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Automotive Bump Steer and how to correct it..?

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  1. Jan 31, 2019 #1
    Hi my name is Grant. I have a Pre-Runner Ford Ranger with a F-150 body kit on it. I imported it from USA to the Land Down Under.... Australia, to compete in Off Road Racing around this wonderful country. Its running standard chassis with long travel Camburg front suspension with King Coil overs and King Triple bypass shocks and Fox bump stops. Running standard steering rack with Camburg steering link kit. But my problem is that i have fitted a Stroked 351 EFI Windsor and with its oil pump being at the front of the sump, I had to lower the rack to obtain clearance so it sat correctly in its hole... So now i have a major bump steer issue that I'm trying to rectify... Any advise would be greatly appreciated ….!!!
     
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  3. Jan 31, 2019 #2

    berkeman

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    You'll get good responses from others about this, but could you briefly explain Bump Steer for me? Does it involve an interference between the body and the tires under full suspension compression?
     
  4. Feb 1, 2019 #3

    Ranger Mike

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    bb-oil-pan-jpg.jpg
    Bump steer means the tire will toe in or toe out to a greater degree than desired as the suspension moves up and down. Typical specs are no more than 0.030" per inch of travel.

    Back in 1960 drag racing days this was a common problem when hot rodders swapped big cubic inch engines into small compact cars. Shoehorning in a 426 cubic inch full size passenger car engine into a small compact grocery getter had major fabrication problems to be over come.
    Opps, the oil pan now hits the steering linkage center link that connects both front wheels to the steering box.. Instead of spending a lot of time and money re-engineering the front suspension, the racers would cut a hole in each side of the oil pan and weld a tunnel tube to permit the center link to stay in the stock position. Not too much of a pain as it meant you had to take off the center link ifin you wanted to pull the engine. Big deal..remove two acorn nuts!
    the alternative is mucho cut and try time to remove the bump steer. Tunnel pans are still the best option even if you have to re-fab the oil pickup tube.
     
  5. Feb 1, 2019 #4
    If only it was that easy... Here is a rough diagram of the rough measurements.. couple of other photo's of before and after rack relocation.. un painted is old and new black paint is moved.
     

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    Last edited: Feb 1, 2019
  6. Feb 1, 2019 #5

    Ranger Mike

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    how much lower did you have to move the rack? Looks like the end of the pan is just on the rack. can you raise up the engine to clear the rack i n the stock mount position?
    This is a rack end we used on the super late model that had rack and pinion steering. It screws on the end of the rack. The bracket attaches to a rod end that runs to the spindle. Can you modify your rack ends and extend the length between the rack and the tie rod you are using. This would put the linkage back to the same as stock and eliminate your bump steer problem.
     

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    Last edited: Feb 1, 2019
  7. Feb 1, 2019 #6

    ChemAir

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    I'm interested as well.

    The first thing I'd do is contact Camburg to see if they have a lowered/adjustable spindle or other solution already, as lots of people have put these engines into Rangers. Do you have a picture from this angle or a little lower and front (VVVV) so we can see how the tie rod/spindle looks on yours? Also, let us know if you have front driveshafts to contend with.

    ?u=http%3A%2F%2Fcamburg.com%2Fwp-content%2Fuploads%2F2013%2F02%2Fp-19953-IMG_0996.jpg
     
  8. Feb 2, 2019 #7
    Hi mate, i think i have lowered it 60 - 70 mm here is a couple of shots...!
     

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  9. Feb 3, 2019 #8

    Ranger Mike

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    Fabricate some tie rods that will put the out side rod ends at the stock level. would be simplest solution.
    place one tie rod at the stock location and another at the new location and fabricate a spacer, weld it and run it! or make a spacer as shoen
     

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    Last edited: Feb 3, 2019
  10. Feb 8, 2019 #9
    Here's latest update.... have fabricated up a dummy steering mount so i can move it a round and test for best location .. so far 70mm down seems to be the best location, have tried 60mm and 80mm as well.
     

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  11. Feb 8, 2019 #10

    ChemAir

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    Picture 01--It looks like the heim is at it angular maximum. If the suspension is likely to travel to this point, it may cause the heim to stick a little. A high strength high angularity (or http://rodendsupply.com/)heim may give you less binding, if that is an issue. Make sure it is strong enough.

    You may be able to make the bracket to where you can adjust up and down 10-20mm or so. It may be that you can use a couple of different thickness tubing spacers on top or bottom to move the rod end up and down a little. If you make it adjustable, you should pay attention to the angle of the new welded bracket, so up/down changes don't add more left-right movement than they have to, and don't bind.

    And, because I'm anal retentive about critical steering parts, when the new brackets are made, I'd make sure they were mirror images of each other with mounting points within 2mm (1/16 inch is what I usually work toward for drag cars).

    Looks like a fun project.
     
  12. Feb 8, 2019 #11
    Hi mate, the heim has plenty of movement still and is free moving still at that point.... It's at it's max downwards position and won't travel any further. And for being aligned it will be moved and squared up as you said mirrored up ... At this stage just trying to get the spacing correct, then will make sure the other is aligned.... Cheers
     
  13. Feb 13, 2019 #12
    Here is a couple of photo's of what i came up with. I measured at 50-60-70-80mm and used a laser level to cast a line that i could measure toe in/out as it travelled through the suspension travel from full droop to hitting bump stop. 60mm came in at the best measurement at 1mm toe in over the full range of travel... i could try and chase that extra 1mm but i think i can live with that...?? The next step would be to cut the steering mount of the spindle and tack it back on at 60mm lower and re-check measurements. The black line in both photo's is roughly a straight line off the rear wheel, and once the steering mount has been moved i can align the front wheels again.
     

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  14. Feb 14, 2019 at 3:14 AM #13

    Ranger Mike

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    Ifin you got the change to stay 1 mm per inch (25 mm) travel, you are are there! So you have better than the factory..
     
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