A Tale of 2 Bushings: Steering Rack Bushings for the 350Z/G35 Comparison

28 May

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Most people will never consider bushings sexy, or even significant parts. But for those who have upgraded them, you know they can pay big dividends in the performance of your car. There are multiple companies out there that make urethane bushings for the 350z and G35. Today we are going to look at 2 versions of the popular Urethane Steering Rack Bushings.

The rack and pinion on these cars is supported in a very traditional fashion – 2 mounts that attach to the chassis via 14mm Grade 10 bolts on one side of the rack, and a third bracket type that uses 2 10mm bolts. Two bushings are in the rack assembly itself; the third is a larger piece that mounted via a clamshell bracket. Very standard stuff. Replacing the bushings can be done in under 35 minutes with the rack in the car. No lines need to be removed nor fluid bled.

But the question we want to look at, should you decide you want to upgrade these bushings: who’s to upgrade to? On the one hand you have Energy Suspension. Their bushings are far and away the most popular. They are a US firm and they’ve been making urethane bushings for cars for decades. They make 2 flavors: red and black. The black has graphite added in which they claim aids lubrication. These are inexpensive to buy ($27.50 shipped for the set). They are quite stiff at 88a durometer.

Then you’ve got SuperPro. This is an Australian suspension engineering firm and have also been making aftermarket bushings for a long time now. The SuperPro kit is a bit softer at 80a durometer. The SuperPro are purple in color. They are far more expensive at around $115 shipped for the set.

Both SuperPro and Energy use a 2 piece bushing for the internal rack mounts with internal metal sleeve for the bolt to ride in. The factory setup is a 1 piece rubber in sort of a coke bottle shape, and are soft and comfy at about 55a durometer.

Get a good screen for the pics and a few things become apparent. Energy is on top, SuperPro on bottom. The first thing you will notice are the SuperPro are much thicker overall. Much more bushing material. This should help isolate NVH better than the Energy ones, even beyond the softer compound permits. It should also help spread any impact loads a bit better as well. The biggest difference between them though were overall tolerances. The factory bolts are a shoulder type, meaning there are only threads on a portion of the shank. All of the bushings had a bit of slop between the bolt and sleeve that goes away when you torque them down. However the SuperPro had a noticeably tighter tolerance the factory or Energy (which had more slop than even factory).

Install wise it’s a snap. Car in the air, drop the front crossmember. Remove the factory hardware mounting the rack….don’t lose it! Using a mallet and a dye, knock the factory bushings out. The new bushings slip right in place. Torque back to spec and reinstall the crossmember and you’re all done. Didn’t take any pics at this stage as it went to quickly but it’s extremely straight forward.

Because of the design differences we used the SuperPro this time around. As soon as you turn the wheel you notice a difference. A bit more of a weighted feel. But at speed is where things really get interesting. The subject car only had about 35k on the rack and bushings so they were in good shape. With the new bushings installed steering response was noticeably more direct. You do notice a bit more front end stiffness over bumps, but much less wheel movement when you encounter a bump mid turn. In layman terms, it all feels much more connected: which of course is the idea. There is no way you will not realize a change immediately…it’s that much of a direct improvement. At speed there is zero noise and zero vibration. Just a very firm wheel that responds instantly to any input. Makes me wonder what could further be improved if we got quicker than the racks’ 15.9:1 ratio. G35s with Active Rear Steer had a bit quicker ratio of 15.0:1. Imagine the response of a rack along the lines of an S2000 (13.8:1 on first gen cars).

While the Energy ones are the most popular as mentioned, the SuperPro, even with their higher cost, are worth a serious look.

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