Bump Steer -- an Idea

[AC4ME]

Rod, when you get your set up done could you take a measurement of the total width between inner tie rod ends at centers? I'm curious if it comes out the same as mine. I don't think many have done this and the tech at Flaming River said that there might be some interest in making a rack for our cars but needed a length. I don't think he should use just one measurement but with yours and if enough of us come up with the same number then he'd have something to go from. Will you have to make boot extenders also? Nice work!

[dv/dt]

Einar,
Will do once I have my set up complete. They should be able to base it off the length of the extensions since they would already have the length (I assume) of the standard rack.

Cheers, Rod

[1686]

Rod,

You seem to be making some excellent progress on this problem! How did you calculate the exact length of the extensions? I will most likely play with this myself this winter, so if I can follow your thought process it will really help! I'm not sure if those thread sizes you used would be the same for all of the racks. I have the 15:1 that looks like the Flaming River, but is made by Unisteer, I think. Do you know if they all use interchangeable inner joints?

thanks, Brian

[dv/dt]

Hi Brian,
Sorry I missed you question back in August! I believe the FR racks may used different rod ends than the stock Mustang rack that i am using. My rack has male threads on the ends and the inner tie-rod has a femal thread. I think the FR racks are the opposite. I think someone else posted a while back about some extensions they made for the FR rack.

Cheers, Rod

[David Borden]

[quote}Kingpin inclination angle. The FFR roadster has a terrible SAI due to the requirement to adapt the stock mcphersion type spindles to a double A arm suspension. About the only thing you can do to improve it is to adapt a different spindle to the chassis.[/quote}

...or you can install these from Whitby Motors:



More info here:
http://www.ffcars.com/ubb/ultimatebb...00732/p/1.html

David

[Rickster]

David, I'm a complete noob when it comes to suspension stuff. What exactly does this invention of yours do to help the suspension in a Roadster? Is it it a "track only" part, or would this be beneficial to the street and country back road drivers as well? I saw this posted quite some time ago in the spec racer forum, but don't have a grip on what it actually does.

Thanks

[1686]

Rickster, I'm also curious about that too.

thanks for finally catching up, Rod.

Brian

[The Student]

Obviously David can tell you exactly what the SAI mod does better than I can, and there is a good discussion of this mod on the auto-x forum, but the adapters that David and others designed will replace the IFS bracket along with changing the mounting point of the upper control arm to help eliminate suspension design compromises that FFR was forced to make by using donor suspension parts (the spindles). Not too many people have done this mod yet, but I remember reading that at least one person felt that stability was improved on the freeway. Also I dont think that the kit was intended for cars with pindrive length control arms.

[f4sfed]

Maybe I missed it, but:

1) does this work the same on a MK3?

2) does this correct bump steer?

I see that it improves SAI, etc...but does that translate to resolving bumpsteer?

[sgspeed]

I have 89 spindles and Gordon Levy's bump steer kit on a Mark III. This is a fantastic setup and very reasonable.

If you want to have a total solution to your bump steer issues you need to check this out with Gordon.

[1686]

f4sfed, It doesn't have anything to do with the bumpsteer, as that is a rack/tierod location issue, so that still needs to be dialed in on a case by case basis. Should matter which MK version the car is...

I'm really curious as to whether it is worthwhile to do the SAI mod for a mostly street car.

[The Student]

Guys, go over to the auto-X forum and check out all the comments made about the SAI mod. There are also lots of fixes for the bumpsteer problem in these cars, Levy has a good kit, some have made rack extenders, others have bought custom racks. Do a search on bumpsteer in this forum and you will find way too much information.

[f4sfed]

Okay....I asked due to the title of this thread. [img]smile.gif[/img]

S [img]smile.gif[/img]

[Sanford]

There has been some time on this, and I have to ask. How is the car to drive with the extensions? Have you added the SAI mod? Is it a beast to drive on what Gordon brought up?

[CobraDVM]

Originally Posted by dv/dt

Hi Mike,
Here's a pic. As I said earlier it is a butchered, but accurate, setup using used parts since I didn’t feel like risking my new parts for the cause.

Might not look like it here but the brake disk is facing straight forward in this picture. You can see that the rack is out further than normal (1-3/4"). And the old stock outer tie rod is tighter to the steering arm than it normally would be. My steering arm is drilled trough for the Comp Eng bumsteer outer rod end so that allowed me to tighten the stock end up tighter. You can see I had to use spacers under the nut because I ran out of threads on the tie rod stud.



Cheers, Rod

Bringing this thread back up - excellent reading. However from what I gather the goal of the extenders is to get the inner tie rod pivot point in the same plane as the inboard pivot points of the upper and lower control arms. However looking at this picture, it appears that it is now outboard. If it was in the same plane, shouldn't it be positioned right in front of the vertical 2 x 2 that sits between the two LCA mounting points? It appears to be sitting well outboard of that.

Am I missing something here Rod?

[Sanford]

What matters is the length of the arm relative to the height of the arm relative to everything else. When you turn the wheel, the inner and outer are no longer in alignment anyway (in front of the verrticle 2x2).

[dv/dt]

Originally Posted by CobraDVM

Bringing this thread back up - excellent reading. However from what I gather the goal of the extenders is to get the inner tie rod pivot point in the same plane as the inboard pivot points of the upper and lower control arms. However looking at this picture, it appears that it is now outboard. If it was in the same plane, shouldn't it be positioned right in front of the vertical 2 x 2 that sits between the two LCA mounting points? It appears to be sitting well outboard of that.

Am I missing something here Rod?

Howard,
Sorry, must have missed this when you brought it back up. Take a look at post #10 in this thread for an answer to your question.

Cheers, Rod

[dv/dt]

There have been some questions about bumpsteer and the extensions lately so I thought I would TTT this thread.

Rod