Dark Horse
2012 BOSS 302 LS 541
zzyzx said:Here's what I consider to be a helpful example of how different parameters affect geometry for a strut based suspension:
Thank you for posting this.
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zzyzx said:Here's what I consider to be a helpful example of how different parameters affect geometry for a strut based suspension:
zzyzx said:Here's what I consider to be a helpful example of how different parameters affect geometry for a strut based suspension:
http://zzyzxmotorsports.com/library/strut-tech-20070918.pdf
I'll simply add that irrespective of your target camber of -2.0, you should set your top camber plate to full negative (inboard). That will likely yield something > -2.0 in your case, so the bolts are not necessary. In fact, I'd advise against them unless you have an explicit need.
If you have any questions about the link I posted, let me know. Though at this point I take the concepts in there for granted, I realize that they are still in the "black art" realm for many.
zzyzx said:Here's what I consider to be a helpful example of how different parameters affect geometry for a strut based suspension:
http://zzyzxmotorsports.com/library/strut-tech-20070918.pdf
I'll simply add that irrespective of your target camber of -2.0, you should set your top camber plate to full negative (inboard). That will likely yield something > -2.0 in your case, so the bolts are not necessary. In fact, I'd advise against them unless you have an explicit need.
If you have any questions about the link I posted, let me know. Though at this point I take the concepts in there for granted, I realize that they are still in the "black art" realm for many.
Flyboygsxr said:I read the article...So am I to understand that installing the extended steeda ball joints this would help to re-raise the roll center and improve the handling? I have the camber plates and plan on setting them at -2.0 and I will also install the bump steer kit. The car is being lowered by Eibach Sportlines. You can see the list of my mods in the first post. Thanks
Flyboygsxr said:I read the article...So am I to understand that installing the extended steeda ball joints this would help to re-raise the roll center and improve the handling?
Flyboygsxr said:I have the camber plates and plan on setting them at -2.0 and I will also install the bump steer kit.
Flyboygsxr said:The car is being lowered by Eibach Sportlines. You can see the list of my mods in the first post. Thanks
Dark Horse said:Thank you for posting this.
jim woodruff said:Steve, Thanks for a great read and link. This help me understand more of the problems I am having and why.
So you want to raise the roll center in the front and lower it in the rear?zzyzx said:That's correct - it'll raise the roll center height.
cp85gt said:If a set of lowering springs like the Eibach sportlines have front/rear spring rates matched to each other relative to the amount of drop they give how will raising just the front roll center effect the handling balance?
cp85gt said:In the case of the Eibach sportline the rear drop is more than the front (1.0 vs 1.8) on the Boss, which is already a bit lower in the front than a standard GT. So without knowing how the front/rear geometry effects roll center when a car is lowered then there are 3 possibilities. 1) The front roll center is lowered more then the rear roll center. 2) The rear roll center is lowered more than the front. 3) The roll centers are lowered equally. It would seem that in only scenario (1) would the extended balljoint help to equalize roll centers, otherwise if you only raise the front roll center, then you could have a handling imbalance that would have to be adjusted out with sway bars, spring rates, tire width, etc.
The only empirical data I have with this is I was one of a few unfortunate souls to mix a Griggs front K-member with a Maximum Motorsports panhard bar on my Fox body. The front roll center was higher than the rear and the car pushed badly. I dialed out the understeer with sway bars. It would seem what Darren505 is doing by using the extended balljoint as a balance tuning idea would be where someone might get to eventually, not just an automatic upgrade when a car is lowered.
3) The roll centers are lowered equally.
zzyzx said:...
2. Always set your camber plates to equal positions L/R, regardless of your target camber. Fine adjustments to equal up camber L/F should be made at the eccentric bolt on the strut (if applicable). If you end up with 2-3 10ths of a degree difference L/R, better to leave it as-is rather than end up with a skewed roll center.
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zzyzx said:For a strut setup, all the theory and my personal experience boils down to a simple set of recommendations:
1. Never lower the car to the point where the inner pivot point is lower than the outer pivot point - what I call "inverted" front lower control arms. Level (e.g. parallel to the ground) is OK.
2. Always set your camber plates to equal positions L/R, regardless of your target camber. Fine adjustments to equal up camber L/F should be made at the eccentric bolt on the strut (if applicable). If you end up with 2-3 10ths of a degree difference L/R, better to leave it as-is rather than end up with a skewed roll center.
3. Target camber for "performance" applications should not be less than -2.5 or so. IMO, -2.0 is not enough camber to maximize grip and on the track will lead to more wear on the outside of the tire. Most (competitive) strut setups I've worked with over the years are at least -2.7, and are as often times around -3.0. Assuming you run zero toe, you should not expect unusual wear with even -2.5 or so. I run -2.7 with zero toe and my Boss is a daily and there's no uneven wear at this point. Same was true with my last Miata; but we know those little guys are easy on tires... Unlike some, I've seen no real benefit to "toe out" setups that is worth the additional tire wear.
On the theory side of things as depicted in the PDF I wrote, one of the goals is to minimize migration of the instant centers. If you have instant centers which have drastic migrations as a result of dynamic inputs, this translates roughly to observations we've all heard: "snap oversteer", "chassis doesn't settle down", "unpredictable handling".
Hope this helps.
Grant 302 said:Just curious, but the WinGEO models are 2-D and don't account for Caster effects, right? That would be awesome info! Still way better than any paper sketches I've made!
darreng505 said:I asked the shop if this difference between the two strut top mount locations was an issue and they said "they would never be centered". Struck me as odd but my knowledge is still new here. Thanks for all the info.
zzyzx said:I'm not sure what you mean specifically, but it does model caster geometry in the side view. The diagrams in the PDF are for front view geometry. In the side view, caster is the delta between the upper mount point (e.g. the strut top/camber plate), and the lower ball joint (outboard) on the horizontal.
Many camber plates also provide for caster adjustment which is a good thing. The Ford OEM camber bolts also come with caster bolts, which I assume provide some eccentric adjustment so you can push the rear mount point of the LCA outboard, thus moving the outboard lower balljoint forward, providing additional positive caster.
On a strut based setup front caster is generally a good thing as it's the one way you can increase the dynamic camber gain with in a turn - dynamic camber gain as a result of steering angle. Unlike a nice SLA suspension (short long arm), struts have little in the way of dynamic camber gain, particularly under compression. Larger positive caster angle is one way to help with this deficiency. Caster also provides for a "self centering" load on the front wheels which may or may not be considered a good thing, depending on the application.
Grant 302 said:I understand all that.