Reply With QuoteYes, that's how it came from the factory.
What makes the rear wheels sit forward in their wells?
My z, and many others I've seen, has both her rear wheels sitting noticably forward in their wells. The suspension is 40 years old, so it's likely due to all those bushings and rubber parts being way past their useful lifespan, but does anyone have specifics?
Yes, that's how it came from the factory.
2/74 260Z
Double post
Last edited by BTF/PTM; 01-06-2012 at 04:45 PM.
I should have been more specific. I know that a z's rear wheels sit slightly forward of center in their wells. Mine sit waaaay forward, indicative of worn rubber. I'm uploading a picture...
Looks fairly normal. If you lowered the back end, it wouldn't be so obvious. The wide gap at the top makes the gap in the front look narrow. Compare the back gap to your front tires' gap, with the wheels straight.
There's really only two bushings on each side that would let your rear wheel sit forward. The inner control arm (transverse link) bushings. Have you taken a look at them?
Good to hear that it's probably just my own eyes worrying too much.
The whole suspension is 40 years old and wonky as hell. I can feel the whole tail of the car scoot sideways just a tad if I mash the throttle, so saying things are sloppy is a big understatement. I intend to do a full overhaul in due time, when I no longer live on the road and actually have time to wrench on the ol' girl.
The previous owner also installed an R200 and put all the original bushings back in place, and if his other handywork I had to correct is any indication, that probably doesn't help my situation.
that looks similar to my car's wheel placement. on another note: though I am not not a big fan of blacked out SS and chrome it seems to work on you're car, Nice Z.
Thanks!
It's still very much a work in progress, it will look even better with the proper black wheels installed, and as mentioned here, a properly overhauled and lowered suspension.
Originally Posted by grantf
Maybe this will help. Phred
That doesn't look normal to me. Although the picture may be deceiving my eyes, it looks like your rear wheels are toed in excessively. I don't know if the bushings have enough slop to cause that. If your rears are truly toed in, I'd look for bent parts or incorrect installation.
2/74 260Z
That shows the early vs late differential placement, but not wheel placement. The wheel placement is the same on the early vs late cars.Maybe this will help. Phred
Run a tape measure on the tires. Just pick a groove in the tread and measure to the same groove in the front and back of the tire as high up as you can manage before the tape hits the suspension or body. That will tell you roughly what your toe setting is. It won't be 100% accurate, but it will be accurate enough for you to figure out if there is a toe issue.
The car probably scoots to the side under power because the halfshaft is bottoming out:
http://www.betamotorsports.com/bench...0handling.html
Last edited by jmortensen; 01-06-2012 at 10:43 PM.
Jon
The binding of one halfshaft makes a lot of sense, thanks for that link! The tail scoots right and thus the nose pulls to the left. I plan to use a pair MMS adapters and 300zxt axles for the overhaul, so that problem will be eliminated.
Yes, the toe is visibly off, I had attributed it to the worn, sloppy bushings and strut insulators. And I'll definitely check everything for incorrectly installed and (hopefully not) damaged parts when I begin the overhaul.
The 300ZXT axles are too long as well. I have a fix for this though: http://forums.hybridz.org/index.php/...fts-group-buy/
I should have the Z31T adapters for 280Z stub shafts around the end of January if you would prefer to deal with me.
Jon
Jon, you should set up a group buy after both those shafts and the pending flange adapters are available. I'd surely sign up!
My Z (1972) developed over time two different wheelbases with the driver's side ending up an inch shorter than the passenger side. It took me a year, a lot of head-scratching, research, and measuring, before I got it doped out.
Hope I have that terminology correct here. The rear mounting bracket on one of the transverse links had loosened and was not in parallel with with the frame crossmember. It wasn't much off, hell I had looked at it several times before, but a close inspection did reveal that it indeed was off. Loosened up the differential carrier frame bolts and whacked it a few times with a small sledge. The bracket moved at most 1/10th of an inch to line up and that brought the wheel back an inch into parallel with the other wheel.
Chris
There will be a package deal. Anyone who bought shafts in the group buy will get the package deal price if they buy adapters. Just waiting on machinists at this point...
Jon
This is great input, thanks! I'd heard of the upper "dog legs" that extend down to hold the rear of the differential warping over time (which is another thing I'll check when the the car is apart), but not having to shift the suspension around with a hammer! Any chance you could snap a few pictures of specifically what was loosened and what you hit to move things around?
BTF/PTM,
I can't really take photos right now because I have the front end in the air and their just ain't that much room left under the backside. I am attaching a photo of the offending bracket. Note the slightly squarshed looking rubber bushing. Didn't realize the significance of it at the time, but this is what I eventually took a small sledge to. I loosened maybe ten to twelve nuts or bolts in all. Any and all of the bolts that attach the differential carrier to the body, including the indirect attachment through the "dog legs." Nuts and bolts attaching the differential to the carrier, I did _not_ loosen. One of the dog legs was bent, but only because it was forced out of position. Once I whacked the bracket into place, the dog leg straightened out and hung nice and perpendicular to the ground.
Chris
This is great stuff, thanks for the picture! It took me a couple days of staring at that picture and reading your posts before I fully understood it. Had to dig all the old four-bar linkage stuff from my college days out of the recesses of my brain. It does make sense, a tweek on a very small bracket at the inner end can translate to a large discrepency when placed across a 14-inch swing arm.
I'm guessing you didn't loosen the bolts much, maybe a half turn or so, just enough to maintain component contact and reduce friction enough to be able to push the parts around?
Since you're thinking about - these two mounting points are supposed to be somewhat self-adjusting when the weight of the car is on the suspension. The mounts are left loose, the car is settled on to the suspension and rolled around a bit to get everything in its proper position, then the eight bolts are torqued down. You can reach the bolts when the car is on the ground, if your exhaust pipe is not in the way. Might be worth some time to reach up under there, loosen them up and see if you can get things settled right. It won't hurt anything and you might get an easy adjustment.
Good point. This is one of the reasons why suspension fasteners must be torqued with the car fully laden. If someone torqued the suspension down with the wheels in the air, problems like this one can arise.
2/74 260Z
FWIW, moving that hanger is only going to affect toe. The fore aft is still going to be the same because the front of the control arm is captured by the front bushing which bolts to the frame via the front diff crossmember. The mustache bar holds the diff completely independently of the hangers.
Jon
Before Jon had the great idea of making the correct length shafts I toasted a rebuilt 3:90 pinion in all of 50 miles after installing a set of aftermarket (autozone) 300zxt CVs in my 240 (with the MMS adaptors).
In this case the ones from autozone were two left (or rights) and of course one side was too long causing the CV to press into the side of the diff. Lots of gray and silver bits came drained out of the diff. I got a set of real 300zxt (both left and right sides but found that there was still the very real possibility that one side would bind on my very lowered car.
To solve this I went out and got a set of Dave's Arizona Z car RCAs and adjusted the angle of the inner tube to match the CV shaft lengths. This also gave me a more upright arm that was lacking in the stock setup once I lowered the car. A time consuming chore but in the end (no pun intended) it worked. The 240 now has over 10,000 miles, including some track time and not a spot of problems (or little metal bits in my diff).
Had Jon's shafts been available back then I would have gotten them as well for added insurance. Nice to see another solution from within the Z community.
if a little knowledge can make you dangerous, I'm a little dangerous
Sorry about the delay.
Actually, it did more than affect the toe. I had the car parallel to the ground a foot and a half in the air and dropped many a line for point-to-point measures. I can't pretend to tell you the mechanism, but every measure I took indicated that center of the rear hubs moved, bringing the right and left wheelbase much closer in length. Professional before and after thrust angle measures also showed a much closer alignment with the body.
Chris
Thrust angle is a function of the front toe vs the rear toe. Sounds like your rear toe was screwed up and you fixed it and that fixed your thrust alignment. No mystery there.
The front of the control arm is still in the same location regardless of where the rear is. There will be a slight movement in the hub when the toe angle changes, but you're not going to get a lot of movement there. This may be easier to visualize on cars that have monoball pivots instead of bushings. With the monoball, there is no slop in there and when you adjust you can really see that the control arm just has no freedom to move fore and aft.
Several of us made what amounts to adjustable uprights for our cars, you can see them here: http://forums.hybridz.org/index.php?showtopic=24100 We took the idea from Ron Johnson who fixed a toe issue in his car by slotting the upper holes in the upright and moving it to set the toe.
Jon
When the previous owner installed the r200, how did they connect the rear of the rear control arms?
The reason I ask is that the r200 won't fit with certain brackets that connect the rear control arms. The PO might have made his own bracket and made it too wide causing toe in.
Last edited by madkaw; 01-23-2012 at 08:57 AM. Reason: Yep
Steve
71 240z,bw-5sp 2.4-40 over,balanced,e-88,big valves,ported&polished, stage2,header, triple Mikuni's 40's
3.90 Subaru STI LSD
Looks like the previous owner may have used the 260/280 struts, which would explain why the rear end is so high.
www.nostalgictrio.com Skyline - Silvia - Fairlady Z
www.ozdat.com The Australian Datsun site.
www.cafepress.com/vintagedatsun
Isn't thrust angle a function rear toe alone?
The hub will move for and aft if you only move one LCA bushing location. The whole LCA pivots about the fixed bushing swinging the wheel side of the LCA. A small amount but it will move approximately by..
(the amount the rear bushing was moved ) * ((Distance from LCA shaft to hub)/(distance front to rear of the LCA bushings))
Steve
I slipped into my jeans
Lookin' hard and feelin' mean
I took a spit at the moon
Yes, essentially, since the front toe isn't going to have a thrust component to it. The fronts are going to go straight and the steering wheel will turn if the "front thrust" is off. The rears can't compensate since there is no steering, so they continue to point in one direction or the other.
Exactly the point I was trying to make. Yours is a much more technical and accurate way of saying: "There will be a slight movement in the hub when the toe angle changes, but you're not going to get a lot of movement there."
Jon
Doradox wrote: The hub will move for and aft if you only move one LCA bushing location. The whole LCA pivots about the fixed bushing swinging the wheel side of the LCA. A small amount but it will move approximately by..
(the amount the rear bushing was moved ) * ((Distance from LCA shaft to hub)/(distance front to rear of the LCA bushings))
Jmortensen replied:
Exactly the point I was trying to make. Yours is a much more technical and accurate way of saying: "There will be a slight movement in the hub when the toe angle changes, but you're not going to get a lot of movement there.
Sorry about the unusual quoting style, but I couldn't figure out how to quote a quote and this was the relevant passage.
Jon,
I think you overlooked that I didn't move just one bushing location. I had loosened every bolt attaching the transverse link / control arm to the frame and those attaching the differential carrier to the frame. I only whacked that one point with the little sledge, but I never intended it to be, nor was it, the only point that moved. I don't have before and after pictures, but I assure you that the support plate (one of the two) that holds the rear of the differential carrier went from a definite angle, with the bottom of it closer to the front of the car than the top went to perpendicular, or at least damn close to, after my ministrations.
Toe? Whose toe? More accurately, which toe?
When we talk about toe-in or toe-out we are assuming that, at zero toe, each wheel's rotation is parallel to the frame of the car and parallel to it's partner on the other side of the car. So, when the rear's toes are identical, even if non-zero, the resulting vector, or thrust remains parallel to the frame of the car. But in my case, the first assumption was wrong. While each rear wheel was parallel to each other, they were not parallel to the frame of the car. Even if both rear wheels had exactly zero toe, the thrust vector was out of parallel with the frame of the car and also with the front wheels. After moving back one side, the rear wheels became parallel with the frame of the car and remained parallel to one another. The thrust vector then became parallel with those of the front wheel, even though the rear wheel's toe remained unchanged.
Chris
You cannot move the front pivot of the control arm, as its location is a welded part of the frame. If you move the rear pivots, you can change the toe. You can't significantly change the wheelbase. Using doradox's formula and estimating the control arm length fore/aft at 12 inches and the width at 14.5" (I know the width is correct), a 1/4" toe change (which is a big change) gets .3" of movement at the hub. You said that the upright moved .1". That would translate to a hub change of .120".
The differential is hung on the mustache bar in the rear, and it doesn't actually connect to the uprights at all. So again, loosen up all the bolts that hold the diff mounts (although I think you said you didn't mess with them), tighten them all up, and you might get a slight change in orientation of the bushings, but this adjustment is WHOLLY unconnected to the location of the wheels in the wells. In the front, it's attached to the crossmember. The front crossmember actually holds the front control arm bushings to the corresponding cups which are welded into the frame, so again I don't think that loosening these bolts and hitting stuff with a hammer and tightening them down wouldn't make any difference.
If you're again talking about the rear suspension uprights moving, as I said before, you're not going to get a really major movement of the wheel forward or aft, because the front bushing cannot move unless the frame gets bent. Squaring up those uprights as you did is great and it can fix a toe issue/thrust angle issue. I don't see how it could significantly change the wheelbase though. Again, that was what Ron Johnson did and it led to that toe adjuster that a bunch of us made, but he slotted the holes in the upright in order to get more movement out of it, since the holes that are there are sized to the bolts, and don't allow for much movement.
Not sure what your point is with the toe clarification. Toe is the relation of the angle of the two tires. Thrust angle is their relation to the centerline of the car. In a Z, the rears have a thrust element and the front do not.
Jon
I understand and accept all you have written.
Eppur si muove
Chris
I love when my threads turn into technical discussionsI always end up learning much more than I thought I would.
The comment about the PO having used 280z struts makes me wonder. It's been a long time since I've crawled under the car. Time to get the car out of storage and tinker a bit, methinks. I'll need an enclosed trailer, though. Damn you, road salt!
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