lowering spindle/knuckle

[bcjammerx]

well that guy emailed me back (I asked if they made any for accords) he said they actually aren't making those for civics anymore and he doesn't know of anyone making them.

I asked how much they went for, I'll post what he says...

so anyone got thoughts on my latest quest.

[johnl]

Assuming we are talking only a 1.5" drop...MAYBE 2" drop...what deficits are there to the handling of the car by doing the drop via typical methods? That being a lowered perch...via adjustable coilovers or struts with set perch heights. Of course assuming you had your camber/caster and toe corrected.

An increase in bump steer, a change in the camber curve (i.e. the camber changes that occur with suspension movement), and possibly a more erratic geometric weight transfer when cornering associated with erratic changes to the location of the geometric roll centre when the chassis (and suspension) is subject to roll motion (highly speculative on this latter erratic weight transfer, so I won't explore it here).

A substantial lowering is very likely to cause bump steer.

Imagine looking at the suspension from the front. On one side, imagine a line drawn from the upper ball joint to the wishbone chassis pivot and extrapolated to infinity, now imagine a similar line for the lower wishbone. We only need to imagine this for one suspension corner, though of course each corner has this geometry.

The point where these two lines intersect is called the 'Instant Centre' of the 'Virtual Swing Arm' (which only exists with non parallel wishbones, but parallel wishbones that are unequal length become non parallel with any suspension motion). I'll call this point the VSAIC, and it's the centre around which the wheel and hub (etc) move with suspension movement (note that this point moves with suspension movement due to the typically unequal length and unequal angles of the wishbones).

Now imagine a line drawn through the tie rod axis and extrapolated to infinity. Ideally this line (tie rod axis) should cross the VSAIC exactly, and if it doesn't then there will be some degree of bump steer (i.e. vertical suspension movement will also cause unwanted toe / steer angle change). Just how bad this is will depend on by just how far the tie rod axis misses the VSAIC.

Now, (unless the tie rod axis exactly matches the axis of one of the wishbones, which is common practice for purpose built racing cars, just look at typical open wheeler steering / suspension design) it won't be possible for the bump steer to be kept within acceptable limits outside of a limited range of suspension motion, but within this range it can be made to be acceptably small (close to zero with a well designed geometry).

This means that even with a well designed suspension / steering geometry where the tie rod is located between the uppper and lower wishbones (i.e. the most common design, especially for road cars), bump steer will increase as the suspension moves further into the extremes of bump or droop.

This occurs because the VSAIC moves with suspension motion more than can be accomodated for in the geometry of the tie rod, being because the arc of motion of the tie rod end is a true arc and the motion of the 'knuckle' (at tie rod end height) is some form of parabola or even a shallow 'S' curve.

Note that the 'knuckle' has two points that do move in pure arcs, being the centres of the upper and lower ball joint 'balls', but that these two arcs are typically quite different and as a result all other parts of the knuckle move in curves that are other than a true arc.

Lowering the ride height will cause static angular change of the wishbones, resulting in the static VSAIC changing location, moving away from the tie rod axis. To potentially make this even worse, it's likely that at the lower ride height, X suspension motion will cause more of a dynamic change in the VSAIC location than would be the case for X motion with the wishbones at the static ride height angles as designed.

A modest lowering probably won't affect this enough to be a problem, but 'slamming' could easily cause substantial bump steer.

Clear as mud...? Sorry, it's hard to describe without diagrams.

Would the shorter knuckle or raised hub actually be that much of a gain over any deficits created by the typical method (if any)? And not considering the added cost and effort that is of making the knuckle...cause that just blows it out of the water.

How long is a piece of string? I don't know, but it's wise to avoid more than a relatively modest ride height change for fear of creating problems for yourself. Fixing bump steer can be difficult, and it wouldn't be unlikely that all you could do was to lessen it's severity.

I strongly suspect this is at least one good reason to use very stiff springs with substantially lowered cars, i.e. the less suspension motion the less bump steer. But then, very stiff set ups are only very rarely a good idea...

Seems to me that using a lowered perch on the strut keeps the upper arms constantly angled up...and that would have a negative effect on handling...I don't know if it would have a negative effect...it's not how it was designed to be so I assume it has a bad effect...but I dunno

I think you should trust your instincts. I don't think there is anything wrong with lowering the ride height so long as it's not too far. Beyond a modest lowering we really do need to consider redesigning the geometry properly (which requires a good understanding of the principles involved), or finding a way to restore the more important aspects of the lost geometry.

[bcjammerx]

Awesome thanks for the reply

I KINDA can visualize that...though I will bust out a diagram and a pencil later on

cool...guess when I do lower I'll not exceed 1.5"...I might just keep it stock ride height...who knows

[TypeG]

there's a guy that put them on his accord over on streetsource.

custom dropped spindles starting with a ryane motorsports civic dropped spindle

Http://www.streetsource.com/Profile....rofileid=25721
later.

[bcjammerx]

Now...with the spindles though, the suspension geometry wouldn't be changed right? I mean assuming they spindles were made properly.

so the civic spindles will bolt right up? Seems the only reason he had to "mod" them was to fit larger rims...he sure doesn't say much about it. Thanks for the info type G, I will have to look into it more.

[johnl]

Now...with the spindles though, the suspension geometry wouldn't be changed right? I mean assuming they spindles were made properly.

Assuming that the upper ball joint is only lowered futher down the steering axis without moving it inward (which would increase the KPI), the physical effect of those spindles / knuckles / uprights is only to raise the hub centre re the rest of the suspension, which causes the ride height to lower with no other geometric changes.

This results in lowering of the centre of gravity, which is the single desireable outcome of lowering the ride height (and no, looking 'fully sick' isn't a desirable outcome, it's an unfortunate and embarrassing side effect...).

Other than this nothing else physically changes and the suspension and steering geometry remains unaltered, which is a good thing as increased bump steer and other potential dynamioc problems are avoided.

so the civic spindles will bolt right up?

Would the stock Civic uprights bolt up to the Accord wishbones, with no unfortunate affects on suspension geometry? If not then the answer is probably no...

[DrSzSoLDIeR]

those were what i was looking for before i ended up gettin my adj. upper control arms but i couldnt find em

[bcjammerx]

WHAT? You mean I shouldn't do something just cause it looks sick? HA HA...
I agree, reason I'm being such a pain about this...I want the lowered car but NO reduced functionality...more importantly...NO reduced safety.


I got another email from that site owner... $550 a piece

hmm...so since these are no longer being made...and since they went for $550 a piece when they were...I guess I should look into adjustable upper control arms?

But would those put the suspension back in it correct geometry? It would mean the upper arm would be shorter...that wouldn't that make change how the suspension travels?

[Tnwagn]

Unless you are involved very seriously in motorsports where suspension geometry is vital to how your car will handle on the track, the gains from a custom spindle aren't going to make any noticeable difference.

[johnl]

WHAT? You mean I shouldn't do something just cause it looks sick? HA HA...

I can tolerate 'sick', it's just 'fully sick' that I have real problems with...

I agree, reason I'm being such a pain about this...I want the lowered car but NO reduced functionality...more importantly...NO reduced safety.

I can't disagree with that, it more or less matches my stance, but we know that for a great many people the functionality and safety aspects are utterly irrelevent compared to the 'fully sick' factor, unfortunately. The great majority of these people seem to be young men and boys, or maybe they are all boys, i.e. immature and childish...

hmm...so since these are no longer being made...and since they went for $550 a piece when they were...I guess I should look into adjustable upper control arms?

Considering that even if the custom uprights were within budget and available, that you could adequately avoid all of the problems that they're designed to address simply by not lowering the ride height too much...

But would those put the suspension back in it correct geometry? It would mean the upper arm would be shorter...that wouldn't that make change how the suspension travels?

When the upper wishbone is shortened this causes some degree of change in the dynamic geometric behaviour. i.e.:

The camber curve is changed, with increased neg camber gain in bump and increased pos camber gain in rebound. The VSAIC will move more with any suspension deflection, probably increasing bump steer, as well as causing increased change in the location of the geometric roll centre (with roll motion, which has implications for the nature of weight transfer).

However, unless the upper wishbone length is changed substantially, these changes will I think be quite small and outweighed by the benefit of being able to achieve desirable static camber angles (and 'desirable camber' doesn't mean with the wheels leaning over like a famous Italian tower...).

[johnl]

Unless you are involved very seriously in motorsports where suspension geometry is vital to how your car will handle on the track, the gains from a custom spindle aren't going to make any noticeable difference.

I more or less agree, so long as we are talking about such custom uprights in comparison with a suspension that hasn't been lowered so far that the as designed geometry has been significantly compromised.

The sensible option to avoid problems is to keep lowering within reasonable limits. Lower the car excessively using shorter springs and the most noticable affect is likely to be bump and roll steer caused by geometry changes. To reduce these symptoms you'll need to reduce suspension motion by stiffening the spring rate, i.e. stiffer springs will be needed not only to reduce bottoming out, but also to minimse bump steer (a band-aid solution).

Now, remember this, excessively stiff springs cause a loss of grip, not a gain...

[Tnwagn]

I more or less agree, so long as we are talking about such custom uprights in comparison with a suspension that hasn't been lowered so far that the as designed geometry has been significantly compromised.

From everything I've seen, cars that are lowered to the point to significantly alter the geometry of the suspension don't ride well at all. While the custom spindles would help some, the ride would still be relatively crappy.

Now, if you were to make custom extended top hats to allow the suspension to travel through it's full range of motion even while slammed then there could be a chance that the ride would remain reasonable. However, know we're getting into the realm of a fully custom suspension, the likes of which are only developed and used in motorsports (which leads back to my original point).

[johnl]

From everything I've seen, cars that are lowered to the point to significantly alter the geometry of the suspension don't ride well at all. While the custom spindles would help some, the ride would still be relatively crappy.

Yes, but the affect is secondary not primary, i.e. the the "crappy" ride is caused by the high spring / damper rates required to prevent bottoming out with the reduced bump travel that comes with using short springs, or by chronic bottoming out if the spring / damper rates are not high enough for the degree of lowering, not from any geometry change per se.

Altered geometry primarily causes different problems, i.e. bump steer, changed camber curve, and (possibly) changed weight transfer characteristics.

Higher spring / damper rates can be used to (somewhat) decrease these effects (simply by lessening suspension motion), but typically this is most likely to be co-incidental and accidental with the rate increase used to lessen bottoming out...

Now, if you were to make custom extended top hats to allow the suspension to travel through it's full range of motion even while slammed then there could be a chance that the ride would remain reasonable.

Because this would allow the use of more reasonable spring and damper rates because bump travel is not reduced. There would still be issues related to the geometry change associated with lowered ride height, and possibly even more so should the suspension travel remain undiminshed (i.e. the possible bump travel and how much will actually get used as a function of spring / damper rate).

However, know we're getting into the realm of a fully custom suspension, the likes of which are only developed and used in motorsports (which leads back to my original point).

And without the will, knowledge or resources to go down that costly and complex path, ride height changes should always be kept within sensible limits, certainly never 'slammed'.