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FJR Motorcycle Forums
Technical & Mechanical Problems
Suspension Settings Recommended by Dave Moss
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<blockquote data-quote="MCRIDER007" data-source="post: 1087398" data-attributes="member: 329"><p>I'm not disputing these comments but I am NOT reading a recommendation for 15 wt fork oil. Street bike forks, such as the FJR, have a very large volume of oil cooled by outside air, and the fork oil temperature rarely exceeds more than 10 degrees more than the ambient temperatures......so the normal operating fork oil temperatures are usually between 40 and 110F. The total variance in viscosity for fork oils in that temperature range is about 25-30 percent or about 15 percent variance from the normal valving design temperature range of 65-85F. If the valving was designed for 5wt oil at 65-85F then you would expect 6wt oil to have the same effective viscosity in 100F temps and 4wt oil to have the same viscosity in 30F temps.</p><p></p><p>The FJR OEM springs are under sprung for most riders and lack sufficient oil flow in the high speed compression circuit for all riders. Increasing the oil viscosity may give a firmer ride over smooth surfaces but it will also give a much harsher ride on rough surfaces. I helped a friend change his fork oil and he insisted on using 10wt oil.....it increased the feedback on his forks, I could feel every little bump or imperfection in the road. My forks in comparison, with the GP Suspension re-valve (that increases oil flow), just soaked up the bumps and imperfections and stuck to the road at the same time.</p></blockquote><p></p>
[QUOTE="MCRIDER007, post: 1087398, member: 329"] I'm not disputing these comments but I am NOT reading a recommendation for 15 wt fork oil. Street bike forks, such as the FJR, have a very large volume of oil cooled by outside air, and the fork oil temperature rarely exceeds more than 10 degrees more than the ambient temperatures......so the normal operating fork oil temperatures are usually between 40 and 110F. The total variance in viscosity for fork oils in that temperature range is about 25-30 percent or about 15 percent variance from the normal valving design temperature range of 65-85F. If the valving was designed for 5wt oil at 65-85F then you would expect 6wt oil to have the same effective viscosity in 100F temps and 4wt oil to have the same viscosity in 30F temps. The FJR OEM springs are under sprung for most riders and lack sufficient oil flow in the high speed compression circuit for all riders. Increasing the oil viscosity may give a firmer ride over smooth surfaces but it will also give a much harsher ride on rough surfaces. I helped a friend change his fork oil and he insisted on using 10wt oil.....it increased the feedback on his forks, I could feel every little bump or imperfection in the road. My forks in comparison, with the GP Suspension re-valve (that increases oil flow), just soaked up the bumps and imperfections and stuck to the road at the same time. [/QUOTE]
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FJR Motorcycle Forums
Technical & Mechanical Problems
Suspension Settings Recommended by Dave Moss
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