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Discussion Starter · #1 · (Edited)
I have several questions I am trying to answer myself and would like help answering if somebody knows the answer.

1) I learned that balljoints do have an role when determining how much bumpsteer your car has.

From what I have read so far. My inverted tie rod ends + J's Racing extended ball joints/roll center adjuster/anti-bump steer kit may be CAUSING bumpsteer.
I am starting to understand why SPOON calls their extended ball joints not roll center adjusters but anti-bumpsteer kit.

I have tried tie rod arm angled down, straight, and angled up. I felt that angling the tie rod up felt the best.

I also learned that (not sure if it's applicable to Mc struts) that if the tie rod arm angle is above or below the instantaneous center it may cause bumpsteer.

How does tie rod arm angle affect camber/toe curve? I will recheck my car soon.. but I think my car toes-in under compression and toes-out under rebound. If I don't feel lazy, I might pull my suspension apart and measure my bumpsteer.

Has anybody ever measured bump steer for the RSX?


2) I have a question I am trying to get answered. My car under hard acceleration wanders fucking everywhere! I cannot drive the car straight when I punch it or when I'm rolling through gears down the straights at the track.

Is this torque steer? From my current understanding, torque steer is when the steering wheel pulls to one side. My problem is the steering goes non-stop back and forth in a very annoying fashion and makes it hard to keep the car in it's lane.

It never happened before.. only happened after my K24A2 and my inverted tie rod ends. I am led to believe obviously its one or the other.
 

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Yes, Stock the car was designed to toe in under compression & toe out under extention. With the idea that it would eliminate the detrimental effects of bumpsteer in most cases.

Bigger issue is making sure people understand the difference between bumpsteer & tracking/Tramlining.


as far as the 2nd issue we have to brake down all the things going on while you accelerate.

1. the car is going to slightly nose up (suspension extension & toe angles more towards toe out)

2. Bushing compliance is going to try and make the drive wheels Toe in. (More or less negated if you are running stiff compliance bushings)

3. if the inverted tie rods are not designed correctly for your car then you may be increasing the amount of toe out as the nose raises.

and 4. add all that in to your static alignment and you may very well be significantly toed out while under acceleration = the car wants to wander in which ever direction it happens to have traction in at the time.
 

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glory to the hypnotoad
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2) I have a question I am trying to get answered. My car under hard acceleration wanders fucking everywhere! I cannot drive the car straight when I punch it or when I'm rolling through gears down the straights at the track.
Do you have an LSD? I can hammer on my car, grab and release traction, hooked or not hooked, and easily go straight. The LSD increased "torque steer" in my case because the hooked tire still gets power, but it's not hard to control in the least. I'd consult your alignment. A little toe in helps keeping the car straight on power. Also, rear toe being out can be a bitch as well.
 

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whats the scrub radius like on your current wheel set-up, i find with my +15 offset theirs a lot more torque steer due to the leverage the tire has on the rotating assembly attached to the steering rack.

And i agree with toe out also being the culprit.
 

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Discussion Starter · #5 ·
I'm in class right now, but the car is in alignment shop.

Asked for 0-toe front and rear.

What about the lower ball joint. Anybody has insight on it?
 

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toe out would be my guess, but xqizit made a good point about your offset, the higher the offset the greater the effect the toe has as far as moving on the SAI
 

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good info in here, from what i was discussing with Brian you don't want your tie rods angled down, it'll increase the amount of toe in you get while decelerating. if anything, a little angle upward is what you'd want. does anyone remember if they were angled up stock?
 

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I'll try to spit out what I remember if it's correct at this late hour. I know a bit about suspensions. Feel free to correct me.

Front wheel drive cars need to have a negative scrub radius for stability, however if you have changed the wheels to a lower offset (e.g. +15) then you'll be in positive scrub radius, unstabilizing the driving wheels.

The stock tie rods are angled up slightly, and for good reason. To minimize bump steer, the steering rod and the front view swing arm (FVSA) paths should be identical, but is rarely possible. So you match the curve and position of the steering rod as best possible such that there is minimal bump steer in dead straight. However changing inverted rods, or lower control arm, or anti-bump steer kits/roll center adjustors, or changing ride height, or changing camber plate location will throw off the small range of grace you had.

End of the day, unless you measure the entire suspension geometry accurately, you won't really know what combo will work or why your setup isn't working. If you can, please measure the entire car's suspension geometry, ie. mounting points on car, on uprights, steering rack location in XYZ coodinates. Then I can tell you what will work using analysis software.

To answer your question, tie rod angle shouldn't effect your camber curve, but does for toe.
 

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im a little disappointed this thread hasnt taken off, bump for a reason for me to visit this sub-forum.
 

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glory to the hypnotoad
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im a little disappointed this thread hasnt taken off, bump for a reason for me to visit this sub-forum.
I think there's only a select few people who truly understand this stuff, so... this is somewhat akin to getting all the folks who know how to rebuild transmissions together at once to discuss gear lube.
 

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I'll try to spit out what I remember if it's correct at this late hour. I know a bit about suspensions. Feel free to correct me.

Front wheel drive cars need to have a negative scrub radius for stability, however if you have changed the wheels to a lower offset (e.g. +15) then you'll be in positive scrub radius, unstabilizing the driving wheels.

The stock tie rods are angled up slightly, and for good reason. To minimize bump steer, the steering rod and the front view swing arm (FVSA) paths should be identical, but is rarely possible. So you match the curve and position of the steering rod as best possible such that there is minimal bump steer in dead straight. However changing inverted rods, or lower control arm, or anti-bump steer kits/roll center adjustors, or changing ride height, or changing camber plate location will throw off the small range of grace you had.

End of the day, unless you measure the entire suspension geometry accurately, you won't really know what combo will work or why your setup isn't working. If you can, please measure the entire car's suspension geometry, ie. mounting points on car, on uprights, steering rack location in XYZ coodinates. Then I can tell you what will work using analysis software.

To answer your question, tie rod angle shouldn't effect your camber curve, but does for toe.
This is a great post, hard to put so many issues in one post succinctly! The Civic/RSX front suspension is a challenge, to say the least. Maybe the classes with limited options to change the geometry are a blessing? LOL.

I posted a pic from SCC of a typical macstrut steering arm and motion path, lots different than ours. One area/opportunity I haven't seen discussed much is that increasing caster with a high steering arm will not cause much bumpsteer change. So orienting a camber plate for lots of caster and getting negative camber at the strut ears/knuckle interface has lots of benefit with minimal downside. Some good discussion recently on the nasioc subie forum about SAI/camber/caster/roll center compromises with this approach. Some of them even advocate reducing camber with the plate, to reduce the SAI, although this moves the roll center a bunch. Lots of compromises!

I've gone over to the dark side, prepping a 90Si for ST this year. Before I bought it, I had been thinking to myself that there were lots of camber/caster changes that people weren't utilizing. Now that I've spent time rebuilding the suspension, I've come to realize how good it is to begin with, and how easy it is to mess up the geometry with small changes to pivot points/arm lengths with camber kits.
 

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Discussion Starter · #12 ·
I thought SAI wasn't a bad thing.

Doesn't it provide directional stability and doesn't it reduce scrub radius when you get larger wheels/lower offset wheels?
 

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I thought SAI wasn't a bad thing.

Doesn't it provide directional stability and doesn't it reduce scrub radius when you get larger wheels/lower offset wheels?
Yes it does. But it has negative effects on camber when the wheel is turned, so more SAI needs more caster. That's why getting camber from plates has compromises, you do get more negative camber but you lose a larger portion of it due to the higher SAI. Caster seems like a win-win, although it takes a lot of it to get much benefit, and there's the bump steer/torque steer issues. Honda got it right on the new civics, caster is 7* or something like that. Sounds more like a BMW than a fwd!
 

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Discussion Starter · #14 ·
Yes it does. But it has negative effects on camber when the wheel is turned, so more SAI needs more caster. That's why getting camber from plates has compromises, you do get more negative camber but you lose a larger portion of it due to the higher SAI. Caster seems like a win-win, although it takes a lot of it to get much benefit, and there's the bump steer/torque steer issues. Honda got it right on the new civics, caster is 7* or something like that. Sounds more like a BMW that a fwd!
DAMN!
SAI HURTS MY CASTOR? :firemad:

I have sooo much SAI too.. :(
 

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I should clarify, if you increase the SAI to get negative camber, the negative effects are small and you will still have most of the negative camber when the wheel is turned.

For example, our stock SAI is something like 18*, and with a caster angle of 2.2* (for my civic) you will lose .04* of camber with the wheel turned 15*. If you bump the SAI to 20* you lose .11* of camber at 15* turned, so you're still keeping most of your -2*. Contrast that with 18* SAI and say 7* caster, at 15* turned you get 1.2* of additional negative camber!

People complain about the lack of camber the mini cooper has in stock class but it's actually quite good; low SAI, good caster, and -.5* static camber is better than most of it's competition.
 

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Discussion Starter · #16 ·
I should clarify, if you increase the SAI to get negative camber, the negative effects are small and you will still have most of the negative camber when the wheel is turned.

For example, our stock SAI is something like 18*, and with a caster angle of 2.2* (for my civic) you will lose .04* of camber with the wheel turned 15*. If you bump the SAI to 20* you lose .11* of camber at 15* turned, so you're still keeping most of your -2*. Contrast that with 18* SAI and say 7* caster, at 15* turned you get 1.2* of additional negative camber!

People complain about the lack of camber the mini cooper has in stock class but it's actually quite good; low SAI, good caster, and -.5* static camber is better than most of it's competition.
No way, our stock SAI is 18*? But.. I swapped my camber plates, slid them all the way back and only have about 18*.

Are those numbers accurate? I want 7* caster.. :( Damn Honda and shitty RSX.
 

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Those are numbers that I've pulled off various alignment sheets, spec sheets, measured etc. Take them fwiw. But the comparison of camber loss at the different SAI & caster angles is just an equation so it's valid.

I'm not suggesting that you or anyone should throw away anything, there are a lot of ways to skin the cat. I think high static camber via plates/bolts/strut ears and low caster is very workable if you have an lsd. But for classes that have open diff, flattening out the inside tire via less SAI, less static camber and more caster seems like a good approach to reduce wheel spin. All IMO of course...
 

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now this is booming.
 
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