Many production vehicles
have mechanical stops mounted on the
suspension that limit the spindle rotation.
If a limiter wasn't provided it might be possible for the steering
of the suspension or the tires to contact other parts of the vehicle.
After making changes to the steering
system or suspension geometry while building or modifying your
suspension, it is
possible that some part of the wheel assembly etc might then interfere
other parts of the suspension or chassis.
Details of why steering limiting might be required
I realize that
limiting the steering the way I did it is nothing new
and has been done many times before.
But I want to present the details and the precautions that need to be
taken for other builders who might not
have seen how it's done.
Some (most?) rack &
pinions can move the rack shaft as far as the
teeth on the rack will allow it to move. The system depends upon
an outside device to limit the maximum amount of wheel angle in a
turn. Often when people build their own cars this limiter
device is left
off or is in the wrong place because of the changes made to the
I modified my steering so that two turns lock to lock of the steering
wheel turned the front wheels the same amount as the old three turns
lock to lock did. The rack and pinion itself could still be turned
three turns lock to lock though. This caused my Heim rod end
mounting bolts to hit the lower control arms when the steering
wheel was turned more than one turn off center. (The bolts are
1" lower than the original hardware.) Obviously
the number of turns the steering wheel could be turned needed to be
What's involved in doing this change?
Basically all you need to do is remove
flexible gaiter from each end of your
rack pinion, measure a few things on the rack and make up some
spacers to limit the amount of movement of the rack shaft. You then
slip the spacers onto the rack shaft at each end and
put everything back together.
Sounds easy enough, but you do have to
make your measurements accurate so the steering wheel turns
the same amount to the lock position left and right and check that the
suspension doesn't bind or cause the steering arms etc to interfere
other parts of the car. And you want your steering wheel to be centered
when the car is driving straight down the road.
Why worry about having the steering wheel turn off
center the same amount?
reason is so that the car will have the same turning radius
turns left or right. Otherwise you may get into trouble later thinking
the car can
turn tighter in one direction when it is really the OTHER direction
that has the smaller turning radius. Also it is possible that one tire
might drag on the chassis and the other does not.
Considerations and precautions
Some racks may have the bearings for
the rack shaft at the end of the rack housing. In this case the spacer
can just be centered on the rack shaft diameter and it will limit the
amount of travel of the rack shaft. I'd taper the hole ends of the
spacer so it doesn't catch on the rack teeth.
Other racks, like mine, have recessed outer bearings for the rack
shaft. i.e. the bearing is not at the very end of the housing but is
recessed a short distance inside housing. In this case the
spacer needs to be made so that it will be a light press fit INTO the
end of the housing (or the inner diameter of the spacer should be only
a slightly larger than the rack shaft diameter to center the spacer on
the shaft to clear the housing).
The reason for this is, if the spacer has a larger diameter hole than
the rack shaft and were allowed to lay on the rack shaft it could catch
on the end of the housing in a turn and change the amount of lock in
that direction. This is not safe!!
So plan on doing a little machining to get the spacers to fit
properly on each end of the shaft or into the housing.
Determining the size of the spacers
First thing is to support both lower control
arms so the tires just clear the ground. You need to do this
that the wheels can be turned through their full range of movement.
Next remove the gaiters from the rack. If you have to take the tie rod
off the shaft to do this and then put the link back on hand tight once
the gaiter has been removed. The outer end of the steering links should
connected to the steering arms.
Measure the maximum diameter of the rack shaft and write it down.
A. If you know how many turns lock to lock
you want your steering to have do this,
Center the steering wheel. Now turn the
steering wheel to one half the number of turns you want the steering
wheel to be in either direction. I wanted two turns (total)
to lock, so I
turned the wheel one full turn; first in one direction from center and
then the other direction. Check the various steering parts
the steering arm, links etc on both sides of the car for clearance with
the steering one turn off center in each direction.
On my setup, one
turn in either direction allowed
the suspension parts to have the interference clearance I wanted so I
was OK to continue.
Again, do the following in each direction. Measure the
distance from the rack bearing to the inside edge of the
mechanism that holds the tie rod to the rack with the steering wheel
turned in the direction you are going to measure.
to put it
another way, turn the steering in one direction and measure the side of
the rack that is sticking out of the rack housing the least.
want to measure the distance from the rack bearing in the housing
to the outer part of the rack that the spacer is going to
finally touch to stop the rack movement.
Turn the wheel to the opposite side lock position and take the
same measurement on the other side of the car.
Write the numbers down as they will more than likely
be different from side to side. These
measurements are the length of the two spacers you need to
There is a picture
below that illustrates where the measurement is taken on my rack.
B. If you want use the maximum number of
turns lock to lock
Center the steering wheel and then while
counting the turns of the steering wheel, rotate it in one direction
until the suspension or tire has interference with some object. Take
note of the number of turns it took to create the interference.
Take into account that with suspension movement up and down
might occur sooner than at ride height.
Re-center the steering wheel and then turn the wheel in the
other direction to see which
direction gives the minimum number of turns to contact something. Use
the minimum number of steering wheel turns as your new lock
to lock MINUS a small fraction of a steering wheel turn to allow for
clearance between the interfering parts. Don't forget to consider that
the interference measurement may change as the suspension moves up and
With the steering wheel at your new off center lock turns, measure
the distance from the bearing to the inside edge of the
mechanism that the spacer is going to finally touch to stop
the rack movement.
Now turn the wheel to the opposite side new off center lock turns and
same measurement. Write the numbers down as they will more than likely
be different from side to side. These measurements are the length of
the two spacers that you
need to fabricate.
I must say though; why you would want the maximum number of turns on a
light sports car is beyond me.
enlarged view of most pictures, left click on a picture or right click
and select "View Image"
This is what one of my
spacers looks like. One of
these sleeves is placed on each end of the rack shaft. The length shown
here more than likely will NOT be the same that your rack needs.
the two sleeves will probably NOT be the same length or even the same
diameter and that may determine how you want to make the spacers. The
bearing on the pinion
side of my rack had a tapered hole beyond the recessed bearing. The
end of the rack had a straight sided tube to the recessed bearing.
I decided to make up spacers that would be a press fit into both ends
rack rather than "floaters". I did this because I had a piece
of thick walled aluminum pipe that the outer diameter of the pipe could
machined down to fit both ends of the rack housing. The inner
diameter of the holes at the end of the rack housing are much larger
than my rack shaft diameter.
This picture shows one
spacers laying on the rack shaft before installation. The spacer outer
machined so it is a light press fit into the rack housing (towards the
right of the spacer).
The recessed bearing is positioned about 1/2" inside the end of the
I first screwed on the
rod end inner retainer (the large, domed piece of metal in the
middle of the picture).
The spacer was started into the housing by hand. I then turned the
steering wheel so the tie rod inner retainer pressed the spacer into
the rack housing as shown here. Quick and simple.
After both spacers were
installed, I tightened the tie rod retainers and replaced the gaiters.
This shows how much
clearance (~1/4") I allowed between my Heim rod end mounting bolt head
lower control arm after I had modified the suspension to correct bump
steer and to give proper Ackermann.. The other side of the car had the
You can see a small chip of paint missing where the bolt head had hit
the lower control arm in setting up the suspension.