240 Quick Steer Roll Correction
- One piece cast 4140 Heat Treated Alloy Steel
- Utilizes factory ball joints and tie rods.
- Fixes suspension geometry issues caused from lowering without adding excessive single shear loads
- Adjustable Steering Ratio
- CAD engineered and FEA validated design
300 USD + shipping for 1 pair (1 LEFT & 1 RIGHT) including mounting hardware.
345 USD + Shipping for 1 pair (1 LEFT & 1 RIGHT) w/ Ackermann adjustment slots and alignment plates.
Quick Steer Roll Correction's purpose is to correct the front suspension geometry issues that result from lowering the car. Suspension systems have an "imaginary" point called a roll center (RC), the roll center is the point at which the cars suspension system pivots around. The location and height of the roll center is very important to how the car handles and accelerates out of corners. The height of the center of gravity (CG) of a car and the height of the roll center have a relationship that can be described as a lever arm. The longer the lever arm the more force the chassis will be subjected to while cornering. When the front of a 240 or any car is lowered the roll center moves below the ground. This increases the distance between the CG and RC, in effect it increases the lever arm length and therefor increases the amount of body roll the car is subjected to. The front suspension has a separate roll center from the rear suspension. The rear suspension in a solid axle car has a geometry where the roll center height changes very little when the car's ride height is lowered. This leaves the rear RC high and the front RC low. If one to draw a line between the two roll center heights you would see there is an angle. The angle can be described as the roll axis inclination angle. The steeper this angle the harder it is to put the power down on corner exit. There are many other things that roll center height dictates but adjusting the front RC will affect how the back of the car works as well.
The Quick Steer Roll Correctors are unique because they have an integrated steering arm, the typical/generic approach has a been a long bolt installed with a spacer off the steering arm and a separate spacer for the ball joint bracket. This is far from ideal because you are putting a large cantilevered single shear load on the bolt that supports the tie rod / rod end and this can lead to failure. The Quick Steer Roll Correctors have integrated steering arms that are compatible with the factory tie rod ends, this means no over loading in single shear. The new steering arm also presents an opportunity to modify the steering leverage ratio. The Quick Steer Roll Correctors have multiple steering leverage ratio options, The stock ratio is available, 20%, and 35% quicker ratio option. For comparison sake, the power steering has a 3.5 lock to lock ratio stock, 20% is 2.8 and 40% is 2.3. The manual rack has a 4.34 lock to lock ratio stock, 20% is ~3.5 and 35% is ~2.8. Now these lock to lock comparisons are not technically correct because the lock of the steering rack is still the same but it is a way to make a comparison that many are familiar with.
The Quick Steer Roll Correctors eliminate the need to use the factory tapered ball joint receiver, The bottom of the roll correction spacer is tapered to match the stock 240 balljoint. The holes on the steering arms are also tapered to match the stock 240 tie rod ends. If prefered to use a rod end and bolt they can drill the tie rod holes to 14mm.
Finite Element Analysis (FEA) helps us to maximize stiffness and strength of the part while minimizing the weight.
The flange is a very tight fit to the factory spindle and the quality of this fitment ensures a good engagement with the machined large diameter arc that is on the factory spindle. By making this tolerance tight it helps to reduce torsional loads on the mounting bolts because the part can not twist without deforming the spindle
This part has an effective height of 2.0" this is ideal for lowering the car between 1.5 and 2.0 inches. To maintain good geometry with addtional lowering we suggest you also purchased an additional spacer. The spacer drops the entire assembly. Spacers are available in 1" and .5" heights.
Thoughts from prototype dynamic testing @ auto-x:
The car has a good amount of grip, it feels more planted and stable then without the spacers. The acceleration out of corners due to the increase in the traction is impressive especially considering the test car is running an open differential.
The steering ratio feels very nice, for 99% of driving I don't have to shuffle my hands or cross over. Driving on a curvy highway at speed requires very small movements to point the car. Another nice aspect is the reduced leverage ratio gives more feed back through the steering wheel, which with power steering is very isolated. Driving through slaloms at a faster pace is easier as less hand movement is required.