Pearl's mod/build LT rear/TC Dual Front/Custom Baja Bumper/Doug Thorley Headers
To me it looks like on his 4th gen, Wishbone Runner on Taco World mounted his forward like the MC 200 rack. He initially was going to use a 200, but ended up going w a Tundra.
Travis' pics looks like he mounts the Tundra closer to the OEM Tacoma location.
Does the V8 oil pan restrict this mounting point?
And does moving the rack forward create a difference in Ackerman angle?
I had a similar thought on the LC200 modification until Mason (who is obviously 3 steps ahead of us at any given point
) shared pictures of his LC200 that he took apart. The only way to shorten the shaft any is to loose the equivalent in maximum steering angle. With the rack at full lock to either side the inner threaded shaft is pretty much fully recessed within the rack. Could a shorter, solid shaft be machined? I'm certain it could, but at that point you're more than likely much better off with a proven cut down tundra rack..
With regards to the oil pan differences, I'm certain there is a difference in clearance between the v8 and v6, but just roughly looking at mine i THINK I could have gone opposite with my offset bushing (instead of the 1-2 o'clock, do the 7-8 o'clock) to push the rack back in stead of forward. I don't know the exact measurement on the offset bushing, but I would be hard pressed to believe you would gain more than 1/2" or so of front/back positioning. The thought of hitting the coil with the tie-rod wasn't appealing to me so I went with the forward-most position with my rack. I think he oil pan would have supported a rear-ward mounting position without a problem, and the clearance to the steering shaft would have been easier to achieve I think. This would help out with bump steer numbers.
With regards to Ackerman, this is just my thought on it from the limited research I did yesterday, but I don't believe that the physical position of the rack impacts the ackerman. I believe the ackerman is impacted strictly by the geometry of where the pivot point of the spindle is vs where the pivot of the steering mount is on that said spindle and where the line that shoots through these two centerlines falls to relation of the centerpoint of the rear axle.
A common thing I did find in my search is that for a quick and dirty approximation of getting decent Ackerman what you need to do is draw a center point on your rear axle, project a line from this point through both left and right ball joints up front, and this is the line that your steering knuckle point should fall on. The further away you get from this line (either inside or outside of it) will impact how good/bad your ackerman is. As long as your interconnection of the two front wheels is solid and does not change, I don't believe the shape of this interconnection (ie: steeringrack/tierod combo and their placement in relation to the knuckles) impacts ackerman at all.
Previously I had not given the Ackerman (or really any of this geometry) any thought at all... but with this newfound knowledge.. I am kind of questioning the LT kits and how they impact ackerman.. If you think about it, going wider, like +3.5" on a spindle, but NOT moving it forward by the same proportion, you are impacting the angle of the ackerman. I'll drop my rough picture in here later lol. Need to re-install my autocad for some quick drafting layouts.. works better than paint.
In order to keep the ackerman same , or close to, as stock with going wider LT in the front you would have to also shift things forward in order to keep the relation of the tierod centerline the same to the imaginary "ackerman line". By the same though process.. if you do have a kit that pushes your knuckle forward, like the RCLT, it would give you an opportunity to slightly shift your tierod pivot point out to keep ackerman the same, which would also result in lesser bump steer.. i think.. Coffee is still processing.
Edit* after giving it some more thought and watching a few more videos on Ackerman.. I believe positioning of the rack in relation to the knuckle will also have an impact on ackerman as well.. If it isn't completely obvious at this point I don't really know what i'm talking about. Proceed as you were
This would certainly explain the "caming over" feeling I mentioned with my rack swap coming to near full lock. I think what I'm feeling is the affects of change Ackermann angle due to the rack being shifted more forward (and also having shorter tie rod length)
I believe what is happening is that by moving the rack forward it allows for more throw at full lock, which is toe-ing the inside tire more in relation to the outside, which in turn makes the road force push the tire to full lock by itself sooner than it did with my factory geometry.. maybe? lol
