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nissan patrol gq
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Discussion Starter #1
hi guys i have a Gq with a 6 inch lift and 2 inch body lift with 35s and i run 31s daily i have only just bought it a few months ago on 35s and it drove great then i put 31s on it for the misses to drive so its a bit lower to get the kiddies in and out then on the weekend i put the 35s back on to go wheeling and at 60ks i get a real violet shake at first i could drive through it but after wheeling it just gets worse the faster u go and i mean the hole car shakes that bad it feels like the wheels are just flapping around.the guy i bought it off has twin steering dampers on it do u think they are rooted????or could it be sumthing else?oh and now the 31s are back on it doesnt do it????any help would be great.cheers
 

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Get your 35's balanced. You might have knocked weights off or moved them, dinged a rim, or maybe just the 35's have chunks missing, or have worn oddly.
 

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nissan patrol
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mine did same when i rotated wheels, i put them back on original corner and is good again,
also replace panard rod bushes with only gen nissan items
check swivel hub bearings
balance wheels
theres plenty of posts on this site about this prob so do a search
common prob half time its the tyres half the time its worn parts
 

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nissan patrol gq
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Discussion Starter #5
all the rubbers are brand new and the rims are 6months old only been offroad 3 times.it was doing it b4 i went wheelin and got heaps worse after it
 

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35's were balanced on the car not on a balancer thus when you put them on a different corner there all out of balance
 

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nissan
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6 inch lift and 2 body lift ?.

Is the steering geometry within spec, drive line angles, pinion angels ?.
 

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nissan
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yeah id be getting the tyres rebalanced first. specially if ok on another set of tyres. you have already narrowed down your problem.
get all tyres done its probably about 10 bucks max a tyre off memory.
 

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anyone know anything about somthing called scrub radius? this is something that can be effected by wheel offset and if reduced beyond standard can induce all sorts of crazy behaviour. Its the center line of the contact patch of the tyer relative to the king pin , something i never considerd until i stuffed i
t up!
 

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BORDERTREK 4X4 & FABRICATION
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anyone know anything about somthing called scrub radius? this is something that can be effected by wheel offset and if reduced beyond standard can induce all sorts of crazy behaviour. Its the center line of the contact patch of the tyer relative to the king pin , something i never considerd until i stuffed i
t up!
Yep it's something very overlooked by modders, It can be outright dangerous as it causes unpredictable cornering.
Latest regs:
Vehicle Standards Bulletin 14 (VSB 14)

Scrub Radius:
Ideally, the scrub radius is as small as possible. Noramlly the SAI angle and the centerline of the tire and the wheel intersect below the road surface, causing a positive (+) scrub radius. With struts, the SAI angle is much larger than the long arm/short arm type of front suspension. This allows the SAI angle to intersect the camber angle above the road surface, forming a negative (-) scrub radius. The smaller the scrub radius, the better the directional stability. Installing aftermarket wheels that have additional offset will dramatically increase the scrub radius. The newly installed wheels may cause the centerline of the tires to move further away from the spindle. This will increase the scrub radius.
A large amount of scrub radius can cause severe shimmy after hitting a bump. Four wheel drive vehicles with large tires use a steering damper to compensate for an increased scrub radius. Scrub radius is not directly measurable by the conventional methods. Scrub radius is projected geometrically by engineers during the design phase of the vehicle’s suspension system.
American Expedition Vehicles
 
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