Unstable at high speeds

[comet_666]

I noticed that around 70-75 the front end of the car feels like its kind of floating. At around 100 it feels downright dangerous. I have completely rebuilt front end with poly bushings, newer generic shocks and a Hellwig 1 3/8 inch sway bar.
Not sure if this is normal or not?

[c00nhunterjoe]

What were the final alignment specs set to? Your concern is not normal. I am 1 handed smooth at 130mph on a 205 tire and no sway bar.

[comet_666]

Geez...I remember taking it in for an alignment but I don't remember if they did it or not..for whatever reason I don't think they were able to...Ill have to check my receipts in the glove box later tonight.

Thank you, I am not sure why that did not occur to me.

[WHITE AND RED 69]

Geez...I remember taking it in for an alignment but I don't remember if they did it or not..for whatever reason I don't think they were able to...Ill have to check my receipts in the glove box later tonight.

Thank you, I am not sure why that did not occur to me.

Take it to another shop and make sure they don't align it to the stock specs.

[JR]

Agreed, I would check alignment first. Especially the caster.

[cdr]

Like others have said, something is not correct, I have been over 125mph & one handed, no big deal.

[Mike DC]

    
Somebody (HPP?) has suggested this one before - Tell the alignment shop to try for early-2000s Mustang specs.  A '69 front end won't get all the way there with stock UCAs but that's a good goal.  

If they give you any protest, point out that the factory '69 specs were intended for skinny bias-ply tires.  Now you have modern radials that need all different settings.

[sccachallenger]

Agree, get the alignment, have  the tech  record settings before and after.
Before you take it in make sure the front isn't too high, this won't help.
try for a slight nose-down look, this should be possible unless the rear is really sagging.

[c00nhunterjoe]

Mine sits level. No issues. If the shop gives you shit, you need a new shop. Bring it to me. I will set it up.

[comet_666]

Mine sits level. No issues. If the shop gives you shit, you need a new shop. Bring it to me. I will set it up.

lol, thanks for the offer !

I found a local shop that does this sort of thing all the time apparently, I will take it to them in the spring and see what happens.

Thanks all for the input!

[HPP]

Generic shocks aren't helping you. T-bars may be undersprung for those types of speeds too. But, the biggest issue is probably alignment.  You want as much caster as possible on these cars for several reasons; caster provides greater high speed stability, as you've experienced. It also increases steering effort, which will help with the  over-assist feeling of a classic Mopar. It also helps improve return to center dynamics, so it will want to track straighter.

Yes, early 2000s Mustang specs are a good thing to shoot for. I suggest this because sometimes you will encounter a shop that will not  have the stock specs for a classic and will say they can't do it as a result. If they require a car model to input to the machine in order to do your alignment, then the Mustang has favorable figures to try for.  You will not achieve them because the Mopar design has a camber and caster inter-relationship that will prevent it. You want as much caster as possible with zero to negative .5 degrees camber.  Radials will tolerate a much wider range of angles than a bias ply, so take advantage of this range and get more modern angles.

Of course the best answer is to find a shop that  knows Mopars, but if that  isn't possible, Mustang specs  are a big improvement.

[Kern Dog]

The floating feeling is due to the cheap shocks.
Positive CASTER helps stability.  As our front suspensions compress, the car gains caster.. A car that has a lower ride height has a better chance of getting a decent caster number because of this. A car with a dramatic rake (Low in front, high in back) negates some of this though.
I was able to get 4.5 degrees of caster in my stock UCAs by using Moog offset UCA bushings.

[c00nhunterjoe]

0 caster is not good, nor is a positive camber number. Stock suspension should have no problem getting +2° caster and -.5° camber. Aim for 1/8" toe in or .10 in per side depending on how their machine reads.

Fwiw, i had stock origonal shocks all the way around on my car and it was stable. Switched to 90/10s in the front and it still doesnt float. Still have the origonal shocks in the rear. Car cuts a 1.4 60' taking it easy with the launch (2,000 rpm) so i dont see changing them.

[comet_666]

The floating feeling is due to the cheap shocks.
Positive CASTER helps stability.  As our front suspensions compress, the car gains caster.. A car that has a lower ride height has a better chance of getting a decent caster number because of this. A car with a dramatic rake (Low in front, high in back) negates some of this though.
I was able to get 4.5 degrees of caster in my stock UCAs by using Moog offset UCA bushings.

I swear the only thing I didn't replace on this car was the front shocks...which were off the shelf from 1998 but only had a few hundred miles on them. I have new Bilstein shocks in the rear though...

[myk]

Hotchkis, Hotchkis,  Hotchkis. 

I'm running 6.5* of positive caster and -1* of camber and with their branded shocks it's as good of a ride as you can get with these old boats at any speed...

[c00nhunterjoe]

Thats a good caster number. How much did you change to be able to get that much? 1 degree neg will feel great on a 2nd gen but can wear tires quicker. Road racing or just looking for more corner grip on backroads?