I'm 200# and I used RaceTech straight rate springs at .95 KG. Turns out these are about perfect for my situation.
I used 15 wt fork oil. All is good.
I used 15 wt fork oil. All is good.
Fork spring preload?
- Thread starter rwthomas1
- Start date
rwthomas1
Site Supporter
Update:
Just finished the Sonic Springs installation. The fork oil was jet black and smelled terrible, so that was way overdue. Drained oil, removed stock springs. Refilled with 10wt oil, to stock fill height. I made a tool for the cartridge side, made it very easy, but still needed three hands. Measured 3" from the spring to the retainer, so I added 1.25", total of 4.25" for the spacer. Sonic said add at least an inch of pre-load. The "normal" side measured 5 7/8" so I ended up with 7 1/8" spacer there. Incidentally, stock fork springs were still in spec for length. Just way too soft.
This is an easy job to do with the forks installed. Put a strap from the center stand to the front wheel to keep the bike from pushing off center stand by accident. Loosen handlebars and simply roll them back. This leaves plenty of room. Loosen the top of the fork clamps and break the 17mm allen head caps loose. Thats it. Just pay attention when the last fork cap is removed. The forks collapse, and the bike nose dives. That's why you put the strap on.....
I haven't ridden far, just around the block, but the bike sits higher now. Maybe 1-1.5" of sag. No more diving or full compression on heavy braking. Seems much more compliant, bumps, etc. are well absorbed. I'll update again when I get a few miles on it but for now it seems like money very well spent.
RT
Just finished the Sonic Springs installation. The fork oil was jet black and smelled terrible, so that was way overdue. Drained oil, removed stock springs. Refilled with 10wt oil, to stock fill height. I made a tool for the cartridge side, made it very easy, but still needed three hands. Measured 3" from the spring to the retainer, so I added 1.25", total of 4.25" for the spacer. Sonic said add at least an inch of pre-load. The "normal" side measured 5 7/8" so I ended up with 7 1/8" spacer there. Incidentally, stock fork springs were still in spec for length. Just way too soft.
This is an easy job to do with the forks installed. Put a strap from the center stand to the front wheel to keep the bike from pushing off center stand by accident. Loosen handlebars and simply roll them back. This leaves plenty of room. Loosen the top of the fork clamps and break the 17mm allen head caps loose. Thats it. Just pay attention when the last fork cap is removed. The forks collapse, and the bike nose dives. That's why you put the strap on.....
I haven't ridden far, just around the block, but the bike sits higher now. Maybe 1-1.5" of sag. No more diving or full compression on heavy braking. Seems much more compliant, bumps, etc. are well absorbed. I'll update again when I get a few miles on it but for now it seems like money very well spent.
RT
I used a tie-down strap differently when I rebuilt the forks on my '96 CB750ST, and set the oil level about 1/4" higher than spec.
rwthomas1
Site Supporter
Update:
1000-1200? miles on the Sonic Springs. None of the old bad habits from the soft factory springs. Spring rate and response between the Sonics and the factory rear shock are pretty close, predictable handling, etc. Not everyone can justify RaceTech or Traxxion, the Sonics are a great budget option. The other thing is the ride height drastically changed. Instead of 3+" of sag, now maybe 1-1.5" The result feels like a slightly more upright riding position, and less weight on my wrists. I may be wrong, but it feels better.
RT
1000-1200? miles on the Sonic Springs. None of the old bad habits from the soft factory springs. Spring rate and response between the Sonics and the factory rear shock are pretty close, predictable handling, etc. Not everyone can justify RaceTech or Traxxion, the Sonics are a great budget option. The other thing is the ride height drastically changed. Instead of 3+" of sag, now maybe 1-1.5" The result feels like a slightly more upright riding position, and less weight on my wrists. I may be wrong, but it feels better.
RT