Steering rack upgrades?

[khughes]

Hi Guys,

do we ahppen to have anyone here that knows anything about steering? i was researching a new harmonic balancer for my RB25DET, when i started to wonder about whether the RB25DET power steering pump (which i believe is dual stage?) would work with the (i believe) C210 steering rack that is in my car.

that then led me into looking for the amount of pressure the C210 steering rack works with.. so far i havn't found anything, but i did find the following website, http://www.datman.co.uk/techtips/index.htm which has the following information:

-------------------------------------------------
C210 C230 Rack
Something for the more technically adverturous of you: Want more precise steering on your C210 or C230? A Front crossmember and power steering rack etc. from a late 280ZX will fit straight onto the chassis rails. Early 280ZX’s had a steering box for some strange reason, even though its predecessor, the 260Z, had a rack. You’ll need to use the 280ZX lower arms, trackrod ends and knuckle arms.
The original C210 / C230 steering column can’t be used though, so you’ll have to invent something there. You’ll need a column that has the first UJ inside the car, so that it comes through the bulkhead at an angle, pointing down to the rack. A 280ZX one may be of use here, but I have not gone this far. You should be able to use the 280zx pipes to connect the rack to the original pump. Whether the sump would need modyfying, I don’t know. I was experimending with this C210 to see if a VG30 engine would fit, and didn’t try the original engine back in with the rack in place. A 300C VG30 fits with the old steering setup by the way, but a 300ZX has the sump the wrong end. A 300zx turbo engine won’t go in easily as the turbo downpipe hits the idler arm, this is why I was trying the rack. Unfortunately, the VG30 starter hits the rack valve body! I suspected the crossmeber and rack of fitting, and tried out this theory on a scrap car, so now you know at least that part fits!
-------------------------------------------------

i am hoping to be able to get hold of a rack and pinion setup from a 280ZX which should then give em enough to measure it up etc. hopefully it won't require the swap over of the crossmember (which i presume may throw out the engine mounts i have), but i have a C210 crossmember that i can compare it against anyways (though the C210 crossmember fits the C110, it seems to throw out the front suspension)

because i am not really that familiar with the C210 or 280Zx, can anyone see a big showstopper with this train of thought?

it still doesn't bring me closer to answering the question about if the RB25DET pump will work, but if the rack is newer, it would have a higher likely chance of it working i assume

[aarc240]

Sorry to say that unless you are prepared to convert everything in the front end to match the 280ZX then it isn't going to work.
There is so much difference in the dimensions of tie rods and rack length compared to the equivalent parts on a C110 that bump steer is going to be uncontrollable.
Then you put the rest of the cross member assembly in and you need to shift the towers to the same width as a 280ZX. Plus the chassis brackets for the 'rods - tension' need to be moved.

All in all, not a trivial exercise.

If you are determined to have rack & pinion then you need to start from measurements of a stock C110 sitting on flat ground.
1 Tie rod length (ball joint to ball joint)
2 Rod assy - cross (tie rod inner joint to tie rod inner joint)
3 Height from tie rod inner ball joint to the inner end pivot point of the lower control arm.
4 Travel of a tie rod inner ball joint (either side will do) as the steering is run through it's full range.

You don't care about the overall length of the 'rod assy - cross' as it has no influence on the rack requirements.

Now you need to find a rack that has total movement at least as great as 4 above and an overall length to the inner ball joints very close to 2 above.
A rack that is close and can be modified to suit is the usual answer.

Once you have that then you can address the easy part - adapters to convert the tie rod to use Datsun ends and give the same length as 1 above.

Last, the new rack has to fitted to the C110 cross member so that the centre line of the rack is in the same relationship to the lower control arms as was recorded from 3 above.

Just to complicate the issue, since the C110 has an adjustable height column you will need to fabricate a mount for the bottom of the column to stop that flopping around and then fabricate an acceptable link between that column and the new rack.

Do you REALLY want rack & pinion??

[aarc240]

So non-Oz people understand why the conversion isn't trivial here.
All Australian jurisdictions use common base guidelines and one of the major points in altered steering is minmal bump steer.
If it hasn't been certified then you don't want to be caught with it on the road or worse still have an accident. It's called 'total liability' for any and all damages and injuries.

[khughes]

Thanks Arc,

that is not exactly what i wanted to hear, but it is makes sense and best of all, saves me so much time and effort!

are there any suggestions you could add to improving the handling / steering other than refreshing the bushes and what i have already done/planning to do?

[aarc240]

A bit hard as I don't know what you have planned!

As a simple guide, my tarmac car has
1. longer lower arms for more negative camber and every millimetre of extra track I can get
2. frame rails plate reinforced under the steering box & idler
3. rails also reinforced for stabiliser bar mounts with tube anti-crush and full thru rail bolts
4. custom steering idler with needle roller bearings
5. custom strut brace with tower to firewall braces
6. boxed junction frame rail to firewall (thin sheet steel)
7. every flex bushing is urethane with a grade chosen for each purpose
8. the usual spring, staibiliser and damper changes

You are probably going to have to do some development of your own as an RB25DET is sure to require differences.

Art

[ctcurnes]

Question about your tarmac set up:

Where did you source parts for items 1, 4 and 7. Did you buy these parts or did you fabricate them yourself.

I just blew out my idler arm bushings and as long as I'm into the suspension, I might as well upgrade. An photos you might have would help alot as well.

Also, if you have any patterns or pictures of the reinforments you did that would be great as well. I assume you did all the reinforcement yourself.

Thanks for any help you can give me, Chris.

[240kconvertible]

Art, I think we all deserve some photos of your little tarmac toy!

[240kconvertible]

Kent, I thought that your car already had rack & pinion? does it have steering box type power steering in it at the moment?

[khughes]

no i'm afraid not.. it is C210 power steering, which is still a box

unless there is a real easy replacement, i probably won't bother until after the car is on the road (and i can see how bad this one is)

[aarc240]

Question about ...
Apologies for the tardy reply - been playing with the 'other' toy (gravel navigational trials 240z - under construction)

All parts are fabricated either in my own workshop or for some specialised stuff, in a friends heavy engineering shop.
Dang, you wouldn't believe the bearing range and variety he's got on hand!!
The lower arms are now 30mm diameter 3mm wall steel tube with fabricated ends and wrap-around reinforcement tying the inner (pivot) end to the tube. The first ones were 25mm diameter 2mm wall and both bent in a heavy landing. Not good.

No patterns kept of the reinforcement plates and crush tubes but it's pretty simple to work out.
Use some thin cardboard to mock up the plates & then fabricate out of 18G mild steel sheet. Sounds thin but it effectively doubles the wall thickness. You need plates on both inside & outside of both left & right rails and they should be stitch welded on, not fully perimeter welded.

Crush tubes go up into the frame rails from underneath, attached (welded) to 16G sheet plates extending 1/4" past the stabiliser bar brackets. The top of the tubes butt against the underside of the top wall of the frame rail, suitable holes are drilled in the frame rail to allow bolts to pass right through the bracket, crush tube and top wall. I used 8mm grade 8.8 high tensile bolts, hardened steel washers both top and bottom and 'Nyloc' self locking nuts.
btw, drilling through from the bottom to take the tubes is 'interesting' as you're going up through the original weld nut and they are hard.

hth

[ctcurnes]

Thanks for the reply. Sounds like the welding course I just finished will come in handy.

[aarc240]

Forgot to include that the plating should extend well past the steering box outer profile (after all, you're trying to spread the load, not increase the stress at the edge of the box).
Same with the idler.