Bump Steer

[Morris]

So we removed the top control arm on the Left Rear and again made an adjustment.....

Turn the forward heim in 1 more Turn ......

As we turn the forward control arm heim in we are moving the top of the upright towards the front of the car.....which is rotating the upright on the axil......

It took many years and lots of books to understand this ...but it does work.....

Now the killer is that the Billet lower control arm has the trailing arm mounted in the middle of the lower control arm ...unlike the old style steel lower control arms where the link is mounted below the lower control arm about 1.5"......

This change that Kirkham has made will make a big difference in Bump steer on the rear of the car and the old style lower control arm would never get the Bump Steer very good at all..... therefore what they did was to dial in more Toe-In to compensate for the poor Bump Steer characteristics ......

Any way .... Look at how we ended up ..... our Bump Steer is Great .... that means as the tire move up and down in the Wheel Well ... it is going to point in the direction we set it when we do our alignment.....

This is very important when you are trying to make a car handle and get around a corner of any kind..... be it at Speed or Street..... probably more important on the street because most race tracks are somewhat smooth....

Check out these numbers.....

[xb-60]

Great thread, Morris. I will be doing the checks and measurements before taking my car in for a “professional” check-over.

I remember on my first car...quite a number of years ago...I changed out the front drum-braked hubs for later model hubs with disc brakes. I found that under relatively mild braking, my front tyres were squealing quite a lot, and the tyres were wearing quickly on the inside edges.
Investigating, I noticed that the tie-rods from the steering rack to the steering knuckles were at a significant downward angle whereas they had previously been approximately horizontal.

Back then, I didn’t know what “bump steer” was, but I sure realized without too much thought what the problem was and what was causing it. The tapers were reversed on the later knuckles, so I replaced the disc brake steering knuckles with the old drum brake knuckles. Problem solved, and lesson learnt.

Thanks for posting.

Cheers,
Glen