Akerman Update, life is change

roverman · June 08, 2011, 11:57:39 AM

Latest "Hot Rod" mag, quoting Carrol Smith,r.i.p., "with modern, wide sticky tires, akerman may be shortened to perhaps 1/2 the wheelbase". Too much is when the car gets "darty", then back-off some, on the amount. Adjusting from toe-in to toe-out will help on turn-in, but too much = "darty". Hope this helps, roverman.

Bill Young · June 08, 2011, 02:16:05 PM

Interesting Art. Problem on most MGs is that the steering arms point forward and to shorten the Ackerman you'd have to angle the arms out more towards the outside reducing the clearance for brake discs and wheels to steering links. On a rear steer car it's not really a problem in most cases. I suppose when designing a suspension for a racing car then fabricating or modifing steering arms isn't that big a deal so "backing off some" is acceptable. For the average street car going to that sort of modification and expense hopefully would be a one time thing.

BlownMGB-V8 · June 08, 2011, 04:38:40 PM

It certainly has an influence on what you can get by with on the brakes, and becomes a fight between space for the tie rod ends vs space for the calipers vs wheel recess outboard of the wheel mounting flange. Like most things it's a compromise.

JB

roverman · June 08, 2011, 08:00:42 PM

Of course there are purpose/bent steering arms,(Datsun Z comes to mind), bent "around the rotor" ? Biggest dia wheels possible-helps. I've seen oems'.-somwhere with steering arms on top. Really doesn't matter top,bottom or in between, as long as you get the pivot points and angle correct, to prevent bump steer. Cheers, roverman.

flitner · June 10, 2011, 01:53:43 AM

After reading about this here and on other forums, I look at the kids' gocart and walk away shaking my head thinking I've gotta fix that!!!!

flitner · June 10, 2011, 01:57:30 AM

From the HAMB
http://img864.imageshack.us/i/ackerman.jpg/
I couldnt find the one that was a pic alone.

DiDueColpi · June 10, 2011, 02:38:37 AM

It takes a while to wrap your head around gokart steering and chassis tuning John.
If you built a car like a kart you couldn't drive it. If you build the kart like a car it won't turn.
As far as the ackerman goes. Shortening it up only works on a heavy race vehicle with a lot of grip and large slip angles. Toe out compensates for the angle change in a turn and makes the turn in more predictable at the expense of straight line stability.
On a dry track it has advantages. On a wet track almost undriveable.
On a street car tire life would be short, around town driving and parking would be a chore. And the car would follow every rut in the road like it was on rails.
Probably good for something like Nascar not so good for something small and light like us.
Just my opinion FWIW.
Cheers
Fred

flitner · June 10, 2011, 09:28:49 AM

Thank You Fred!!
I gathered the basic concept but didnt take into consideration the road course and racing aspect with IFS, all I was picturing was hot rods with straight axles and skinnys for some silly reason. Lack of sleep I guess.

DiDueColpi · June 10, 2011, 12:01:08 PM

Nothing wrong with straight axles and skinnys.
My A sedan wouldn't look right any other way.
Cheers
Fred

Bill Young · June 10, 2011, 01:46:04 PM

As Fred says "My A sedan wouldn't look right any other way."
I don't want to think of all the early Ford spindles I've heated and bent the steering arms on to reset the ackerman. I even did it on a shortened Corvair once and that was a front steer, but used a drag link and idler arm setup so the steering arms pointed inwards instead of out like our MGs with the rack and pinion steering.