Bump steer with new spindles

[FFRSpec72]

So with the new spindles on I finished up the frontend and set the alignment, I have the camber set @ -2.5 and caster @ 5.0 and toe-in at 1/16 and then went to set the bump steer and I can't seem to eliminate it, I get .1 inch for bump for every inch of suspension travel so at about 2.5 inchs of travel I get a 1/4 inch bump steer (wich seems quite a bit). To get this close I had to remove all the spacers. Anyone one else set/measured the bump steer?

[Jim Schenck]

Tony,

I think you are stuck in between the low caster setting (having the tie rod on top of the spindle) and the high caster setting (having it below). I bumped my car and with the tie rod spaced just off the bottom of the steering arm I had about 1/32 in. of toe out per inch of travel but I have a couple degrees more caster than you. I also like a little bit of toe out in bump as it makes the car more stable on turn in. You could try to dial in more caster and see if your steering isn't too heavy or you could dial it back and move the tie rod above the steering arm.

[johngeorge]

Tony, switch to power steering so you can run more caster!! almost everyone has switched to power steering.

[FFRSpec72]

Tony, switch to power steering so you can run more caster!! almost everyone has switched to power steering.

Mo money and mo to go wrong ! I have a pump and bracket (never installed), so I need a PS Rack and hoses, what is everyone running for a PS rack (any cheap ones out there ????)

I also have done the Ackerman fix on the MKII x-member (move back the steering rack), do I have to redo that if I get another rack? or are all the racks the same size and they will fit in the slot that was made in the x-member?


Drivers side, notch out of the x-member
WP_000141.jpg

Passanger side had to move the mount

WP_000140.jpg

[Jeff Kleiner]

what is everyone running for a PS rack (any cheap ones out there ????)

A rebuilt Fox Mustang rack from Autozone runs right at $100:

#6406; 3.0 turns lock to lock
#6439; 2.5 turns lock to lock
#64163 2.25 turns lock to lock

I think a power rack will physically fit where a manual one was. The shaft splines on the rack are different so if you switch you will need to change to the lower steering shaft.

Jeff

[FFRSpec72]

What do I need for hoses, as I have none to start with now, I assume the stock pump will work? I have a adapter for the rack. Which rack is recomended out of the 3 that you listed (Right now I have Flaming River 15:1 rack)? Do i need any of this Heidt's valve stuff?

Oh, I so did not want to do this.

[johngeorge]

Tony, no Heids valve, we usually cut the spring one and a half turns (think its under high pressure line going into pump) to reduce the pressure. As for hoses, the only custom one you need is the high pressure hose which you can switch to AN fittings/AN hoses or go to the ford dealer and buy the stock hose (which is what I did when I switched.)

[FFRSpec72]

HELP, I think I'm screwed here, when I did the ackerman update to the steering (moved the rack), I thought that I changed the lower steering shaft to a universial one (and I would just change the end adapter) but looks like I did not do that so I'm not sure what I need, as I looked at the FFR parts site and did not see any thing. I can see this is not going to be cheap

Does someone make a 3/4-36 spline (I assume that is the size of the 87-93 power rack) to 3/4 dd universal joint and then I can just replace bottom joint

WP_000142.jpg

[Jeff Kleiner]

I think you may find that the lower shaft has to be longer for a power rack because the shaft on the rack itself is shorter. My car is a Mk3 and configured differently so I can't get that dimension for you. Maybe John or someone else who has the intermediate bearing block with a power rack can measure the lower shaft length for you. I'm pretty sure that Flaming River can help you with the U-joint if it turns out that is all you need.

Jeff

[Jim Schenck]

Tony,
The lower shaft should be the same length, you just need to change the lower joint. Flaming river or Unisteer both have that joint for the 3/4 double D shaft and the power mustang rack.

You might take a weekend or two to get used to the power steering but it'll be worth it, just too much easier to catch a sliding car to ever go back to manual.

[FFRSpec72]

Ordered the new u-joint 3/4"-36 to 3/4 DD. I have done the ackerman fix (moving rack back, notched out x-member), do I need the rack extenders at all ? Was #85 runing with the ackerman fix or stock MKII rack position?

[Jim Schenck]

The rack extenders aren't legal, though they would make the bump a little better. The 85 does have the rack moved backward like you have done.

[FFRSpec72]

#6406; 3.0 turns lock to lock
#6439; 2.5 turns lock to lock
#64163 2.25 turns lock to lock
Jeff

Anyone use a NAPA rack NAPA Power Rack 361011 ?

[Jeff Kleiner]

Have not used the NAPA rack (I built a street car with Autozone #6406 and my street/track/autocross car with Autozone #64163). What is the application for that NAPA PS 361011? When I pull up the power racks for '87-'93 Mustangs I do not find that part number listed.

Jeff

[FFRSpec72]

When I do a search (term "rack") on a 93 Mustang I get this one (361011) included in the list, as it does have a note: Important Information:w/ Performance Suspension (no idea what this relates to as far as factory options). My application is road racing.

[johngeorge]

Tony, I have the 2.25 turn ford rack out of a 87-92 mustang.

[FFRSpec72]

Tony, I have the 2.25 turn ford rack out of a 87-92 mustang.

OK, so that must be the one for "performace suspension"

[johngeorge]

What I dont get is the NAPA site does not tell you how many turns the rack is.. waked

[mhoward1]

Tony, I have the 2.25 turn ford rack out of a 87-92 mustang.

I have the same one myself.

[FFRSpec72]

I had a hard time getting my bump steer out (not all the way though), I have camber @ -3.1 and caster at +9 and 1/16 toe out. I have about .020 toe-out for 2.5” of compression. I had 0" toe-in for 1” drop and 2” drop I had .10 toe-in. What is strange is that the passenger side takes an additional .10 thick spacer whereas the driver’s side takes no spacers. So comming from -.5 camber and +2 caster the front end does look different as I can see more lean in on the top of the tires. I also installed 650# springs in front.

I installed the new NAPA power rack (2.25 lock to lock), all I had to do was change the u-joint to a 3/4 DD X 3/4-16 and all was OK. I have not hooked up pump or gotten lines yet as I'm still waiting on the heads to arrive.

[mhoward1]

I'm actually dialing in more Camber with the new setup and trying -2.75 (vs the old -2.5). I almost went with -2.9 but I wonder how much braking would be affected.

[FFRSpec72]

I was impressed with the lack of bump steer with the new spindles, when I set it up I had a little (was not zero and could not get it to zero) but I did not notice anything on the track, much inproved over the FX or SN95 spindles, nice job ! Now If I can only tame the power steering.

[Scott McKay]

Is there a link anywhere on how to properly check and set the bump steer?

[FFRSpec72]

Is there a link anywhere on how to properly check and set the bump steer?

I use a Longacre Gauge and here is a video on how to use it

http://www.youtube.com/watch?v=Stp9kHAGfXQ

[jimgood]

With the power steering, isn't there an issue with fluid expansion and overflowing PS tanks sometimes? I seem to remember a couple of people having that issue. I vaguely recall wrapping the cap on my reservior with a small towel and a zip tie to absorb overflow.

[FFRSpec72]

With the power steering, isn't there an issue with fluid expansion and overflowing PS tanks sometimes? I seem to remember a couple of people having that issue. I vaguely recall wrapping the cap on my reservior with a small towel and a zip tie to absorb overflow.

I have not had this issue, I'm running the stock unit but running a Honda fluid

[Ed Gaven]

Carroll Smith's book Prepare to Win C hapter 10 has a good explanation on the why's and how to measure and adjust bump steer. With a little imagination a broom handle, Carpenters square, bungee cord, tape measure and a few scraps of 2x4 or4x4 blocks will due the trick. Have fun, Ed