Rack And Pinion exploration

[icehouse]

Julian the article in the DQ is wrong.

[okayfine]

Small errors "wrong" or completely absolutely "wrong"?

Small errors I can correct. Otherwise I'll just not refer people to it any longer.

[icehouse]

Just the main point is wrong. Swapping in a early crossmember increases bump steer not decrease bump steer. The crossmember does not do the same thing as bump steer spacers. bump steer spacers "change" ball joint and tie rod together not just one point like changing the crossmember. One bad two sometimes good if done right. See chart. So the main point should make sure to keep all the original equipment if you want minimal bump steer. Later parts have better bump and if you want to swap everything over that would also work. I think the newer components are better. We are going to write up a summary when we are done. So more data and interesting finds to come.

[Byron510]

Jeff, I can certainly see where you are coming from here.

Over the years I have truly "built" two cars in particular for real weekend battle. I have put together many 510’s in this period (street, ice race, rally ect), but only two were serious efforts regarding purely handling. The Bronze is the latest, and it still isn't as good as it could be. The best car however that I put together from a driving point of view was my green ‘68 4 door – built in 1994 and passed along in 2000. For comparison sake, both cars had corrected rear suspension utilizing an adjustable inner bracket for toe and camber adjusted to 1/8” toe in and ½ degree negative camber. This car was the very first version of what eventually became my now widely available rear adjuster brackets 10 years later. Both cars had entirely different adjustable TCA’s, but both ran 5.5 to 6 degrees negative caster and 0.5-1 degree negative camber up front. Both cars were built for solo II, ran race and street rubber and both cars were similarly powered regarding output. And that’s about where the similarities end.
On the ‘68, it's parts comprised of the original 68 cross member, but incorporated a '72 sedan steering box, center link and tie (side?) rods and LCA (spherical mounted on the stock stud), with 1” bump steer spacers under 280ZX struts (shortened to utilize VW Rabbit inserts) and camber plates. The TCA’s were a clevis style with effectively shorten the TC rod – this design I have recently considered geometrically incorrect. Wheels were simply multiple sets of 14X6 280ZX wheels (Iron X +10mm and 6 spoke +12mm offsets) holding Toyo R compound race rubber and Yoko A520 street rubber.
The Bronze runs a modified late style cross member with the inner pivot moved up 1”, LCA’s spherically bushed and widened track by ¾”/side, 1” bump steer spacers, A510 struts housing MR2 inserts and camber plates running 280ZX hubs (to reduce scrub radius the maximum utilizing Nissan parts) running ½ degree negative camber. TCA’s are a for forward mounting design maintaining nearly the stock pivot point and adjusted to 5.5 degrees negative. Wheels are 15X7, 0 offset.
What this discussion has recently taught me is that I do not know what steering arm or pitman arm has been utilized and installed, and how this can affect the mucking around I’ve done with the various mix of parts and personally modified/fabricated parts.

Neither car received a physical bump steer measurement, so obviously this is the next step. Everything else I say is conjecture. Remove the spring, and do a physical sweep of the suspension with a jig like those shown below is what “has” to be done. I can tell you that the ’68 felt way better, was better behaved on the road and was simply more precise and predictable onthe track – but there are so many variable as you can see above.
Jeff, I will do this on the Bronze, and for shits and giggles I’ll do this on Ole Blue as it’s an entirely stock 68 car. I could go all crazy and use the same jig on the Greg Terry car as it’s a entirely stock '71. What I haven’t been able to figure out is why the green 68 was right, and I can’t duplicate this on the Bronze. Be interesting to compare all three cars of my own as they are sitting next to each other in the shop…. But not now – I’m moving :-/

Byron

[icehouse]

Byron, I thought when you swapped steering boxes on the 68 you pulled the pit-man arm off and swap it that way? I remember you saying something about building a cool puller. If that is the case the geometry would still be correct.

[Byron510]

Byron, I thought when you swapped steering boxes on the 68 you pulled the pit-man arm off and swap it that way? I remember you saying something about building a cool puller. If that is the case the geometry would still be correct.

This is true on the Bronze car, however the Green 68 received the steering column, steering box, steering arm, pitman arm, center link and tie rods from a 72 sedan (the ‘68 Canadian cars came with a one piece steering box/non-collapsible steering column combo which didn’t excite me, so it all got swapped out!).

Byron

[icehouse]

Byron why do the wagon/vans have the least amount of bump steer? They had the Lower LCA pivots from the beginning. If wagons didn't get a different line like the sedans did ("early sedan" and "late sedan") does that mean they had the early idler arm and cross link for the entire production run? I'm going to go dig through junk yard alley and measure some parts.


This is really turning into a bigger project than I was expecting.

[icehouse]

Byron we are going to do a bump steer test in the next few days. We are setting up the test front end. Found a few interesting things.

I had one of each steering box arm. The weird part is I know for a fact that the one that came off my 68 and the one that are on this 72 front end both have the same offset seen in the picture. The one with the other offset I think it off a 70 column shift auto. Maybe the idler height of the drag link on the late model car you pulled the box off of shared the same offset.

[Mattndew76]

Oh sweet! This data will help some with the steering arms I am looking at machining.

Bump steer

Ackermann angle

Scrub radius......

[icehouse]

Oh sweet! This data will help some with the steering arms I am looking at machining.

Bump steer

Ackermann angle

Scrub radius......

What are you machining? Do tell

[icehouse]

UPDATES!!!!!!!


Byron what part number is steering arm on your car?


We did more research over the last week or so. Here is a graph that shows all 4 possible front suspension combo's. We did this to prove our model and decided why not check all 4 combo's while we were at it. Byron if you have the wagon or column shift auto steering arm on your steering box I can see why your bump steer is so bad!





So it turns out Wagon's have the least amount of bump from 68-72 they all used the lower LCA pivot points ("late X-member") and a steering arm with matching idler arm that drops the drag link 6mm. This combination provides very little bump. The problem is if you swap the 68-69 crossmember into a wagon (or column shift auto sedan, they have the same steering arm and idler) the bump goes through the roof!!! An easy way to tell if you have this very bad setup is, well without checking part numbers is to see how close the LCA nylock nut is the the drag link/ drag link joint. If it almost hits thats the wrong combo! haha I've driven ton's of 510's over the years and I always asked myself this question. "why do some of them just drive so bad?!?!" Now I know!!!!!!!!!!!!! Only took like 17 years to find out why.....







Cool huh

[510rob]

Q.E.D.!!!

[Mattndew76]

Oh sweet! This data will help some with the steering arms I am looking at machining.

Bump steer

Ackermann angle

Scrub radius......

What are you machining? Do tell

I will be putting in the research on a shorter steering arm made from the aluminum. Slotted for Ackermann adjustment and bent drag links n such.

Quick steer capable type without the sacrifice of drive-ability.

[dislexicdime]

Makes me wonder what happens when you swap in a 210 box and steering arm

[indy510]

My old 510 had a 71 510 wagon steering box, and steering arm, but it had a 70 510 sedan idler arm ... and a 69 sedan front cross-member .. ... now I know why it felt alot better when I swapped in all the parts off my 71 4dr. ... Any chance this rack/pinion will work with a rear sump oil pan?