FOUND THE HIGH SPEED WOBBLE PROBLEM

As most of you know, I had been tweeking with tire pressures to get rid of a wobble I had at about 80 mph.
I found that 32psi was the best, BUT, I still had a bit of a wobble (not much) but when I was following a big trunk or semi, the wobble would return at 72mph. This got me thinking, and I had read somewhere on here, that the rear CT would amplify any turbulence caused from riding on windy days, and/or when following big trucks.
So I removed the windshield to test it out, and still no difference, which in a way I was glad, cause I like being protected from bugs and stone, and even rain to a degree. So through the process of ilimination, I realized the shield was ok. So I figured, the problem must be coming from the rear of the bike. I have a large fiber glass trunk on my luggage rack, so I decided to remove it, and see what that did. BINGO !!!!!.....up to 95mph, wobble was "totally" gone !!....I mean ZIP, NADA, as in NOTHING !!!!. I then pulled over, and waited for a large semi to drive by, then chased it. It's a very windy day here today, and the trucker was doing about 70 mph, and I tucked up behind him, playing with various distances from the trailer to test, again NOTHING !!! I could feel the wind around me that he was creating, but no back and forth wobble like before. SO, obviously, on windy days, following trucks, or riding at 80+mph, the wind would hit my rear trunk, causing turbulence on the rear of the bike, which would make rear swagger from side to side a bit,, however, it would amplify and transfer that small wobble to the front of the bike, making the front feel light, and as if something was loose etc. Go figure !!! lol
Anyway, I thought I'd share this with any of you who have an aftermarket rear trunk, and are having wobble problems at high speeds.....this could the cause of your problem as well.....worth a try. (took me 10 minutes to remove the trunk a luggage rack)
As for my rear trunk, I only really need it when I'm on weekend overnight trips, and I usually am not hitting the throttle as hard on those kind of rides, meaning I usually don't ride over 75mph, and that would be only to pass another vehicle or truck. It pays not to give up, so I'll be staying DS now for sure.
Hope this has helped someone (God knows you people have helped me enough )

Good find!!! Thanks for the data!



.....................bobby

I am new to this Darkside riding, need new tires, want to try the Darkside riding.
Question I have is what size tire will fir this bike, I have been reading and from what I have seen the tires for the 1500cc like the Vulcan Classic or Nomad both must have 16" rims for the tire sizes shown have all been 16". Which brings me to my problem which is my rims are 17", so can I just do the same size but do it in a 17" or is there a different combo?

I have arranged fro a place to install the tire but not sure which size is preferable......help please....I'll check back today or I can be reached at email slj22@live.com

Thanks in advance!!
Steve James :

What size bike tire do you have on there now ? e.g. 205/55/17 If that's the size, a 205/60/17 car tire would fit your Mean Streak almost perfectly and correct your speedo error if you have an electronic speedometer instead of front wheel cable.
Here's some important data that can help you with some of your questions.
http://darkside.nwff.info/

Interesting thing about the air pressure, Dudester. If it ever stops raining and is warm enough here, I may try lowering the pressure beyond the point where it feels 'mushy', to try and get ride of the over 100 MPH wobble that's still there on the Concours and not on the 900C. Using same brand tire for both.

Fly wrote:Interesting thing about the air pressure, Dudester. If it ever stops raining and is warm enough here, I may try lowering the pressure beyond the point where it feels 'mushy', to try and get ride of the over 100 MPH wobble that's still there on the Concours and not on the 900C. Using same brand tire for both.

It could be the different geometry of the two bikes and one might require a different air pressure than the other bike.


...........................bobby

Fly wrote:Interesting thing about the air pressure, Dudester. If it ever stops raining and is warm enough here, I may try lowering the pressure beyond the point where it feels 'mushy', to try and get ride of the over 100 MPH wobble that's still there on the Concours and not on the 900C. Using same brand tire for both.

I tried that too, but it didn't fix my problem. If your Connie has a rear cargo trunk, try removing it, you may be surprised. However, the Connie's saddle bags and tail end are set very high compared to the front, because of the height of the exhaust pipe, so the saddlebags alone could be causing the turbulence. By lowering your tire pressure below the mushy feeling, and attempting to test ride the bike over 100+ is something I really wouldn't recommend. Your wobble could get increasingly worst, to the point of losing control, your tire bead could come off the bead due to the low pressure and high speed, and you Sir, would become part of the scenery in bits and pieces. Not trying to scare you, but rather just give you a reality check here. I know if you're like me, you want that "right" to be able to do those speeds if you have to, but from what I've experienced, tire pressure is a very important factor for DSing, however, to me, if you haven't found it by trying 30 to 42psi, chances are, it's not a pressure problem. Just sayin, be careful Dude, and ask yourself....is the wobble really that important at over 100mph ??

Thanks for the reply, I am running 170/60-R/17 Meztler German tires (sp)
So I should be able to use a Hancock Optima 170/65/17 with a width of 5.5 inches

stvjas wrote:Thanks for the reply, I am running 170/60-R/17 Meztler German tires (sp)
So I should be able to use a Hancock Optima 170/65/17 with a width of 5.5 inches

Didn't know they made the Hankook Optimo H426 in that size. I'm running a Metzler ME880 up front. If you get the Hankook for the rear, you are going to love it. The ride is sooooo smooth, and it corners like it's on rails. Also very very quiet tire....all you'll hear is the wind and your engine. (and I have stock pipes)
Do you run tubeless or do you have spoked wheels ? If spoked, you'll need to replace your rear tube, with another 'bike' tube....don't reuse the old one.
Let us know how you like the DS once you get it on and tested.
Good luck.

Fly,

What tire(s) have you tried on the Concours? Using an Eliminator 15" wheel I have tried the Nankang and it had too much side wall flex, Federal which works well but has a slight wobble at 90 plus. And on the stock 16" wheel the Vredestien Comtrac that is a van/light truck tire providing approx 5% overdrive, hard compound and was good for dry riding but no miles on wet. It likely would have less traction in the wet. Likely a very high mileage tire and will use it on a LD ride.

Fly wrote:Interesting thing about the air pressure, Dudester. If it ever stops raining and is warm enough here, I may try lowering the pressure beyond the point where it feels 'mushy', to try and get ride of the over 100 MPH wobble that's still there on the Concours and not on the 900C. Using same brand tire for both.

Fly,

OK, read on the wobble thread you are using the Vredestien.

[quote="Danodemotoman"] Fly,

What tire(s) have you tried on the Concours? Using an Eliminator 15" wheel I have tried the Nankang and it had too much side wall flex, Federal which works well but has a slight wobble at 90 plus. And on the stock 16" wheel the Vredestien Comtrac that is a van/light truck tire providing approx 5% overdrive, hard compound and was good for dry riding but no miles on wet. It likely would have less traction in the wet. Likely a very high mileage tire and will use it on a LD ride.

I've got a Verdestein light van tire on the Concours, same as on the 900C, but different sizes. There is no trunk on the Concours, but there is a 3 gallon fuel cell where the trunk would normally be.

Right now, time just isn't there to do much testing, but I will take the fuel cell off and give it a try. Try to remember to post here if it works or not.

My Vredestein is fantastic in the rain, even has braking power almost as good as a MT in the dry. I said "almost". Wet is wet.

quadancer wrote:My Vredestein is fantastic in the rain, even has braking power almost as good as a MT in the dry. I said "almost". Wet is wet.

That is one of the first things I noticed about the Vredestein on my Concours. On wet pavement, coming out of a sharp corner, twisting the throttle too hard will slip the rear tire, much more traction on the car tire than with any of the bike tires I've had in the 88K miles on the Concours.

Fly wrote:

quadancer wrote:My Vredestein is fantastic in the rain, even has braking power almost as good as a MT in the dry. I said "almost". Wet is wet.

That is one of the first things I noticed about the Vredestein on my Concours. On wet pavement, coming out of a sharp corner, twisting the throttle too hard will slip the rear tire, much more traction on the car tire than with any of the bike tires I've had in the 88K miles on the Concours.

Not to mention quite a rooster's tail compared to the mc tire too.

Dudester60 wrote:

Not to mention quite a rooster's tail compared to the mc tire too.

That's there for spraying your buddy behind you.