Author Topic: Progressive suspension spring upgrade and fork oil cheat  (Read 889 times)

Offline chris900f

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Progressive suspension spring upgrade and fork oil cheat
« on: May 28, 2021, 02:37:21 AM »
Decided to install the progressive springs today with 1010km on the clock. These springs are the replacement set for about 20 bikes listed, including the Ninja 500...and also some bigger bikes.



I'm going to cheat and just swap the springs and "most" of the oil.



I use a 6x1mm threaded rod as a dipstick. The threads hold the oil. making it easy to mark the spot. Measure the distance (50cm). So that's the oil-level, with the springs in and the bike on
the centerstand, with the front wheel jacked up just a hair so there is no weight on the front wheel.




The stock preload is pretty high.


After fishing out the springs and spacers with a magnet, it's time to get rid of the old oil.

I found these x-large medical syringes at an industrial plastics (resin molding) shop, where they are used for fine measurement of resin hardener. $5.00 a pop.

I'm using very flexible 1/4" fuel line...it's a little messy.



After you get the top half empty, you need to insert the rod into the hose to get it down to the bottom of the fork. Remove the rod and then use the syringe.



After getting out as much as I could, the threaded rod still measured a couple of inches of oil. I probably removed about 80%

I put in the new springs and used the syringe and dipstick to get the oil to same level as my original measurement. Note how high the springs are
in the tubes. Recommended preload is .75" or about 20mm. I'm using Bel-Ray 15w because I had it left over from my 900.



The instructions say that it doesn't matter if you have the closer coils at the top or bottom of the fork. I decided to run them with the more open coils
at the bottom. If the closer coils were down at the bottom they would take up more space, and therefore I would get less oil at the same height on the dipstick;
so for the sake of a little more dampening I'll run them with the close coils at the top.

I also installed these "bar-backs" They fit with no problem, I cut one redundant cable tie and the cables/hoses are all free with no strain. The NOS set I got cheap on ebay needed a little work with a tap to open up one of the holes but it only took a minute to fix it.



The bar-backs have the added feature of allowing you to access the springs and spacers without removing the bars. Not quite as good as adjustable preload caps but not bad.



I started with just under the recommended .75" about 15mm, a bit too soft so i moved up to a 20mm, then a  25mm(1 inch) spacer and finally settled on 34mm. This was about as
much as I was willing to use as it gets difficult to get the forks caps in safely.

These springs are quite firm under hard stopping and pretty much eliminate dive, but still have near-stock sag and ride height. They are not particularly heavy/stiff so heavier riders may not like them. I find that they can handle the rougher "b" roads, including bumps that would bottom the stock springs, very smoothly and the rising spring rate works well at speed and in the corners.

I installed the R6 shock a few weeks ago, and coupled with these springs the improvement is night and day.  Suspension mods are probably your best bang-for-the-buck on the GS500s. The bike just works and feels better under all conditions.













Offline SK Racing

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Re: Progressive suspension spring upgrade and fork oil cheat
« Reply #1 on: May 28, 2021, 03:51:44 AM »
Thanks for the nice how-to. :cheers:

I will probably do mine as well sometime in the future now that I have the R6 rear shock installed. 
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Offline chris900f

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Re: Progressive suspension spring upgrade and fork oil cheat
« Reply #2 on: May 28, 2021, 12:40:57 PM »
Thanks, what do you think of the R6 shock? Were you able to get a soft enough ride?

Are you going with the Racetech or the Progressive fork springs? I probably would have gone with the Racetech's because they are so popular here,
but the import cost/exchange and shipping costs had me looking at other options.

Offline SK Racing

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Re: Progressive suspension spring upgrade and fork oil cheat
« Reply #3 on: May 28, 2021, 01:23:07 PM »
The R6 rear shock is superb. Preload is on position 2 as per your recommendation and I managed to dial in a much smoother ride by playing with the slow and fast compression settings. Last Sunday on the Gentleman's Ride I did about 80km and my back was fine afterwards. With the stock shock the previous week, I suffered from back pain after a 10km ride.

I'll probably go for the Sonic springs if and when I upgrade the front. It will have to be a special import as we don't have access to such luxury upgrades off-the-shelf where I live.
You donít stop riding when you get old, you get old when you stop riding!
1939 Panther 600cc Single - Stolen, 1970 Suzuki 50cc - Sold
1969 Triumph Bonneville 650 T120R - Sold, 1981 Honda 750F - Sold
1989 Suzuki GS500E - Sold, 2004 Suzuki GS500F - Current ride

Offline chris900f

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Re: Progressive suspension spring upgrade and fork oil cheat
« Reply #4 on: May 28, 2021, 03:40:42 PM »
Cool. I'm glad to hear the shock is working out for you. I noticed that with the R6 shock set-up
the forks don't dive nearly as much, even with the stock springs.

What did you do with the compression settings?...I still haven't changed mine from the Yamaha stock set-up.

Offline ShowBizWolf

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Re: Progressive suspension spring upgrade and fork oil cheat
« Reply #5 on: May 28, 2021, 05:40:05 PM »
Thank you for sharing!

If anyone is interested in adding your specs and settings to my thread here, please do so... I made it years ago in effort to get as much suspension setup info in one place as possible. :cheers:

http://gstwins.com/gsboard/index.php?topic=69391.0
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Offline chris900f

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Re: Progressive suspension spring upgrade and fork oil cheat
« Reply #6 on: May 28, 2021, 09:37:06 PM »
Thank you for sharing!

If anyone is interested in adding your specs and settings to my thread here, please do so... I made it years ago in effort to get as much suspension setup info in one place as possible. :cheers:

http://gstwins.com/gsboard/index.php?topic=69391.0

Done!  :cheers:

Offline cbrfxr67

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Re: Progressive suspension spring upgrade and fork oil cheat
« Reply #7 on: June 08, 2021, 07:36:51 AM »
Another thread I missed,...  WOW them's so low miles!  What's the story on it being such low miles, if any?  Thanks for sharing tips! 
I also like a firm ride.  Recently did a Voyager and upgraded suspension.  Sent to my bro n law down in Mejico who said it was stupid uncomfortable.  I couldn't figure out why he was saying that til he tells me that the roads are so bad a stiff suspension is almost unbearable.  :icon_sad:
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Offline chris900f

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Re: Progressive suspension spring upgrade and fork oil cheat
« Reply #8 on: June 08, 2021, 01:35:13 PM »
Another thread I missed,...  WOW them's so low miles!  What's the story on it being such low miles, if any?  Thanks for sharing tips! 
I also like a firm ride.  Recently did a Voyager and upgraded suspension.  Sent to my bro n law down in Mejico who said it was stupid uncomfortable.  I couldn't figure out why he was saying that til he tells me that the roads are so bad a stiff suspension is almost unbearable.  :icon_sad:

I bought the bike last year. It had been in storage almost since new; it only had 480kms when I got it. I'm not sure why, probably something to do with the clackity-clack noise
these bikes (and esp the 04/05 bikes) make at hot idle--I'm gonna fix that one way or another. I guess I should have taken a longer test ride :D :hithead:


I'm in Western Canada, the roads can get pretty beat up by the winter-spring freeze-thaw cycle, so I understand what your brother-in-law is saying. Too stiff and the wheel loses contact and

hops; too soft and you can bottom out and possibly even lose control. These springs work well here, they start out quite soft and get exponentially stiffer as you use up the travel.

I used the zip tie method (see Dave Moss Tuning vids on youtube), to compare the stock vs progressive springs on the same rough lake road: The felt pen line where the zip-tie got pushed up to

with the stock springs(bottom-out???), the current zip-tie position is with the new springs/oil. In both cases I was hitting the big bumps a sane person would normally dodge :icon_lol:, and the road speed is 50-70kph (30-42mph)


Offline The Buddha

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Re: Progressive suspension spring upgrade and fork oil cheat
« Reply #9 on: June 08, 2021, 06:10:27 PM »
You put zip ties on both legs and see equal travel too.
Cool.
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Offline chris900f

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Re: Progressive suspension spring upgrade and fork oil cheat
« Reply #10 on: June 09, 2021, 10:18:47 AM »
You put zip ties on both legs and see equal travel too.
Cool.
Buddha.

That's a good idea.

Offline moe_tunes

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Re: Progressive suspension spring upgrade and fork oil cheat
« Reply #11 on: June 09, 2021, 02:55:29 PM »
You put zip ties on both legs and see equal travel too.
Cool.
Buddha.

That's a good idea.

I hope The Buddha is having a lend of you there...
With the sliders being bolted solidly to the axle the only way you wouldn't have equal travel with cable ties on both is if one fork leg isn't clamped in the triple tree. You only need the one. The GS has 120mm of travel in the front fork so on big bumps the cable tie should be moved close to 120mm and on smaller bumps much less if the springs ae right for the weight.

Hope that helps.
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Offline The Buddha

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Re: Progressive suspension spring upgrade and fork oil cheat
« Reply #12 on: June 09, 2021, 04:51:16 PM »
Dude I've seen some turkey's like my old vulcan 750 which didn't slide equally. And a zip tie is what 1/100's of a cent ??
Why would anyone even think of putting 1 I dont understand. I dont even grab less than 10 when I manage to find the baggie or the tube or where ever I seem to lose these million zipties I know I have but can never find.
Cool.
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Offline chris900f

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Re: Progressive suspension spring upgrade and fork oil cheat
« Reply #13 on: June 11, 2021, 05:38:30 PM »
"With the sliders being bolted solidly to the axle the only way you wouldn't have equal travel with cable ties on both is if one fork leg isn't clamped in the triple tree"

Your argument self-negates as it admits that there is enough play in the front axle to allow some amount of pivot. If you have ever set the height of the fork tubes
in the triple-tree with the front wheel mounted, it becomes obvious that you can indeed set them unequally...so where is the pivot point?

This is why we go to the trouble of getting springs/oil level/preload matched as exactly as possible. Think about the stock set-up with the long spacers: what would happen
if you took 1/2" off one spacer, but left the other at stock length? Would the axle compensate perfectly, or would the tire begin to show an off-center wear pattern? What would
happen under heavy emergency braking?

I'm not sure if the zip-ties would show these issues, but as Buddha says, they are so cheap---why not use two?

Offline moe_tunes

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Re: Progressive suspension spring upgrade and fork oil cheat
« Reply #14 on: June 12, 2021, 03:46:31 PM »
I think you need to have another read of my post to understand it better.

If you look at the front end of your GS you will see that the sliders are bolted together with the axle at the bottom and the brace at the top. They can only travel up and down the fork legs togeter as a unit.
It doesn't matter what you do with springs, spacers or oil. The sliders are bolted together and can only travel in unison.
You're just jealous because the voices only talk to me.

Offline chris900f

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Re: Progressive suspension spring upgrade and fork oil cheat
« Reply #15 on: June 19, 2021, 09:33:40 PM »
No worries bro, I understand you perfectly. :D


 

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