Chris, whilst I am always keen to promote AVO dampers, on first sight I think a standard spec AVO front damper is unlikely to cure your bottoming out problem. We tested several dampers including a newly reconditioned Koni. Looking at the chart for the Koni, I would not describe it as unsophisticated, in fact the basic shape of the bump stiffness chart for all the dampers we tested was very similar, except for the original Vincent damper.
The Vincent damper bump characteristic looks roughly like this:
The bump stiffness for everything else including the Koni was generally this shape:-
The exact shape of the curves varies a bit and there were larger variations in rebound characteristics.
But the important thing for control, comfort and control of bottoming out is where what I have called the "plateau" is.
These are the
approximate numbers for the dampers we dyno tested:
DAMPER ........... "PLATEAU" FORCE (lbs)
Armstrong .......................10
AVO front.........................25
Koni front.........................25
Vincent.............................25**
Thornton rear...................40
AVO rear...........................45
Ikon universal...................50
**The original Vincent damper, being a simple fixed orifice design has no plateau, but for comparison, in the middle of the velocity range, it produced a bump damping force of about 25lb.
Rebound stiffness's differ more widely, but are less noticeable in use than bump stiffness. (Racers may disagree Greg?) The Koni was a lot stiffer on rebound than the others. I suppose it is possible that a combination of this high Koni bump stiffness and your soft springs could be resulting in the suspension being "ratcheted down" a lot of the time.
Note that the AVO external adjustment has a much greater effect on rebound stiffness than bump stiffness, but even on max the rebound stiffness is appreciably less than the Koni.
The above numbers should be taken with a large pinch of salt, as the flatness of the "plateau" varied and I don't know if the dampers we tested are typical, especially the newly rebuilt Koni.
But they give the general picture.
I started testing the front damper with the 45lb setting used for the rear, but it was quite a lot firmer than it needed to be.
The 10lb of the Armstrong was just too lively and bottomed out too much.
Hence I settled on the 25lb setting for the front.
So Chris if you wish to experiment with a stiffer front damper, you could fit a new Ikon. AVO are a bit busy at present with the newly expanded and updated range, but in a while they might be willing to produce for you a front damper that had rear damper settings.
But PEI and others advise against compensating for under-springing with over-damping.
Obviously there is some wiggle room, as even standard D springs tend to bottom out too much with an Armstrong damper.
From my and Eddy's road testing, we found 45lb/inch springs to be usable but rather too soft. And that was without the loss of travel caused by your revised geometry.
What about the effect of the new geometry on the required damper length? Or might the springs be bottoming out?
All of this assumes that your revised geometry has not radically altered the spring and damper effective rates at the wheel.
If it has, I stand to be corrected.
.
