Front end experts: Ackerman?

For anyone really interested in this, Google "Ackerman dirt track" there is a lot of really good stuff to be found there in the first few hits.

 

Ok, I generated a lot of arguements.
And I obviously was wrong in thinking that the angle had to do with Pitman/idler arm alignment...but I had the principle right, just transfer it to the balljoint/kingpin and steering link relationship to the rear wheelbase.
So if I decide to go this route, I narrow the subframe, install it in the car, then heat and bend the steering arms so they intersect (theoretically) at the center of the rear axle?
Again...this is for an entirely street driven cruiser, not a hot rod, or race car.

 

Just narrow the sub and install it. Don't worry about the Ackerman because bending the steering arms will force you to modify the tie rod length which will cause you a lot more grief than the Ackerman being off.

I sure hope this ain't a rack & pinion steering sub.

 

I agree with Johnny Fast, just install it. Bending the steering arms can open up a whole possible can of worms regarding bump steer. Ackerman is arguably the very least important factor in front end geometry, and people can and do argue about what is optimum anyway. Unless it is really badly screwed up, just leave it alone.

 

It's usually a compromise. If Ackerman is out to an appreciable amount, tire wear due to scrub in turns will be quite apparent. Extreme tire wear(***uming toe is correct) is a clue, driving around with tire pressure elevated on hot smooth pavement is a good way to check for excessive scrub in the turns. Some cars(observe them at meets all the time) are so bad that the front tires squawk in low speed turns in the parking lot!

On my jalopy with modified tie-rod/rack I noticed that after only a couple of hundred miles there was definate scrub wear. Since steering isn't affected any more by straight-ahead toe-in than it is with toe-out, I corrected it by some simple interpulation, deducting that (in my particular case) that going from toe-out to toe-in (straight ahead) would reduce the obtuse Ackerman by a couple of degrees, and reduce scrub in the turns. Since then there is virtually no tread wear evident after a couple of thousand miles.

Remember, with it set up correctly, then a change, such as wheels with different offsets, or adding spacers, will put it out of kilter.............Changing the offset of a wheel moves the middle of the tire tread's relationship to the pivot(kingpin or balljoint) which changes ‘effect’ . This results in the inside tire being behind the outside tire(whilst in the turn), resulting in the turning radius’ of both tires to change in relation to the other, the result being increase in scrub; therefore a change of wheel offset can be a remedy in some cases.

 

I am sorry I did not mean unsafe without ackerman. I meant they appear to me as a pro mechanic to be unsafe period. Flimsy poorly designed front ends , two of my friends have to keep checking their king pins since they keep workin out despite the set screws, no bracing (radius rods) on the straight axle even though the rules clearly state it must be there and yet both cars are tagged for 750 and were done recently) . To me the front end looks like it was copied from a lawn tractor only made lighter. Seems to me a much better job could have been done. It was one of these guys who was having constant trouble that drew my attention to the lack of thorough design in these front ends. A days work and some care i think could drastically improve them and put a stop to the tire scrubbing and constant annoying problems. It is true that at 250 inch the Ackerman would be small but still it would at least be there. Right now I have to close my eyes when they are turning their cars. I cant stand seeing all the stress on such flimsy parts when a simple redesign could completley eliminate it. But i didnt mean to imply that they were unsafe BECAUSE they had no ackerman. I was speaking in more general terms. But to be truthful Do I think they should have it. YES!
I do
Don

 

I agree with Johnny Fast also cut it and don't worry about ack. .

 

Ackerman is seldom used on dirt track sprints since the 2 front wheels would be at different angles in a turn. Should one wheel bounce through a rut and leave the ground, the car would dart towards the wheel still in contact with the track. I learned this from Carl Adams. He raced the CAE house var for several years and both he and Jim Culbert were students of Hank Henry. All three of them built some well designed ansd fast cars.

 

Once I truly understood the princeables of Ackerman, I realized how far off the susupension would be on a streached limo.