S15DET- after going through a rack setup I have discovered this....
1. Most 510s run tons of caster. I was thinking on my next rack setup I want to move the LCA piviot points forward. This will give room to make a straight shot from strut to strut for the tie rods. And add caster for high speed ass kickings
2. Remember the zx "quick steering" joints? I forget exactly what they are called but they are basically shorter than the 510 ones. This combined with the relocated LCA's should make the rack angles much better. Just a couple thoughts.
"People don't like it when shit doesn't match their rule of thumb." Sam
icehouse wrote:S15DET- after going through a rack setup I have discovered this....
1. Most 510s run tons of caster. I was thinking on my next rack setup I want to move the LCA piviot points forward. This will give room to make a straight shot from strut to strut for the tie rods. And add caster for high speed ass kickings
2. Remember the zx "quick steering" joints? I forget exactly what they are called but they are basically shorter than the 510 ones. This combined with the relocated LCA's should make the rack angles much better. Just a couple thoughts.
Another rack that is known to be the right width is a manual 280zx rack. They are rear steer. Byron mocked one up a while ago...there is a thread on here somewhere.
icehouse wrote:S15DET- after going through a rack setup I have discovered this....
1. Most 510s run tons of caster. I was thinking on my next rack setup I want to move the LCA piviot points forward. This will give room to make a straight shot from strut to strut for the tie rods. And add caster for high speed ass kickings
2. Remember the zx "quick steering" joints? I forget exactly what they are called but they are basically shorter than the 510 ones. This combined with the relocated LCA's should make the rack angles much better. Just a couple thoughts.
what is the zx "quick steering "joints
I call it the pitman arm... I will try and look up there correct name.
"People don't like it when shit doesn't match their rule of thumb." Sam
duke wrote:Another rack that is known to be the right width is a manual 280zx rack. They are rear steer. Byron mocked one up a while ago...there is a thread on here somewhere.
Here's some pics of my rack set up & the bracket I fabbed up real quick for it (I'll make something a little nicer after I'm done with all the other stuff related to the swap). As mentioned before the rack seems to be 1/2" wider pivot to pivot than the LCA's are. You'll also see that the tie rods are angled back a little because the KA wouldn't allow me to move the rack further back. With the VQ I hope move it back or see if I can find some shorter steering arms, like the ZX quick steers mentioned above. So if anyone knows of any that are shorter, please mention them.
I got under the car this weekend and took a couple measurements for reference. The factory tie rod pivots are approx 45mm (~1-3/4") inside the LCA pivots.
The service manual says the stock steering ratio is 15:1 which means that for every full turn of the steering wheel you get 24 degrees of steering. In order to get "faster" steering, you would need a lower ratio rack like 12:1 for 30 degrees of steering - something to keep in mind.
I just read that the 1984 MR2 steering ratio is 18:1, but there are other variables that affect that ratio besides the gearing of the rack and pinion (or steering box for that matter). http://www.mr2.com/MR2TechData.html
Attachments
Last edited by Dimebag on 16 Oct 2007 11:05, edited 1 time in total.
xlr8r wrote: You'll also see that the tie rods are angled back a little because the KA wouldn't allow me to move the rack further back. With the VQ I hope move it back or see if I can find some shorter steering arms, like the ZX quick steers mentioned above.
On page 74 of the Woodward document, Fig.19 shows that having the rack closer-than-parallel to the steering centerline is the best setup for obtaining Ackerman geometry. It looks like that's how you're mounted now, so don't go trying to push it back too far.
Yeah, I now understand that principle a little better & my Rack is set up that way. They describe that at the extremes, most amount of turn, the tie rods should be parallel. My set-up is almost there but could probably be located slightly further back to be parallel at the extremes.
After reading the article I'm going to try raising &/or lowering the racks position & observing how it effects the amount of bumpsteer in order to find a more optimal position for it. Considering how the racks pivot points are further apart than the LCA pivots I don't think I'll be able to eliminate bumpsteer, but can at least minimize it.
Hey S15DET - I can help you find the location that will cause "no" bumpsteer and ackermann if you can send me some measurements of the front suspension. I haven't tried this for a MAC STRUT but I think i can figure it out.
steering box/rack ratios aside, there is approx 1 7/8" movement in the pitman arm for every revolution of the steering wheel. I've replaced a few racks in my day and payed so so attention the them but i'm thinking the standard Mercedes P/S rack doesn't move nearly that far per 1 turn of the head. still plan on hitting the yards when i get a chance.
Hi all,
When I started my 280ZX rack thread this past spring, I was hoping that it would generate some interest. It appears that this thread has taken off, and there are a few people here that are really putting their minds to use- good job.
So I thought I'd weigh in again.
Dimebag - I like that photo from the Datsun manual. It shows an important feature. Check out the line drawn from the T/C pivot point back to where the inner tie rod mounts to the center link. If you lay a strait edge across these two points, you'll notice that this line intersects (roughly) the inner LCA pivot point. To keep all the geometry in check, I think you want to mimic this.
I measured the 280ZX rack that I had at ~ 568mm wide (between the center of the pivots).
As Dimebag noted, the stock center link is ~ 561mm – pretty darn close!
Xlr8r – you’ve got the right idea – find that sweet spot location for height that minimizes bump steer.
So my thoughts to add:
1) Mounting the rack: When I looked at this problem on my car, I felt that a mounting bracket fabricated to bolt into the same mounting holes that the current steering system uses would be the best method (I don’t have a reversed X member, so in my case the rack is really out there in space under my stock L series oil pan). If we were to make a few of these mounts, then the new rack system becomes universal, no matter what X member you use, or front/rear sump pans. I would simply fabricate the mount and rack to fit into the L powered 510, as most non L powered 510’s, reversed X-member or otherwise, still seem to use the stock 510 setup without issues. If that same space can be utilized for our rack swap, then we have a universal kit – perfect.
2) 280ZX steering knuckles: I once did swap the shorter 280ZX steering knuckles into my first ‘68 (pail yellow) L2.2 510. And it does make the ratio quicker. However, I need to put a point of caution out here. Years after I did this mod on my own car (and years after I sold the car), I was told the ball joint angle is different in the ZX steering knuckle. When the ZX knuckle is mounted onto the 510 ball joint, it may be possible for the ball joint to run out of travel and bottom out against the side of the ball joint housing. This is obviously a very dangerous situation that could lead to a total and very sudden ball joint failure – your cars life (and yours) become seriously in peril. I was told of this possible issue well after I sold the car. I never did check this scenario – I guess I was young and naive. So before we explore this as an option to alter steering ratio, can anyone weigh in on this ball joint angle situation? It does need to be checked.
I spent the summer’s free time on other projects for the Bronze and set this rack idea aside. But I should check the rack ratio of the 280ZX manual rack that I have, as the tie rod threads and input spline both match our 510’s and would make a good swap option. However I have no idea what the availability is, as the manual rack 280ZX’s are a rare find in the first place.
The reason I placed the whole rack option on hold is that there is a header collector right where the rack would need to be in the cars current guise. However, if the Bronze becomes a turbo car, then I get to actually play with a bit more space in that same area, as the stock steering box will no longer be there.
Let’s keep our heads together on this one. I will find the steering ratio on that manual ZX rack I have.
Byron
Love people and use things,
because the opposite never works.
Thanks for your input Byron - I think a mounting system that picks up the existing steering locations is a great idea.
JeffGreg wrote:I do know someone that does R&P swaps. He can do them for regular, or reversed crossmember. His name is Nelson, and he owns a shop called Altered Motives in Sherwood, OR(USA)
I called and talked to Nelson the other day to find out about his method. He wrote me an e-mail to answer my questions and said that he only does power rack conversions for the 510 and only for front sump (reversed x-member) applications. I think he said on the phone that he uses the 240sx power steering systems. He said he had the whole thing checked out by an engineer, who approved it for a piece of the action every time Nelson does this conversion. He thinks he's done 10 of these so far.
After looking at xlr8r's picture of his steering linkage, I am very curious to know how Nelson manages to get the power steering servo in there somewhere too. Has anybody got access to photos of his handy work?
