Bump Steering on the Rear Wheel

[ChatMaven]

Ahoy !

Simply rejoined. Find your website challenging!

Have just placed No. 1 son's 2B back on the road and am quite delighted with the outcome! When one encounters a disturbance, the vehicle jumps and points either at the edge of the road or, more alarmingly, at oncoming traffic. Suspect that the rear wishbones, which have been depressed to achieve proper wheel clearance, are to blame. Understand that tapered spacers are available, but that they only rectify the inclination? What is the solution?

[WordSmith]

What tyre pressure do you have?

When I switched the rear coil overs to gas, everything settled down significantly. 

[Motoman]

double taper spacers are used by Peter Bell to correct toe and camber.

[BEERMAN]

When wedges are used between two flat surfaces, they must have only one curve -- or??

[drummer]

Verify the back seat height.

Approximately 7 inches up from the base of the side panel is ideal.

forward of the back wing.

Space above the 2B's rear wheels was "designed" to be quite spacious.

If it drops below that, rear camber and toe-in will be exacerbated.

Bump steer will be caused by both of them.

Double taper shims will correct the problem.

Maintain a tyre pressure of 18–20 psi front and back.

[Mistral]

What matters is the taper angle (0 45 90)? (complete camber / half and half / complete toe)

However, since the pivot angle for the trailing arm is around 30 degrees, there will always be bump steer from the rear; Ford purposefully built it this way.

This is also how the BMW Z axle works.

In a PURE back axle, the rear wheels track inside the front wheels while turning, and the front wheels take a greater side load (due to the larger diameter circle they take), resulting in understeer in the limit (BAD). Having some rear steer due to roll (the inside wheel is lightly loaded and simply skids) evens out the side load and makes the car safer.

Because they were built for a rear suspension with the trailing arm pivot across the vehicle and no rear roll steer, the cheap modified tiny dampers that became zimerides couldn't control the back end.

[Matt865]

When my suspense runs out, I feel the same way.

Really scary on country roads, and I almost drove it into a bush once.

It was fine before I changed the rear gas shocks that were leaking.

I think the guy from Gaz, dampertec, sent me the ones he thought were best. The stroke on them was shorter than on the old ones.

To get the right ride height, I had to change the rear top shock support.

Now, if I set them up for a softer ride on the road, they easily bottom out.

I now have new ones that are the same as the originals and have put the rear top bolts back to how they were.

I have major back problems, so when I run normally, I like a softer ride.

My seats are big and comfortable, but they aren't good enough for stiff settings.

[ChatMaven]

Thank you everybody for your prompt responses! When'me lad' picked it up, it went aground on a minor bump in the road and had to be lifted off by six big firefighters from a neighbouring station. On examination, the ground clearance was about 2". We gradually increased it to around 4, but it still grinds on speed bumps. It reminds me of a worm-infested dog! Even at the danger of huge holes beneath the arches, it seems that another inch is in order. Should I try Mr Bell's wedges as well? This solves the Christmas gift dilemma.

Apart than needing to remove my left leg when cruising, it's a fantastic drive. It reminds me of the Ford-powered Morgan I had in my childhood, which I thought was the best thing ever but was really a technical nightmare! However, if I push my right buttock to the starboard side, I can just fit my port knee between the wheel and the dash support! OK, till we need to shift direction!
 

[drummer]

What's your back suspension?

Sierra springs and shocks can work fine if they are not clapped.

But they can be too soft and let the back end touch the ground on bumps and when accelerating quickly.

But coilovers are better for height and damping adjustments.

 

BTW, when I'm cruising, I hook my left foot under the clutch button.

Most of the time, it's easy to raise the steering wheel.

on how the builder put it together. Or putting the seat back further?