Thanks for the positive update. So is Patrick using "Dunfey Springs" too?
Peter B
Bristol, UK.
Peter,
No, Patrick is using a coil-over front damper, so there are no spring boxes. This is exactly what Greg Brillus is doing and it shows that you can have the same problem with a coil-over with too much preload. This is why changing the steering stem was necessary.
I also believe that the new steering stem is the best solution for this particular type of bad handling. The short springs are an easy and inexpensive fix that will give you a big margin of safety. However, the new steering stem changes the geometry while the springs simply cause the front end to stay away from the effects of the bad geometry.
I think it is interesting that John Emanuel and I both came up with new steering stems independently. John did it much earlier, but it is a small amount of confirmation that the steering stem is a solution. I would also not that the geometry of the our steering stems differ by a very small amount. To me, this also confirms that we were both on the right track.
As it turns out, I was helping Patrick with an unrelated issue when he mentioned that Bruno had reported wobbling and hopping of the Girdraulic under heavy braking. I knew that Bruno was headed to the TT and I could not imagine being stuck on an ill-handling bike for hours. I had noticed in photos that the angles of the fork links were not what I would want to see on my bike, so I mentioned it to Patrick. Of course, when Patrick was racing he used engine braking rather than the brakes, which would fade rather quickly. Now that he had solved the braking problem by installing very powerful brakes, the forks protested.
In a corner like this I would expect the bottom link to be straight out from the eccentric, not pointing down as it is. This means the fork is at or near full extension, so any braking will cause the wheel to bounce up and down as the fork goes rigid.
I wanted to send Patrick my own steering stem as I could make another, but I had never had a chance to test it, so I thought it would be better to send the Emanuel steering stem that Norman made. I felt that the testing that Greg did was sufficient. I have to thank Pat Manning,who loaned me the stem as well as Norman, who would have driven one of his half way to Patrick upon his return.
I mentioned earlier in this post that if you improve the front brakes you should seriously consider the consequences. Additionally, if you convert to taper roller steering head bearing, I would definitely consider changing steering stems. If you are doing the disassembly any way I would also want the benefit of having a clean round steering stem tube, which is necessary for seating the new bearings. Often the original steering stem tubes are not uniformly round or are corroded.
Best of luck to Patrick with the new Flash. Also, to Bruno, who is a great rider, I hope he can now focus on having a good ride with a good result!
David
