So my autox only na Miata is moving to track only use so some changes are in order.I have poly bushings everywhere except the upper fronts are isc offsets,sounds like this is going to cause problems with the 15x9's that I didn't have with 13x9's and 255 hoosiers.
I'm thinking to clear the turrent AND achieve the camber I need that a pair of the new extended length lower balljoints will be best and since I've got a bunch of other things to throw money at I'm wondering if I can still use the upper offsets by rotating them back to center on the vertical plane.
The question then becomes if I were to do that(the bushings would be repined so no moving around)would the roll center change/camber curve benefit from the inner pivot moving up or down from center??
Roll stiffness is under reasonable control with 800lb front and 500lb rear springs combined with the typical big azz front sway bar.
codrus
Dork
12/20/15 12:58 a.m.
15x9s can work with the ISC offset UCA bushings, it really depends on what size tire you run. I use 15x9 6ULs with 225 RRs and a 5mm spacer (required to get them to fit over the TSE 11.75 brakes) and it does not rub on the shock tower on my NB. It does rub the sway bar (1.25 inch RB bar) and it does rub the control arm at fully lock, but not the shock tower under simple compression.
That said I think the extended length lower balljoints are a better solution all around, so I have a set on order.
Yes,if you rotate the offsets to the center, you will either raise or lower the upper control arm inner pivot points by the offset amount. This will change the camber curve -- I think lowering it will give you more camber gain with suspension compression, whereas raising it will give you less. I have no idea if this is desirable or not. I'm not sure how the roll center changes.
There's a double-a-arm simulation program that locost builders often use for setting up this kind of stuff here (be warned, it's a DOS program):
http://www.locostusa.com/forums/viewtopic.php?t=1438
I plan to reinstall the non-offset poly bushings in the UCA pivots when I put in the extended balljoints.
Yes lowering that upper pivot should increase camber gain with compression,I think that's not a bad thing and could get away with slightly less static settings for increased braking.
Roll center should be lowered even further,normally that will just take away roll stiffness all else being the same.How much of a change it will amount to is the real question I guess.
Emilio says the ride height works best with 1/4" rake,I might be screwing that up a bit unless I lower the rear a touch....maybe.
What ride heights are you running? Using the V8R upper front control arms at 949 suggested ride heights I was able to get almost -4° up front.
I know this is slightly off-topic vs your question, just pointing out it's not that hard to get the camber you need. I was also running the 800/500 XIDAs.
I'm staying right around 4-3/4" front ride height,custom valved but stock length sport konis.They will remain while I upgrade the rest of the pkg.
This is simply a reuse what I have to minimize what I need to buy exercise.
