I have an 82 firebird and we've replaced all of the front end components from bushing to steering linkage. I've had it aligned 2x because ever since the rebuild the tires scrubb terribly when turning.

I'm not sure if that's the best word but basically with full lock turns in drive at idle the car won't move. Give it some gas and the front tires squeal (like wheels aren't rolling) and if gas is taken away the car stops.

Anyone know the cause of this? TiA

 

'Sounds to me like the caster is misadjusted...

 

It depends on what wheels/tires you have and what front end components you have. My car has 9 in wide wheels and wide tires. This coupled w the lowered suspension causes a little scrub at full lock. Is the front end all stock style parts w stock size tires/wheels? Any non oem spec parts? If its all stock then likely an alignment issue. Are the springs original and sagging?

 

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Thank for the reply,

Everything is stock. It's a KITT replica and has the factory 15" turbocast wheels and factory size tires. Shocks are also new. It's pretty much a frame up resto with everything new.


The only thing not stock suspension wise it the 4th gen rearend with the disc brakes.

 

Bad Ackerman causes that. It is not adjustable, w/o casting/forging new knuckles. All F-bod's do that. It's lame.

You could double check your toe....

 

Thanks for the reply, that does suck. I hope it's not the toe since it was aligned 2x.

 

Let's see some pics...

 

I only suggest the toe, b/c if the ackerman is off, then the toe spec might be somewhat of a compromise to "split the difference", so to speak. In my "3 F-body experience", it's the nature of the car.

I don't have a 3rd gen anymore, but it would be interesting to crank the wheel and then measure the toe and/or the tow front wheels' steering angle and see if how far off it is.

 

Are you sure the parking brakes are not dragging?

 

Pretty sure, it rolls fine in a straight line

 

I'm not sure I'd call the situation "lame", butt it's DEFINITELY built into the front end's design. Partly it's because they optimized the geometry for higher-speed handling, and sacrificed the low-speed tight-turn geometry to get that. Specifically, the toe-in INCREASES as the wheels are turned, whereas at low speeds, it needs to DECREASE (i.e. they need to toe OUT then instead of IN... toe OUT in tight turns is what "Ackerman" is) to not "scrub". Furthermore, the "better" the car is aligned, the worse it tends to get.

Best advice is, ignore it, and just teach your driver to NOT ever turn the wheels all the way to the lock if it can be avoided. And of course, DO NOT use the factory "specs" for the alignment; they are LAUGHABLE. Not sure what they were thinking when they wrote those: they EAT the outside edge of tires. Proper setup is, as much positive caster as you can dial in (should be around 4° or so), with slightly more on the pass side, like ½° or so, depending on the "crown" in the roads in your area; negative camber, about -1° on the pass side and slightly less on the driver's, again depending on the road crown where you drive; and about 1/16" - 1/8" of toe-in, more toward the high side of that if you use more negative camber. Be warned, positive camber moves the wheels rearward in the wheel well, and may make them rub in front of the doors at the very bottom where the ground effects attach, adding further to the problems in tight turns.

 

Thank you for all of that info! I'll see what the alignment place had to say with this info. Thanks again

 

General consensus is that the factory alignment specs suck.

Below is what people here have been touting for decades.



As to the trying to turn at full lock. It sounds like a smart azz answer, but the answer is just don't turn the wheel all the way.

 

Thanks! That's great info!

 

It's LAME because there is no excuse for poor Ackerman geometry in this day and age. Or even the '80's one. This **** was figured out in the 1800's.

Plenty of other sports cars can turn w/o doing that....and also handle better than a 3rd gen.

 

Those other sports cars don't share suspension and brake system components with an Chevy S10 pickup truck either. Everything about the 3rd gens we love is a compromise except the styling.

 

The early 3rd gens steering box has no stops and relies on the steering stop brackets on the control arms. The IROC boxes have internal stops to accommodate the wider tires. You could look into getting an IROC steering box, but it will decrease the turning radius. Good luck.

 

Thanks

 

I know. That's kind of the point that I was making. Lame.
I will say, the knuckle should be F-bod only; it's not S-10 since the S10 had an upper arm...and therefor the 3rd gen knuckle would've had the opportunity to cast/forge the thing correctly to have ackerman that that works right. I know cost/compromise is a factor, but I feel that is a basic thing that could have been done right.

 

I have the same problem on my 1984 Trans AM with original wheels. I have 245R60x15 BFG Radial T/A tires on all 4 corners.
The tires are too wide for the front turning radius & scrub on tight turns. Solution would be for me is to buy narrower tires maybe 235R60 .
Coat me over $1100 cdn in 2021 to buy these tires so car would pass a safety check. Not prepared to buy more tires.
These wide tires surely do make this car handle around tight curves!

 

The original tires on my base Firebird were P215/65 R15 and I replaced them with P215/70 R15 tires.
Because of the higher profile my tires rubbed as well when cranked over.


I installed a threaded rod to pull back the inner fender to create the required clearance.

This set up solved my issue.
There is not much extra space in these wheel wells.

 

The max size tire you should run up front on a factory 15x7 wheel on a 3rd gen that doesn't have lower control arms from a later 3rd gen factory equipped with 245/50 R16 tires is 235/60 R15. You can also run factory 16x8 wheels with a 235/55 R16 tire. There are different steering boxes with different internal stops and different lower control arms with different steering stops mounted on them depending on which factory wheel & tires and the Level I, Level II, or Level III suspension system they came equipped with.

Factory equipped 3rd gens with 245/50 R16 tires also will rub at full lock. Very late 3rd gens have different inner fender liners that mount inside of the fenders that help with the rubbing problem.

 

Or, use common sense.

DON'T CRANK THE WHEEL ALL THE WAY TO THE LOCK. Problem solved.

Fix the HUMAN. Leave the car alone.

 

There is no sound more beautiful than a power steering system at full lock screaming for dear life.