Np300 stx vibration

[mika]

Pedders and Bob Jane have both done alignments.
The Pedders guys stepped me through the numbers and they are all good, no adjustments required.

 

[Old.Tony]

While I don't have 100% faith in Pedders, let's say for the moment the alignment is out of the question.

What about tyre pressures? Are you running about 36psi or have you taken it up higher?

 

[mika]

While I don't have 100% faith in Pedders, let's say for the moment the alignment is out of the question.

What about tyre pressures? Are you running about 36psi or have you taken it up higher?

Running 40 as recommended.
Think 35 might be better?

 

[Old.Tony]

It depends on the tyres, the road conditions and the load. When I'm not towing, using AT tyres, I'll run 34-36psi. When I'm towing, I'll up the rears to 38-40psi. When I'm on loose surfaces briefly I'll leave them, but if I'm on really loose stuff or going to be on it for a while, I'll drop the tyres to around 24psi. For beach work you'd even consider going as low as 18psi.

But with that said, your tyres will have a recommended pressure on them, and that's because the manufacturer recommends that pressure for the build of tyre. If you are getting even tyre wear across the tread, your pressures are probably just fine.

What I am struggling with is the description of the issue where the road surface causes the wobble to commence. Caster angle is the first thing that comes to mind, because it governs how the wheel wants to sit on the road with respect to the axis of the steering and its motion in a particular direction.

The only other time I've seen something like this (experienced it myself, in fact) is where a light motorcycle uses a tyre like a Pirelli Phantom (not sure if these are still around, I use Pirelli Night Dragons now and my bike's not light). My little 250cc bike, fitted with a Phantom, would 'wobble' in time with the zig-zag of the centre tread pattern. It was made considerably worse with a firmer tyre. On a heavier bike, you didn't notice it. I really don't expect this to be the issue on a car especially with such a wide tyre, noting that they generally have a fairly uniform tread pattern - although that's for HT, MT and AT tyres. I'm not sure if LT tyres would be different in their handling.

So unless your power steering pump is on the verge of doing silly things and is triggered by the change in road surface, I'm running out of ideas.

 

[mika]

It depends on the tyres, the road conditions and the load. When I'm not towing, using AT tyres, I'll run 34-36psi. When I'm towing, I'll up the rears to 38-40psi. When I'm on loose surfaces briefly I'll leave them, but if I'm on really loose stuff or going to be on it for a while, I'll drop the tyres to around 24psi. For beach work you'd even consider going as low as 18psi.

But with that said, your tyres will have a recommended pressure on them, and that's because the manufacturer recommends that pressure for the build of tyre. If you are getting even tyre wear across the tread, your pressures are probably just fine.

What I am struggling with is the description of the issue where the road surface causes the wobble to commence. Caster angle is the first thing that comes to mind, because it governs how the wheel wants to sit on the road with respect to the axis of the steering and its motion in a particular direction.

The only other time I've seen something like this (experienced it myself, in fact) is where a light motorcycle uses a tyre like a Pirelli Phantom (not sure if these are still around, I use Pirelli Night Dragons now and my bike's not light). My little 250cc bike, fitted with a Phantom, would 'wobble' in time with the zig-zag of the centre tread pattern. It was made considerably worse with a firmer tyre. On a heavier bike, you didn't notice it. I really don't expect this to be the issue on a car especially with such a wide tyre, noting that they generally have a fairly uniform tread pattern - although that's for HT, MT and AT tyres. I'm not sure if LT tyres would be different in their handling.

So unless your power steering pump is on the verge of doing silly things and is triggered by the change in road surface, I'm running out of ideas.

The vibration/wobble seems to be first felt through the rear then sometimes, but not always, in the steering.
Because the wheel offset is different this may need to be compensated for in some sort of revised settings but finding a reputable and knowledgeable place for that advice is scarce these days.
Though factory set caster angles have never varied. The camber would, I guess, be the only casualty in the changed wheel offset but caster shouldn’t be affected as there has been no suspension changes from new to the Nav and both alignments are showing the correct set of angles.
Currently away for the week so will give the tyre pressures a go when I get back and I will also get some tech support from Yokohama on whether the All Terrain LT spec tyres were perhaps a poor choice.

 

[phantom1221]

Vibration at 105 kph

Hi D23, I purchased a STX in January and also had a vibration at 105 kph. Took straight back to the dealer and it was fixed straight away. They said that they found a fault when hooked up to a diagnostic machine. Apparently there was a loose sensor ? Now no vibration.

Any more information on this would be much appreciated. I have the same problem.