I have tried to do my homework on trail variables- but have only succeeded in getting more confused, as on the interweb there are diametrically opposing statements of "fact" regarding the impact of the differing variables. So have now given up on the abstract theory and am appealing to you from a practical perspective.
Haha, me too!
It is a little bit scary quoting me in a thread like this.
From my rough measurements, quite a while ago, and they were rough, relative to the fork tube centre, the WP50 axle centre seemed around 13 mm forward of the G/S fork axle centre.
I don't know how that compares to a 4860 fork, from images I've seen it must be a bit different, so it might a be a good thing for us to actually accurately re-evaluate and compare these measurements.
It would be interesting to look into the big DRZ forks (and others) as well in this regard.
There really are so many variables. I'd love to hear from people that can actually predict the results of so many different changes let alone only one (which I have also read of and been told of diametrically opposite effects), but for me it will have to come down to the actual riding of the thing.
I've done a bit of short test riding on my new front end, at a few different fork lengths, before I had to put the project on hold, and it feels pretty good- but really Roadsacalling, Solo Lobo and Hardwaregrrrl and any others who have done a good amount of real
riding on this front end should comment.
As you would have seen the WP50 forks are very easy to change the length of. For starters you can slide them up through the triples, but shortening them from within is also pretty simple. I found changes in the fork length made for some very significant changes in how the bike felt. Too long felt all choppered out... short feels a lot more 'flickable'.
I don't know of any HPN mods for 'flickability'. I think they sometimes change the rake of the headtube (or at least there has been a lot of speculation on this?)... increasing rake, increases trail... with common theory saying that would increase stability, not 'flickability'...
But again, most of these builds really do have a lot of different changes going on at once so it probably can't be that simple.
- I don't know the length of the R1100 shaft, but it longer yes?
I'm keeping mine 'short' (ie stock) and will be raising the rear a little by attempting to emulate a mod that Rucksta here on this forum has described a few times- by moving the the lower shock mount on the swing arm forward a little (and then a bunch of other stuff to make sure it works).
With the shortened forks (to somewhere around G/S length) which I probably shortened a bit too much, I really do like how the bike rides now- it feels very 'flickable'. I am leary of creating a super stable long and tall beast that would be great for bashing through deserts but not so great for twistys and trails and touring and basically most of the riding I do. I'll sacrifice some stability for a nice turning bike that I can still touch the ground on.
but I do want a bit more travel than I currently have, so I am going to raise the rear a little, and see how much I can raise the front and have it still feeling right like it does now.
It is really just going to come down to that with mine- changing things more subtly from now on and seeing how it feels.
What might help deal with 'instability', I've got a scotts stabiliser on the bike as well.
With the 50mm forks (and other smaller conventionals) and with some creativity, there are quite a few triples from big USD forks that could be made to work (sleeving down the tube holes which are usually bigger than 50mm) which allow for different offsets. I've got a set with 24mm offset on the shelf I want to try one day.
HPMGuy told me, for an extra cost he could make the same kind of Rdubb triples but with a different offset, so that might be an option as well.
In the end, I probably would not let the geometry issue rule my fork choice- I'd choose the forks I wanted and then try to deal with geometry... and yes, the 4860's do seem to come in a quite a few different versions, not just in length but in internals... confusing to me.
And that is me done. Sorry for the ramble.