Bump-steer? Need some learning

[Z_Dust]

I hear a lot about bump-steer on this forum and about ways to deal with it but I am still not sure what is causing it. I have felt the bump-steer effect and it aggravates the heck out of me. I replaced the shocks on my 77z with Tokikos and installed new MSA springs. The car handles much better and it lowered about an inch. For street driving it's more than perfect.

 

Now, how do I get rid of the bump steer. there are bump steer spacers on the MSA catalog that go for $59.95 for wheels 15" or larger. Is this a good investment. Does it really gets rid of it or does it just helps. Also how hard is it to get this installed. I do most of the labor at home, unless it involves pulling the engine or major body work. I just dont have that much hands-on with suspension.

 

One more question. How about sway bars. Any comments/recomendations, does and dont's. MSA sells them for $234.95.

 

Thanks in advance

[johnc]

Bumpsteer is exactly what it says, the steering of the car is affected by changes in bump travel.

 

When the suspension travels up and down, the wheel moves up and down in an arc or half circle around a pivot point. This pivot point is not a physical location or suspension part but is an imaginary point on the chassis, similar to a vehicle's center of gravity. The distance from the pivot point to the wheel and spindle is equal at all points in the wheel's range of vertical movement. The tie rod and steering rack must be positioned so that as the wheel moves up and down, the tie rod follows an arc which is parallel to the arc followed by the spindle. If the steering rack or tie rod is not positioned correctly, the distance between the steering rack and wheel may differ from the distance between the pivot point to the wheel at different suspension heights. When this occurs the steering rack will push or pull the spindle as the suspension moves up or down thereby turning the wheel and causing a change in toe angle.

 

This change in toe angle causes a change in the direction of travel of the front wheels. As a driver you see and feel this change and a difference in where you told the car to go with the steering wheel and where its actually going.

 

What you feel through the steering wheel is called "kickback" and is often confused with bumpsteer because they tend to go together. But, bumpsteer and kickback are two separate things.

 

Now, from the explanation above it should be easy to understand that to correct bumpsteer the arcs of the the suspension and steering need to be in sync. This can be done on the early Z front suspension by modifying where the tie rod connects to the steering arm or by relocating the lower control arm innner pivot point.

 

The MSA bumpsteer spacers should actually be called kickback reduction spacers. They reduce steering kickback and only indirectly reduce bumpsteer. In fact, the spacers generally make the front suspension worse from a performance standpoint because they reduce the built-in camber gain in bump.

 

The bumpsteer that occurs in a lowered Z is not something that needs "fixing" from a performance standpoint until the car is lowered more then 3". If the steering kickback is bothersome then install the MSA "Kickback" spacers.

[TimZ]

Originally posted by johnc:

Now, from the explanation above it should be easy to understand that to correct bumpsteer the arcs of the the suspension and steering need to be in sync. This can be done on the early Z front suspension by modifying where the tie rod connects to the steering arm or by relocating the lower control arm innner pivot point.

 

The MSA bumpsteer spacers should actually be called kickback reduction spacers. They reduce steering kickback and only indirectly reduce bumpsteer. In fact, the spacers generally make the front suspension worse from a performance standpoint because they reduce the built-in camber gain in bump.

 

The bumpsteer that occurs in a lowered Z is not something that needs "fixing" from a performance standpoint until the car is lowered more then 3". If the steering kickback is bothersome then install the MSA "Kickback" spacers.

As usual, an excellent explanation from John.

 

I do have a couple of comments, though. First, there is another solution adjusting the bump steer chacteristic - change the height of the steering rack. This will achieve the same effect of the tie rod end mod, but will not require heim jointed rod ends. It most likely will require some fabrication wizardry to make the rack height adjustable reliably, though.

 

Second, I have mentioned this before, but there is NO guarantee that blindly applying the bump steer spacers (or the JTR mod for that matter) will improve your bump steer characteristics. The only thing that is guaranteed is that the characteristic will change. On my car, the bump steer curve got worse when I installed these. As I have also mentioned before, this was most likely because at some point in the past an alignment shop had relocated my inner pivot points inboard in order to correct the camber change that came from lowering the car. Point is - this was common practice for alignment shops on these cars, and after 30-odd years, you have no guarantee whatsoever that the pivot points are in the stock location.

 

The only way to know is to measure it before and after (which I did).

 

Finally, my car had about 1" of toe change, measured at one wheel only (so double this to get to a traditional toe measurement), through it's travel when I first checked this. The car was only lowered about an inch.

[260DET]

So where do the MSA spacers go?

[Z_Dust]

Per MSA catalog, they install between the ball joints and the bottom of the strut assemblies.

 

Thank you so much for the replies. Great info. It's good to know there is a place where I can go to get all the answers (z related) instead of the confused empty stare from the local alignment shop.

 

For now I guess I'll accept the bump steer and tune the suspension as best I can to my preference. The car rides really well and besides I don't race it. This is just my weekend hobbie/driver.

[Guest Carlissimo]

John, How do the kickback spacers work ?

[johnc]

I was jokingly referring to the MSA bumpsteer spacers as "kickback" spacers because they don't really fix bumpsteer, they just move the problem somewhere else. Some folks, when they install the spacers and feel a reduction in steering kickback, think the bumpsteer problem has been solved.

[GAZRNR]

Z-dust

 

On my 78 I am using the tokios, suspension techniques springs and msa sway bars. My advice is to use the front bar from the kit and retain the stock rear bar. I found that using both bars with my springs & struts causes the car to "push" in the turns when driven hard. The car seemed a little more balance when I was using the stock springs & struts and did not experience the push until I changes springs & struts.

[Zerrari GTO]

I have the MSA bump steer spacers and am ready to install but have a quick question. There is a pair of o-rings to be installed with these spacers; do they go between the strut assembly and the bump steer spacer or between the bump steer spacer and the steering knuckle?

 

I emailed MSA customer svc three times and they are clueless.

 

Also, what is the purpose of thes o-rings? There will not be any fluid or grease in this cavity (area inside the bump steer spacer).

[zcarnut]

...Also, what is the purpose of thes o-rings? There will not be any fluid or grease in this cavity (area inside the bump steer spacer).

 

It just keeps water away from the ball joint nut to prevent possible corrosion of the ball joint stud threads.

[Zerrari GTO]

Thanks zcarnut-I guess I should seal the side of the bump steer spacers that don't have the o-rings with a little silicone.

[Here comes trouble]

If you have not done so...get some

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

if not done so get some new bushings for your rack and pinion steering unit to better secure the steering unit to the chassis. The JTR manual also details what John C is advising... details how to relocate transverse link on front lower control arm.. eyeball your front lower control arms which should be in a horizontal position to the pavement (General rule of thumb)

[preith]

I do have a couple of comments' date=' though. First, there is another solution adjusting the bump steer chacteristic - change the height of the steering rack. This will achieve the same effect of the tie rod end mod, but will not require heim jointed rod ends. It most likely will require some fabrication wizardry to make the rack height adjustable reliably, though.

[/quote']

 

An easier way to do this is using rod ends on the outside w/straight arms and changing the spacer height in between the steering knuckle and rod end.

 

EDIT: I guess I should have noticed that the post is from 2 years ago, and has probably been covered else where. Oh well, I'll leave it.

[JMortensen]

Preith that is on my list of things to do. I was going to use a 5/8" rod end, but the only way I've figured to attach a 5/8" rod end to the 12mm (it is 12mm, right?) inner tie rod is to get some 1" hex aluminum and drill and tap both ends. Do you happen to know of an easier way? Whatever you do it has to fit the taper in the steer knuckle, or you have to remove the taper in the steer knuckle AFAIK.

[TimZ]

Preith that is on my list of things to do. I was going to use a 5/8" rod end, but the only way I've figured to attach a 5/8" rod end to the 12mm (it is 12mm, right?) inner tie rod is to get some 1" hex aluminum and drill and tap both ends. Do you happen to know of an easier way? Whatever you do it has to fit the taper in the steer knuckle, or you have to remove the taper in the steer knuckle AFAIK.

 

I used steel rod and drilled and tapped both ends. Also, you have to drill out the taper in the steering knuckle to get a smooth bore.

 

One other thing you want to watch is the misalignment of the rod end. Because of the shape of the knuckle and its orientation in the car, a straight tie rod will cause a regular rod end end to bind (at least it did on my car) - they only have about 12deg of travel as I recall. I had to put a bend in my tie rods in order to get the rod end at the correct angle to prevent binding throughout the suspension travel.

[tube80z]

Preith that is on my list of things to do. I was going to use a 5/8" rod end, but the only way I've figured to attach a 5/8" rod end to the 12mm (it is 12mm, right?) inner tie rod is to get some 1" hex aluminum and drill and tap both ends. Do you happen to know of an easier way? Whatever you do it has to fit the taper in the steer knuckle, or you have to remove the taper in the steer knuckle AFAIK.

 

Here's what I did. I cut an old set of tierods apart and chucked the end in my lathe and turned it down to make a bushing. This was welded into some thick wall tube that was tapped for the 5/8 heim on the other end. Your way sounds easier on all honesty. I have a welder and seem to like to figure out how to make all my projects into welding projects. Maybe I need to by some hammers ...

 

For the heim on the steering arm I'd recommend some safety washers/misalignment bushings. I got mine from spidertrax. These will allow about 22 degrees of motion before binding.

 

To drill out the arm I used a 5/8 bridge reamer. These are for aligning rivet holes in buildings and are fairly cheap. Most people don't know the taper part is the same as a Ford tierod end. This is a cheap way to make effective linkages that don't use heims and can hold up to dirt a lot better in case you want to go that way. I think the Datsun taper is also the same as some international parts if that helps.

 

Cary

[JMortensen]

My plan here is to move the inner pivots even higher than they currently are, then use the rod ends and spacers to fix the bumpsteer on the outer end. So my misalignment on the outboard end is probably going to be pretty severe. After Tim said 12º I looked up some high misalignment ends and found this: http://www.racing-stuff.com/high-miss.htm which appears to say that the Aurora high misalignment ends can go up to 38º. If I put those safety washers in that would limit quite a bit. Are they really necessary? I've seen them before but haven't seen any in use.

[tube80z]

I guess the question would be how much travel would you have? That's going to be the key. For the steering arms you may want to consider having them cut out of structural steel rather than playing with the stock pieces anymore. I've used T1 and Formualoy 4040 (or something like that) with good results. You can bend the steering arm to have the correct alignment with the tierod. Somewhere I have some pics -- just need to figure out how to post pics here.

 

The trick way would be to change the inner heim to have the bolt going vertical through it. It is lower friction and you could use spacers to set a specific RC.

 

If you mount the outer heim in single shear you will want to use a safety washer on top and bottom. They allow more angle and if teh bearing falls out of the race will mechanically trap it.

 

Cary

[TimZ]

After Tim said 12º I looked up some high misalignment ends and found this: http://www.racing-stuff.com/high-miss.htm[/url'] which appears to say that the Aurora high misalignment ends can go up to 38º. If I put those safety washers in that would limit quite a bit. Are they really necessary? I've seen them before but haven't seen any in use.

 

Just be aware that the high misalignment ends have a larger thread than the bore (the regular ones use the same thread size and bore size). So, for a 5/8" bore you'll have to use a 3/4" thread.

 

The main thing is just to make sure that you don't bind the rod end through your full range of travel. Just wanted to point out that this is not a given.

 

I think you could probably space the safety washers away from the ball by putting some small spacers between the washers and the ball. Maybe use a lockwasher or a small section of the same tubing that you are using for the bumpsteer adjustment, for instance. That way you should be able to retain the travel in the rod end.

[preith]

Preith that is on my list of things to do. I was going to use a 5/8" rod end, but the only way I've figured to attach a 5/8" rod end to the 12mm (it is 12mm, right?) inner tie rod is to get some 1" hex aluminum and drill and tap both ends. Do you happen to know of an easier way? Whatever you do it has to fit the taper in the steer knuckle, or you have to remove the taper in the steer knuckle AFAIK.

 

There's not much more to add except that I have not done this yet, but plan to with the hex tubing that you mentioned. Also in going along with this, I still want to make a new crossmember and mount a Coleman or Appleton steering rack in place of the stock one. These come threaded for the inner tie rod ends and you can play with the height on that end too. The racks are square, easier to mount, and it wouldn't be too difficult to make a slotted mount tab to make VERY easy Ackerman adjustments. Cary had mentioned you can achieve all of this by modifying the stock rack, but I'm pretty much set on doing it this way.

 

The only drawback, which I consider a positive, is because the splines on the stock column shaft are different, it can't be used, and I can't find any type of adapters. I was going to swap this all out with the stock car style shafting and rod ends. It my sound a bit complicated, but I don't think It'll be too bad. They also sell intermediate colaspable shafts which also double as and easy way to remove it from the car. I would think the end result would shave a little weight off too.