bump steer initial settings.

[toddf]

I have heard that the closer to parallel the tie rod is to the lower control arm is the better.
Not sure if that is true or not.
I have MMS coil overs in the front, caster camber plates. No offset bushings yet for the rack. torque arm panhard bar in the back with their springs
and sn95 spindles.

car drives fine it has been aligned already, but super twitchy at higher speeds 70 plus, MMS said it was bump steer settings so I just want to get it close for the moment

Any thoughts or ideas or pictures of a set up that is dialed in would help get it close.

Thanks

todd

[ashley roachclip]

I would suspect the twitchy steering at speeds to be a castor setting that is off .

[wraithracing]

I would tend to agree with their not being enough caster. Keep in mind that if you had a regular shop do a standard alignment then they are going to use the OEM specifications for the alignment. NOT what Maximum Motorsports recommends. That will generally mean that you have very little caster and not enough camber. When I have had a shop set the alignment on any of my Foxes, I have always had to pay extra for them to set them to the MM specifications because there is "extra" work involved in doing an honest to GOD alignment that includes Caster, Camber, and Toe!

[toddf]

That is what I thought too. I have the caster maxed out, but the shop said they couldn’t get to 3.5 degrees of caster only 2.5 of caster

[ashley roachclip]

How much camber did you get?

[toddf]

2.5 degrees or there about. Oops misread 1 degree or close to

[erratic50]

Unless you are racing it, that’s too much camber

I would dial out some camber to center the strut in the strut tower. Use a camber bolt or oblong a strut flange if you need to. Centered in the strut tower opening is what lets you get the most positive caster possible.

Do make certain the rack sits square to the K member and the caster is even on both sides. Those things cause different bumpsteer behavior on each side which is a disaster to how a car drives.

the old HPM caster camber plates recommended -1.75 camber. I don’t remember what camber setting is recommended by MMS but it can’t be more than -2 for a car driven on the street ..... no way

as far as tie goes, it depends your steering setup. Factor outer tie rods have a lot of give so the stock setting is 1/8” tie in — narrower towards the front than the rear of the tires when the car is resting. It’s supposed to get the tires basically parallel when driving

MM bumpsteer kit has vastly less give to it. With those you only need about 1/16” of toe in or even parallel in a race app where you want help with initial turn-in

But in general I would say you have too much camber and it’s causing camber thrust like you’re on a pair of roller skates in the front

Make a lower K brace out of square tube and add an upper strut brace then play with stuff to get your settings close

You can have it bumpsteer adjusted but that does get expensive as it is labor intensive.

Doing all of it will get your best results


picture of what 85-86 Saleens had to brace the lower k member

[cb84capri]

Had the same issue on my Capri with maxed out caster and lowering springs before I bought the bumpsteer kit. I almost wrecked the car on the highway when it spun out, scariest moment of my life. Every car is going to vary to some degree. The way I did mine was to zip tie a laser pointer to a solid part of the spindle, and with the car jacked up relatively level with no spring in place, ran the suspension through its range of motion with my jack and changed stacks accordingly until I got a straight line plotted on my paper on the wall. No more drama there.

Cale

[mudgepondexpress]

I would agree, 2.5 degrees of chamber on a street car is a ton! I would try to get it at 1 degree if at all possible.

Caster is usually split, drivers side 1/2 degree less than the passenger side. The more caster you have, the more stable the car should be at speed, the less you have, think of a shopping cart. Caster adds to chamber gains on the outside wheel as you turn (and vica versa the inside wheel, picture a road grader). High caster settings also increase the steering effort (not normally noticed unless you are at the extreme).

So for a good handling street car that won't chew the front tires up, -1 degree of chamber and as much caster as you are comfortable with (I would stick with max stock setting, or 2.5 ish) and split the drivers side .5 less.

My short track oval car (Mercury Monarch) ran -7 right side, 0 left side caster, -5 degrees right chamber, +1 left side. Turned like a pig as slow speed and working it in the garage was a two handed affair. On the track, it sucked right down into the asphalt! (granted I was running a slick based on a 235/70/15 carcass, thus the extreme settings to combat tire flex).

This is just my experience. Others, especially MM with have probably much better base settings. Running a short track stock car will definitely help your understanding of suspension and alignment.

Don't forget about chalking your tires, old school but it works.

Kenny

[Jack Hidley]

It is IMPOSSIBLE to look at the FCA and tie rod and set the bumpsteer that way. You can't see into the inside of the ball joint, so you can't see where the FCA is. You can see the FCA body, but that is 100% irrelevant as it has zero affect on the steering geometry. It could be shaped like a pretzel and it wouldn't matter.

-2.5 degrees of camber with only +2.5 degrees of caster is going to make the quite twitchy. Post a photo of your complete alignment sheet. The static toe setting is going to have more affect on stability than anything else.

[cougman67]

I heard that Jack can perform some magic and estimate bump steer for you if necessary. I’m first on the list, right Jack?

[4eyedblind]

yer gonna love this...when I put the 87+ K member in my car, I measured it for centre but, alignment was what looked ok and swag...the car tracks straight, doesn't chew tires and is relaxed on the freeway. Hmmm....