Have thought about this for a while. Am looking at fitting TT Hubs as the balljoint sits lower which Im told will help with bump steer. Also going to fit TT Wishbones and change the rear bush on the wishbone to the off centre version.

Has anyone else done this with an Octo?

Do you actually have a bump-steer problem? (variation of wheel track angle with suspension load)

Also, what do you mean by the ball joint? The wishbone to hub mounting or the outer track rod end? The conventional remedy for bump-steer is to raise or lower the outer rod end or the rack, so that the track rod is parallel to the wishbone in both planes with the car at rest and straight ahead.

I call the piece that connects the wishbone to the hub the ball joint.

I seen this on MK4Forums and they seem very happy with it. When its tracked they track it as an TT.

I have had bump steer as some of the road in Meath are just terrible.

Edited 26 November, 200916 yr by countryboyhaha

Yeah I get a bit of bump steer now that I've lowered it, nothing crazy though.

I was wondering if you could swap the track rod ends from left to right etc, and then fit them upside down (rod ends currently sit ontop of the steering arms). Lowering the rod end and flattening out the angle that the tie rods make. Which should make the rod ends last longer, and reduce the bump steer. If the steering arms have tapered holes for the rod ends, then obviously this wont work!

Are the bearings/shafts the same size in the TT? I guess if they are geometrically identical then there's no problem. I know Sweedish was working on this too, so might be best asking him.

Countryboy, I was asking if you actually had bump-steer because a lot of people think the (un)loading of a tyre by bumps or potholes is bump-steer. It's not, and geometry work to correct bump-steer is a waste of time and money if you don't have it.

Bodge, I like your thinking about the rod ends, but I think the holes are tapered.

Then what is bump steer?

As per #2.

What happens is that, when the load on the suspension varies, and the steering arm and wishbone are not parallel, the vertical movement of the hub causes the plane the wheel is spinning in to twist relative to where it was.

ok you lost me there.

Ok, you've turned into a corner, and the car has settled in roll. The inner ends of the wishbone and trackrod are now fixed points (near enough, unless you change steering lock they're fixed). The outer ends are free to move reacting to surface changes (bumps, potholes and the like, not changes in tarmac). If we view the pivot points on the ends of the arms (ignore the wishbone compression or tension link; its function is to keep the outer pivot a constant distance from a transverse datum line) we see that the 4 pivot points form a quadrelateral in elevation, and another one in plan. Ideally, these quadrelaterals should be parallelograms, but they probably aren't.

If they aren't, then, when the suspension deflects, the links remain constant length, but the change in the included angles between the trackrod and the steering end axes lines causes the angle the road wheel makes to vary from that commanded by the driver. That is bumpsteer.

Be aware that the wheelbase of the TT is considerably shorter than other Mk4 Platforms, so it's likely the steering arms are slightly different to maintain correct akerman angle, which would make them wrong on the Octy.

I'm in the lengthy process of doing this and have most of the parts except hubs and new track rod ends, you want the fwd tt hubs not r32 ones as they are different. hth