I have searched and have not found what I'm looking for.
I am changing the fork springs on my 2006 f to .85 sonics.  I have a good idea where I want the fork oil level.   Are most of you using 10w or 15w fork oil?  Thanks!

10 is way too light. 15 is a good starting place for .85s... Go up to 20 if you decide 15 isn't enough, or if you live in the desert. I'd also recommend a starting fork oil level of 120mm, rather than the 98 specified in the OEM guide. After-market springs usually occupy more volume in the fork, so the resulting air gap will be much smaller than stock.

The bike comes stock with 10w, I believe. I've found it soft but none of the "bottom out under breaking" reported in US bikes. When I changed the fork seals last week I had 15w put in. Much better now.

Michael

I had mine bottom out. Both the older crappy springs and the newer ones that were beefier.
I notice it most when going over the 2" bump into the parking lot at the gym. I'd hear a "clunk" and wondered what it was. I changed springs in Trey to 0.85 Sonics and never had that clunk again.
After a couple of us rebuilt a bunch of forks last week, we noticed the short travel, weak oil and bad springs (old and new were bad by comparison to 0.85 or progressives - see other threads on this)
Now that all bikes have either 0.85 or progressives and 15w oil, no more bottoming out and "click: going to the gym parking lot.
I suppose we could try 20w oil, but 15w seems find with the better springs.
Also I no longer feel like I'm doing stoppies when braking at the bottom of a steep hill just before the gym.

I think my preference is now for progressives. They are soft for the small bumps but get stiffer with bigger bumps. I find that a good ride for city streets. (Advantage of having more than one bike so you can set each up with different springs) Racers may have a different opinion. But, hey, you make a bike work for YOU so whatever you do is OK as long as you like it. And remember - you need to select springs and oil based on your weight and riding style.

thanks.  i will try the 15w with the .85 when they get here and report back. 

For what it's worth, when I raced on the stock GS500 forks (with emulators,) I ran 15 weight in 100+ degree weather. IMO, 20 weight is going to provide too much rebound damping with .85 springs, especially when the bike was cold. I did experience some bottoming out with 15 weight oil, but resolved it by raising the oil level up a little and adding a few MM of preload via washers.

I would not advise starting with 20 weight oil unless you weigh upwards of 220 and are running very stiff (>.95) springs. If you're doing that, a multi-weight fork oil might also be a good call.