Caster Issue...how to fix Radius Rods? or Control Arms?

[Losiracer2]

I just came back from the alignment shop and they said I had uneven caster angles in the front end.

This my DD, so suspension is bone stock, brand new UCAs and lower BJs. I had the Alignment done about 3 months ago, so everything is still in spec, Camber is .1* on both sides, Total toe is 5/32"

My LF Caster is 1.8* and my RF is .4*, both positive.

How do I make my RF match the LF? or should it be the other way around?

Right now, my car pulls to the right pretty noticeably. So I'm thinking the right radius rod needs to be adjusted?

Now, to make it match the LF, would I have to add or remove washers from the Pass. Radius Rod?

Alignment sheet attached:

[sonikaccord]

How are your radius rod bushings?
To decrease caster, you want to push the knuckle to the back of the car.

[johnl]

Such a large discrepancy in side to side caster may be due to badly repaired accident damage, or, the front sub-frame could be fitted poorly (forward on one side and rearward on the other), or, it could be that the radius rod bushes have been fitted incorrectly.

Note that each bush has two rubber 'blocks', one located in front of and one behind the mounting point in the front cross member. These blocks are of different lengths, so if you were to have (say) the longer block fitted at the front of the cross member and the shorter one behind it, then the caster would be greater than vice versa.

You could have the longer block to the front of the cross member on side of the chassis, but to the rear of the cross member on the other side...? If so then you would have appreciably different side to side caster.

IMO the CB7 has way too little caster, so anything you can do to increase it is likely to be a good thing. From memory the spec caster is about 2°. On my car I've increased it to about 7° (which involved shortening the radius rods). This improves steering feel and creates greater steered neg camber at the outside wheel (= more front grip in tighter corners when substantial steering lock is used).

Beware though that a substantial increase in caster angle also causes the end of the steering arm to be lowered significantly, which promotes bump steer as it messes with the 'horizontal' angularity of the tie-rod. Increased bump steer was certainly noticeable with my car after the caster increase, necessitating the steering rack being lowered to eliminate the affect.

[Losiracer2]

I bought this car back in Oct. 14' with a blown head gasket and fixed a whole of bunch of things. New UCAs, LBJs, Quick struts (Leacree, CD5 accord kit), new sway bar endlinks.

I did notice underneath that the front crossmember had some pretty bad gouches on the lower side on the D/S and one of the factory LX alloy wheels was missing a big chunk on the lip. So most likely it was in an accident. D/S headlight is also aftermarket. Hood is aftermarket and the cruise control vacuum box on the D/S inner fender was broken. Not to mention the car was repainted black.....with a cheap flaking paintjob.

So i most likely have some components that are off. I'll take it all apart and see if they installed the bushings correctly. Big one in front and small in back right?

I was going to start with new radius rod bushings to restore things hopefully. Would I need to realign if only these components are replaced? I was planning on just removing that nut in front and the two nuts holding onto the LCA. That shouldn't mess with the toe or camber right?

I guess if it does, I've got a 6 month warranty on the alignment that I can just take the car back and have it redone.

You think LCAs would affect caster? they didn't look bent when i put new suspension on.

[Fleetw00d]

Big one in front, small one in back; both with the larger/flatter end toward the cross member. Particularly with the warranty, I would take it back for an alignment, if not just to check what the caster is. Changing the caster may in fact affect the toe, the camber probably not so much.

[Losiracer2]

Big one in front, small one in back; both with the larger/flatter end toward the cross member. Particularly with the warranty, I would take it back for an alignment, if not just to check what the caster is. Changing the caster may in fact affect the tow, the camber probably not so much.

Yeah its just a pain in the ass waiting at shops. I even had a 5pm appointment today and didn't get in on the rack until 5:50. Only for them to tell me that my caster was not adjustable 5 min later and I've still got the pull issue.

I'll do both sets of radius rod bushings, but how much does removing or adding 1 washer do to the caster adjustment? is it 1 degree each? or 2?

[Fleetw00d]

Yeah its just a pain in the ass waiting at shops. I even had a 5pm appointment today and didn't get in on the rack until 5:50. Only for them to tell me that my caster was not adjustable 5 min later and I've still got the pull issue.

I'll do both sets of radius rod bushings, but how much does removing or adding 1 washer do to the caster adjustment? is it 1 degree each? or 2?

Majestic's site shows just one washer on each side (on the shoulder of the rod before the retaining washer for the aft bushing). I think this is what I have typically found on my Accords when I've taken them apart. So, with the bushings installed correctly, I'd start with one washer on each side and see what that gets me.

The distance from upper to lower ball joint is approximately 19 inches, so if my math is correct, a 1/8 (0.125) inch thick washer is good for about 0.38 degrees. I do not know how thick the stock washer is; you will have to measure one and ratio it to 0.125.

Edit:

93 OEM Service Manual shows caster setting as 3 +/-1 degrees. One adjusting shim changes the caster angle by 25 minutes (0.417 degrees). The caster angle can be adjusted by 50 minutes maximum. One adjusting shim is 3.2 mm (0.13 inches) in thickness.

[sonikaccord]

OT: 7 degrees? Wow, I'm going to try to set mines to 3, I already hate the bump steer I have now at 2.5

You'll definitely need another alignment after fudging with the caster, or at least a print out

[illinois_erik]

the alignment guy i used to work with, told me when he did my SE that the LCA mounts(subframe) are flimsy and its common for the driver side to get bent which throws off the caster, I had about the same readings on mine. I wouldnt worry about it too much, theyre close enough together, and the specs are within -4 to +4

your other readings kinda suck too..not to be crude.. but like the rear toe one reading + and the other - that wont help things at all

[Losiracer2]

I just want to fix my pulling to the right. So I'll start with the new bushings and see how far that gets me.

I doubt the LCAs are bent, they look beefy as hell, seems impossible to bend those.

[johnl]

It's possible to check caster angle yourself (near enough) using a digital 'inclinometer' placed against the small machined area on the front of the suspension 'upright'. On the 'upright' there is a small protrusion that has been machined flat in production. I'm 99% certain this will be near enough parallel (in side view) with the steering axis.

It's what I do to check caster angles, but be aware that some of the cheaper digital inclinometers are less than accurate due to the base not being at exactly 90° to the internal mechanism. With mine I had to sand the base on a surface plate (sheet of glass with emery paper) until it would give equal readings regardless of which way around the inclinometer was placed on the test surface.

I chased a steering pull for ages in my car, and one of the things I tried was messing with the caster angles, to the point of using very asymmetric experimental side to side caster angles. What I found was that the 'pull' was quite insensitive to even quite substantial differences in side to side caster, which I think is due to the car having very nearly zero 'scrub radius' (with greater scrub radius I would expect a pull to be more sensitive to differences in side to side caster).

You could try using the difference in radius rod rubber 'block' length to attempt to equalise the side to side caster. In your case (with greater caster on the left side), on the left side you might try placing the longer 'block' behind the sub-frame (and shorter in front), and on the right side place the longer 'block' in front of the sub-frame (and shorter behind). This will in effect lengthen the left side radius rod (decreasing caster) and shorten the right side radius rod (increasing caster).

It may be a rather blunt tool though, i.e. not a fine increment of adjustment. In theory it may affect dynamic caster angle under heavy braking and acceleration, since the longer block is softer than the shorter block. So, under heavy braking (or acceleration, but less so) you would have at least somewhat more compression in the loaded block on one of the car side and relatively less compression in the loaded block on the other side of the car, which would equate to the change in caster angle (caused by heavy longitudinal loading) being at least somewhat different side to side. Whether this would cause any noticeable problem I'm not sure...

[Losiracer2]

Another thing i was considering doing was putting better or different tires on the car.

The tires on there right now are pretty shitty Primewell PS850s. Basically a crap economy tire, made in china. ehhh, i'm not happy about them, they're pretty new too, only 5k miles or less, but came with the car when i bought it so i figured i'd use them up at least.

I was thinking maybe it could be a tire pull? I haven't yet tried to swap the fronts side to side or rotate the right side and see what that does.

I'm getting free 17" 215/45/17 Yokohama YK580s with 5k miles on them from work, I durability brake test vehicles for my job and one of the perks is the manufacturers always request new tires for each test, and don't really care what happens to them after test so I've got 2 Toyota Prius' with 17s coming off test in about a week.

Just need to find a set of 17s to put them on. (free balancer and tire machine at work too, which I know how use since I worked for Discount tire for 5 yrs).

But this weekend I'll be sure to document what I find, pictures of the old vs. new etc. Going to go pickup the new bushings, tomorrow after work. Wanted to get Energy Suspension ones since they're a lot more durable, stiffer and cheaper, but no one can get them in time so I ended up with O'Reilly Auto Masterpro units.

[johnl]

7 degrees? Wow, I'm going to try to set mines to 3, I already hate the bump steer I have now at 2.5

The bump steer (and by association, roll steer) is caused by the increased rearward inclination of the 'upright' causing the end of the steering arm to be lower than the suspension designer intended. The steering arm is rigidly 'attached' to the steering axis in side view, so when the side view angle of the steering axis (i.e. caster) is changed so to does the vertical height of the tie-rod-end.

When the tie-rod-end is lowered (as happens when the caster is increased) the tie rod angles more upward to the steering rack end, which causes the wheel to gain toe-in with bump motion and toe-out with droop motion. The fix for this is to raise the end of the steering arm (not really possible), or to lower the steering rack.

Note that most car manufacturers will design the steering geometry to have some degree of minor bump steer. This is to achieve a degree of roll understeer. The wheel will toe-out slightly with bump motion, and toe-in slightly with droop motion, so that as the chassis rolls when cornering the outside wheel will 'toe-out' (i.e. steered angle will decrease with roll motion) and the inside wheel will 'toe-in' (i.e. steered motion will decrease on this side too). Car manufacturers typically do a lot of things to induce understeer...

Pulling numbers from my memory, increasing caster from stock (I think it was around 2&#176 to about 7° (might be near 7°, say 6.5°?) resulted in the end of the steering arm lowering by 7mm. To obtain this 7mm number I measured the relative locations of the upper and lower ball joints and that of the tie-rod end, and plotted them (side view) in a diagrammatic drawing in CorelDraw, from which I could measure the affects on tie-rod-end height of any changes in caster angle. It was necessary to estimate as best as I could the locations of the centres of the 'balls' in the ball joints and tie-rod end (since you can't actually see the 'balls'), but for practical purposes this is near enough.

If the end of the steering arm lowers by X with a caster increase, then to maintain the original geometric relationship of the tie-rod to the upper and lower 'wishbone' angles, the steering rack should be also lowered by Xmm. This should in theory restore the original bump (and roll) steer characteristics.

Without lowering the steering rack, the increase in bump steer was quite noticeable, but not so much as bump steer, more so as roll steer. The car would turn in, then as roll motion commenced the outside wheel would gain additional steered angle (bump toe-in), while the inside wheel would also gain additional steered angle (bump toe-out). The car would then steer more than you expected, requiring the steering to be 'backed off' mid corner.

At first it felt kind of more responsive, but after a short while it just felt 'wrong' and 'non-linear'. Note that my car doesn't suffer from much roll motion, the stiffer springs, stiffer rear ARB, and modestly lowered ride height (i.e. lower CG) help a lot, but enough that the roll motion and 'bump steer' induced 'roll steer' was significantly a problem. Lowering the rack helped a great deal.

There is another minor geometric change caused by increasing caster angle, the effective vertical heights of the upper and lower ball joints changes relative to each other (in effect slightly changing the angle of the upper wishbone), but IMO it's not nearly enough to be an issue.

Note also that increasing caster by means of (effectively) shortening the radius rods also increases the length of the wheelbase, the front wheel will be noticeably more forward in the wheel arches (how much so depending on how much shorter the radius rods are).

It will also move the lower control arm forward relative to the ends of the ARB, which makes attaching the ARB to the control arm somewhat more difficult as the link no longer aligns quite as well as it did, and results in the ARB bushes (where they attach to the control arm) being asymmetrically loaded, which seems to shorten the life of these bushes to some degree. This is no longer an issue for me since I've deleted the front ARB (less understeer, though the reduction in roll stiffness does mean you need stiffer than stock springs and a decently stiff rear ARB).

You'll definitely need another alignment after fudging with the caster, or at least a print out

I do my own alignments with stringlines and the afore mentioned digital inclinometer. I also place weights in the driver's seat to simulate the condition in which the car is most commonly driven, i.e. with me driving and no passengers. There is a significant difference in side to side camber angles when the car is unladen compared to having the driver (only) in the car.

[illinois_erik]

I just want to fix my pulling to the right. So I'll start with the new bushings and see how far that gets me.

I doubt the LCAs are bent, they look beefy as hell, seems impossible to bend those.

not the actual arms, the stamped metal theyre attached to. stripping the old cb it took me 20 seconds to cut the arm free with a sawzall because of a seized bolt wasting my time. for the pulling like i said b4 with the rear toe being what it is, its probably dog walking a bit.
the caster will be a minimal contributing factor to the pulling, i could understand if one side was like -3.8 and the other side was +1.2..but your values are close enough to each other to not really matter. casters more for like the steering wheel "auto centering" when coming out of a corner, if you have to "help" the steering wheel along coming out of the corner, then caster is an issue. The pulling will be the toe, specs like -1 degree front 0 rear. youre sitting slightly pigeon toed up front and the ass end isn't trailing the front.

[johnl]

Caster is associated with 'trail', which is one of the things that create the self centring action. Increasing caster increases trail, which increases self centring. When scrub radius (the lateral offset of the effective contact patch centre relative to the steering axis projected ground point intersection) is at or very close to zero, then regardless of the 'trail' length or caster angle the wheel will always try and self centre directly behind the point at which the projected steering axis intersects the ground in front of the effective centre of the contact patch. The self centring action will be the same at each front wheel, only the strength of it will change depending on trail length. If trail is significantly unequal side to side, and scrub radius is zero (or very close to it), then the car will track true with no steering pull, but may steer more easily (lightly) in one direction relative to the other.

On the other hand, if the scrub radius is significantly large (common on RWD cars, less so with FWD), then the effective centre of the contact patch will try and 'swing' around the steering axis until it is directly 'trailing' (following behind) the steering axis ground intersection. The longer the trail (by implication the greater the caster angle) the more strongly it will try and do this. So, if the trail / caster is significantly greater on one side of the car than the other then a steering pull will result because the forces trying to align the centre of each contact patch directly behind the steering axis ground intersection are stronger on one side relative to the other, and the wheel has to turn in order for this to occur (when significant scrub radius present).

Note that I've used the term "effective centre of the contact patch'. This is because the effective centre isn't always in the actual centre of the contact patch, but is strongly affected by the camber angle. So, if there is (e.g.) nominal zero scrub radius and there were say significant negative camber then the effective centre of the contact patch will be to the inside of the actual centre of the contact patch. That is, the effective scrub radius will be negative, and this will introduce forces that could affect steering pull despite the nominal scrub radius being zero...

The other cause of self centring is king pin inclination (i.e. KPI the front steering axis angle as viewed from the front of the car, aka steering axis inclination or SAI). This acts with gravity 'pulling' the car mass down until it finds it's lowest possible point, but isn't affected by car speed (as self centring created by trail is). KPI also has very little if any affect on steering pull (even if side to side KPI is significantly different), since the forces involved equalise through the tie-rods and steering rack.

Tyres can cause a steering pull, whether due to wear pattern and / or internal problems with how symmetrically the belts have been laid up during manufacture. All radial tyres have an inherent degree of tendency to pull in one direction or the other, depending on the angle of the cords in the outermost belt, but it's normally so small as to be unnoticeable.

Front toe doesn't cause steering pull, the forces equalise through the linkage. If front toe is unequal side to side then all that happens is for the steering wheel to be off centre. Rear toe may cause a pull, because rear toe can't equalise through a steering linkage. The car will 'crab' if rear toe is unequal side to side. Crabbing will cause the front wheels to be steered off centre, which may cause some degree of pulling.

Sorry to be less than clear, haven't got time to edit better, off to work...