Piston Engine

By Black91n/a

How to: de-power your steering rack the right way(please read this whole thing and the link posted before trying this)


This mod is for anyone who wants the improved steering feel of a manual rack without the slowness of the factory manual rack. It also gives you the benefit of never getting ahead of the power steering during hard driving (autocross). As an additional benefit, this will get rid of a fair bit of weight off the front left corner of the car and free up a lot of space in the engine compartment if you don’t have air conditioning (the a/c bracket bolts to the p/s bracket I think). Finally, in my view, the absolute best part of this is that it’ll help you improve on the weakest part of your car’s performance, the driver. For reference, the manual racks are all 20:1 whereas the power racks were available in a 17.4:1 and a 15.2:1 ratio. I WOULD NOT RECOMMEND THIS FOR THE 15.2:1 RATIO RACK. The steering effort would be too high to be liveable on the street. The 17.4:1 rack, which I have, will be perfectly liveable on the street though.

The cars that got the 17.4:1 ratio racks are as follows:

  • The 89-90 GTUs
  • 90-91 Infini
  • 90 GXL
  • 90 GTU
  • 91 Coupe
  • 90-91 Vert.

The cars that got the 15.2:1 ratio racks are as follows:

  • 86-89 GXL
  • 86-87 Sport
  • 88-89 GTU
  • 86-87.5 Base
  • 87.5-88 SE
  • 86-87.5 Luxury
  • 87-91 US spec Turbo
  • 88-89 Vert with power steering

This mod took me about 4 or 5 hours of work to complete, so it’s not a trivial job.

First, you need to get the stuff off the car. I’d recommend getting the belt, pump (you can just cut off the wire going into the bottom of the pump), bracket and hoses off first (after draining the system). You’ll need to get the dust boot off the steering column u joint also. Then take the outer tie rods out of the steering knuckles and remove the front anti-roll bar. Then undo the bolts holding the rack clamps on and remove the rack. Once the rack is off, undo the inner tie rod dust boots and remove the inner tie rods. Once you are at this point you can follow the instructions on Flyin’ Miata’s site

There are a few differences between the RX-7 rack and the Miata rack. First of all to get the retaining cover off the end of the rack, instead of punching the retaining ring out like for the Miata, simply rotate the cover counter clockwise to remove the retaining ring that holds it in, it’ll come out of the slot on the end of the rack (the cover has a groove in it that you can use to spin it). Secondly, there is no supporting barrel in the middle of the shaft (or at least it didn’t come out of mine). The rest of the procedure is exactly the same for a Miata and an RX-7.

Assembly is the reverse of disassembly. Be sure to properly torque all the bolts and make sure there is nothing loose. Do not tighten the adjusting cover very tightly; this will cause you to have much heavier steering. You want it to be just barely tight; the lock nut will keep it from coming loose.

I just recently did this mod after having seen it posted on Flyin’ Miata’s site in the winter and after reading a few reports from Miata owners on miata.net, but as far as I’m aware, mine was the first RX-7 to have this particular mod done to it.

Now for driving impressions: For reference I’ve got 225/45/17 Falken FK-451’s on 17”x8” wheels with a 32mm offset and the 17.4:1 rack with a stock steering wheel and energy suspension bushings. There is a decided increase in steering effort at low speeds (like when parking), but it’s manageable assuming you’re not a weakling. The steering is also quite a bit heavier under low speed hard cornering (up to about 35mph or so, it’s most pronounced below 20mph or so though), but that comes with the much-improved feel. The steering effort during normal driving varies from being no heavier, to being slightly heavier, except when parking. I’d say that this mod is perfectly liveable on the street. The feel is very much improved and now I can quite easily tell what the front tires are doing as the power steering isn’t acting as a buffer for all that feel and helping out so you can’t tell how hard the tires are working. All in all it’s a great mod as it strips weight off the corner that needs it most, gives better access to the engine on the driver’s side, gives better feel, removes a source of parasitic losses for the engine, simplifies the system making it more reliable, and is 100% free. I’d recommend this mod, but not to everyone, it takes a certain type of person to appreciate it.