ChrisMag

Anyone have the OEM spring diameter and length? I have a spare set of 0.95mm springs at home which are the standard size for a 25mm cartridge kit. It'd be easy enough to pull my forks apart and measure oil level and swap springs, but I'd prefer to be prepared when starting a project like that. I'm curious to know also if Ducati is consistent with their fork settings among like models.

ChrisMag

The OEM piston on the right is similar to an Ohlins piston. The one in the right is more typical of a Showa piston. The left side one will pass more oil, but might require a bigger shim stack to get the desired damping curve.

If the OEM piston is restrictive, it could be intentional if the stock springs are as soft as what is reported in this thread. As a side note, it may also explain why others have reported liking switching to a lighter weight oil.

I'm inclined to think that my initial impression of the fork is consistent with what I'm reading here... Good low speed damping, soft springs which allow some forward pitch, poor high velocity bump compliance suggesting hydraulic restriction. Anyone have a photo of the OEM piston with the shim stack installed?

ChrisMag

So, I had some time to check a couple things. Sag with me on the bike is ~41mm. I weight ~172 in street clothes. Measurement was in full riding gear, sans helmet.

Total stroke usage with me breaking as hard as I dared (disks howling) was 5" of the 7" of exposed slider. Ducati specifies 5.9" of total travel, which means some form of bottom-out must occur ~1" off the axle casting.

At some point in future, I'll remove the forks and measure mechanical bottom-out with the spring removed. I'm wondering if the hyper's fork has a hydraulic bottom-out similar to the OEM Showas on the CBR or OEM Sachs on the RSV4. If not, then I'm wondering how Ducati arrived at that specification.

Overall, my gut feeling is that oil level is pretty high as a precaution from the factory.

I spoke to my local suspension guy a bit (tunes for AFM/AMA level riders) and he agreed that my suspicion is likely. He said some of the Ducati forks have spring-only on one fork leg, and that the OEM cartridge is peen in a way which makes modifying the OEM shim stack impossible, in that once you remove the peening to take the cartridge body is apart, there's no way to put it back together.

I asked Ben about changing the oil viscosity as others here have done. He recommended against it, as the fork would likely lose enough compression damping performance to be a problem. His recommendation was to measure the installed preload and oil level, and to consider a possible change to spring rate and/or oil level.

I'll report back once we've had more opportunity to gather data and consider what, if any, changes to make to the setting.

zippy49

I've posted pics in this thread of the stock setup. It only has damping on the RHS. Although I was warned about the "peening" by another suspension guy, Racetech was able to replace the valving (w/shim stack) by machining the mounting post. In other words, they were indeed able to "put it all back together." Not a job for the average shop, though. And my sag is only 30 mm, 40 sounds like too much.

Increasing the spring rate will require more rebound damping and less compression. You won't get that with the stock valving no matter what you do with the oil viscosity or level.

ChrisMag

41mm is 27% of total travel, provided the entire stroke is available. General rule of thumb on a street bike is 25-33%. at 41mm, the available stroke is around 3.4 inches factoring that even under maximum braking yesterday, I was not able to access the bottom 1" of travel (likely due to oil level). What we don't want is a fork which tops-out quickly under acceleration, as it can lead to tank-slappers when powering out of corners, and can cause ride quality issues when the road surface falls away quickly (read: speed bumps, pot holes, etc), depending on other factors such as the top-out spring length and rate, and given how much preload is said to be installed, the top-out spring is likely to be very short and stiff.

On a typical street sportbike, 30-40mm is the target range. For reference, I run 32mm of front sag on my RSV4, for both street and track use, and that's with a 1.0kg/mm front spring, and a 140mm oil level, on a fork with 126mm of total travel (with 25mm GP Suspension) cartridges. One difference though, is that I can actually use the complete stroke on the RSV4 less maybe 5mm, but the only time it occurs is braking from 170mph on the track with a hot race tire on the front.

On to the bigger topic - the issue is not 35mm, 40mm, 45mm of sag, because functionally the fork will behave the same at any of those points in the stroke, and we're only worried about geometry. Thankfully, the Hyper has a decent base trail value and isn't on a razor's edge in terms of setup.

My primary concern is oil level. I want access to the entire stroke, less maybe 5mm. Additionally, I do not want a fork which is so progressive at the bottom of the stroke as to overwhelm the rebound damping of the fork, as it affects feel under heavy braking.

I have a lot more thoughts on the topic and the Hyper, but I'll wait until I've had more time to experiment with the setting.

gatdammit

Chris,

From a Hoon's perspective with much less technical mastery:

-My issue from day 1 with front suspension was it's abrupt dive tendency; not that it was actually stroking all the way out, just it's propensity to smash downward with quick force under even moderate grab of the lever. This could be a bit of the amazing brakes being a little on the grabby side.
-Another issue with front suspension was I had a lot of "noise" when the suspension was working in the slightest bit. Very hard to explain but, as the forks were even barely moving over normal pavement imperfections, it just felt like a port or switch was tripped to provide direct feedback to road-to-pavement connection. Under certain unloading situations or coasting on very smooth tarmac, the forks were smooth as silk. The demo bike didn't have nearly the same problem when I tested back-to-back but I also had a lot of front brake issues.
-As far as tank-slappers go, I don't think this is a problem with the stock setup but it would be a good poll for the group. I flog her out of corners and will pop the wheel up under sanitized conditions. When I say flog out of corners, I'm pretty comfortable with quite a bit of rear slip with DTC set to 1 or 0 as I straighten her up from a lean. Now, much less extreme versions of these manuevers would send my R6 ('00, albeit) bars into a frenzy. I was so used to slappers on my Yami that entering and calming them was just SOP on any given ride, and I had a couple coming down from a wheelie at 100+ mph.

I think a steering damper will be helpful in other aspects but, it wouldn't be to solve the tank-slapper issue.

ChrisMag

I wonder what the noise would be. Generally, I've only noticed noisy forks in a couple scenarios. Topping out the forks with a stiff top out spring can produce a clicking sound, as can loose steering head bearings. With the former example, the sound is metal on metal and is not dangerous to the function of the fork.

Another example is the sound of the compression check plate and spring clicking as the rebound rod changes direction. It's usually hard to hear unless the bike is moving slowly or is stationary, ie you're bouncing the frond end to test compression with the bike off. I have not noticed this with the hyper, but I usually wear earbuds or plugs when I ride.

As far as the brakes, I agree. The OEM compound does feel grabby. I wonder what ratio the master cylinder is. A possible change would be to switch to a different compound, or perhaps to install a Brembo RCS master to give some additional adjustment.

I use the rear brake a lot, which tends to reduce the initial chassis pitch as I apply he front brake. That may be part of why I don't experience a lot of dive normally. My RSV4 forks use a mid-valve stack which eliminates the bulk of the initial dive as the front loads, so that's a different solution also, but it comes at the price of more feedback on rough surfaces.

zippy49

Different strokes, I guess. Based on their level of experience, I go with Racetech's spec of 20 -25%. I got 20% when I first bolted the forks on, and I suspect it might have settled a bit. I am still quite happy with their setup. It required minimal effort on my part, too.

I don't notice any topping out, and my bike does not need a steering damper. But I don't ride with a giant topcase or saddlebags full of tools. Keeping the weight forward improves stability.

Gat, I put a GPR damper on my R6 within weeks of buying it. Now that was a twitchy and stiff ride!

BlueSwede

This is a nice thread, thanks for sharing so much detail. Suspension is a tricky matter to define and discuss, because it is subjective and depends on personal goals, riding styles, weight..... I know I want to upgrade the fork internals. My Hyperstrada 13 is just getting broken in. It is not compliant or planted over what seems like minor bumps, seams, ripples, uneven pavement. I expect my 03 V-Strom to wiggle the bars and stutter over minor bumps, but I cannot accept it with my HS. I know enough that I know I need help to pick the fork gear and the settings. I will see what Duc Pond I'm Winchester, VA says when I take it in for regular service.

greghubbs

Just like to see exactly what is inside left fork leg.
Does anyone know how to get the left fork leg on the 2014 Hyperstrada apart. Do you just unscrew the fork cap and pull? I had mine apart but it did not want to come apart, didn't pull very hard.

Right leg Went to 20 wt oil And added 45 cc oil. It does work a bit better for me, helps the dive, unstable feeling when on the brakes going in to the turns.