CIH
Posted a lot
Posts: 1,466
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Dec 14, 2011 22:24:12 GMT
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Despite what everybody has said bump steer can be a real problem to sort out. First thing to do to identify bump steer is with car stationary and the wheels straight ahead, get somebody to bounce the front of the car up and down whilst you watch the front wheels. If the toe in/out changes as the car bounces then you have a bump steer problem. This is caused by the steering rack being the wrong height in relation to the steering arm on the hub, this means as the car moves up and down the track rod effectively becomes shorter or longer in relation to the steering arm. The only answer is to modify either the rack mounting or the steering arms on the hub. Neither of these is something a novice should undertake its really a job for a specialist custom builder. That would be much, much easier to observe on the alignment ramp with the 'gear still attached. Also bump steer is a failure of the steering arm and lower control arm to maintain their positions relative to one-another during suspension travel. It can be caused by many different things, rack placement is only one of them.  It could be something as simple as the trackrod end balljoint being preloaded due top the angle of the track arm. |
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Last Edit: Dec 14, 2011 22:25:24 GMT by CIH
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will930
Part of things
Decked K11 Micra - RetroRunner Mk2 Golf
Posts: 521
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Dec 14, 2011 23:03:35 GMT
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when the car was on the four poster i looked and the lower are and rack arms are pointing quite drastically upwards, which if my thinking is correct as the suspension bumps its pulling on the tie rod arm! causing it to bump steer
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Dec 15, 2011 17:54:34 GMT
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I certainly agree bumpsteer is more easily detaected whilst all the tracking gear is connected up. and as you say it can be affected by ball joint tension but in view of the drastic angle of the track arms in relation to the stub axle steering arms its unlikley. I think if you want to keep the amount of lowering you hsve csrried out you will need to invest in some modified steering arms.
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Dec 15, 2011 18:23:05 GMT
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You said on the first page of this thread that you had adjusted the camber by virtue of slotted holes on the lower arm mounts. Care to elaborate? Ive set it by using slotted holes in the bottom mounts of the suspension as its the only at with my set up Because as I said on page one , changing the relative position of the lower arm pivots outward would certainly make geometry changes that could lead to bump steer characteristics as to retain correct toe you would then have to adjust the track rod ends out accordingly. Your rack arms would then be longer relative to your lower arms and thus swing through a different arc. |
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1962 Datsun Bluebird Estate - 1971 Datsun 510 SSS - 1976 Datsun 710 SSS - 1981 Dodge van - 1985 Nissan Cherry Europe GTi - 1988 Nissan Prairie - 1990 Hyundai Pony Pickup - 1992 Mazda MX5
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Dec 15, 2011 18:25:18 GMT
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Theres a reason you cant buy that amount of lowering off the shelf, I had similar issues with a chaps 106 he bought because it looked good. Had cut down lowering springs on the front and the rear was sat on the bumpstops even when jacked up. His issues were much the same as yours and more horrendous bumpsteer, tyres wearing really quickly, tramlining, wheel bearings would only last a week etc etc. On the ramp the issue was clear to see. The driveshafts were at too extreme an angle (iirc 20 degrees is the max for inboard joints)and forcing the wheel bearings at an angle, also found that the drive shafts were bottoming out and had cracked the gearbox case. Same as you have found the track rod was at too extreme an angle. He ended up replacing the gearbox, 2 wheel bearings, both driveshafts, full set of dampers and top mounts both track rod ends, we fitted a 40mm lowering kit and raised the rear to match and it felt like a completely different car. What was more disturbing was he only bought it to us to see what the clicking noise was when turning which was the gearbox getting ready to explode  Saying all that it could be done but it would take a lot more work than makes it worthwhile IMO. |
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Last Edit: Dec 15, 2011 18:27:41 GMT by damien4884
1977 datsun 810 180b estate |
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CIH
Posted a lot
Posts: 1,466
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Dec 15, 2011 22:07:50 GMT
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when the car was on the four poster I looked and the lower are and rack arms are pointing quite drastically upwards, which if my thinking is correct as the suspension bumps its pulling on the tie rod arm! causing it to bump steer The arms pointing upward relates more to the roll centre and camber behaviour. |
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will930
Part of things
Decked K11 Micra - RetroRunner Mk2 Golf
Posts: 521
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Dec 16, 2011 19:26:33 GMT
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Well all points taken and duly noted! After trying to set the camber and then the tracking its better but not great
It will be raised soon onto standard gear for ease of life!
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