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diving with "crown" of the road

4K views 52 replies 13 participants last post by  rslorenz 
#1 ·
Hey guys,
Have some funky steering issue that is getting worse. I have a 69 coupe that the suspension is all "new"... 3 years old but has all been replaced. It is the stock power steering setup with the small block 302. I only cut one full coil out when I installed the suspension a few years ago to make it sit lower in the front. (the springs i bought had it sitting like it was 4x4). All was well until I installed a set of american racing shelby vn427s this spring.. They are 17x8 front and rear. Prior I had the 14x6 magnum 500s. I had the car aligned when I had installed the new suspension years ago and have only put on about 2000 miles since then. I put the wheels on once spring hit and could drive it again. I immediately noticed it was much more sensative to the road than the old wheels. I put it off as just having alot less rubber to take the abuse of the road.THE ISSUE: while going down a straight road I have to go back and forth slightly to stay straight. But if i hit a bump in the road or sewer lid I have to correct back and forth to keep it in the lane. If I'm on a road that has a slight grade to the right I have to hold the wheel at 9 or 10 oclock to stay straight. And the same goes for the other direction. This issue is getting worse and at times having some close calls. After driving it all summer it seems to be getting worse and getting harder to control. I rotated the tires-no change. I checked the rag joint and the steering box and there is no play whatsover. I put a jack under the control arms and can't get any movement out of the ball joints. The tie rods and everything are completely solid. So I have no back and forth or up and down movement. I took it to where it was aligned and the guy was nice enough to check it out again for free, since i had put hardly any miles on it. Came up dead center as had been set before. I told him my issue and he checked the suspension as well and said he thought it looked good as well. He did pretty much the same tests the suspension as I had. I'm hoping maybe you guys can give me some ideas on what to look for? I'm having some close calls with cars next to me because this thing is starting to get so wild. Thank you all for your time-I'm open to trying anything at this point.
 
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#2 ·
If it was fine before the rims & tires but bad after I think you can guess the issue...

If the offset of the new wheel is different than the old then the contact patch of the tire is in a different place which will throw off your steering geometry. It would be hard for me to believe that the alignment has not been affected by such a substantial change.
 
#7 · (Edited)
I see positive front camber and negative front caster on the chart. I bet it understeers badly and is quite unstable at high speeds.

Best to have a little negative camber (-1/2* to -3/4*) and to always have positive caster (at least +2* to +3*) and preferably more if you can get it. The positive caster is the secret to straight line stability.
 
#10 ·
I was able to open the image in a new tab and "blow it up". It's fuzzy, but what Dennis says...

The original Ford specs are good for bias tires of the original size with no suspension modifications. Better settings are camber of zero and caster of 1* positive with a 1/4* bias if you drive a lot of crowned roads (more caster on the left wheel). If you want better "return to center" on the wheel increase the caster to 2* positive.
 
#12 ·
thanks the for the input and blowing that picture up for me. Have you guys tried any of the "home alignment" tools they sell? I have seen one by on two guys garage made by quicktrick. It supposedly does camber, caster, and toe. Its $295. But at $100 each alignment I am wondering if one of these would be a good investment. Heres a link to what I'm talking about

https://www.amazon.com/Pro-Wheel-Al...=1477183597&sr=8-2&keywords=camber+caster+toe
 
#18 · (Edited)
thanks the for the input and blowing that picture up for me. Have you guys tried any of the "home alignment" tools they sell? I have seen one by on two guys garage made by quicktrick. It supposedly does camber, caster, and toe. Its $295. But at $100 each alignment I am wondering if one of these would be a good investment. Heres a link to what I'm talking about

https://www.amazon.com/Pro-Wheel-Al...=1477183597&sr=8-2&keywords=camber+caster+toe
Early Mustang alignments (especially on 65/66's) are becoming a lost art in today's commercial world.

Like Zray mentioned, I use the Longacre alignment tool. The tool itself is simple to use for caster/camber but the real time is spent making repairing any faults that you found on the car. (A tape measure gives accurate toe adjustments.) You should also have a flat place to do the alignment and a system needs to be decided to use as turn plates (proper turn plates, heavy plastic waded up, greased steel plates, etc--or else you just to push the car backwards several feet and then forward coming to a gentle stop) to verify any changes as free movement of the wheels where they touch the ground is needed.

With that said, poor machine alignments was the reason that I learned to do alignments on my own. Going straight without clenching your butt cheeks is a real necessary when your accelerating at over 135mph . . . . . .
 
#15 ·
As others said, you've got too much camber and not nearly enough caster! But assuming my conversions are right, you also have too much toe. 1/4" of toe is a lot. I run 3/32" total toe on mine. Once I accidentally set it at 1/4" and had exactly the same issues as you're describing - wandered into every pothole, crack, crevice, and uneven surface it could possibly find and swayed around super alarmingly upon entry and exit of said surfaces.
 
#20 · (Edited)
front end alignment

rsl, why are the front end numbers you have green ? Those numbers are WAY off from where you need to be. Go back to the alignment shop and tell them to do it correctly. If your guy's book or computer program tells him the specs you are set to are okay, his information is not correct. If he is a younger guy ( less than ~55 yrs....) he may just not know any better. LSG
 
#22 ·
rsl, why are the front end numbers you have green ? Those numbers are WAY off from where you need to be. Go back to the alignment shop nand tell them to do it correctly. If your guy's book or computer program tells him the specs you are set to are okay, his information is not correct. If he is a younger guy ( less than ~55 yrs....) he may just not know any better. LSG
I think they are in the "green" because the Ford shop manual has them in it's acceptable range, however outdated that might be....

From the '66 manual for a V-8:

RANGE:

Caster: -1.0 to +1.0
Camber: -1/4 to +1.25
Toe: 1/8" to 3/8". (Total)

DESIRED:

Caster: 0
Camber: +1/2
Toe: 1/4". (Total)

Z
 
#21 ·
It seems that green on the machine is not always good. You would think the designers of it would have better specs to stop this with so many people having these issues. I thank you all for your input and am about ready to pull the trigger on the longacre tool. Do you guys prefer the "bubble" style of the tool or the digital? its about a 80 dollar difference on amazon. The metal turn plates are definitely a great idea.
 
#24 ·
Because roads are never perfect, I see no reason to go with the digital style. You don't need that type of accuracy as 1/4* that the bubble style offers is quite close enough. Because of its simplicity, if you take care of your bubble gauge, it will last forever. Replacement bubbles are readily available too.

With modern tires I stand by my originally quoted specs (-1/2* Camber and +2 to +3* of caster) for a driver concerned about handling on the highways. If you parallel park a lot or do a lot of very low speed maneuverability, less caster will make that easier (at some expense to highway driveability.)

Although camber and toe has a direct affect on tire wear, changing caster doesn't. You are free to experiment with it, but never set it negative. The more positive that you can get it, the more stable the car is at higher speeds (at the expense of very low maneuverability.

The good new is that once you have the tool and the basic knowledge you can decide what you prefer and if you don't like the results, you can try something a little different that better matches your driving style.
 
#23 · (Edited)
A couple years ago I revamped the suspension on my 66 with aftermarket performance parts. I did my first ever alignment. It turned out great. What I learned is check everything even if you think it's good. What about the struts bushings? Street or Track has a YouTube clip, I believe from one of the VFM members of just how much these bushings deflect even if they look good. This will effect how the car handles.

You could very well be at that cross road with your car and want more out of your suspension then stock. As the others have said about your alignment, you need more caster and less camber. You could be at the point to think about making upgrades. Your car has the caster set with the strut, not shims. Camber is set with the eccentric on the lower control arm. If you went to a set of adjustable struts with a rod end and a camber kit which replaces the eccentric with square plates drilled in 1° increments both available from Opentracker along with adding shims for additional caster on the upper arms. Combine that with lowering the upper arm you're going to have a completely different car.

I can't stress enough as I found out doing my car how important it is to do your own alignment. I have the Longeacre caster/camber bubble gauge. It's very easy to use and not that expensive, about $100. You can set toe with either a folding ruler or tape measure. I used folded up garbage bags for turn tables as Dennis111 suggested. It's really worth it to take an interest in getting more involved.


 
#26 · (Edited)
alignment specs

Z, I wouldn't call the shop manual specs 'outdated', they're just WRONG. I'm not saying that is not what the shop manual says, but the shop manual is sometimes just CYA specs for Ford. I like the numbers Dennis gave as a starting point, minus 1/2 camber and plus 3 caster. More caster is better if you can do it. Older guys who worked on an alignment rack would know this stuff, hence my question of how old is rsl's alignment guy. LSG
 
#28 ·
You guys are right-he is younger, in his mid 30s. As am I (29) So this stuff is like dinosaurs to us. So all he had to go off of was the specs that were in his machine. He even looked up to make sure he was adjusting the correct parts. He was even telling me anymore with late model stuff its basically only a toe adjustment, and most cars don't even have camber adjustments. Only some trucks and even those are getting few and far between. I am ordering the bubble style longacre and will attempt this and get back to you guys with results. Its worth a shot since its only about 20 dollars more than an alignment. So that should pay for itself
 
#31 ·
You guys are right-he is younger, in his mid 30s. As am I (29) So this stuff is like dinosaurs to us. So all he had to go off of was the specs that were in his machine. He even looked up to make sure he was adjusting the correct parts. He was even telling me anymore with late model stuff its basically only a toe adjustment, and most cars don't even have camber adjustments......."f

With all due respect to this alignment guy, as many places won't even look at vintage cars, this is same line that many alignment shops use. It sounds like he doesn't "know" that the early cars use shims for camber and caster alignment. Before I wised up (a little) I went to a shop in Austin TX that specialized in alignments. They, also, only changed the toe settings and then called it a "full alignment". Translated that means, " we don't FU*K with shims because it doesn't PAY to FU*K with shims..."

OP: you might need one of these depending on what wheels you are using:

https://www.summitracing.com/parts/lng-78428



Z
 
#35 ·
I think that's the one most are referring to. I use the digital version of that one, I think it cost about $80 more +/-, but it's not any better at doing the job than the bubble one. But the digital one can compensate for an uneven floor, that could be a plus

Z
 
#40 ·
Yeah but not necessarily for the resultant change in weigh distribution found at the wheel.

The change might be negligible, but racing makes me think of such things. I even go so far as to put 225lbs on the driver's seat to simulate my fat butt.
 
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