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Discussion Starter · #1 ·
I READ A LOT ON HERE ABOUT BUMP STEER AND THE AMOUNT OF DIFFERENCE IT MAKES WITH THE KITS THAT
ARE OFFERED. IS THIS PROBLEM PRETTY MUCH A GIVEN AND SHOULD A BUILDER JUST ALLOW THE DOLLARS FOR A KIT IN THE BUDGET. MY INTEREST IS IN STREET CARS AS MY RACING DAYS DISAPPEARED AS QUICK AS MY BUDGET FOR THE RACING DID...THANKS AGAIN FOR YOUR RESPONSES.

[ June 23, 2004, 08:37 PM: Message edited by: champion ]
 

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The Never-Ending Builder
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Champ,

Bump steer does exist in these cars due to the design of the chassis and the geometry of the suspension parts. There are several vendors that offer the mild to wild fix for this problem. Mike Forte has a very good fix that includes steering rack bushings and a tie rod end kit that address it, along with Breeze, and others. Gordon Levy has the most compressive fix in the near $800 bracket. So mostly it's picking your level of engineering and then paying for it. For all around street work, Mike or any of the standard vendors do a good job of minimizing it. For full race applications, Gordon Levy, HTH.


Hank
 

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Pro FFR Builder and Moderator
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Hank, Our kit works great for street use but gives the level of adjustment needed for all out race applications. The kit is far more pieces involved than a couple of brackets.
 

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At the open house I spoke to Jesper (an FFR Engineer) and a couple of other people who said that the bumpsteer issue was corrected on the MkIII frames by relocating the steering rack.

I have no personal experience yet as my kit is very far from done but I will be trying it as supplied from the factory. If you are considering a MkII or MkIII this may be important to you.

I'm sure others will have more info on this though.

Steve Borne :D
 

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The Never-Ending Builder
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Gordon Levy has the most compressive fix in the near $800 bracket
Bracket as in "Cost" :D

Hank
 

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The reason why the FFR has bumpsteer issues is because when they designed the car they were limited to using the donor steering rack, donor lower arms, and donor wheels, and since the cobra has a different track width than the Mustang, the inner tie rods for the rack are in the wrong position for zero bumpsteer.

Craig
 

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Discussion Starter · #8 ·
WITH THAT BEING THE CASE....IF YOU CHOOSE TO GO TO AN OUTSIDE VENDOR FOR A STD STEERING RACK SUCH AS FLAMING RIVER...DOES THIS PROBLEM STILL EXIST BECAUSE IT'S A REPLACEMENT FOR THE MUSTANG RACK OR DO THEY OFFER DIFFERENT ENDS TO ALLOW FOR MORE ADJUSTMENT?? :eek:
 

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FFCobra Craftsman
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What is "bumpsteer"?
 

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There have been many threds discussing bump steer, try using the search function and you will find more information than you want. You should not have and bump steer problems with the MK III chassis though.
 

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Bump steer is the change in toe through suspension travel. I am expecting our first MarkIII next week. I do know that they have moved the rack backwards. If that is all that was done, bump steer wasn't corrected. We will work up the suspension on the Mark III when it arrives and see how the new geometry is.
 

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Too Cheap to paint!
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For the MKII Chassis, can the rack be moved to help, and in which direction? Is the bump-steer caused by different pivot points in the vertical axis in relation to the Upper and Lower suspension pivot points, or by the tie rods not being parallel in both X & Y to the lower control arms?

I have a set of BAER Tracker ends from a previous application, so I am curious about re-positioning the rack if it is needed.

[ June 24, 2004, 12:33 PM: Message edited by: Chepsk8 ]
 

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Craig,

I'm well versed there, having written many tech articles for various Mustang Magazines, one even concerning bump steer. I went through alot when I converted my 69 Mustang to Rack & pinion using a Taurus Rack, and there were Many BIG issues to deal with, probably MUCH worse than on our roadsters! I'm curious what the specific problem(s) are, so I may be able to identify and possibly correct while the body is off!
 

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Craig,

I'm well versed there, having written many tech articles for various Mustang Magazines, one even concerning bump steer. I went through alot when I converted my 69 Mustang to Rack & pinion using a Taurus Rack, and there were Many BIG issues to deal with, probably MUCH worse than on our roadsters! I'm curious what the specific problem(s) are, so I may be able to identify and possibly correct while the body is off!
 

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Oops!

double post, sorry!
 

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Chepsk8,

Any good suspension book will show where the inner tie rod pivot has to go for zero bumpsteer, but that means a custom rack or custom lower arms. The outer tie rod is shimmed up or down to get the correct geometry. If I get time, I can post a picture of what I'm talking about. But it's moot, unless you are willing to make custom changes.

Like most everyone else, I reference Milliken's "Race Car Vehicle Dynamics".

The standard kits will get you close, but you need to use trial and error with the adjustments. Gordon's kit will get you very close to zero and sounds easy to setup.

Craig
 

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Craig,

thanks for the info!

I was just trying to get a specific problem, such as inner tie rod end to far inboard, rack not in alignment with OTR holes in spindlse, or tie rod not parallel with lower arm. Something like that.

I had those issues in a big way with my conversion on the mustang! I've got two great pics in my article in Hemmings Mustanf Market & Tech gude Magazine, the article was published about a year ago!
 
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