Correcting the handling problems.
1. Front steering rack adjustment.
Over the winter there has been a great deal of progress made to improve the handling and ride of this 1952
Chevy truck. Although some improvements had been made, there was still a “bump-steer” problem and the ride
and handling were far from perfect. The Mustang II type front suspension upgrade is fitted to this truck and
a problem was identified relating the position of the rack. Originally the rack was a manual one. The truck
had bump-steer problems and when the power rack was fitted in the same place as the manual rack last summer,
the bump-steer problem was exactly the same. It was noticed that the arms at the end of the rack were not
horizontal. They were pointing upwards at an angle of about 35 degrees looking from the front. Also they were
pointing forwards (looking from above). It was realized a misalignment problem of that type would cause any
slight dip or bump in the road surface to pull the wheels all over the place during normal driving – and
they did! Looking at pictures of the Mustang II kits in catalogues always showed these arms to be horizontal.
An example of a Mustang II hub to hub kit.
Talking to the suspension company “Heidts” it became clear that the welded-on brackets on the front of the
cross member that held the rack, did not angle upwards and also that there should be two additional round
thick spacers that moved the rack further forwards of the cross member. Angling of the rack has an additional
benefit, it allows the angle between the lower parts of the steering column and the rack input shaft to be
less acute. The brackets and spacers were ordered from Heidts and they arrived. Taking the rack off and
fitting new (angled) brackets would have been a two day job as the access is very poor. It was decided instead
to cut the bottom of the existing (non-angled) brackets, then angle them upwards and weld in some metal to fill
the gap at the bottom. This would make them similar to the new brackets. An additional benefit of this method
is that the angle could be adjusted in the bending / tilting process so that the rack could be as high as
possible without touching the chassis. If new brackets were to be fitted, the rack might then foul the chassis
rails and then the whole rack would have to be pulled off a second time to modify the new brackets. Working
with what we had would be much easier. After the alteration was completed, the round spacers were also fitted.
To summarise, the rack was tilted, moved forwards and lifted. The result of this did not bring the ends of the
rack horizontal (looking from the front). The final angle was, maybe about 15 to 20 degrees (much better than
35 degrees). The mod. did, however, move the rack forward as well so looking from above, the rack ends were now
correctly aligned. During this upgrade it was decided to check the upper and lower suspension arms. It was found,
by measuring to a central reference point at the front of the truck, they were in fact misaligned. The top and
bottom arms on each side were not the same distance from the reference point. To put it another way, the top
arm was either forward or backwards of the lower arm and they were not even the same when comparing the left
and the right hand sides. This was all corrected during the rack modification and completed by the end of Feb. 08.
When the truck was road tested, the handling of the truck was much improved. It was not clear how much the
misalignment of the arms had contributed to the problem but the corrected position of the rack was a key factor
2. New front springs.
The next plan was to bring the ends of the rack fully horizontal by fitting new stiffer front springs, or use a
spring spacer. It was decided to buy both but to try the stiffer springs first. 325 lb springs were ordered
from “Heidts” and were duly fitted. The amount of lift was smaller than expected. The truck did not rise more
than 12mm (and that would probably settle back down) and the arms were still not horizontal although they were
better. In the middle of this corrective upgrade it was also discovered that one of the ball joints was not
tight and this certainly contributed to the steering having an unpredictable feel to it. Also the hole in the
arm that held the ball joint had been elongated by the loose ball joint and was now a slot! The ball joint was
tightened up and a note was made to correct the slot problem later. The road test showed another big improvement.
We could have fitted the spring spacers but the new springs did not seem to be any stiffer than the old springs
(after a bouncing test). Heidts were contacted and agreed to take back the springs and supply 375lb springs.
This was done and late in March the stiffer springs were fitted. This made a big difference to the angle of the
rack ends. The front of the truck rose 50mm (although it could settle back 10mm or so) and the ends of the rack
were now horizontal. During this upgrade to stiffer springs the elongated hole in the control arm was expertly
welded back to a circle. Clearly this saved having to order and pay for a new arm!
In the road test, bump-steer had now been completely eliminated and the ride was also much better. Road surfaces
seemed remote and really the ride and handling was similar to that of a modern truck or SUV even though the rear
springs still needed attention.
The next step was to fit new rear leaf springs. It was expected there would be an improvement here as the existing
springs were old and the left side had 5 leaves and the right side and 4 leaves! The original springs for this truck
have 8 leaves on the left and 8 on the right. These were ordered from “Obsolete Chevy Parts” and fitted late in
March 08. They had the effect of raising the truck about 100mm and making the rear suspension so stiff that the
truck bounced along the road! At the beginning of April it was decided to take 4 leaves out of each 8-leaf spring.
This brought the suspension back down to a level about 25mm above the level of the old springs (and 10mm might
disappear with settlement). The truck now drove smoothly. In fact the final ride is very comfortable. It may be
necessary to put another leaf back in making 5 on each side if the settlement ends up being to too much in the
next few weeks but at the moment it looks ideal. New U clamps (plated steel) were ordered and fitted from
“Speedway Motors”. A new leaf spring plate was manufactured to suit the width of the new bump stops (see part 3)