999S Swingarm Length and Ride Height - Ducati.ms - The Ultimate Ducati Forum
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post #1 of 11 (permalink) Old Aug 18th, 2019, 10:34 am Thread Starter
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999S Swingarm Length and Ride Height

Hi All -

In conjunction with refurbishing my track only 999S that was on stands for 6 years, I fitted new new race rubber (SC1s ver 2 - 200/55 rear). To make this happen, I needed to pull the rear axle back and install a 520 chain (100 links) with 15/40 gearing. This resulted in a swingarm length of about 502 mm. I also dropped the front forks with 3 lines showing. Please note that the forks and shock were sent out for service so springs, valving (just the shock) and oil were on target and I had "good" sag at both ends - I'm 6'2" and 220 lbs so the springs had to be changed. The ride height adjuster was set (and was always set) at 285 mm.

I did not increase the rear ride height as the rear SC1 was "taller" than the previous rear tire.

Recent track day results: bike that wouldn't turn or hold a line, rear tire shredded, front tire barely showed wear. I attempted to "dial out" the bad geometry (drop forks one more line, reduce front preload, increase rear preload) to no avail.

The question/confirmation:
Did the lengthening of the swingarm reduce my rear ride height?
With a 502 mm swingarm length, how much should the ride height adjuster be lengthened 285 mm plus X mm?

I want to try and make the 200 rear work.

Many thanks.
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post #2 of 11 (permalink) Old Aug 18th, 2019, 1:28 pm
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Quote:
Originally Posted by Butchie999 View Post
Hi All -



Recent track day results: bike that wouldn't turn or hold a line, rear tire shredded, front tire barely showed wear. I attempted to "dial out" the bad geometry (drop forks one more line, reduce front preload, increase rear preload) to no avail.

The question/confirmation:
Did the lengthening of the swingarm reduce my rear ride height?
With a 502 mm swingarm length, how much should the ride height adjuster be lengthened 285 mm plus X mm?
First things first. What was track surface temp and what kind of surface, new or old asphalt? What pressure did you use in tyre? Did you try to change it during day? Cold tear or hot tear? Did you try to change shock settings? Picture of the tyre might help..
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post #3 of 11 (permalink) Old Aug 18th, 2019, 3:15 pm Thread Starter
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Tire variables

The track is Auto Club Speedway so its a mixed bag with respect to surfaces (primarily old asphalt). I don't know the track temp but I went with the tire pressures per the on track Pirelli vendor - F32/R25 off warmers. I tried different pressures (F and R) but only up and no more than 2 lbs. For the rear, I primarily focused on increased compression (slow down). I've attached pics of the tires. The rear looks like hot tear to me. The front looks more like a tire off a commuter bike.

The input is appreciated.
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post #4 of 11 (permalink) Old Aug 18th, 2019, 5:04 pm
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Fwiw, following are my track bike settings:
Swingarm: 510
Ride height using a Ducati 999/1098 tool: 258 (I don't have the length of the adjustment rod)
Fork length: 686 (measured from bottom of the top triple to the center of the axel)
** ride height and fork length are measured with the wheels suspended / off the ground)
180/60 SC2: circumference - 2064; radius - 329

I'm 6'4", 205 w/ gear.

Hope this helps
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1998 SS FE #194
2005 749R #362
2006 999 S
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post #5 of 11 (permalink) Old Aug 18th, 2019, 6:06 pm
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Tyre heating and cooling has nothing to do with small changes in geometry. Suspension set up, ie spring and damping AND tyre selection and pressure have. And also the speed or lack of in the rider. The majority of cold tearing I see comes from the latter.
One of the riders I help out weighs 110kg and rode a 999. He had a similar issue when he first started. The faster he got the better his tyres worked. All I changed was spring rate. Now on his Pani the suspension is still stock with a change in the spring rate. His tyres wear and grip perfectly. Since he started 3 years ago he’s dropped 10-15 seconds and 20kg. Food for thought.
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Last edited by xracer; Aug 18th, 2019 at 6:37 pm.
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post #6 of 11 (permalink) Old Aug 18th, 2019, 7:04 pm
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Something is out of whack... The tire surfaces should be smooth as silk.... Possibly too slow rebound as well.

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post #7 of 11 (permalink) Old Aug 18th, 2019, 7:56 pm
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25 psi rear might be slightly low but probably not too bad. I think 26 -27 is what I use hot for the sc2 rear. The sc1 will prob heat up even more. Your wear doesn’t look too bad from those pictures. If you don’t work the front hard you won’t see a lot of wear on it. Could be how you ride.

Your front settings might be too stiff if you feel the bike isn’t turning well. How much of the front fork travel are you using? Zip tie should be close to the bottom if you’re using one.

Honestly there are many things to discuss but difficult over the internet.

FYI my 999 only has 1 1/2 lines showing on the fork and I run the 180/60 rear. Turns great. You might have that 200 so flattened out seeing as you only have a 5.5” rim. Try a 180/60 SC2. I bet you will like that better. You might need to raise the front though.

I’m personally not a fan of slamming the front down. I’ve tried it in the past and the lack of trail is not great leaned way over imo.
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post #8 of 11 (permalink) Old Aug 19th, 2019, 1:37 am
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Quote:
Originally Posted by xracer View Post
... speed or lack of in the rider. The majority of cold tearing I see comes from the latter.
Quote:
Originally Posted by superfly999 View Post
.. Could be how you ride.
... yup, more rolling speed .... maintaining momentum.


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post #9 of 11 (permalink) Old Aug 19th, 2019, 3:36 am
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is the chain too tight?

know all wanker
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post #10 of 11 (permalink) Old Aug 19th, 2019, 8:17 am
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Quote:
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is the chain too tight?
Ah! Good one!


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