I think that a problem here is that bump stops are different on different dampers. I don't have a Thornton to look at but I do know that the one on the AVO is specially shaped to give a more progressive stopping action than is obtainable just from the material used. My understanding is that Chris was finding it difficult to distinguish between too much or too little damping, too much preload or not enough and exactly when the bump stop was being hit. The measuring device gave the information required to distinguish between these variables.
FF: Forks Modified Steering Stem
- Thread starter greg brillus
- Start date
It also becomes a bit confusing when there are several things that have been changed and you are trying to pin point a certain issue. Because the Thornton shock absorber up front is not adjustable ( ordinarily) It was easy to eliminate this as a potential problem, because I figure that the shocker is light years better in function than an original Vincent shocker and it has a good amount of overall travel. I thought that by going weaker in the front spring rates that the front would end up nice and soft (comfortable) but that was not to be the case, as it basically got to the stage where it would near bottom out of travel just doing a decent stop by hauling on the front brakes. The front did feel softer, but the effect of the all up weight still seemed to feel quite heavy. This is quite a contrast to a Comet, where the lower machine weight feels much lighter in the front end ........This was how it felt to me after I had ridden Neal's Comet last year. That is not to say that the ride quality of my bike has not improved, it is definitely way better than with the original front spring set up.
The roads are so atrocious around here it really is hard to tell the difference sometimes, honestly.
I haven't had it bottom out but it was hitting the bumpstop. which is to be avoided on a regular basis as you say, the indicator tells me how much too much travel I had.
I haven't had it bottom out but it was hitting the bumpstop. which is to be avoided on a regular basis as you say, the indicator tells me how much too much travel I had.
A further update today from Chris. He has sent me a ten minute video of the forks working with the new set up. The eagle eyed amongst you will notice that he has a rear AVO damper on the front. This has taken quite a lot of work to fit and it was used as when Chris tried the Thornton damper he felt that the extra travel might have had some advantage. We have been trying the new AVO dampers with different setting from those which were arrived at by Hadronuk. Those setting worked well when the Oilite bushes were used but both the damper settings and spring strengths turned out to be too weak when the Oilite bushes were replaced by either needle roller or ball races. We now have the damping (and spring strength) sorted out if a front damper is used on the front and this particular damper was set up with the same damping characteristics as the new setting for the front damper. Remember that this is all on the front of the bike. 45 lbs/inch springs are being used but Chris had to pack these to get the correct lower link angle as he weighs about 280 lbs, 127 kgs, so it seems that there might still be some advantage in various riders tuning the installed length of the springs to suit their usual loading. With this set up he is still only using about 2" of travel so more tuning by others might produce some improvements.
There is still a hold up on machining the holes at the rear of the lower links to take the ball races. Having had a long delay with the original machinist the new one told me on Thursday evening that he had a problem as well. He has set up a jig to allow the eyes to be line bored to ensure that they are both in line and parallel with the front bearings. It turns out that the eyes are so far out of line that if he used one side as a reference he would be 3 mm out on the other side. This is with trying to remove about four thou only to go from 1.25" to two thou under 32 mm. I have arranged to go down to the factory after the holiday and, once the machine is free again, have a look to see if there is something that can be done other than machining/honing each side independently. I will keep you all informed via this Forum. In the mean time I am going to try to attach Chris' video and if I fail then I will seek help from one of the experts on this Forum.
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There is still a hold up on machining the holes at the rear of the lower links to take the ball races. Having had a long delay with the original machinist the new one told me on Thursday evening that he had a problem as well. He has set up a jig to allow the eyes to be line bored to ensure that they are both in line and parallel with the front bearings. It turns out that the eyes are so far out of line that if he used one side as a reference he would be 3 mm out on the other side. This is with trying to remove about four thou only to go from 1.25" to two thou under 32 mm. I have arranged to go down to the factory after the holiday and, once the machine is free again, have a look to see if there is something that can be done other than machining/honing each side independently. I will keep you all informed via this Forum. In the mean time I am going to try to attach Chris' video and if I fail then I will seek help from one of the experts on this Forum.
003.MOV
Just an update to what TT has said, the measurement was taken with the bike on it's wheels so that equates to 2-1/4" total movement used, the normal AVO front damper having 2-1/2" before the bump stop means I had 1/4" unused and I had no emergency stops or hit any severe speed humps, in other words I'm using all the movement usable in normal riding with a little left in hand for emergencies.
Chris.
Chris.
Went to buy four rubber door stops for tank mounts (not for a Vincent) but they turned to be plastic.
