Been playing around a lot today with the steering on the car, after modding it earlier last week. I've since trimmd the upside down steering posts down, and had a play around with the bump-steer shimming.
Actually, the whole bump-steer thing is something that I think is starting to become more used, and dare I say it, something that the Xray boys have picked up on more than anyone else. Looking at setups from the T4, there is a big difference in the bump steer spacing used on carpet vs asphalt (3mm difference).
The bump steer is the main reason I believe that the lowered (411FF) steering posts seem to work better on the rug as well... but I'll come back to this.
So, anyway, some more pics of the finished mod. I'm actually using a 1mm shim under the posts now, which overall drops the rack 3mm compared to standard.
I've also switched out the drop-down ball joint on the servo horn (that's something I've never been totally keen on, as I think it does some strange things with the geometry on turning), and using a standard ball joint (2nd pic), and with the link low on the cross brace, there is plenty of top deck clearance.
The other thing I've had to do, and it's only because I want the option there in-case I want to run more ackerman shims, and that's shave some material off the rear of the 1.5 suspension block (3rd pic). I run 1.5mm shims most of the time (Keeps the ackerman close to kit when running 2.0/1.5 front blocks, which moves the front wheelbase forward), but with 2mm (4th pic, left joint) there is now more than enough room.
Anyway, what's the point of all this?
Simple put, it gives way more options to play with the bumpsteer as previously mentioned. Now usually, you don't want any bumpsteer, as it can make the steering do strange things, but as I already mentioned, the Xray boys are making use of bumpsteer to improve the car on asphalt.
The theory behind bumpsteer is to have the steering link parallel to the wishbone, so that under compression, the steering doesn't gain/lose toe-angle. At extreme's, the car can start to be very nervous with a lot of it, as small bumps will cause the car to turn on it's own..
But (and I'm getting there slowly!) this can be used to advantage. Adding shims to the steering hub induces toe-in under compression... which when turning adds outer wheel steering angle. And this is where I'm thinking there is something to start playing with. Outdoors on asphalt, mid-corner steering is king. Having the suspension add angle mid-corner (whilst under compression) would more than likely be advantageous. Thats why, IMO, the T4's are running large numbers of shims under the steering hub outside.
However, on carpet, to try and stop the car flipping over-itself and/or parking mid-corner, using less shims can take away mid. And this is why I think running the FF posts are working well indoors, with less bump-steering effect, due to the greater angle of the links. Lowering the steering without adding shims to the hub achieves the same effect, as there is a greater link angle added.
The 5th pic shows the difference between say an Asphalt and Carpet setting. The left side is low/asphalt link (4.5mm shims), whilst the right is the FF posts copy (2.5mm shims). Quite a big difference in the angle, with the left hand side very flat, and the right being close to parallel with the arm.
Of course, having the steering lower in the car will help a bit from a CoG point of view, but overall, the biggest effect, IMO, is link angles/bump steer.
Won't get an opportunity to test out this until the new year unfortunately, but it's high on my list to work through