My new trunk and the high speed stability issue.

[red2003]

Just installed my new trunk last night. Got to take the bike for a test ride today and at speeds above 45 mph, the rear of the bike is borderline dangerous. It feels like you are running close behind a truck in the air wake, but there's no truck! I have seen several posts here lately about stability issues. For my bike the trunk really messes up the aero. Luckily it's a quick release style (30 seconds on and off), and I will only be using it for trips to the grocery store once in a while.

[daveJ]

make sure your rear tire is lined up to the front

[red2003]

Originally Posted by daveJ

make sure your rear tire is lined up to the front

No, it's definately related to the trunk. I have over 2000 miles on this bike and have never felt this until now.

[alonzo]

Looks good,

I do like the trunk and the fact that it is a quick release really makes it a handy item to have.

can you tell me where you got it from? and it it big enugh to put a helmet inside?

Thanks

[katoranger]

I have no troubles related to my trunk unless I load it down with heavy items. I even strapped a little tykes plastic slide to it and crusied a 55mph home. I got some looks.

Maybe you need to add a spoiler to the lid for more downforce. 8O

Allen

[fatboy250]

Interesting. I haven't had any major issues, but mine isn't as "tall" as your's appears to be. One thought though, could you mount it in reverse. It appears to be more aerodynamic the other way.

[kczukiman]

Whats weird is that the box isn't that wide.You would think the box would be sheided by the rider for the most part.

[theENIGMATIC]

Yeah.maybe you could position it different so it is easier to handle?
Either that or tie on the back of the seat :wink:

[red2003]

I bought the trunk on eBay. It was a scooter take-off. Bolted right on, and is definately narrower then my body is, but it IS the cause of the aero instability. I pulled it off tonight and the wiggle is gone. I'm not worried about it forcing me off the road or anything, it is just not as planted in the rear as it was. Doesn't begin to wiggle until I am up to roadway speed. Just thought I would throw that out there as info. BTW, my bike is still getting 80 - 90 + mpg. Not bragging or boasting, but the fill-up today was right at 92 mpg. Mileage verified accurate. Amazing.

[fatboy250]

Awesome! I know Dad said he's gotten over 80 several times, but I just calked it up to Dad math Then too, I do weigh 250lbs and he's only 180lbs...So me getting 75mpg is pretty good.

[lego1970]

I don't know if these bikes have adjustable suspension, but on my sportbike I would have the same problem (at real high speeds) when I put on the saddlebags and roll bags and like you, it was aerodynamics not the weight that caused the problem. The drag pulling on the rear of the bike would make the front loose, so I clicked one on the preload, front and back, then barely increased the compression and rebound. I'm not a suspension tech, but it did smooth it out and that was without a steering damper. I thought I saw where you put an R-1 shock on, that's pretty interesting. Good luck, thanks for the info.

[red2003]

Originally Posted by lego1970

I don't know if these bikes have adjustable suspension, but on my sportbike I would have the same problem (at real high speeds) when I put on the saddlebags and roll bags and like you, it was aerodynamics not the weight that caused the problem. The drag pulling on the rear of the bike would make the front loose, so I clicked one on the preload, front and back, then barely increased the compression and rebound. I'm not a suspension tech, but it did smooth it out and that was without a steering damper. I thought I saw where you put an R-1 shock on, that's pretty interesting. Good luck, thanks for the info.

That's not a bad thought. I DO have the R1 rear shock. It has 27 position clickers for rebound and compression. I may have to play around with them a little. Thanks for the idea!

[ambassador]

Red,
I thought you were a physics major or something??? Didn't you custom build your own scissor shock linkage/ R1 shock/ 105 inches of travel or something of the sort???
Just messing with you bro, when I ride 2 up I feel a big difference in handling but I guess that's true for anybike.. Do you notice it when the carrier is full/has weight or is it the same when it's empty? As far as aerodynamics I'd think your body would block most of the wind flow, I'm sure you'll figure it out...

[red2003]

Originally Posted by ambassador

Red,
I thought you were a physics major or something??? Didn't you custom build your own scissor shock linkage/ R1 shock/ 105 inches of travel or something of the sort???
Just messing with you bro, when I ride 2 up I feel a big difference in handling but I guess that's true for anybike.. Do you notice it when the carrier is full/has weight or is it the same when it's empty? As far as aerodynamics I'd think your body would block most of the wind flow, I'm sure you'll figure it out...

No, Mathematics Begree, Physics minor. Yes custom scissor, yes R1 clicker, no not 105 inches of travel. Seriously though. I haven't even loaded the trunk yet. The wiggle happens with NO WEIGHT in there. The trunk and mount is all plastic and maybe weighs 5 lbs total. It's gotta be a funky aero deal. Maybe it'll be better WITH weight in it to stabilize it some. I have ridden two up before with my son who weighs 110 lbs, and the bike rides and handles fine. Dunno.