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Fork Oil Weight?

  • Thread starter Thread starter ryonker
  • Start date Start date
R

ryonker

Guest
I am switching over to progressive springs and I am wondering what weight most of you guys used for fork oil.

I am guessing 10 or 15, right? Does rider weight affect this? On a good day I am 200 pounds:D!

Thanks!

Rick
 
Here's a couple of data points for ya:
I put progressives on my "82 850GL last year & refilled with 15w. I also installed 2" spacers, based on the installation recomendations that came with the springs explaining how to determine spacer lengths. The ride is harsh, and am planning on cutting the spacer lengths down to 1" (to start) to see if that improves the ride... Progressive does not list front springs for this bike, so I measured up the OEM ones & essentially bought Progressive ones with similar dimensions - I'm not sure the "out-of-box" spacer recomendation applies in my case because of this.
​
I just this weekend flushed & cleaned out the front forks on my "81 750L, kept the OEM springs, and refilled with a 50/50 mixture of 15w fork oil & ATF. I also installed a .75" spacer & the ride is MUCH improved. I may yet remove/reduce the spacer but at the moment I like the way it handles...
​
I am 185# and ride a little on the aggressive side, but I'm not a knee scraper yet - need to get the suspension dialed in first!
 
50/50 mixture of atf and 15Wt fork oil is around 11Wt.

I am around 235 and use the equivalent of a 13 Wt fork oil. it is firm, but not too obnoxious over bumps.

aggressive rider 15Wt

easy rider :D 10Wt

or blend 10Wt and 15Wt to suit your taste.
 
At your weight I would use the 15 weight to start with & tune the preload from there. Ray.
 
On my 1100ES, I went to Progressives, who swear up and down to use 15wt only. I'm 260lbs, and the dampning of 15wt is pretty brutal on the wrists, especially on the 1100 where i lean forward on them just a touch. Now, with my fat arse, even tho Progressive says "no preload or damping" at first, I went with the 1107 springs (i will go 1108s next time tho) 1.25 inch spacer, and to get it STIFF ( im a bit aggro with the bike, so i like it a little stiffer) I am 3 clicks down on the front preload, and "2" on the damping adjust. I dunno if your bike has those adjustments or not, but if not, you may find that you want a little bit longer spacer in there to stiffen it up.. I went with 10wt oil...
 
On my 850G / 170lbs / 15wt fork oil / cut the spacer to specified length:

I found it a littler harsher than I'd like, but not enough to want to tear it back apart to change oil/spacer. Maybe as the oil wears it will get more bouncy :)

It is a good overall starting position though and I think everyone else has given sound info.
 
It all works as a system. First you determine the proper spring rate. Progressive Suspension has done a good job of this. Next, you use a spacer to set your ride height. Finally, you use the oil to control the movement. A thicker oil will resist movement more. If you and/or your bike are heavier, or you tend to ride rather aggressively most of the time, a 15w fork oil will probably work very well for you. For average-size riders on lighter bikes or ones who are looking for a smoother ride, a 10w oil will do.

Keep in mind that a lot of oil recommendations will change if your bike changes drastically. For example, a dirt bike will have different components, along with different needs, and for that bike, a 20w might be necessary. Another dirt bike from a different manufacturer might only need a 5w oil, so you have to keep comparisons to other bikes to a minimum.

All that being said, to answer ryonker's original question, I would recommend 10w fork oil after properly setting up the ride height with the correct spacer length.

.
 
Thanks for all the great input:clap:!

I am going with a 15wt to start out.

Rick
 
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