Not only friction but the geometry of it all. Like I have said before, I have never been able to install any of the springs without them being hugely "Topped out" this means that you have to shorten the springs, or at least one side. That last Comet I did, after i installed the 33 or 36 Lb springs with the front shocker left off, it would readily bottom out, well the outer spring case would hit the front of the lower fork lug. I did trim some off the inner and outer spring cases, the inners were like a knife edge at the top anyway. With anything but the softest action shock absorber on there, the front end felt heavy and stiff. It was a juggling act between springs and shock absorbers, ending with a pair of 45 Lb springs with about 25 mm chopped off both, and an original Armstrong shock absorber used. The Thornton I had (brand new) worked very well, but I would not part with it, the second hand Koni was probably a bit stiff (heavy) even on its weakest setting, and the AVO was way too stiff..............Anyone with an AVO on the front of their Comet is going to have a very stiff action front end no mater what springs they use, the bike simply does not have enough weight to overcome the set up of that shock absorber. I have used the stock Vincent shock abosrber, (I think this was one of the new ones available from the Voc spares co) at full extension it's action was very stiff, almost felt like it was locked up, until the suspension compressed with a rider on, and then it felt ok. It is possible with that design that at full extension the upper bushes in the shock internals are binding as the piston is trying to overcome the rod bushes friction, and this gets better if the shocker starts to move further down its travel. I would recommend he use another type of shocker. He needs to back off the spring pre-load, cut the springs down so the suspension is not topped out.......................This goes for all of you trying to install this setup........................... Done about 30 or so of these now...................