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Thread: P11 Auto-X Setup help

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Posts: 201-210 of 220
2017-06-07 14:01:48
#201
Nice Vadim, I was surprised that I didnt have that much -camber with the LCA extended. May be best to have most -camber with UCA and fine tune with the LCA.
I can try and measure my LCA as well just to give you more detail for the math.
2017-06-07 14:07:00
#202
Having a shorter UCA is much more forgiving to other geometry items too. It seems like lengthening the LCA really messes with bump steer, have you noticed an increase of that?

Sadly there is no way to shorten the UCA or LCA and not increase the SAI, but I'm less worried about it now since I graphed it all out. SAI camber loss is far less then a lot of of people make it out to be. So the biggest issue with lots of SAI is scrub radius, but lower offset wheels fix that.
2017-06-07 16:01:08
#203
Originally Posted by Vadim
Having a shorter UCA is much more forgiving to other geometry items too. It seems like lengthening the LCA really messes with bump steer, have you noticed an increase of that?

Sadly there is no way to shorten the UCA or LCA and not increase the SAI, but I'm less worried about it now since I graphed it all out. SAI camber loss is far less then a lot of of people make it out to be. So the biggest issue with lots of SAI is scrub radius, but lower offset wheels fix that.


Oh yes, bump steer is very present, on un-even roads the car darts around. used to be darty before as well but not this much, during auto-x it is less noticeable. adjusting with the LCA also reduces caster as well, which is why i am looking at making a smaller bearing housing to replace the rear bushing so i can offset it a bit.
2017-06-07 17:50:52
#204
I wonder how much of that is from your ride height, were you bumpsteering before the LCA mod?

The reason I decided to peruse camber adjustment through the LCA is because that's how my friend's Miata adjusts camber and caster stock. Using eccentric bolts and what not, as far as I can tell he hasn't complained about bump steer on his car.

Good call on smaller LCA rear bushing, since I have 4.5* of caster I don't mind loosing say 0.5* caster for -0.5* of static camber gain . Even with stock LCA rear bushing housing I think I can squeeze in a little more caster by slotting the housings a little more.

Depending on your luck with the rear bushing, I might do the same too, rear bushing can be solid metal and it still shouldn't increase NVH all that much.
2017-06-07 21:52:39
#205
Originally Posted by Vadim
I wonder how much of that is from your ride height, were you bumpsteering before the LCA mod?


I did not notice the bumpsteer before, now two hands have to be on the steering wheel as un-even roads will pull the car car in one direction, could also be alignment but i am fairly confident that it is very close to 0 toe.
2017-06-08 03:12:10
#206
Hmm your making me reconsider messing with the LCA. I noticed a slight increase in bump steer doing the 10mm shorter UCA's, but it's very minor so I'm not worried about it. But more violent bump steer is not good for tire wear or racing in general (especially on my awful autocross surfaces).
2017-06-09 04:33:32
#207
Took some measurements today of my latest UCA bracket caster mod, and going from stock holes to new ones gained me 0.55* of caster. So you should definitely do this mod too along with the lower drilled UCA attachment points.

2017-06-09 21:55:54
#208
Remember I did not fix the issue with the tie rods being at different angles now to my LCA which should correct bump steer, also having less compliant bushings(bearings in my case) also add to this feeling since there is much less play. i plan on getting a set of s14 aftermarket outer tie rods and redrill to fit a bolt and spacer setup.

that sounds good about the new mounting location for the UCA, for sure got to get that done this weekend.
2017-06-12 13:59:28
#209
You guys are beam-Beasts!
2017-06-12 14:04:38
#210
I gotta say seeing 2JR beat a lot of cars and getting first place in Road Atlanta in the B15, made me see that beams are not a total loss on these cars.
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