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Re: Datsun 1200 Rack and pinion
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We should get back to "Datsun 1200 Rack and pinion". If you have questions about other that "Datsun 1200 Rack and pinion", please create a new Topic for them.

The nice thing about a Rack & Pinion conversion is a nice tight box, a rack has less steering linkage than the 1200 box. The guys I've talked to who have done it say it's all good.

Posted on: 2011/12/12 10:09
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Re: Datsun 1200 Rack and pinion
No life (a.k.a. DattoMaster)
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I can comment in general about rack conversions. They are popular (well relatively so) for aussie a-body mopars.

There was an 'early' kit offered by one vendor. This vendor didn't even know how to spell bump steer, let alone what it was, and people actually went back to steering boxes in some cases as the result was so bad,.

The thing is - once you have a rack with the 'right' width and tie-rods of similar fashion, well to get it 'right' and avoid bump steer (or at least to avoid adding any more than the factory setups have) the rack has to be placed in a certain position, and pretty much, that's that, it _must_ be there.

In the case of the mopars, this requires either some sump modification, or shims under engine mounts to lift the engine a few mm, or usually a combination of both. Some even used a die grinder to relieve bits of the rack outer casing (not in any critical areas I want to stress) to get sufficient clearance.

Done right, it's a wonderful setup. It does increase the turning circle a little, but it's not really noticeable in 99% of situations.

I should point out too that rack positioning - bad vs good is a game of millimetres.

There are other reasons besides the ones datto owners have, for mopars to go with the rack setup. Namely that aussie mopars copied the US a-body floorpan (which actually offset the engine a little to the right hand side to help clear the steering box on LHD models). Instead of the steering box being attached to the k frame (front crossmember) it was put on the chassis rail. Over the years the constant forces left and right basically crack and rip the chassis rail around the steering box. in some cases ripping them right out. It's a bit like 'strongmen' and how they work back and forth to tear a phone book in half. Obviously the rail can and will be repaired, but for that and all the other reasons, people go the whole hog and use a rack and pinion. It's probably also because of the fact that a couple of local commodore racks happen to have acceptable dimensions to be a great candidate for the swap - not much work needed to slot them in.

Anyway point being - yes it can be very fruitful, but the bottom line is that once you find a rack of suitable dimensions, you still are faced with the requirement to place it in a position where the geometry is right. And sometimes that can be easy, and sometimes it can be next to impossible

Aside from bump steer, you then also have to look into ackerman angles (which is basically a reflection of trhe fact that on any car, when cornering, the inside wheel is turning a tighter circle than the outside one, so ideally the steering angles should reflect that. The steering knuckles are the 'big' players there.

But here's the spanner in the works. With some race tyres and their slip angles (this may not apply to anything short of slicks I suspect, and even then just how much it would matter is a question I don't have an answer for specifically for dattos) they actually want a little bit of reverse ackerman, or at least less ackerman than a streeter might.

So basically you'd then have (potentially) a rack setup that would work for street dattos that do the occasional circuit day, and possibly a different rack setup for something like sports sedans.

Posted on: 2011/12/13 8:22
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John McKenzie
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