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 Slow returning steering

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booster



Posts : 251
Join date : 2020-04-21
Location : Andover, Minnesota

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PostSubject: Slow returning steering   Slow returning steering Icon_minitimeSun Jul 25, 2021 3:08 pm

I have always thought the RMW steering returned to slowly, and even my wife commented on it so I know it was obvious. I have incrementally tried different things to see what helped and what didn't since I rebuilt the entire front suspension shortly after I brought it home 8 years ago with 117K on it. I got rid of the variable assist very early on as it was messing up in turns by changing the effort.

* Ditched the damper---helped some

* Aligned to max caster I could get within the range of shimming---got to 2.5 degrees ----helped some

* Modified the upper control arms to get more caster---now at 5.5 degrees---helped noticeably

* Put in a Lee Power Steering rebuilt gear with 14 to 1 fixed ratio and 30 inch pound torsion bar---helped some

* Replaced the way too tight Mevotech junk upper balljoints from the rebuild with tall Proforged ones and aligned to negative camber---helped some.

* Got rid of the stock oil lines to the gear and replaced with -6AN hose for both pressure and return, running them across in front of engine so much straighter with sweep fittings and shorter path---helped a lot, probably even more than the caster increase but hard to quantify. It surprising also improved the centering and center hold so improved straight line stability which was a surprise bonus for me.

It now has the pretty much the exact feel I prefer in a street car. Medium effort, moderately fast gearing, good return and feel. It comes back just fast enough to keep the exiting a turn smoothly just as if I was doing it by hand like I used to have to do. It doesn't have enough overshoot at center to be of any concern and nearly comes to a completely smooth stop on center by itself if released.

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Fred Kiehl

Fred Kiehl

Posts : 6013
Join date : 2009-11-13
Age : 72
Location : Largo, FL 33774

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PostSubject: Re: Slow returning steering   Slow returning steering Icon_minitimeSun Jul 25, 2021 6:46 pm

You should have less than 1 degree of negative camber on both sides. Camber will not affect the return, only tire wear.

The 5.5 degrees is a bit much for the caster. 4.5 is about the most you should need. Caster will affect the return to center. I have never heard of modifying the arms to get more caster.

Toe will also have some affect on centering. 0 to 1/32 inch toe in is the best. Toe out will make it feel like it is wandering.

The ratio of the box will have no affect of the centering, although the pressure on the wheel will be slightly higher with a lower ratio (12:1). What the 30 in. lb. torsion bar is I do not know. I do not know of any torsion bars in the front suspension, or steering.





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booster



Posts : 251
Join date : 2020-04-21
Location : Andover, Minnesota

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PostSubject: Re: Slow returning steering   Slow returning steering Icon_minitimeSun Jul 25, 2021 6:51 pm

Fred Kiehl wrote:
You should have less than 1 degree of negative camber on both sides. Camber will not affect the return, only tire wear.

The 5.5 degrees is a bit much for the caster. 4.5 is about the most you should need. Caster will affect the return to center. I have never heard of modifying the arms to get more caster.

Toe will also have some affect on centering. 0 to 1/32 inch toe in is the best. Toe out will make it feel like it is wandering.

The ratio of the box will have no affect of the centering, although the pressure on the wheel will be slightly higher with a lower ratio (12:1). What the 30 in. lb. torsion bar is I do not know. I do not know of any torsion bars in the front suspension, or steering.

I have it set at -1/8 to -1/4* on the camber. Going the tall ball joints changed the geometry from positive camber progression on bump to minus progression so that allowed me to change to the negative alignment point. Camber changes the edge the tire is riding on and they all go negative someplace in the turning amount increase, which I can usually feel. With the positive progression and positive static that I had before, which is the stock setup, I could feel it go from positive to negative during right hand turns which is kind of weird feel of better turning happening all of a sudden.

I kept increasing the caster until I had the best balance of directional stability, cornering smoothness, and centering and it just kept getting better as I went up. I have more on the right than left, which is typical in almost all specs these days and the car drive really well that way with not tire scuffing at all that I can see or hear, even on gravel which is the best place to test it for scuffing.

I normally run the toe in at whatever the parts tell me to do, with 1/32" in the starting point for nice tight new parts. As they wear and get loose, I check while it is on the tables by pushing the rear of the wheels in as far as they will go and then the same thing with fronts pushed in. If the difference in them is measurable with the front being able to go to zero or out when set at 1/32" I will increase the toe in until the front can't move out that far. If a driver gets to be getting near 1/8" it is time to start replacing parts. I fix the fun cars much sooner, though. With negative offset wheel centers on a rear drive the wheels will toe out from driving load so that needs to stay toe in all the time even it is bigger on the gauge check.

Modifying upper arms has been the go to process for "stock parts only" racers for as long they have had those rules. Often you can just move the ball joints to get what you want, but in this case I also wanted to give more adjustment range also and there wasn't room to do that. I cut the arms about an inch from the frame pivot bushings and either added or subtracted some material on the front and rear sections of the arms, then fixtured them up and rewelded them with fish plates for good measure. This is the upper arms so not as high a stress as the lowers. This was several years ago and no problems at all with them.

The torsion bar in the steering gear is the link between the steering shaft and sector but it is flexible and made to twist. When you turn the input the bar tries to move the sector but the sector has all the force of turning the wheels to over come, so the torsion bar starts to twist. The actuators for the hydraulic assist valve are on the torsion bar so when it twists it will open the valves as far as it twists. More traction means more force to overcome which means more twist and more assist. The 30 in-lb is how they rate them, measured by using an in-lb torque wrench to see how much force it takes to twist the torsion bar far enough to actuate the valve. Higher rating means higher steering wheel force needed so the more "firm" steering description. I think the overly boosted stock RM steering uses like a 15 in-lb bar in it. Road racers and handling geeks that aren't looking for ease cruising might to 35 in-lb or higher for more feel. I think the Impala SS cars had firmer bars in them and maybe the 9C1 cars also.
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PostSubject: Re: Slow returning steering   Slow returning steering Icon_minitime

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