Shaking? Its trying to kill me!

Submitted: Saturday, Nov 29, 2003 at 09:18
ThreadID: 8836 Views:1459 Replies:1 FollowUps:4
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I know we've delt with the steering shake before, but I think think this is diferent so please bare with me

I recently purchased a 91 swb 3ltr petrol which was fitted with wide road wheels, and it came with the originals.

I re-fitted the originals as the wides needed a couple of tyres (or 4) but the original all have very good tread. I then fitted my hand clutch (being a leg short) and took her out.
All was well until a guy pulled out of a side road on me as I was at 45mph, so I moved into r/hand lane but so did he causing me to break hard. Thats when the steering wheel started to try and shake itself out of my hands.

15 miles further on as I traversed a left hand bend at 50ish she hit a pot hole and off she went again, not stopping shaking until I get her down to 15mph.
It transpired that the steering damper was US and had pulled on its top braket breaking two of the 3 welds.

With her all fixed up by MR 4x4 the problem seemed fixed, so fully loaded (even on the cab rack) I drove her 450miles from the UK and through France.
I hit a couple of bumps on the M/roads on left handers at about 65mph where I felt the slightest twitch, as if the damper was catching it, but the jurney transpired without a hitch.

Heading down the road this afternoon however (with the load off another bump on a left hander set her into "terrier with a rat" mode even though the repair is still holding good. I belive this problem might be what knackered the bracket and the damper in the first place.
I've seen some talk of wheel balance here, but this isn't a constant problem that I can feel comming on as I aproach the unbalenced speed, but rather near total loss of control provoked by forces impacting something on the front offside wheel/suspension from that quarter.

Any help,advice, pointers you guys can give me will be very much apreciated.

Thankyou
Doc

PS. Are there any real gains to running her on 10" wide rubber over the standard tyres when offroad?
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Reply By: Member - DOZER- Saturday, Nov 29, 2003 at 10:29

Saturday, Nov 29, 2003 at 10:29
Doc
Had a similar problem with my lifted cruiser. If yours is lifted, then get the caster checked...if it is out- this is what it causes... (tank slap on a bike)
Also, loose wheel bearings and/or buckled wheels/out of round tyre will agrevate this underlying situation.
For starters i would get an ride disturbance/alignment done, where they will check the wheels for out of round, wheel bearings for looseness, damage to suspension, etc.
Andrew 0zwheredayathinkwer mike?
AnswerID: 38869

Follow Up By: DocTheBiker - Saturday, Nov 29, 2003 at 11:32

Saturday, Nov 29, 2003 at 11:32
Cheers Dozer
Tank slap! Thats it compleatly (been riding cruisers so long I'd forgoten it). She's not raised, so the geo' should be standard. Would swaping the tyres round help to show up a knackered wheel? I'll give it a try.

Alignment was my first thought and was checked out at the local "kwickfit", but maybe I should try somewhere else as he didn't spot the broken bracket on the steering damper.

By "caster", do you mean the Bush the leaf springs hang down from?
There is a little rust around the front one on the suspect side and it does look a couple of mil out of line, but I didn't think that was enougth to throw it out as bad as it is, but I'll move that up in my work maintainance priority list if thats what your talking about.

Its the tweeks and tinkers I need to sort out before I go investing in a HD damper that may not do me any good anyway.

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FollowupID: 82722

Follow Up By: Member - DOZER- Saturday, Nov 29, 2003 at 17:23

Saturday, Nov 29, 2003 at 17:23
LOL
Caster is the measurement in degrees that the wheel turning centreline is forward (or back) of 90 degrees from the road plane. Sorry but thats the best i can do. Im not a pro with geometry, just enough to get me into trouble. Try jacking up a front wheel or both and spinning them to see if they are out of round or buckled. Then you can shake it back and forth feeling for any play in steering linkages. Maybe it is a stuffed damper, another friend with an old Nissan had thesame and a damper fixed it (or should i say made it go away for a while)
Another possibility is that the settings for widies are different to skinnies.
Its all something you need to check yourself bit by bit or get a professional to check for you.
Andrew
wheredayathinkwer mike?
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FollowupID: 82739

Follow Up By: DocTheBiker - Saturday, Nov 29, 2003 at 21:56

Saturday, Nov 29, 2003 at 21:56
Ahh I understand, we call that tow-in up here. You get my missunderstanding, those bushes do look like the lil wheels you get on furniture LOL.
She is wearing a new damper, but its a budget item (well with the broken braket and whistling damper that apeared to be the prob) mayhap I'll give it a beef up.
Thanks for the info.
Time to done the woolie hat and grab the spanners, I'll let you know how it goes.
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FollowupID: 82755

Follow Up By: Bonz (Vic) - Sunday, Nov 30, 2003 at 09:20

Sunday, Nov 30, 2003 at 09:20
Doc, Toe-in and caster are different things. Hard to describe but I'll use an analogy (probably poorly)

sit in a chair, knees bend 90 degrees ankles bent 90 degrees, feet pointing straight ahead and parallel, so everything is "square". Now if you move your feet so your big toes are closer together, thats TOE-IN, and if you move your toes apart, thats TOE out. Toe settings have a major impact on directional stability and loose bits in your front end controlling the toe settings may be some of the terrier RATtle you have.

Now with your toe in adjusted, slide forward slightly in your chair, to change the ankle and knee angles from 90 degrees to a smaller angle less than 90. This is the CASTER effect and it works both forward (positive caster) and backwards (negative caster) from 90 degrees. Positive caster tends to straighten the wheel when the vehicle is traveling forward, and thus is used to enhance straight-line stability. Its also why those infernal things on shopping trolleys are called casters, althought I prefer to use much more colorful terms for them) Get that checked too.

Now back in your chair again. If you move your knees apart then you have positive CAMBER, if you move them knees together then you have negative camber. Camber is used to control cornering forces and may well be the cause of your consternation. Most vehicles run a slightly negative camber although I do not recommend keeping your knees together. Get the camber checked too.

Nissan have specs for all these settings and a smart suspension mob should be able to solve your problem, ask at your local 4WD club who is good with front ends and go there.

Good luckLaterally Literal
Seriously Cerebral
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FollowupID: 82781

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