Most modern sports cars use rack-and-pinion steering, a system elegant in its simplicity and precision, especially when compared with, say, a recirculating-ball system.
It’s simple because it has a rack gear mounted to the frame, a pinion on the steering shaft and inner tie rods and outer tie rod ends that connect to the steering knuckle on each side. When everything is bolted together, it’s essentially two moving parts. It’s brilliant, especially for racing applications.
That simplicity makes it easy to replace parts if you have an incident on track, whether it’s contact with another car or a fixed object. Even at the track, repairs are simple if you have the parts.
I needed to replace an inner tie rod at the track after contact with a passing car bent it. I didn’t have a spare, but I found one from a friend in the paddock. I had the whole thing removed and replaced in 30 minutes, and I learned a few things along the way, and I’d like to share them here.
On a Miata, the inner tie rod threads into the rack shaft and locks in place with a one-time-use-only washer that keeps it from backing out. I didn’t have one of those. I also didn’t have a boot, which ripped as a result of the contact and I didn’t have the safety wire to secure the boot to the rack. I just used a zip tie for a temporary fix, but zip ties don’t tighten as firmly as steel wire.
When I got back from the track, I had to do the job all over again so I could replace the torn boot and the washer I had to reuse. While I was at it, I replaced the inner tie rod on the opposite side, which was already bent from its previous life as a street car. That solidified in my mind the list of spares I was going to need to keep in my trailer:
Part Description Part No.
1. Outer tie rod end (R model) N021-32-280A
2. Inner tie rod (manual) NA01-32-240
3. Inner tie rod (power) NC10-32-240A (R) NC10-32-250A (L)
3. Inner tie rod lock washer HA14-32-146
4. Rack boot and wire retainer NC-10-32-125
On a Miata, the inner tie rods are different for manual racks and the more common power racks that were converted to manual for racing. They’re the same length, but the threads are different. I ordered the wrong parts from Mazda because I was in a hurry and didn’t see the notations in the parts catalog. To this day, I’ve never seen a Miata with a factory manual rack.
When I did the job at home, I had time to research how to get the outer tie rods out of the steering knuckles without damaging them. For years, I had been loosening the castle nut, then tapping the castle nut with a hammer to pop them out, but I damaged a lot of threads that way and went through a lot of outer tie rod ends, which was something I always kept in the trailer.
I contacted Josh Smith, who is Mazda Motorsports’ technical development specialist. He suggested either tapping the steering knuckle with a hammer or using a ball joint puller, you know the one that comes in that front-end tool set from Harbor Freight? We all have that kit, right?
I tapped it with a hammer and it popped out like a rabbit out of a hat. It was like magic. It probably helps that I always use a generous amount of antiseize compound on the outer tie rod end. I also picked up a fascinating fact from the factory service manual. The castle nut has a torque spec! And it’s a lot lower than what I likely had been grunt-torqueing them to! Factory spec is 32 to 41 foot-pounds. I settled on 35.
You always try to avoid damage at the track, but spare parts can get you back out on track if anything does happen. A proper set of spares can keep you from having to do the job again when you get home.
We’ve run for thousands of miles including several 25 hour races using only zip ties for the tie rod boot. Never been a problem. The groove is what keeps it in place. You can practically run it without the zip tie.
This is valuable information to me thank you very much for sharing your wisdom and taking the time to share it with your fellow Miata owners.