CSG and RCE tag-team suspension Q&A thread! Ask us anything!

[jack43]

I've got RCE Zeros on and have been sorting out my suspension. Thanks again as I would be lost without these threads.

I recently purchased the Whiteline Upper Rear Control Arm Bushings #63225 to go along with the LCAs I'm about to install. But it looks like a fair bit of a hassle to swap/press them in -- are those worth it?

cheers!:happy0180:

[OICU812]

Originally Posted by jack43

I've got RCE Zeros on and have been sorting out my suspension. Thanks again as I would be lost without these threads.

I recently purchased the Whiteline Upper Rear Control Arm Bushings #63225 to go along with the LCAs I'm about to install. But it looks like a fair bit of a hassle to swap/press them in -- are those worth it?

cheers!:happy0180:

They're a pain in ass and meant to be an option to an LCA to also rid of use of toe links, so can't be certain here but I'd think your existing LCA with some toe links would get you in perfect check and rid of the UCA bushings. I have the UCA bushings and they're also so difficult to get the alignment matched left to right and after some wear that setting seems to dissapear as well. I will be removing mine soon and going with WL upgraded NON camber UCA bushings and LCAs with WL toe links soon and be done with it...

[wootwoot]

I think the upper control arm is the best place to adjust camber in the rear. Changing the length of the lower control arm can hinder suspention performance.... At least that is what I have gathered from around these parts. OP should have good info in this regard.

[ZDan]

Originally Posted by Dimman

Goddamn it... I'm not understanding it. Let me find my geometry set and graph paper to show you how I see it, and hopefully you can point out what my error is. Be back in a while...

Edit:
@ZDan

This is how it works?

Yup! The offset/scrub radius has a LOT less influence than I was originally and incorrectly assuming, but it is still there because of the strut angle changing, increasing camber which increases wheel travel the more outboard it is. But it takes a significant (to the extent of impracticality) change in offset to give even a few % change in motion ratio. For *practical* purposes, the offset makes essentially no difference to the motion ratio and wheel rate.

When a strut starts to lose camber the motion ratio starts to increase too?

Yes, but for most struts, in a practical application (stock to ~1.5" lowered) you're not going to get into the range where you lose camber with bump.
You have to go way way WAY beyond LCA horizontal to get the point where you start losing camber with a strut, as you show in your diagram.

So it's a myth that struts lose camber with bump. They gain camber in the practically usable range of travel.

[Calum]

Originally Posted by ZDan

Yup! The offset/scrub radius has a LOT less influence than I was originally and incorrectly assuming, but it is still there because of the strut angle changing, increasing camber which increases wheel travel the more outboard it is. But it takes a significant (to the extent of impracticality) change in offset to give even a few % change in motion ratio. For *practical* purposes, the offset makes essentially no difference to the motion ratio and wheel rate.

Yes, but for most struts, in a practical application (stock to ~1.5" lowered) you're not going to get into the range where you lose camber with bump.
You have to go way way WAY beyond LCA horizontal to get the point where you start losing camber with a strut, as you show in your diagram.

So it's a myth that struts lose camber with bump. They gain camber in the practically usable range of travel.

I've been following along with you guys, reading, learning, and trying not to think about my old statics classes. First off, thanks for doing this in a public forum so others can learn.

Second I've got to ask what your definition of losing camber is. Do you mean anything less then the peak negative camber gained through bump, anything less then the static camber setting, or anything positive?

Personally, (and take this with a huge grain of salt) I would be concerned with the point that camber changes from getting more negative to getting less negative. It would seem that range could be the most unpredictable to drive in.

Am I way off base? Am I correct in my understanding that peak negative camber will be at LCA horizontal? Is there any practical down side to increasing the down word angle of LCA and tie rod end to give more camber gain through bump? Of course at some point ground clearance becomes an issues, but aside from that?
:happy0180:

[ZDan]

Originally Posted by Calum

Second I've got to ask what your definition of losing camber is. Do you mean anything less then the peak negative camber gained through bump, anything less then the static camber setting, or anything positive?

You start losing camber when you start losing camber! I.e., bump travel moving beyond the point of maximum camber. On my approximate 240Z model, this point really isn't reached within normal suspension movement.

Personally, (and take this with a huge grain of salt) I would be concerned with the point that camber changes from getting more negative to getting less negative. It would seem that range could be the most unpredictable to drive in.

Quite the contrary, that is the range when you are getting almost no change in camber with bump travel, the camber is more consistent with bump/rebound.

Am I way off base? Am I correct in my understanding that peak negative camber will be at LCA horizontal?

I've said it twice in this thread, but it's not getting through, so AGAIN, *you don't start losing camber when the LCA goes past horizontal*. You have to go way WAY beyond that, to the point where the LCA is perpendicular to the strut, before you start to lose camber.

BIG and widespread misconception of strut suspension, I see that repeated all the time, and it's just not true. If the strut is angled inward at 15 degrees, you have to go so far in bump that the LCA is at 15 degrees before you stop gaining camber and start losing it. Look at the diagram that Dimman made. That should make it indisputably obvious to the most casual observer!

Is there any practical down side to increasing the down word angle of LCA and tie rod end to give more camber gain through bump? Of course at some point ground clearance becomes an issues, but aside from that?
:happy0180:

If you are lowered a huge amount, you might benefit from moving the inner LCA pivot upward, but realistically, if you aren't tremendously lowered, I wouldn't bother. Basically, this would raise the roll center back up and give less roll per cornering g's, but then another way to look at it is that the lowered roll center from lowering the car effectively increases mechanical grip.

I would be very surprised if the stock FR-S setup isn't optimized around a lower ride height with the existing geometry anyway. Unless I was lowering more than ~1.5", I wouldn't even worry about it.

From a camber-gain standpoint, I think you have to be in a very different ride-height realm before this would be considered necessary.

Another thing to consider: If your suspension is reasonably well set up, you don't necessarily want more camber gain with bump beyond a certain point anyway. Figure that any additional travel beyond what you would see at the front under max braking, or at the outside wheels under maximum cornering is there to take up bumps and road imperfections under those conditions, and in either case you wouldn't really want or need more camber beyond optimal (this is assuming you have a non-stock setup with a reasonable amount of static camber).

[Calum]

Originally Posted by ZDan

to the point where the LCA is perpendicular to the strut, before you start to lose camber.

Trying to bash this into my head. I think I'm see it. Excuse me while I return to lurking.

[Dimman]

Originally Posted by ZDan

Look at the diagram that Dimman made. That should make it indisputably obvious to the most casual observer!

@Calum





Heh...

Educated myself there.

Thanks, ZDan!

[Calum]

Originally Posted by ZDan

Look at the diagram that Dimman made. That should make it indisputably obvious to the most casual observer!

In all honesty, that didn't help me at all. Sorry @Dimman. I kept looking at those and imagining the horizontal position of the balljoint relative to the chassis, determining the camber angle. As the control arm moved up it moves through an arc that causes the ball joint to move farther from the chassis until the control arm gets goes horizontal at the peak camber and from there as the control arm moves up the ball joint gets closer to the chassis again and camber would get less negative.

I get it now, I think. But looking at the arcs only further convinced me that I was correct. I'm pretty mechanically inclined but I still needed to picture the whole assembly including; the knuckle fixed to the strut, the rotate of the knuckle relative to the control arm, the rotation of the top strut mount as the strut angle changes slightly... Sorry, but even something as simple as this isn't obvious sometimes.

[Dimman]

Originally Posted by Calum

In all honesty, that didn't help me at all. Sorry @Dimman. I kept looking at those and imagining the horizontal position of the balljoint relative to the chassis, determining the camber angle. As the control arm moved up it moves through an arc that causes the ball joint to move farther from the chassis until the control arm gets goes horizontal at the peak camber and from there as the control arm moves up the ball joint gets closer to the chassis again and camber would get less negative.

I get it now, I think. But looking at the arcs only further convinced me that I was correct. I'm pretty mechanically inclined but I still needed to picture the whole assembly including; the knuckle fixed to the strut, the rotate of the knuckle relative to the control arm, the rotation of the top strut mount as the strut angle changes slightly... Sorry, but even something as simple as this isn't obvious sometimes.

From the two different sketches, you can see that lengths can make changes in the position.

To me it also looks like it does lose past horizontal, but it's not drastically shooting towards positive. But more in the second sketch than the first.vMore drawing is in order, with wheel and tire to help visualize.

Proper lengths and points would help...

Real secret to camber is matching it to roll.

[Calum]

Originally Posted by Dimman

From the two different sketches, you can see that lengths can make changes in the position.

To me it also looks like it does lose past horizontal, but it's not drastically shooting towards positive. But more in the second sketch than the first.vMore drawing is in order, with wheel and tire to help visualize.

Proper lengths and points would help...

Real secret to camber is matching it to roll.

I keep thinking about the rear camber gain vs the front and wondering if I should attempt to match them. I'm not disagreeing with you, at all. More I'm wondering what's more important matching camber to roll, or camber curves front and rear as I doubt either is going to be possible in the real world. My thinking is that matching camber to roll will give the best ultimate grip and use of the tire patch, while matching front and rear will be the most predictable allowing the driver to better utilize what grip is available. I guess it would come down to the driver.

Along those lines, how does lengthening the RLCA or shortening the RUCA effect the rear camber curve? And as was asked by @wootwoot is it better the adjust the rear camber via the upper or lower?

[ZDan]

Here's Dimman's first pic:

Originally Posted by Dimman

Remember that the hub is fixed to the strut line of action (line from ball joint to top of strut) as far as camber is concerned. I.e., as long as the strut angle is getting bigger relative to vertical, we are *gaining camber* at the wheel hub.

The strut angle obviously gets bigger going from the lowest position to LCA horizontal. As LCA goes *past* horizontal, the strut angle *continues to get bigger*, and CAMBER continues to increase. The strut angle doesn't stop getting bigger and we don't stop gaining camber until the LCA is *perpendicular* to the strut line of action.

You can *see* in the highest LCA position that the strut angle is greater than it was when the LCA was horizontal. Likewise, camber is greater.

[Dimman]

Originally Posted by ZDan

Here's Dimman's first pic:


Remember that the hub is fixed to the strut line of action (line from ball joint to top of strut) as far as camber is concerned. I.e., as long as the strut angle is getting bigger relative to vertical, we are *gaining camber* at the wheel hub.

The strut angle obviously gets bigger going from the lowest position to LCA horizontal. As LCA goes *past* horizontal, the strut angle *continues to get bigger*, and CAMBER continues to increase. The strut angle doesn't stop getting bigger and we don't stop gaining camber until the LCA is *perpendicular* to the strut line of action.

You can *see* in the highest LCA position that the strut angle is greater than it was when the LCA was horizontal. Likewise, camber is greater.

Originally Posted by Dimman

But the geometry changes whether it gains or loses. Which strut/LCA proportions are more representative of actual?

[ultra]

OK, sorrry for being so profuse here and in these suspension related threads but I'm still looking for some pointers.

Current setup:

Lowred 30mm on RS*Rs.
225/40/18 Continental Sport Contact 2s.

Usage: 90% spirited street driving, 10% track days/AutoX/drifting.

Front:
-2.0 Camber
0 toe
OEM crash bolts + Whiteline front camber bolts + AVO caster bushings. Non adjustable rubber top hats.

Rear:
-1.7 Camber
0 toe
Whiteline rear camber bushings

Stock sways.

Impressions: Very balanced and controllable overall. Very capable on street, handles track decently given the mild setup. Crisp turn in, weight transfer characteristics feel i tuitive, pretty very well balanced overall and the rear end responds nicely to throttle lifts. Tad much more corner entry underster on tight bends than I'd like when pushing up to the very limit (perhaps due to driver error). No excessive tire wear. Great all-around setup, haven't felt like fiddling with it in 7 months.

If were competing for trophies, or maybe 2% out of the 10% of the time I spend driving the car really hard, I'd really like to try out some stickier tires combined with more camber in the hopes of gaining a little more ultimate grip and front grip bias.

The other 98% of the time I'm completely OK with with it as-is.




Question:

That 2% of the time where I'm going for it and feel that I'd like more front grip going into corners - whare my best options to increase front grip and/or overall grip, short of changing up my coilovers? Tires? Alignment? Swaybars? Damper settings (even though my coilovers are only single adjustable, average level units)?

I'd basically like to reduce the amount that the front scubs out in tightish turn-in, AutoX type situations.

As mentioned earlier I run a street biased setup but if I could milk a little more put of that 2% I"d be really happy.