Suspension tuning; S4

spuggy · 19-07-2020, 10:38 PM

So, I don't know a single thing about Ducati suspension tuning I didn't read here - and only know enough to be dangerous. So could use advice from someone who knows what they're talking about

My M900ie Dark handling was pants when I got it. The (non-adjustable) forks were too stiff & didn't have enough (any?) damping, the rear was lowered and soft/saggy/bouncy - like it was worn out and had been owned by someone under 5ft tall; had to bend my knees when flat-footing it... Fitted S4 front forks dropped slightly in the yokes, and a Nitron R2 with a spring spec'd for my weight, and it transformed the bike. It'd fall into corners - but went round them like it was on rails, and soaked up bumps like they weren't there. Sorted.

My M900Sie was saggy as crap at the rear (Ohlins) shock; jacked it up with slugs on the hoop (front already dropped), and increased pre-load until static sag was correct; much, much better. Ohlins doesn't seem as good as the Nitron to me, but could just be it needs a stiffer spring...

My S4; I've been riding it and was not especially thrilled by the handling at first; don't know why it had tire pressures of 36 in the front and 38 rear, but I can tell you that doesn't seem like an improvement on the factory settings to me...

Now I'm not actively trying to avoid leaning the bike(!), what I notice next is weight distribution changes on slow greasy roundabouts. As you roll tiny amounts of power in as the line straightens (from literally slightly over idle speeds, I can still hear clutch knock), I can feel the front suspension unloading.

Yeh, the S4 is noticably more powerful than the injection 900s - but I mean with the smallest amount of throttle you can realistically feed in. This feels more like a suspension issue than "clumsy ham-fisted git tries to wheelie banked over"...

Oh, also the 900s fall into the corner quite quickly - but predictably/linearly.

Unless I'm imagining it, the S4 seems to fall into corners slow at first and then quite abruptly speed up the deeper the lean angle gets. Does this suggest anything in particular, or is it maybe a foible of the different frame? It's not scary, but seems odd.

So, the bike's got 21K on it. I'm pretty confident before I look that the rear spring will be both way too soft and won't have enough pre-load. I don't have any way to adjust the pre-load right now, but am intending to check rebound & compression damping is set per factory settings and adjust the pre-load to get sag somewhere in range Real Soon Now. Checking fork oil levels (or even changing the oil) might not be a bad idea either.

Just how good is the adjustable Sachs shock? I'm thinking 21K could be getting to about where it needs a service - right? - and if I need to yank it for a spring change, I could easily be tempted to get another Nitron R2 with the appropriate spring rate anyway...

Thoughts?

19-07-2020, 10:38 PM	#1
spuggy Registered User Join Date: Apr 2016 Location: Farnborough Bike: M900sie Posts: 171	Suspension tuning; S4 So, I don't know a single thing about Ducati suspension tuning I didn't read here - and only know enough to be dangerous. So could use advice from someone who knows what they're talking about My M900ie Dark handling was pants when I got it. The (non-adjustable) forks were too stiff & didn't have enough (any?) damping, the rear was lowered and soft/saggy/bouncy - like it was worn out and had been owned by someone under 5ft tall; had to bend my knees when flat-footing it... Fitted S4 front forks dropped slightly in the yokes, and a Nitron R2 with a spring spec'd for my weight, and it transformed the bike. It'd fall into corners - but went round them like it was on rails, and soaked up bumps like they weren't there. Sorted. My M900Sie was saggy as crap at the rear (Ohlins) shock; jacked it up with slugs on the hoop (front already dropped), and increased pre-load until static sag was correct; much, much better. Ohlins doesn't seem as good as the Nitron to me, but could just be it needs a stiffer spring... My S4; I've been riding it and was not especially thrilled by the handling at first; don't know why it had tire pressures of 36 in the front and 38 rear, but I can tell you that doesn't seem like an improvement on the factory settings to me... Now I'm not actively trying to avoid leaning the bike(!), what I notice next is weight distribution changes on slow greasy roundabouts. As you roll tiny amounts of power in as the line straightens (from literally slightly over idle speeds, I can still hear clutch knock), I can feel the front suspension unloading. Yeh, the S4 is noticably more powerful than the injection 900s - but I mean with the smallest amount of throttle you can realistically feed in. This feels more like a suspension issue than "clumsy ham-fisted git tries to wheelie banked over"... Oh, also the 900s fall into the corner quite quickly - but predictably/linearly. Unless I'm imagining it, the S4 seems to fall into corners slow at first and then quite abruptly speed up the deeper the lean angle gets. Does this suggest anything in particular, or is it maybe a foible of the different frame? It's not scary, but seems odd. So, the bike's got 21K on it. I'm pretty confident before I look that the rear spring will be both way too soft and won't have enough pre-load. I don't have any way to adjust the pre-load right now, but am intending to check rebound & compression damping is set per factory settings and adjust the pre-load to get sag somewhere in range Real Soon Now. Checking fork oil levels (or even changing the oil) might not be a bad idea either. Just how good is the adjustable Sachs shock? I'm thinking 21K could be getting to about where it needs a service - right? - and if I need to yank it for a spring change, I could easily be tempted to get another Nitron R2 with the appropriate spring rate anyway... Thoughts?