MrGrumpy wrote:I guess one man's tank-slapper is another's minor wobble....
In more ways than one - there are a huge number of variables even on the same type of bike. Not just centre of gravity but the relationship to the wheelbase etc.
Perversely, the better the aerodynamics, the more effect minor changes will have.
First off, adding weight and aerodynamic surfaces clearly alters handling, it is measurable and repeatable.
Often it isn't enough to be noticeable but even when it is you can get different opinions because the riders weight and riding style etc are all part of the equation and if you don't do 120 you won't know that there is a problem at that speed. If you ride with a pillion it will mask the weight of the top box and will also place it in the aerodynamic shadow of the pillion.
Perception comes into it too. Irev has done test riding for boffins so he is familiar and experienced with what to look for than others might be. However, even experienced testers can't always be trusted. I've had testers say that cars were faster purely because it was louder, had more induction noise or their seat had been lowered- even when it was slower according to the stopwatch.
Most riders will just adjust to the bikes new dynamics without realising they have done it and serious changes probably won't show unless you are at the edges of the performance envelope - either because you are a hooligan or in an emergency.
Does it matter?
Most of the time, no, but occasionally it can matter a lot
As Irev mentioned he was involved with one case (Hyabusa I think?) but some here will remember that the police in the UK, Europe and other countries withdrew their ST1300's from service . An officer died here in the NW and several were injured when their bikes became uncontrollable at speed. The heavy loads panniers and other additions were shown to cause violent wobble at high speeds
If you haven't cut your throat from boredom I put some stuff about aero effects I'd top boxes etc in this thread when we discussed it before
http://www.maxi-muppets.co.uk/forum/viewtopic.php?f=5&t=13867