S2000 Roll Center Adjusters Explained

     Roll Center Adjusters (RCAs) are a common mod for S2000's but not generally very well understood. I'd like to try to clear up some of the misinformation by going over what a roll center is and what benefits a roll center adjuster can provide.

What is a Roll Center

     A roll center is the point around which the chassis rolls in a turn. The primary importance of the roll center is that it's height has a large impact on the amount of body roll in a corner. Because of the difference in vertical position between the roll center and the center of gravity (CG), a roll moment is created any time the car is in a cornering.  A higher roll center (thus closer to the CG) produces less roll moment for a given lateral acceleration,  a lower roll center (thus further from the CG) produces more.  For a given set of springs and anti-roll bars, a car with a higher roll center will roll less.  Because stiffer springs and anti-roll bars produce a harsher ride,  if you can get additional roll stiffness for proper roll center heights, that allows for a smoother, more supple ride without any additional harshness.  

     On a lowered car, the roll center is also lowered,  because of this it's very beneficial to raise the roll center back up to it's original point.  By adding a longer lower ball joint, you're able to restore the original roll center height and have the benefits of a lower car as well.

What a Roll Center Adjuster is NOT (camber adjusters)

     Although typical front RCAs do provide additional camber, camber has nothing to do with roll centers. The offset camber function is very helpful as s2000s cannot achieve sufficient front camber for best performance on track but is separate from the roll center adjustment function.  Between the variety of manufactures that produce lower ball joints,  you can get any combination of RCAs with or without added camber or visa versa.

     Sakebomb has used and installed front and rear roll from many companies including J's Racing, Spoon, Buddy Club and Hardrace. Here is a rundown of our experience with each.

Front Roll Center Adjusters

Hardrace 

     The best overall choice in our experience. The ball joint and seal boot quality is fantastic with our development S2000 having over 65,000 miles over 8 years, countless track days and no issues. They are a great value being a bit cheaper than J's Racing and provide the sweet spot in terms of RCA and Camber offset.

J's Racing 

     Typically a bit more expensive than Hardrace but other than that there is no real difference. They offer several different configurations of different RCA offset and camber offset but none provide a measurable benefit on track in our experience. Can't go wrong with J's racing but there's no real benefit over Hardrace.

Spoon

     The only steel RCA, good quality but more expensive than other options. As we've never seen any issues with the aluminum offerings from J's or Hardrace there is no need for steel and with the extra price you can purchase a set of Hardrace rear roll center adjusters.

Buddy Club 

     These offer an easy way to change camber in discrete intervals but as changing the ball joint offset effects toe, an alignment must be performed after adjustment. As a result this is no easier than using the factory camber adjustment. Additionally most of the buddy club RCA's we've seen at the shop have had failed seal boots, this leads to premature wear and possible failure if not replaced.

Rear Roll Center Adjusters

Hardrace 

     Again the sweet spot between price and performance. Like the fronts, we've put tons of miles and abuse into the rear RCAs without issue. Provides a 15mm offset compared to stock rear ball joint.

J's Racing

     Same as above. Very good but not worth the price premium compared to Hardrace for the same performance. The one difference is that they offer 12 and 20mm versions but in our testing the 15mm Hardrace RCA is a good sweet spot for the vast majority of cars.

     Ready to try out Roll Center Adjusters on your S2000? We stock Hardrace S2000 RCAs along with our complete line of suspension products here:

Hardrace S2000 Front Roll Center Adjusters

Hardrace S2000 Rear Roll Center Adjusters

Interested in more details?

     I won't go into the details here about what happens if your roll center is too high, but if there's interest I can do a much more in depth. If there is interest I can do a follow up post going into more technical details about the kinematics and forces at play. Please let me know in the comments below if you're interested in even more details or if you have a question that hasn't been discussed.