How much caster do I really need?

All,

I am working on setting the alignment for my Duster with the Hotchkis UCAs installed. I'm shooting for a performance street alignment, so I was trying to hit the Hotchkis specs of 1.5 degrees camber and 6-7 caster.

I could have sworn I put the rod ends in correctly in their UCAs to the directions, but I am only able to get 3 degrees caster on the passenger side and 5 or so on the driver's side.

Before I tear the front end apart, would 3 still be decent or do I really need to get it to have 6-7? and if so, how much should I turn the rod ends on the UCAs when they are out? I have to remove camber with the rear bolts because the front ones are pushed outboard as far as they go.

Thanks for any help!

Anything above 4 is going to make the car track straight and improve the on-center feel. If you're not looking for every last .10 on a track, don't worry about it.

You don't NEED any positive caster, in fact I believe a lot of manual steering vehicles used NEGATIVE caster for ease of steering.

But you will surely want as much as you can.

Well I decided that for now I'd leave it with 3 degrees on each side (adjusted the driver's side to match the passenger side). Seems to drive pretty nice. Pretty responsive - I'm not sure if more caster would make it slightly less responsive on center or not. It at least goes straight and seems to transition well side to side (and consistently).

For a street car 2-3 degrees is about right.

Agree 3 should be enough and sounds like it drives fine. 1.5 degrees (negative I assume) camber sounds like a track setting... may wear the tires unevenly. If mostly street driven .75 degrees negative may be a better "balance".

If you really want the higher caster, may need adjustable strut rods. I did mostly because of part variation and poly LCA bushings. Cranking them in a bit helps caster... just can't overdo it and bind up the LCA bushings.

I actually have adjustable strut rods as well. They are the RMS ones. Anyway, those are set just to get the slightest amount of pull forward on the poly LCA bushings.

I wouldn't call 1.5 degrees negative camber a track alignment. Most people who are going for that have 2-3 degrees in there. In any case, I'm not too worried about tire wear. Have you seen the alignment specs on most of these compact SUVs, or anything like a BMW? The rear camber is, in a lot of cases around 2 degrees.

It handles pretty much amazing with it set this way, It's never felt anywhere near this good. I ended up with 1/16" toe per side.

If your willing to settle for 3* of caster, you should have saved yourself $800 and just used offset bushings in stock arms.

A big part of the point in going with the Hotchkis arms is the additional caster they provide. With the stock eccentrics and the heim jointed ends, you should be able to get much more than 3*. Ideally you want to have at least as much caster as you have Steering Axis Inclination, if not an extra 1-2* over that. Since the stock SAI is between 6-7*, there is a your caster target.

The whole point of high caster angles is the additional stability it provides in a straight line as well as the negative camber gain it provides as the car steers into a turn. I'm not sure what t-bars you have, but this negative camber gain is a very important gain on most cars, and especially on softly sprung cars that generate more body roll. Caster will also allow you to get the steering back to center much faster when exiting a corner as it leverages the suspension coming out of a turn and will move the linkage back to center with greater ease than you can whip a steering wheel around.

You paid for high tech parts, why not use them as intended.

Well, I didn't pay $800 for them, I paid about the same price as any of the other tubular arms (they were sold to me as unused second hand with some minor blemishes). I also think there must be something else going on here other than the ability for extra caster. The camber change on the car is noticeably different (I have run the same ride height before and after).

I'm good with taking them out and messing with the heim length, however, I want to do it once and was hoping that someone was experienced enough to tell me about how much I should turn them relative to their current position. I can get more caster, just with more camber as well right now. In any case, it will work for right now, and I can mess with it once I have some other things done to the car.

The car has the 1.06 Torsion bars from Firm Feel, RMS Strut rods, the hotchkis UCAs, Hotchkis/Fox Non-adjustable shocks, and the Hotchkis sway bars (need to put my new/different exhaust on so the rear fits), and the Hotchkis subframe connectors, oh and the Borgeson steering box.

For an initial "rough in" setting I run the forward heim to half way out and the rear heim to one thread showing above the lock nut. On most cars that will net you 7-10* caster and still give you plenty of room to run between 1-3* of Camber. Best of luck!

So Dan, does half way out mean exactly half the total threads showing on the heim?

I kind of wish the directions would have said this originally if that's the case. Not sure where the .33" came from.

If you remove the heim, run the adjuster nut so that it has an equal number of threads showing on each end of it. Reinsert the heim into the UCA and reinstall.