George is right. PSI = Pedalling-Steering Interference. Some call it PIS (pedal induced steering). Someone with english mother tongue might tell us which one sound more correct ...
Wheel flop (WF) should carefully be separated from PSI because it is a different thing.
WF is caused by the angle of the steering pivot being too small, or the weight of the front part being too heavy, or the CoG of the front part being too high.
The PSI is dependant of the position of the steering pivot relatively to the riders hip joints (at least in my theory). If the steering axis goes right through the center between the riders hips then PSI is minimized. You will find this at all center-steered bikes. See pictures on my modifications page.
That is why TT-clones like Cruzbikes have noticeable PSI and need additional arm force to compensate it. However TT-clones with very low BBs and followers of the a<b rule like Laurent's Speculoos and Jürgen Maier's bike also can minimize the PSI.
Unfortunately no scientific essay or proof exists for these assumptions. It is just empiric observation from the practice. Looking forward to someone who is expert in technical mechanics ...
Cheers, Jürgen. On 28.11.2007 07:42, Dirk Steuwer wrote:
Hi Listies,The other Dirk has added a page about the pivot angle and his influence to the wiki:http://en.python.data.he-hosting.de/Pivot_AngleWhat should follow this is a closer definition of wheel flop and pedaling induced steering. They do have in common that the front part start to wobble. Buzt what sets them apart? Isn't wheel flop also related to the wheight of the front? Does the a<b distance matter as well, besides the pivot angle?See this image http://python-lowracer.de/pics/TT%20Juergen%20Maier.jpgfrom Jürgens Modification page: http://python-lowracer.de/modifications.htmli was going to dig through old posts and prepare an additional graphic for illustration.Should we handle the two in one wiki page?Why do we call it PSI, when we talk about pedal induced steering? Or do i mix up things here?
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