

I got 115mm

That adds up to 33mm rider sag , maybe

 

[FinalImpact]

L1 134mm
L2 86mm
L3 115mm << are you still on the bike? Wha?????

L1 - Fork fully extended.
L2 - Rider on; push down on the front end and let it extend very slowly.
L3 - Rider on; Lift up on the front end and let it drop very slowly.
. . L2 vs L3 is the Average of these two! These numbers should be VERY CLOSE to the SAME.
. . L2 + L3/2 = avg
. . 86 + 115 /2 = 100.5mm, which is a good RIDER SAG number 134 - 100.5 = 33.5 mm, but your forks are STICKING! Why?

IMO That is WAAAAAAAY too much difference from Pushing down vs pulling up. It should land you within 4mm of each other unless something is wrong (say L2 @98, L3 @102 is still 100 mm avg, but NORMAL stiction amount. Does that make sense?

What is the BIKE sag w/out rider, using the same method?



EDIT: bottom line, you need to know WHY there is so much difference L2 vs L3. Yes, NEW seals and bushing have more drag so the forks STICK. By pulling UP, they stick high. By pushing down, they stick low. The difference is the middle and it should only be about 4 - 5 mm tops. On used parts its usually way less like just a few mm.

Does that make sense. Do you have a helper? If not, use the Zip tie. ALSO - what is the BIKES SAG W/OUT you?

 

[sheltiedave]

L1 134mm
L2 86mm
L3 115mm << are you still on the bike? Wha?????

Nope , I wasn't on the bike :spank:

So had a remeasure and its down to 100 mm for L3 now , still too much of a gap between L2 and L3 for whatever reason .

 

[FinalImpact]

L1 134mm
L2 86mm
L3 115mm << are you still on the bike? Wha?????

Nope , I wasn't on the bike :spank:

So had a remeasure and its down to 100 mm for L3 now , still too much of a gap between L2 and L3 for whatever reason .

So:
Bike 134-115 = 19mm, ~ 9mm too much, but new springs relax
Rider 134-86 = 48mm; ~ 14mm too much

It appears as tho you lack preload. Add 10 - 12mm and repeat. Again, springs relax a few mm over time so go long (add 12+), then chop OFF MORE later if need be.

If you don't mind sharing, what do you weigh and what is the new spring rate? Does bike have luggage racks loaded?

 

[sheltiedave]

I'm 67 kg / 147 lb and the spring rates is 0.85kg . No luggage racks fitted just pretty much standard bike.

There is already 14mm preload , would taking it up to 24-26 mm preload be ok?

I put 10w oil in the forks and set the emulators 2 turn with the blue springs if that makes any difference?

 

[FinalImpact]

Grab some PVC and try it. That said, it is not the norm to have to "Pre-load" the springs that much. But it does become more of an issue as rates drop vs rates increasing.

Just so we are on the same page;
With the fork tube fully extended, your spring/spacer assembly is currently about 3mm below the top of the stanchion tube?

FWIW: the cap depth is 17mm, so if the new spring was flush with top of tube, threading the cap down would create 17mm of preload.

You state it has 14mm of pre-load. Is the spring 3mm down the stanchion tube?

Some details here:
http://www.600riders.com/forum/fz6-mods/54555-will-wont-forks-parts-interchange-fz-r6.html

 

[sheltiedave]

Had a quick look , and the washer is 4mm , nearly 5 mm down the tube , so probably 13-12 mm of preload.

 

[sheltiedave]

FWIW: the cap depth is 17mm, so if the new spring was flush with top of tube, threading the cap down would create 17mm of preload.

You state it has 14mm of pre-load. Is the spring 3mm down the stanchion tube?

Some details here:
http://www.600riders.com/forum/fz6-mods/54555-will-wont-forks-parts-interchange-fz-r6.html

That made a lot more sense , so I cut another pair of tubes that ended up just about flush with the top of the tube.

Did another batch of measurements and ended up with,

Unladen bike push down 112mm
lift up 116mm

Laden bike push down 101mm
lift up 105mm

L1 was still 134mm

 

[FinalImpact]

That made a lot more sense , so I cut another pair of tubes that ended up just about flush with the top of the tube.

Did another batch of measurements and ended up with,

Unladen bike push down 112mm
lift up 116mm

Laden bike push down 101mm
lift up 105mm

L1 was still 134mm

WOW! Who made the springs? For being 0.85kg/mm and you being on the light side, it looks under-sprung! It will still be FAR BETTER than the dual rate OEM with no damping.... But it looks as though 0.90kg/mm may have been a better fit.

Bike = 134-(116+112/2)=20.0mm << ideal here would have been 10mm
Rider = 134-(105+101/2)=30.5mm This is good but a bit firm.

Go ride it and see what you think! Its Going to be BETTER! Much Better! Good Job! :thumbup::thumbup:

 

[sheltiedave]

I use the race tech spring rate calculator and it came up with 0.824 and 0.85 was the closest so I went for that .

Probably should have said the fuel tank is completely full( laid up for winter with fuel stabiliser ) so that's adding more weight , maybe when the tank is half full/half empty the measurements might average out a bit better.

I don't know if it made any difference , or it just felt different, but realigning the fork seemed to help a little . But getting someone about my own weight and taking the measurments myself did help !!

It's more than likely going to be about March before I get the bike out again to notice if this saga has been worth it !! But a huge thanks to you FinalImpact for taking the time and having the patience for helping me .:thumbup:

 

[sheltiedave]

So it's mid March now and the weather has been half decent for a bot of a run on the bike with her new springs.

I would say for normal riding the bike is smoother , soaking up the bumps better than the old springs . But it has been 5 or 6 months since the last run .

I can say for sure the bike is better in the corners It feels more planted and I feel more confident in the corners with the bike, maybe a bit faster too If thats a good thing or a bad though !!


So it's been worth the hassle of me not understanding in the previous posts and getting there eventually . New tyre up front and HEL braided line have made a big difference too .

So it's been a good if somewhat cold first run out this year .

 

[FinalImpact]

Thanks for the update!
Log some more miles and measure it again if you don't mind.
But it sounds like: linear springs, emulators, and new oil has stopped or reduced the see-saw effect when going through the corners where the bike changes it line from minor irregularities? Very Good!

 

[sheltiedave]

I will get some miles on her and do a re-measure .

Am I right in thinking you did a thread showing how to take the measurements by recording with a camera , or am I just making stuff up ?