Theoretically, all a dropped spindle does is relocate
the tire vertically with respect to the rest of the truck.
It doesn't change the suspension geometry so bump
steer isn't affected. The current gen Daks can't use
the stock rim diameter when you go to a dropped
spindle. To get a two inch drop, you probably have to
increase to at least a 17", most likely an 18". This is
due to clearances between the wheel and the upper
and lower ball joints. On older suspension designs,
the ball joints resided inboard of the wheel. Modern
suspensions are migrating towards positive offset
wheels. This tucks the ball joints inside the wheel.
My experimenting has shown me that bump steer is
not a big issue on a 2" drop (via coils) as long as you
aren't running a low profile tire. The larger sidewall
of the stock tire profile absorbs a lot of the impacts that
would cause bump steer. One advantage to dropping
with a coil is you can change the rate of the spring,
allowing the designer to fine tune the performance
characteristics.
Gary Pinkley
97 Reg Cab V-6 5 spd
lowered monochrome red
255/50-17 BFG Comp T/A ZR4
Budnik 17x8 wheels
-----Original Message-----
From: Michael Z-Sykes <msykes@su.edu>
To: dakota-truck@buffnet.net <dakota-truck@buffnet.net>
Date: Wednesday, November 11, 1998 2:43 PM
Subject: Re: DML: BUMP STEER attn Gary
>You seem to be the Guru on this, so I ask, would a dropped spindle
>correct bump steer?
>
>-mike d.
>
>>>> Gary Pinkley <gapinkley@earthlink.net> 11/08/98 01:08pm >>>
>The Western chassis dropped A-Arm does not correct
>bump steer.
>
>Dakotas have bad bump steer when lowered beyond
>2". This is caused by the angle of the steering tie rods
>with respect to the rack. The factory designs steering
>geometry to cause slight understeer. In this condition,
>the tie rods point slighly downward from the rack at ride
>height. This allows the wheels to point slightly outward
>during cornering. Subjective testing by automakers has
>shown that normal drivers feel more comfortable with
>slight understeer versus oversteer. Slight understeer can
>be corrected by simply lifting off the throttle on a rear wheel
>drive vehicle. This is a natural reaction when your car is
>pushing towards a guard rail. Lowering beyond 2" on a Dak
>angles the tie rod upwards. This gives oversteer, i.e. the
>truck's steering seems to be overly sensitive and twitchy
>when cornering. Also if you encounter a bump during that
>corner, the truck will seem to dart to the inside, seeming
>to change lanes without warning.
>
>As I stated above, the dropped A-Arm DOES NOT correct
>bump steer. The only way to correct bump steer on a lowered
>Dak is to change the angle of the steering tie rod. The dropped
>a-arm only lowers the spring pocket, changing the pre-load on
>the spring, allowing the vehicle to sit lower. Only by relocating
>either the rack (can't be done without major surgery to the Dak)
>or by lowering the outer tie rod ball joint can you return your Dak
>to the factory geometry. Changing the outer tie rod location can
>be accomplished in several ways, all of which require increasing
>the rim diameter above the factory 15" size. You can cast a new
>spindle which has it's steering arm lower than stock, you can try
>to put spacers between the tie rod and the spindle, or install a new
>tie rod end that has a longer stud. Looking at the factory spindle
>with 15" rims, you will see that there is no room to play with the
>vertical height of the ball joint.
>
>Gary Pinkley
>97 Reg Cab V-6 5 spd
>lowered monochrome red
>255/50-17 BFG Comp T/A ZR4
>Budnik 17x8 wheels
>
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