Front fork Upgrade/Fix

[stelbo]

Hi all,

After many efforts to make the front suspension (Showa) work as smooth as the rear (Ohlins), it seems that I failed. I tried all possible settings but it still returns back a hard way.
The bike is an ST4s 05 MY (the new look) 18,500 Km, fork oil changed in 12,000Km 7.5 SAE, with spring preload only 1/2 turned in from completely free.
The rear suspension is raised.

I' m asking for your thoughts-opinions on the following.
I would like to change the spring with a softer one and make the re valving adjustment. Any idea, how to recognize how many Kg the current spring is and what to go for? the rider is a little less than 100 Kg with gear on and most riding is a bit sporty.

I looked a lot through this site for a great write up on DIY spring replacement and re valving with pictures, but I couldn't find it. Please can you point it to me.

If any has done the above mod. can you inform on cost of materials, so I can have a point of reference?

Thank you all and Ride safe

[Puffin64]

I've got a mod I'm working on since buying a set of 916/996 Showa forks with Ohlins internals, I'm planning to use the bottom yoke of the 916/996 and the top yoke off the ST2 which has been bored out to the size of the other forks.
Got to change the fork seals and get some tapered roller bearings before I can finish the job off.

[stryder]

Originally Posted by stelbo

Hi all,

After many efforts to make the front suspension (Showa) work as smooth as the rear (Ohlins), it seems that I failed. I tried all possible settings but it still returns back a hard way.
The bike is an ST4s 05 MY (the new look) 18,500 Km, fork oil changed in 12,000Km 7.5 SAE, with spring preload only 1/2 turned in from completely free.
The rear suspension is raised.

I' m asking for your thoughts-opinions on the following.
I would like to change the spring with a softer one and make the re valving adjustment. Any idea, how to recognize how many Kg the current spring is and what to go for? the rider is a little less than 100 Kg with gear on and most riding is a bit sporty.

I looked a lot through this site for a great write up on DIY spring replacement and re valving with pictures, but I couldn't find it. Please can you point it to me.

If any has done the above mod. can you inform on cost of materials, so I can have a point of reference?

Thank you all and Ride safe

When you say you've made all types of adjustments, I'm guessing that means you tried various dampening settings for both rebound and compression adjusters, various pre-load settings, thinner fork oil like 3 or 5 w, and have tried to "fix the front by adjusting the rear." If so, then it doesn't matter what the spring rate is in there now, as you want a softer one. My guess is a .80/85 rate will get you where you want to go if you like it more on the plush side than the sporty side. Call Rick at Cogent Dynamics. He works on a lot of Ducatis and can supply you with good advice, parts and prices. I think he ships overseas too.

[stelbo]

Frank,

your guess is right, that's what I meant.
Your suggestion on the weight of the spring could be right or not. I could only have a opinion on that if I knew what the standard is as a point of reference.
I would rather source the required parts from the local market, so in case I mess it up, I will be able to get advice or even part exchange them.

Any idea on the write up of the DIY post.

thenk you

Stelios

[scottieducati]

The standard springs are progressive, not linear rate.

[stryder]

Originally Posted by scottieducati

The standard springs are progressive, not linear rate.

True, if the stockers are still in there. I always think of linear springs since that's what I prefer. Here's a Race Tech spring rate chart:

Race Tech Fork Spring Rates

I use .95 linears and find they work well for my needs. OP wants plush, so my guess is at .85 he'll get it.

[erikrichard]

The stock spring rate for the ST2/ST4 is .83, not sure if that's the same for your bike. If you are only using 1/2 turn of preload and aren't bottoming out, I strongly suspect your fork oil level is too high - have you checked that? what do you have your rebound/compression adjusters set at?
The correct term is damping, "dampening" is something you do with a wet towel.

[stelbo]

When I changed the oil I did with the forks on the bike, I collected the old one, measured them and they were 0.5lt. I put in 0.495 lt of the new one to anticipate whatever was left in.
The bike does not bottom out even in hard brakes, I have attached a zip tie so I can see the distance travelled.
The settings are rebound from fully in 4 clicks out.
The compression is from full in 6 clicks out.
Your hypothesis on the level of the oil might be true.

''The correct term is damping, "dampening" is something you do with a wet towel''
I am not the one that used the above phrase, by the way, what can you do with a wet towel?

[erikrichard]

I think your damping settings are set way too hard, especially the rebound. I have my rebound set to 10 clicks from full in (out of 15), compression set at 8 clicks from full in. Too much rebound will make the forks feel locked up over bumps more so than too much compression in my experience.
How did you take the fork fluid out with the forks installed? You can check fork oil level at this point with the forks installed on the bike and only the caps removed. Assuming your 2004 forks are the same as previous models (I'm pretty sure they are) you are looking for about 3.75 inches or about 95mm from the top of the fork to the oil level. Use a zip-tie for a dipstick - that's with the forks completely collapsed.

[jobst3]

I do notice the front of my ST3 is a little harsher over sharp bumps than I'd like, but my adjustments are way different: 12 clicks out on re-bound and 10 out on compression. Stock springs and oil.
Personal preferance accounts for alot though.

I grabbed a wet towel on my last ride, but the bike seemed to ride the same...