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General Category => General Discussion => Topic started by: OlderSlower on August 09, 2016, 08:23:30 AM
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Weird, but important problem here. My 2009 Norge feels very unstable when in turbulent air. It isn't tank slapper unsteady, but it is significant. Here goes with the description of when it happens: when on the freeway passing some, but not all semi trucks, when there are some odd side winds, I notice it especially in mountainous terrain when one side of the road has hill or going through a valley. It happens mostly when bags are on. As for modifications to the bike that may impact situation: Large California Scientific windscreen in highest position, Helibars, Tank Bag, Russell seat which raises me at least an inch, Matris fork update and Matris shock, Michelin Pilot Road 3's with 4000 miles. Steering head bearings, adjusted, tire pressure 41/36. Bags minimally packed.
When on two lane roads it tracks straight as an arrow. I don't recall it ever happening when I ride without the bags on, and I have ridden at 100 mph+.
I have a feeling it may be my beloved California Scientific windscreen, but I don't want to lose my still air riding pocket.
Please bestow wisdom, I am perplexed and in need...
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Could be you need to relax your grip on the bars.
Have you tried taking your left hand off the bars when the weave happens?
My Quota was bad about this on the interstate around trucks. 90% solved when I'd release my grip on the left bar.
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The windscreen is probably the culprit. Does it change if lowered? Can you try the stock screen?
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Is 41/36 PSI what the wise heads and manufacturer recommend?
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I try to be conscious about the light grip, but understand the point. I'm going to switch out the screens and see. The odd thing is that it seems to happen more often than it used to which leads me to think of tire issues. PR3's are supposed to be great, and I love the way they handle, but I do have a bit of a flat spot from so much straight up riding.
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Hasn't someone solved the problem by installing a top trunk ?
Dusty
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Air pressure as recommended, but open to try options, ideas? All input is much appreciated !
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Ha ha on the trunk! I'm an old guy and learned that one in 1978.
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Ha ha on the trunk! I'm an old guy and learned that one in 1978.
We're all old guys :laugh: Seriously , one of our Norge owners solved this problem with a trunk .
Dusty
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My guess is the larger envelope created by the bigger wind screen has increased the low pressure area immediately behind the rider, increasing the Karman Vortex Street problem.
Air alternately filling the void behind the rider from the left and right, contributing to the weave. The rider increases the weave by instinctively holding tighter on the bars.
Try running with a passenger, or a large duffel bag on the passenger seat and see if that changes things.
Something as simple as adding a couple of Vetter pop vents to the screen may work. Or, you may have to lose the large windscreen.
On my Sport 1100, I've found it to be much more aerodynamic with a duffel bag or tail bag immediately behind me.
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Wow, I never would have believed that. I am really not a trunk guy, minimalist here and probably can't change that part...
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A duffel bag or trunk smooths the trailing airflow .
Oh , a true minimalist rides naked :laugh:
Dusty
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Never heard of the Karman Vortex Street problem. could putting the tank bag on the passenger seat be big enough to impact the aerodynamics? I understand it is probably a try it and see issue, but just asking...
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well, that riding naked stuff is for a different forum...
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Never heard of the Karman Vortex Street problem.
If you've ever been behind a semi-truck and felt the left/right alternating buffeting, that's it.
Here's a pretty good explanation:
https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_vortex_street
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In terms of aerodynamics, better to leave tank bag on tank and add duffel bag to passenger seat or leave tank bare and put tank bag on passenger seat? I am grateful for all of the feedback, I really want to solve this problem.
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Rocker 59, that is how it feels, a left right buffeting.
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Are you feeling any updraft ?
Dusty
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Not sure what "updraft" feels like, so I don't know.
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I know it sounds counter intuitive, but would travelling without the saddlebags and just a duffel bag on passenger seat be an aerodynamic improvement?
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Rocker 59, that is how it feels, a left right buffeting.
That's air rushing in to fill the low pressure void created by the windscreen.
In your experiments, change one thing at a time. If you normally run with a tank bag, leave it in place.
Add a duffel bag placed longitudinally, running from the passenger seat onto the luggage rack.
This is my camping gear on my Sport 1100.
(https://photos.smugmug.com/Motorcycles/2010-May-22-MGNOC-25th/i-qCxp6Zw/1/O/DSCN6008.jpg)
The Cortech tail bag works well, too.
(https://photos.smugmug.com/Motorcycles/2015-June-18-Western-Adventure/i-qrZrzT9/0/M/DSCN4627-M.jpg)
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Wisdom appreciated, going to investigate options!
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Something as simple as adding a couple of Vetter pop vents to the screen may work. Or, you may have to lose the large windscreen.
vent the negative air behind the screen. note how a Swannee fairing has opening at bottom to let airflow inside the shield.
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There is a vent at bottom of the screen
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At the Minnesota rally this summer I met a Norge rider from Iowa who had a taller screen, he had an opening shaped like a cross the opening was at least 1-1/2 wide , probably 3 inches tall and 2 -1/2. Inches side to side, it was centered near the lower attachments on the shield, he claimed it made the ride quieter and less turbulent, and his windshield had no bug guts on the inside lower like mine gets.
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Olderslower.....rer ead you post a couple of times. You said the problem is more pronounced with the bags on and while passing a semi-truck, going through a ridge cut on a highway. Sounds like you're getting crosswinds coming down that valley. The bags will catch it like a sail. More weight on the back helps. Loosen your grip and lean into the wind. Possible that upping the front tire air pressure may help. 40psi. We have some mean crosswinds out here when crossing ridge cuts and the small valleys. Winds will be 25mph+. Most of the friends with bags will make the same comments about crosswinds being strong. I normally on a day ride don't use the bags.
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I swapped out the tall screen for the original one, kept the bags on and played on the freeway for an hour. Bike was rock solid passing semis at 80+, well OK around 90+. Also cruised behind semis and tried to get in the turbulent zone; I felt some wind as is normal, but bike was solid. I guess I am going to keep the stock shield on for now, but will experiment with the input that I received today. Thanks so much for all of the info! Nice to solve a problem and learn some new stuff. BTW, I loved my California Scientific windscreen, it's an excellent product, and I had one of the funniest conversations ever when I ordered it. I forget the name of the guy I talked to, but he was hilarious... Maybe I will order one of their tinted shorty windscreens, might make me look trimmer.
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Maybe an option for you here:
I have been running a Cal-Sci Tinted shorty now for a couple of years, and had a Cal-Sci medium that I tried only once or twice...it was too buffeting for me and too tall even in the lowered position as it was in my sight line.. I ended up selling the medium on Ebay for a nicely reduced price - a mistake I later found out as I should have kept it...
Just a few weeks ago, after getting back from the National, I called Cal-Sci and talked to them about making me a Custom screen - same width as the Medium (also with the vent), but only 1 inch taller than the Shorty. The guy at Cal-Sci said..just send me back your Medium and we'll cut it down for you...unfortunately I had already sold it several months ago.
So...lessons learned - you can get it cut to the right height...I'm very pleased with my new "tweener"...wide as a Medium, just a bit taller than a shorty, no buffetting, much quieter air at the helmet level and very stable when passing trucks.
Hope that gives you some options to think about as well...if you want to try the Tinted Shorty, let me know, and I could sell you mine (2008 Norge)...
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Not sure what "updraft" feels like, so I don't know.
How long have you been riding a MC with body work including a windshield? First thing you have to learn is to adapt to your vehicle. You are reminding me of a guy I knew who bought a new ST1100 Honda who 2 weeks later sold it because he couldn't accept how it felt in cross winds. Normally Guzzis are not effected much by cross winds like some other bikes.
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Yep, the more air your bike 'moves', the more you will feel the buffeting.
If your bike creates a nice 'bubble' around you, the feeling will be worse for two reasons.
First, being in a bubble that is constantly being 'burst' by the turbulence feels much worse than the turbulence itself. Where being on a naked bike you feel all the turbulence all the time, so a little more doesn't feel bad.
Second, those vortices are behind your 'bubble' too so they are effecting your bike's motion. If you change to a slightly smaller screen the 'bubble' collapses at your shoulders, which causes a lot of smaller scale turbulence, which you do not feel as much. Again, with no larger vortices behind you then additional disturbances are felt less as well.
This is also the reason why packing some stuff on the bike behind you will lessen the effect of external disturbances, they move the majority of the turbulence further behind you, and, it 'breaks up' the larger 'swirls' into smaller ones.
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Thanks again for all of the ideas and information. I have had lots of bikes over the years, with and without bodywork. I expect some wind turbulence with bags and fairing, this situation was significantly different and frankly I am surprised at how much difference the changing of the shield made, both positively and negatively. I am an old guy who likes to think he is a freaking genius, so thanks for giving me some new information to tell young riders who make the mistake of talking to me about bikes. I sometimes see their eyes glaze over as I pontificate. Seriously, I really appreciate all the help from this forum!
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There ARE downsides to wrapping your ass in too much plastic and plexiglass. It's a motorcycle!
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Good point Cam, it's a challenge to know when to say when. Glad I have a retro cafe new Bonneville for bare bones fun.
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Best fairing to sit behind is a Jammer in the day. Oh..... :1: with Charlie B.
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Best fairing to sit behind is a Jammer in the day. Oh..... :1: with Charlie B.
Best MC fairing I've ever had is on my Guzzi CX100, Rifle Sport (15" windshield) fairing on 750 Breva, and MP3 400 w/ aftermarket windshield. :thumb: Some Maxi scooters have the best weather protection, period. They out perform MCs because they protect your feet, legs better too. :thumb:
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Full SP1000NT is better than the CX100. I have both and ridden both in heavy rain.
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Full SP1000NT is better than the CX100. I have both and ridden both in heavy rain.
I find the SP fairing too close to my knuckles on a SP. On the CX I just hunker down a little and @ 65 mph the rain goes right over the top of me. On my Aprilia Scarabeo 500 GT or 400 MP3 scooters it's much better for more rain protection. :thumb: + on the MP3 you have no worries about the front tire ever washing out on you even in corners. :boozing:
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:1: on your impressions. I guess the SP1000NT is a better fit for me and don't have the problems that you have. On CX100, slide the bum back on the seat and hunch down low for protection. I agree on the BV500 and MP3. Both underrated rides.