Ae86/xe7x With Ra40/60 Struts Bump Steer 3d Explanation

[beerhead]

Warning! This might take a minute or 2 to load. (Thought I should put this in a new thread too)

 

I got bored and did a 3D model to explain what words have great difficulty to express.

 

This comes up so often it needs to be explained properly. Steering arms are meant to act on the same plane as the steering rack.

 

The further you are from the plane of the steering rack, the more bump steer you get as the steering arm moves in and out as the strut compresses and rebounds because the pin for the tie rod is not perpendicular with the rack.

 

Don't try and look at the whole thing, just watch the link pin for the tie rod end.

 

Not 100% to scale, but it clearly shows what's going on.

 

Corolla Strut Not too bad in a lowered position, but the steering arm is not on the same plane as the steering rack.

 

RA40 Strut Fitted to corolla with longer LCA's and/or camber tops ... Steering arm is not acting on the same plane at all.

 

Now lets have a look with some Roll center adjusters added:

 

COROLLA RCA Notice that the steering arm now nearly operates on the same plane as the steering rack

 

 

RA40 RCA There is an improvement of the angle, but it still isn't as good as a factory strut.

 

 

To some people this kinda thing won't worry you, but it's all about how hard you drive your car, or if you're planning to race competitively. Things like this to the eye don't look like much, but when it comes to shaving a few seconds a lap on the track to mow down a racer with more power it can mean all the difference :fuzz:

 

The steering arm references aren't spot on, but I hope you can visualise what I mean

[Golberg]

Awesome explanation mate, those images make it really clear :P

[reTRD]

yea man i aggree you have put in what looks to be a lot of time to help explain that out more to people well done you have done a great job

[beerhead]

Cheers guys. It was pretty much impossible to get the message across in any other way. There are other forms of bump steer, but I'm fairly certain the reason RA40 gear feels strange and unpredictable is related to this. If you want a good laugh read the same thread on AE86DC. I think I rattled the ego's over there by the way some people where posting, trying to say it's all nonsense. But the fact is, Toyota know heaps more about designing car's than all of us, if you're doing a strut swap you want everything to be as close as the standard geometry as possible, doesn't seem that hard to comprehend to me.

Edited September 2, 2008 by beerhead