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front end help ?????
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Skunkworkx
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1968 Chevrolet Camaro

PostPosted: Sun Apr 07, 2013 4:21 pm    Post subject: front end help ????? Reply with quote

Just made a full blast down a closed stretch of blacktop....
The pass felt great...except the frontend being twitchy.

What can I do to fix that ?
The frontend isn't that old and neither is the alignment.

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clay
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PostPosted: Sun Apr 07, 2013 4:48 pm    Post subject: Reply with quote

The two things I have had affect that are toe in and caster. Depending on what you are trying to achieve will determine how to set toe in. If fastest e.t. then supposedly the best way is to jack the car up to approximate front end height under power and set toe to "0" at that point. Since I drive mine on the street more that the track I usually go for around 1/8" in at ride height. Toe out can cause a vague wandery feeling. Older cars like ours usually called for caster to be around -1/2* to +1/2* or something around 0. This worked for bias ply tires that actually deformed at speed and in effect put positive caster in the front end. Now with radial tires that don't deform you probably don't have enough positive caster. Since your front end is very similar to my Nova you can get around +3 or so before your camber starts getting out of whack and you can't correct it. I can't remember exactly but I think I have about +4 and my camber is slightly off but I can live with that for stability at 140 plus. As a quick test you can take a shim out of the front bolt on the upper control arm (pick one about 1/8" thick) and move it to the rear. Pick the same thickness shim for driver and passenger side otherwise it can pull left or right. Then you should check toe to make sure it is still in the ballpark. You can use anything to do this. Something like a 2 x 6 about 26 - 28 inches long pushed up against each tire. Then pull tape front and rear. Even though this can throw camber out it will put some more caster in it and see if that's what you need. Here is a link to show what's happening. Clay
http://www.circletrack.com/howto/138_0306_how_to_measure_caster_and_camber/photo_02.html

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Knarley Darley
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PostPosted: Sun Apr 07, 2013 6:51 pm    Post subject: Reply with quote

Basically what Clay said in a nut shell is that you want the upper ball joint behind the lower one. Think of the forks on a motorcycle, and how the front wheel is raked way out in front of the pivot point. Castor is like the rake of the forks. I like 7-8 degrees of castor on my drag car. What this does is makes the steering wheel center when you let go of it, or the front wheels point strait ahead if you let go of the steering wheel. It (castor) makes the car ultra stable more than any other thing. I have my wheels perfectly parallel, but if not than slightly toed in is the best especially under braking because the force toes them out slightly (front of tires slightly pointed in toward each other). Put some castor in that bad boy, and it will drive itself.
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Skunkworkx
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1968 Chevrolet Camaro

PostPosted: Sun Apr 07, 2013 7:48 pm    Post subject: Reply with quote

I understand caster/camber/toe... just not what a street/strip sould be at.
Last alignment the guy got the max he could (no shims on one side) and just matched up the other side (close).
.....................L..../..R
Caster ~~~0.15/0.15
Camber~~ 0.80/1.00
Toe~~ ~~~0.07/0.06

Cross Camber ~~ 0.00
Cross Caster~~ -0.20
Total Toe ~~ 0.13

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af2
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1933 Willys Coupe

PostPosted: Sun Apr 07, 2013 8:17 pm    Post subject: Reply with quote

Skunkworkx wrote:
I understand caster/camber/toe... just not what a street/strip sould be at.
Last alignment the guy got the max he could (no shims on one side) and just matched up the other side (close).
.....................L..../..R
Caster ~~~0.15/0.15
Camber~~ 0.80/1.00
Toe~~ ~~~0.07/0.06

Cross Camber ~~ 0.00
Cross Caster~~ -0.20
Total Toe ~~ 0.13


You need to find a front end shop that will work with you and leave the book or computer alone.....
As clay stated and from many years of messing with cars you NEED all the caster the front end will allow period.... 3* will be the target point.... If the camber ends up at 1# it is not a big deal.

Toe has everything to do with whether it is front or rear steering on how much or less you need.. Just never out.
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af2
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PostPosted: Sun Apr 07, 2013 8:23 pm    Post subject: Reply with quote

And to Knarley..... So true of that statement.. I run a little more caster than you have and it has saved the car a couple times.
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Skunkworkx
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PostPosted: Sun Apr 07, 2013 8:24 pm    Post subject: Reply with quote

Thats the problem...I gave him specs and he ended up removing all the shims on one side trying to hit target...then matched up the other side close as he could.

So yes...O (zero) shims on one side.(may have added to get some caster ?) need to re-look Confused

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Last edited by Skunkworkx on Sun Apr 07, 2013 8:29 pm; edited 1 time in total
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Paul P
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PostPosted: Sun Apr 07, 2013 8:27 pm    Post subject: Reply with quote

If you have urethane or if everything is in like new condition then it is alignment related. That being said I am assuming that is inches you are talking about. .15 is about 3 degrees so caster should be OK.

Ride height will change toe and camber obviously. What might be going on is that the toe is nearing 0 when you are accelerating and the front end is up. If toe is near 0 or positive (toe out) it will be twitchy because the front end is losing that toe that keeps it set.

There are Global West and other control arms that can get you better settings than stock but I think you should be able to get something that will work with the stock stuff as long as the frame hasn't sagged too much over the years.


Basically all the replies are correct. If you can take some pics when you get on it from the side you should be able to get an idea of how high the front end is when you are accelerating and jack it up to the same height in the shop and use a tape measure to check the toe. I have been using tapes for years on my daily drivers using the tire tread and a tire crayon. Use the crayon to mark the point the tape is in the tread and your measurement in the tread on the other side. The roll the car forward so the points are at the same height and check the measurement again. 1/8" is easy to see with that method. It is "old fart" old school but it will let you know what is going on quickly and simply. Then you can get the front end aligned at a shop if you want or tweak each tie rod to get the 1/8" you want.

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Skunkworkx
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1968 Chevrolet Camaro

PostPosted: Sun Apr 07, 2013 9:01 pm    Post subject: Reply with quote

I'll try jacking up the frontend some (2" ?) and get a before and after measurment.
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Knarley Darley
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PostPosted: Sun Apr 07, 2013 11:00 pm    Post subject: Reply with quote

Add shims under the rear stud of the upper control arm, and set the toe, and the camber will just have to be wherever it ends up. More castor will make it handle better in a strait line. Just curious, do you have a sway bar?
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Skunkworkx
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PostPosted: Mon Apr 08, 2013 6:00 am    Post subject: Reply with quote

Yes, stock one.
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af2
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PostPosted: Mon Apr 08, 2013 5:12 pm    Post subject: Reply with quote

Skunkworkx wrote:

Caster ~~~0.15/0.15
Camber~~ 0.80/1.00
Toe~~ ~~~0.07/0.06

Cross Camber ~~ 0.00
Cross Caster~~ -0.20
Total Toe ~~ 0.13


Paul, if you are saying the caster equals 3* given .15" then the camber would be way off??

Was the toe in or out? If it was "in" you would be buying tires sooner than expected. If "out" it would follow every crease in the road and eat tires also.
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af2
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PostPosted: Mon Apr 08, 2013 5:21 pm    Post subject: Reply with quote

Skunkworkx wrote:

Last alignment the guy got the max he could (no shims on one side) and just matched up the other side (close).


I just picked up on this????


Unless the car was hit at one time... That is not the way to align the car.

No shims on one side is wrong...... Factory cars came with shims. What makes your car special?
Not being an ass, bet something is out of the aligners thinking..
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Big Dave
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PostPosted: Mon Apr 08, 2013 6:54 pm    Post subject: Reply with quote

I agree with the caster (which rather than motor cycle forks I get people to visualize with shopping cart front wheels), needs to be maxed out as you are not going to be doing a lot of parallel parking with this car.

Second issue is with all first generation Camaros and 1968-'74 Nova's has to do with the front end geometry that Paul addressed. As the car lifts you gain camber to the point where you loose two thirds of your tire contact patch. Toe in also changes with the suspenion rising (going positive, or out) and falling as the car nose dives on braking.

The aftermarket addresses this issue with taller ball joints (it has a much longer stud on the ball joint than a stock one), and shims where you then modifying the top rear mounting point of your upper A-arm on your sub frame which is cut off and relocated inboard and lower than stock to correct camber gain (this is the Guldstrand mod developed by a suspension engineer from Pontiac who road raced Firebirds).

The easier method is to use a tall aftermarket dropped spindle steering knuckle and tubular upper and lower control arms. This fixes all steering geometry issues and still leaves you with full suspension travel (we raised the height of the steering knuckle moving the A-arms further apart, and dropped the spindle to get you a net ride height change of zero). These aftermarket parts are lighter and stronger than the factory parts and they will keep your wheel planted as the suspension is worked to maximise the contact patch for road racing. It also helps on the street. Just not sure if you are going to be able to justify the cost with a dedicated drag car as I don't think is worth the gain with a tall thin drag tire.

Think of the round cross section of a motor cycle tire. It really doesn't care at which point the tire contacts the road as the contact patch is so small it can traverse from one side of the tire to the other and be the same everywhere on the tire). Your drag tire works the same way.

Big Dave
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Skunkworkx
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1968 Chevrolet Camaro

PostPosted: Mon Apr 08, 2013 8:09 pm    Post subject: Reply with quote

I tried 8 times to post the slip.

The alignment pins are good

Car wasn't hit to my knowledge

He tried to get to the settings I wanted and ended up pulling all the shims under one nut to hit the number I wanted and shimmed the other side to match.

all the numbers are in range....at ride heigth. I think thats where the problem is ?

I'll have to swing by the shop and see what he says.

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