greezemonkey

iTrader: (14)

Allright fella`s- I need some help here, I went to the 4.5 x15 wheels from the stock iroc`s and now at about 60-70 mph going down the track this front end starts shaking and it goes away round 80-90 mph...usually I can drive thru it and it has not been a big deal, even though I have been looking to find out what is wrong but nothing looks bad front end wise...idler has a bit of play but it was not a problem at all with the other tires and radials...btw I have moroso ds2`s 28x4.5`s. I have to be honest this thing hasn`t seen a alignment rack in a while but I can`t find anyone who will play with these hodge podge strut coil-over mounts for caster/camber...being a certified master tech for Mi for the last 20+ years this front end looks fine....what are some good front end spec`s for a drag car (3rd gen) I have a caster camber gauge that magnetic`s to the spindle hub/rotor but mine is aluminum One thing I noticed last time I set toe with a toe bar was moving the car backward changed the toe setting, moving it forward toe`d it in..Unless that idler had like an inch of play I couldn`t see it changing th alignment by 1/8 inch...

Watching video of the runs the tires both look to "snake" a few times then straighten up....one run was soo bad the whole column was shakin` right and left and no matter what it became uncontrollable past 60mph...that`s the last time I drove it.

mod313

I'm assuming you swapped to a manual steering, if so you need to add the Ed Quay steering damper to the front end. The damper will take out the shimmy shake you're describing.
As far as the align specs: raise the nose approx. 3" from rest (measured at the frame rail) and adjust to zero toe, put as much caster as you can in (this will help down track stability) and get camber as close to zero as possible.

xpndbl3

iTrader: (5)

dumb question but did you get the skinnies balanced? and have you had them rechecked for balance again? I personally like discount tire if you have one in the area because around here at least they seem to have the newest wheel balancer machines which I feel are more accurate.

87_TA

alignment is generally set with toe in, as you drive the wheel begin to try and seperate them selves from one another - I run 1/32 toe in. But truefully - at one point my trans am had about 1" or more of toe in - when I finally aligned it I figured I would gain atleast 1 mph trap speed - nothing at all!!!!!
Except I picked up a shimmy when the front end would loose contact then regain - it would shake violently then go away about like yours.. prior to that there was so much toe in and force on all joints it would not shimmy.. I changed all tierods - no change - pretty sure it was from play in the manual vega box. Guess a damper would have fixed it as mentioned abouve - or adjustable caster may have..

greezemonkey

iTrader: (14)

Thanks for the spec`s I will get it close...I did order that dampner today from ED Quay, I actually ended up talking with him, he suggested 3.5 caster would be fine enough...I guess I will try it as it sits first with just the addition of the dampner, Thanks for the advise!

xpndbl3,
NO that`s not a dumb question, I did not have them balanced and I believe it could have something to do with it, I`m getting them spun before the next outing, Thanks as always for your good advise.

87_TA
You know that is a good explantion and my situation sort of follows the same, I had ran the 255 50`s with a good amount of toe in, not enough to show in the wear pattern but def not close to a factory setting, I could look at it and see one tire pointed out with the other straight, well after putting these moroso`s on I decided to set it to about an 1/8 in and they have done it since they have been on the car, they did sit most of the winter and flat spotted a bit but I figured that would work out in a few runs and so far I belive it has, the small "hop" they had seems to be minimal now. Also on a side note...long story short I learned how to rebuild a TH350 this week...the cases are somewhat weak for use in this car apparently

mod313

NP, when I set mine up 3.5 was as much as I could get with all the adjustment max'd out.

greezemonkey

iTrader: (14)

yea it looks like pre 87 cars were limited to the 3.5 and 87 and up were good to about 5.5 or 6.0...
Should I set the camber with the car lifted 3 inches too?

mod313

Yes, set all at 3" raised. This will simulate how the car is going down track.

greezemonkey

iTrader: (14)

Thank you ,will do!

BlueBeast

When I did my gront suspension the guy that alligned it also did it with the car raised up about 3 inches or so and I have had no problems so that shuold work out for you.