Project EP3 Civic Si: Fixing EP3 Bumpsteer with Hardrace

by Mike Kojima

In prior editions of Project EP3 Civic Si, we went over the history of the car, the worst handling Civic made with suspension geometry taken right from the Stream minivan. Well, so far we have gotten rid of squishy rubber and added swaybars with help from Whiteline. We also got rid of the flaccid shocks with a set of coilovers from Fortune Auto.

Perhaps the worst issue with the suspension of the EP3 is the large amount of bump steer present in its steering geometry. With its origins coming from a van, apparently, the steering was designed for ease of running a steering column instead of any kind of aspirations of good handling. In fact, the layout of the steering is perhaps the worst that we have seen in a modern car!

Ideally, in a McPherson strut front suspension, the steering rack should be placed so the inner tie rods pivots are in line with the lower control arm pivot bolts with the outer tie rods being in the same plane as the ball joints. On an EP3, the steering rack is midway up the firewall. The rack is also very short and the tie rods very long; this makes for a lot of toe in under suspension moments.

The constant big changes in toe makes the car squirm around and wander which is annoying, and in some cases, it's so bad it makes it hard for the car to stay online. All is not lost- we have obtained some parts to help reduce the bump steer, hopefully, to manageable levels.

To read more about Project EP3 check here!

We got a set of these bump steer correcting tie rod ends from Hardrace. These parts relocate the tie rod from the top of the knuckle to the bottom. This moves the tie rod pivot point down about 2 inches from stock. This is about an inch too far for optimal bump steer reduction, but since it is on the far side of the knuckle, it at least can be moved.

Here you can see how the shank of the Hardrace tie rod end has the taper on the opposite side as normal. The tie rod end itself is a spherical bearing rather than a ball joint. This makes for less play. The spherical bearing is shielded from the environment by a rubber boot.

We also installed Hardraces roll center correcting ball joints. The balljoints have a longer body which relocates the pivot point of the of the balljoint almost an inch lower. This raises the roll center and goes a long way to correcting its location which dropped when the car was lowered. Correcting the roll center height increases geometric anti-roll and helps improve the poor camber curve of lowered McPherson strut suspension. If you want to learn more about roll centers check this out.

On an EP3, the ball joint presses into the knuckle instead of the control arm so to relocate the pivot of the ball joint, it has a longer body to move the pivot down. Your typical roll center correcting ball joint that presses into the control arm has a longer shank to do the same job. The relocation of the ball joint pivot lower corrects the too low position of the inverted Hardrace tie rod end!

7 comments

David Estey says:
August 13, 2018 at 5:57 am
This EP3 series is awesome. I love all the insight Mike gives into this car’s weird handling dynamics.
I have a question about replacing all these bushings and roll center adjuster ball joints and tie rod ends: Is it OK to replace these parts on the stock suspension or is a lowered ride height needed for these adjusters to be effective? Thanks!
1. Mike Kojima says:
  August 13, 2018 at 9:52 am
  The bushings and steering rack spacer work fine on a car at stock ride height but the roll center adjusters and bump steer correctors are best on a lowered car only.
  1. David Estey says:
    August 13, 2018 at 11:47 am
    Mike, thank you so much! I will plan my replacement parts/upgrades accordingly.
Richard says:
March 5, 2019 at 7:29 pm
My Civic Si is the ’04 EP3, and Hardrace’s website say the roll center correcting ball joints are for 01-03 only? What parts do I need to replicate this on my EP3 if it’s lowered a 1-2 inches?
1. Mike Kojima says:
  March 5, 2019 at 10:43 pm
  Later years use the RSX Type S parts. The geometry needs to be corrected at stock ride height!
Helmi says:
March 12, 2019 at 8:09 pm
Hi Mike, I just bought the RCA and Front LCA spherical bearing to replace the OEM parts on my ‘03 EP3, should I replace both or either one. Thanks in advance.
1. Mike Kojima says:
  March 12, 2019 at 11:05 pm
  If you got them use them!