Ducati.ms - The Ultimate Ducati Forum banner
  • Hey Everyone! Enter your bike HERE to be a part of this months Bike of the Month Challenge!

1 - 6 of 6 Posts

·
Registered
Joined
·
337 Posts
Discussion Starter · #1 ·
First let me start off by saying I've read all the old threads/papers. All of them. No seriously, all of them. I'm familiar with the 'common good numbers' for trellis framed Ducati Superbikes. One thing I always found weird was the hangup on rear ride height measurement. People counting threads, people counting distances using tools from different manufacturers etc. Ultimately, are we not chasing the proper swingarm angle not necessarily ride height?

Here's the hardware being used
998 Frame
Podium Racing clamps - 28mm offset inserts currently
Ohlins FGRT forks (standard length and caps) forks flush with the triple trees (only the tapered edge and cap are above)
Corse Dynamics rear ride height adjuster
Factory ohlins rear shock
98 link chain with rear tire as far as rearward as possible for maximum swingarm length (15-40T sprockets)
180/60 rear SC1 (656mm diameter) and 120/70 front SC1 (604mm diameter)

Everyone knows 23.5* or 24.5 degree is possible using the eccentric steering head with 916-999, but has anyone actually measured them at home? I use a little digital angle finder (and "verified" with a phone app). With my 998 head angle in the "23.5" position, I'm actually seeing 22* measured on the fork tube. I've measured this with the rear on a pitbull rear stand as well as with the bike resting on it's own weight and repeatedly show between 21.9* and 22.3*. Awfully steep.

Swingarm angle measured with both tires just off the ground and bike very close to level (jackstands under pegs and headlift stand as low as it'll go) = 11* exactly
This resulted in a "ride height" using Corse Dynamics ride height measuring tool of 256mm as measured from top edge of the tool to the center of the rear axle.

I have ridden the bike in this basic configuration (but with slightly lower rideheight front and rear) and it felt really good with the exception of dragging bodywork on the ground a little bit and running toward the outside of the track under throttle. I was hoping increasing the swingarm angle (previously apprx 9* measured in the same manner) would help correct this as well as gain me some ground clearance.

As an aside, I also have a Triumph 675 and have measured it's front end to be Apprx 21.5* resting on it's own weight. So I'm assuming the measuring device is pretty accurate. So has anyone actually measured their 24.5* or 23.5* angle to see if they were actually as advertised?
 

Attachments

·
Registered
Joined
·
337 Posts
Discussion Starter · #2 ·
Update:

These measurements are extremely sensitive to the bike being level when the suspension is fully extended. After all, we're talking about a degree or 2 over the length of 500+/- mm. I swapped the rear sprocket to a 39T from a 40T for my home track as I was running out of gearing. This lowered the rear of the bike apprx 7mm. I ended up with a 248mm measurement using my ride height tool (top of tool to center of axle). This resulted in exactly 11* of swingarm angle as measured with both wheels hanging in the air and both tires within 1" of the ground.

After setting the bike down on its weight, I measured front rake and saw 23* exactly. I've not yet measured trail, but calculating it I should be in the 97-98mm range.
 

·
Premium Member
Joined
·
5,151 Posts
I am assuming that this is a track bike. Use the chassis numbers are for reference only. Don’t get fixated on them. Always set your bike up when YOU are warmed up and settled in with consistent lap times. Then play with the bike and record what you are feeling, the lap times and the chassis numbers. It’s unlikely that you will be happy with ALL parts of a track. It’s important to focus on the fastest parts as that’s where you gain the most time. I included gearing in this as well. Swing arm angle affects traction so keep it more or less the same for every gearing setup.
Adjustable clamps are best. 28 offset is good for tracks with HIGH speed corners and 30-32 for tight tracks. More trail equals more stability and feel in high speed corners and less trail for tighter.
 

·
Registered
Joined
·
337 Posts
Discussion Starter · #4 ·
Yes this is a track/race bike only. Last time out was only my 2nd day on this bike, so I’m trying to get it all dialed in.

I was shocked at how quickly an ‘old heavy’ bike steered, nearly as quickly as my Triumph 675. The Ducati did however squat quite a bit on exit even with correct preload on the spring. It’s a factory spring and linkage, so it isn’t perfect, but should be perfectly adequate.

Checking over the bike and my notes after the event I find the swingarm angle was quite flat, increasing this should aid in antisquat and help drive the rear tire into the pavement while keeping the front planted under corner exit.

My home track is quite fast with sweeping esses that are taken in 4th gear somewhere around 110mph. I’m hoping to feel even more comfortable next time out.

I also chose to raise the entire bike a bit because I was dragging the belly pan in some areas. So by increasing ground clearance and getting my far ass off the seat more, I should eliminate that issue.


Sent from my iPhone using Tapatalk
 

·
Retired Pipe Polisher C2H6O+
Joined
·
19,081 Posts
Oh what a twisted rabbit hole you’ve dove into. :)

Measurements based on what smart and fast people have come up with are great places to start. But from there you have to make the bike handle the way you want it to for you.

Best advice I ever learned is from that starting point, when you start going fast enough to matter, remember going into a corner is generally controlled by the front of the bike. Coming out of the corner is mostly the back of the bike.


Sent from my iPhone using Tapatalk Pro
 

·
Registered
Joined
·
3,531 Posts
if it has a factory 64 spring on the ohlins shock that's probably too soft, depending on how much you weigh. get the springs sorted for your weight first. that may help with the clearance issues too.
 
1 - 6 of 6 Posts
Top