Ducati.ms - The Ultimate Ducati Forum banner

1 - 8 of 8 Posts

·
Registered
Joined
·
77 Posts
Discussion Starter #1
My 01 ST4 is back from the dead after a cam belt break. All is well in the engine department. On the suspension end of things, there is slight trouble. When I ride 2 up like today and hit the occasional dips in the road, the back end bottoms out. I only weigh about 160 and my girl is about 125 so the rear end should be able to handle it (the bike's not hers). The adjustment is nearly maxed out on the SACHS. Unlike the shock on my monster, I don't see a pressure valve to check the gas level. Just the big canister that seems to be sealed. I have no idea how to check the gas pressure but it has to be the problem. The bike only has 13k on it so I don't think I should need a new shock unless there is a unrepairable leak somewhere.

Ideas outside of a new shock?
 

·
Registered
Joined
·
2,794 Posts
You need a new, heavier rear spring. Common issue.
 

·
Still needs a life.
Joined
·
12,618 Posts
You need a new, heavier rear spring. Common issue.
I agree. Ducati lore has it that factory suspensions are set up for a mythical 160 lb. Italian rider. My first Ducati was a yellow 01-ST4. The ends of the center stand scraped the pavement at the bottom of frost heaves on a solo ride up to Windy Ridge.
 

·
Premium Member
Joined
·
5,645 Posts
I don't see a pressure valve to check the gas level. Just the big canister that seems to be sealed. I have no idea how to check the gas pressure but it has to be the problem.
Like others have said. Spring. BTW, that pressure valve you reference is just a way to put Nitrogen in the canister. Its purpose in your shock is to provide a pressurized expansion chamber of sorts for the shocks dampening oil. This keeps the oil from “sloshing around” as it moves in the shock’s body which would cause it to become bound with air and ineffective as a dampening fluid. It doesn’t have anything to do with your spring rate. I understand what you mean though. I have a mountain bike with an air shock. More air pressure = higher spring rate. Not the case with your Duc’s rear shock.
 

·
Registered
Joined
·
77 Posts
Discussion Starter #5
Thanks

What's weird is that on my 97 M900 Monster, I used to put a girl on back (with a bigger butt) and the thing never bottomed out.

I'm assuming that I'll need a complete new shock or can a beefier spring just replace the old one?
 

·
Still needs a life.
Joined
·
12,618 Posts
What's weird is that on my 97 M900 Monster, I used to put a girl on back (with a bigger butt) and the thing never bottomed out.

I'm assuming that I'll need a complete new shock or can a beefier spring just replace the old one?
I replaced the OEM spring on my 02-ST4s with a heavier one for riding two up with my son. I had it transfered to my 04-ST4s after my 02 was taken out by a gal in a Focus doing a u turn from the curb. I assume you can do the same with your ST4, although it would be a good excuse to upgrade to an Ohlins.
 

·
Registered
Joined
·
434 Posts
One other possibility is that your exhaust pipe mount is missing the spacer and the sound you're hearing is actually the bracket on the pipe hitting the swing arm. Don't ask me how I know this happens. :rolleyes:
 

·
Registered
Joined
·
77 Posts
Discussion Starter #8
I replaced the OEM spring on my 02-ST4s with a heavier one for riding two up with my son. I had it transfered to my 04-ST4s after my 02 was taken out by a gal in a Focus doing a u turn from the curb. I assume you can do the same with your ST4, although it would be a good excuse to upgrade to an Ohlins.
I think I'll have to wait for the Ohlins right now but I definitely need to upgrade. The frequent bottoming out has caused the chain to stretch which is very bad. I might have already ruined it.

One other possibility is that your exhaust pipe mount is missing the spacer and the sound you're hearing is actually the bracket on the pipe hitting the swing arm. Don't ask me how I know this happens. :rolleyes:
Oh No, it's definitely the shock but that's something to look out for. I've seen those little H shaped spring helpers for cars. I wonder if something like that might be a temp solution on a bike. Just when I'm riding 2 up. The shock is fine when it's just me but an extra 130 lbs on the back is sure a different story.
 
1 - 8 of 8 Posts
Top