Ducati Monster Forum

Moto Board => Tech => Topic started by: K3V1N on July 02, 2012, 06:54:55 AM

Title: Paging suspension experts! S2r1000
Post by: K3V1N on July 02, 2012, 06:54:55 AM
So I'm fine tuning my suspension setup. So far it has new RT spring and valves up front, the sag has been set and damping and rebound adjusted. There is a lot more damping now then the stock setting.

Here is my question I seem to have a slight vibration or semi rhythmic bounce right around 40 mph. It feels like the road has slight washboard bumps when it's smooth. It happens with at different RPM ranges and with the clutch in. Has anyone else experienced anything like that and if so what might make it better.

I brought the front down 5mm to help the bike turn in but I don't think it was needed I might ether bring it back up or lower the rear a touch. I'm shorter and not tracking the bike that is the only reason I would come down in the back.

I don't think I noticed the vibration before I switched to a Pilot Power in the front and did all the adjustments but maybe it was there.

Any feedback is welcome.

Thanks! 
Title: Re: Paging suspension experts! S2r1000
Post by: Slide Panda on July 02, 2012, 07:17:12 AM
Is the tire balanced properly? I'd confirm that. Vibrations right after getting a new tire fit might be down to the tire. A little harder to tell as you changed out other stuff at the same time - but I'd start there.
Title: Re: Paging suspension experts! S2r1000
Post by: K3V1N on July 02, 2012, 07:26:29 AM
Thanks for the reply Panda,

I thought the same thing, plus the weights on the wheel were in 2 spots with made me question the balance. But I had them re spin it on their computer balancer and had someone else static balance it. It might have a extra weight on it but it is weighted right at least I hope. If I try everything with no change I might buy a balancer to check it on.
Title: Re: Paging suspension experts! S2r1000
Post by: ducpainter on July 02, 2012, 07:30:44 AM
You can check balance staticly on the bike.

Remove the calipers and tie them out of the way.

Raise the front and spin the wheel.

It will show an unbalanced condition.
Title: Re: Paging suspension experts! S2r1000
Post by: Slide Panda on July 02, 2012, 08:08:57 AM
Money is still on a balance issue - though you seem to have investigated that

But - how is your rebound set? it should take about 1 second for the bike to fully (100%) return to neutral after one bounces the suspension.

Too little rebound will allow for 'pogoing' Too much, and the suspension will pack down and not be able to recover in time over rough sections. Rebound is the easier to ballpark in the garage. Compression is tougher - in the absence of any other info a good bal park starting point for compression is to take stock of how much adjustment (# of clicks, turns etc) and set to the mid point of the range and give it a ride with a zip tie on the fork leg. Given that your springs/sag are correct that zip tie, and your feeling/preference can help you tune that compression. 

Hallmarks of too much compression - harsh feeling ride where you feel every pebble and larger bumps give you a shot. Reduced effect of brakes. Feeling that the front is pushing or hard to tip in.

Hallmarks of too little compression - Mushy vague feeling. Front dives under brakes, unstable in the bends

http://www.gostar-racing.com/information/motorcycle_suspension_set-up.htm (http://www.gostar-racing.com/information/motorcycle_suspension_set-up.htm)
Title: Re: Paging suspension experts! S2r1000
Post by: K3V1N on July 02, 2012, 08:29:35 AM
Thanks this is helpful.

The suspension on the 1000 is the first work other than mounting tires I have had done by a shop in 10 years of riding. They did a AWESOME job. I didn't want to mess with taking forks apart right now. The bike feels so much better after their work and lowering the front a tiny bit was something I asked for.

Suspension work is the one thing I haven't messed with much since my other bikes only really had rear adjustment. But even with a great baseline I'm guess I'm going to have to adjust and feel everything for myself. I will have to back out the current settings so I know where it is now and start making small changes and testing.

If anyone does read this and has had some bouncing or vibration around 40mph let me know what you did to improve it.
Title: Re: Paging suspension experts! S2r1000
Post by: Slide Panda on July 02, 2012, 09:47:03 AM
Be sure to record the current settings!  [thumbsup]
Title: Re: Paging suspension experts! S2r1000
Post by: K3V1N on July 03, 2012, 09:47:20 AM
Update!

I had someone that I trust ride the bike. They told me to check for a out of round tire. I did and it seems like it is out of round. I'm going to see if it can be re mounted to fix that or if I need a new tire.

Title: Re: Paging suspension experts! S2r1000
Post by: K3V1N on July 10, 2012, 12:22:43 PM
Update, Looks like I have a bent rim :(  I'll have to deal for now and send it out to be straighten this fall.