Extending Miata Steering Shaft

So...as a consequence of extending the wheelbase on the Miata by 7.3" I need to extend the intermediate steering shaft in order to reach the new rack position. (That is the bit that goes into the rack side U-joint)

Something tells me this is going to be harder than it needs to be because of metric.

Is there a supplier out there that can help or is this a DIY event? Would another Mazda product potentially offer a longer shaft?

Open to ideas.

Buy 2 and weld them together?

Cut in half and find a steel pipe that both ends slide in to and weld together?

Mazda 323 uses the same spline count as the Miata Rack, that's where I got the U-joint for my Midlana. I don't think it's any longer though. Find some tube that's nearly the same ID as the OD of the shaft, cut shaft, slip tubing over ends and perimeter and plug weld to each end of the shaft. That's how I did mine.

It's easier to do on the upper section that's not in your picture. The one pictured collapses.

Cut shaft, put a piece of pipe over it, weld up. Bonus points for drilling holes in the pipe and throwing some rosette welds in there. I don't remember having much trouble finding the pipe when I did this years and years ago - you can always drill it out if you want.

Cone_Junkie wrote: Buy 2 and weld them together? Cut in half and find a steel pipe that both ends slide in to and weld together?

Yeah, that is the obvious answer. The reason I ask is that the easy way always has a catch and I do not know enough about the metallurgy and design of this column in order to make a good decision. I also have some kind of built in aversion to welding on axles and steering columns. I don't know that the loads are that high, but they sure are constant!

The loads are a lot higher in axles than they are steering columns. The load on the column is limited to what you can put through the steering wheel.

I'd weld it like Keith suggested, but if you're not comfortable with that, look to the street rod world. In fact, pick up a copy of StreetRodder and you'll find a million ads for steering stuff.

Woody wrote: I'd weld it like Keith suggested, but if you're not comfortable with that, look to the street rod world. In fact, pick up a copy of *StreetRodder* and you'll find a million ads for steering stuff.

Seems they dont do Miata splines

The part you pictured can extend like 7 inches, the bigger and smaller pieces are just held together with some injected in place plastic. Yank on it and it'll come apart. Let it be known, you will never get it back together with the plastic pieces in it ever again if you pull it apart.

If you're really freaked about welding it, drill some holes in your tube and plug weld it on top of welding around the end of the tube.

NOHOME wrote: So...as a consequence of extending the wheelbase on the Miata by 7.3" I need to extend the intermediate steering shaft in order to reach the new rack position. (That is the bit that goes into the rack side U-joint) Something tells me this is going to be harder than it needs to be because of metric. Is there a supplier out there that can help or is this a DIY event? Would another Mazda product potentially offer a longer shaft? Open to ideas.

I used a failed RX-7 suspension link. Turned out to be almost exactly the same ID as my steering shaft's OD.

I'm pretty sure that it was 17mm and that a 3/4" tube would also have worked, but I had the link sitting there.

NOHOME wrote: Seems they dont do Miata splines

It's probably 16mm x 36 spline which might be close enough to 5/8x36 to work. Haven't tried this yet, haven't needed to either.

Like Keith said, cut it. Find a piece of tubing that the I.D. is the same as the shafts O.D. and weld. The closer the two the better. Leave a little bit of over lap on length on both sides. Bolt through it if you are not comfortable about this. If you feel odd about bolting this get a I.D. that is slightly smaller than the O.D. and heat the pipe up. Insert the two shaft ends at the proper length and then when it cools you can weld it. Warning, if you do the heating route and get the length wrong, it will not be easy to slide. So I do not recommend it.

Cut shaft, add tube, weld togther, done.

I am guessing that the cut and weld might be the way to go. Found out that the shaft is heat treated so that makes it a little less ideal.

I liked Keiths idea of messing with the upper shaft, but it moves the angle of attack and things will not line up with the rack.

NOHOME wrote: I am guessing that the cut and weld might be the way to go. Found out that the shaft is heat treated so that makes it a little less ideal.

Think you're ever going to put enough torque on the shaft for it to matter?

Yeah it's heat treated and this and that and the other - the shaft is held at a 6-8" radius by your outstretched hands against the normal steering forces of a car. If it ever gets loaded enough to cause a failure, your main concern should be finding out which cabin openings are big enough for you to crawl out of the wreck.

If you have to extend the lower section, do it on the solid bottom half and not the hollow upper half. Make sure there's a gap between your new sleeve and the upper half so the column can still collapse at least somewhat.