C5 Fork Tutorial

[Arizoni]

That's why I mentioned the manuals screw up on the amount of oil the engine needs.

[barenekd]

The "Service Manual"  lists 265+2.5 ccs in each leg for the C5 and G5, page 02-7
Bare

[Ducati Scotty]

The "Service Manual"  lists 265+2.5 ccs in each leg for the C5 and G5, page 02-7
Bare

Thanks for the page reference, couldn't find it this morning.  And that's wrong for the C5.  The C5 take 195ml per leg.

Scott

[barenekd]

That's why I refer to it as a "Service Manual", those are airquotes . I don't think I trust much in it. Things are very difficult to find. Not to mention the totally unusable electrical schematics. There is no index. Without a doubt the worst shop manual I've ever seen.
Note to Kevin, this pub needs severe help!
Bare

[jartist]

Hmmm... now you got me second guessing my fork oil amount. Any problems associated with adding too little oil?  I know too much and you can blow seals.  The G5 seems to work fine for me solo and two up with 200ml.  Unfortunately I already buttoned the forks up so no pics but I suspect the caps are the same except the 12mm hex goes straight through. I imagine it wouldn't take much to drill out the c5 caps or swap for g5 caps. Why do you suppose the went with soils caps anyhow? Perhaps they vent to the atmosphere less than relying on the outer caps?

[Ducati Scotty]

As long as the oil covers the damping mechanism it will 'work'.  Anything above that just lowers the air space.  The air space in forks acts as a secondary and progressive spring as it compresses.  Make it smaller and it essentially becomes more progressive since it compresses more for any amount of fork movement.

It's a very easy way to make a fork dive a little less and make it less likely to bottom.  Take it too far and as you said, you'll blow seals.

I found that the proper amount of oil made my forks less divey after some inital compression.

And from what I heard the reason the C5 is 195ml is because 200ml was blowing seals.

Scott

[barenekd]

And from what I heard the reason the C5 is 195ml is because 200ml was blowing seals.

Sounds like a good reason to me!

Bare

[Ducati Scotty]

Just a little update...

I noticed a tiny trickle of oil down one of the fork legs, looks like I've blown a seal.  I guess even 190ml is still too much oil.  I'll go with 180ml next time.  Oh well, I wanted to change the springs anyway.  I'll get some new springs, new seals, and the tool to not crack the fork when I take the seals out in a few weeks.  It's a tiny leak, nothing that needs to be addressed today.

Scott

[Ducati Scotty]

Just a little update...

I had the fork apart today to measure some things.  The inside diameter is 28.92mm so we can't fit 29mm springs in there.  I'll be calling Sonic Springs to see what they might have in 28mm.

Also, I'm currently running 10wt fork oil but wanted to try lighter.  I filled the fork with 7w and could barely tell it was there.  It was like there was no compression damping at all and not much in rebound either.  Now I'm a fan of light damping but this was too far.  I didn't even put it together, just dumped it and put 10w back in.

Finally, I timed myself and it took me about an hour to get both legs off the bike and on the bench with one torn down.   A little longer to get it all back together.

Scott

[Ducati Scotty]

The 26mm Sonic Springs did not work out.  Whenever the fork compressed or rebounded it made a squeaky/screachy noise, mostly on large rebounds.  I took the fork tubes out, turned them around to get the oil all over the springs, but they wouldn't quiet down.  I put the stock springs back in and they were quiet as a mouse.

I'm back to stock for now.  The 0.85kg/mm rate felt pretty good and I only had about 13mm of preload.  RaceTech makes some 28mm springs but they only go up to 0.80kg/mm.  I may try those with around 20-25mm of preload or as a base spring to cut a few coils off and raise the rate.  We'll see.  They're pricey ($140) and I've got some other things to do for the next few weeks.

Scott

[1 Thump]

What did the sonic springs folks say about the noise ?

[Ducati Scotty]

They said it was common to hear it until the fork got worked a little and the spring got some oil on it.  I either neede to find a nice bumpy road or take the fork legs out and turn them over to spread the oil.  I did both, no luck   I'm still waiting for a response to my last email.

Scott

[Ducati Scotty]

Just heard back, they can't figure out what it is either.  They're sending me a prepaid label for return and giving me a full refund including shipping with no re-stocking fee.  THAT"S customer service!  I'll certainly be keeping them in mind for any future bikes.

Scott

[GSS]

Scott,
Just an FYI to add to your brilliant write up.  Our old friend ScooterBob had recommended using ATF type F for my C5 fork oil.  I modified that a little and used Amsoil Synthetic ATF instead.  All I can say is that the ride has been really nice and smooth with that.

GSS

[Ducati Scotty]

Thanks.  It seems everything is an improvement from stock   I think getting the proper amount in helps a lot. 

I prefer fork oil since I ca select the weight but many people use ATF of one flavor or another with good results.

Scott