[angelix]

tale about P38, 18" wheels, bad mechanics & Death Wobble

Many years ago, in 2006, we decided to purchase a P38 V8, this was not our first RR as we had in past the family a couple of Classics, but this one was going to be our first P38 auto.

We found our car a 1996 V8 4.0SE auto in very nice condition with some service history, low miles , well maintained and with what it looked like a "Hurricane 18" wheel conversion" ; after testing the car around London I decided to purchase it and took it home the day after.

All good until the very first time I took the car on the motorway few weeks later.... a wobble around 55-60Mph was very present and at the time I thought it was "just the balancing"; I got the wheels balanced and the wobble was now between 40 and 45mph at the front and around 70mph at the back.

At the time I blamed the tires (it had mismatched pairs of Wranglers fitted ), but I kept using the car as it was for few months until I decided to fit a full set of new Coopers.

The garage guy showed me around 500 grams of weights that he removed from one wheel and another 300g from another.... these were the remains of previous really bad balancing procedures... non only, the wheels had pressure sensors fitted which were not working so completely useless...

Anyway , with new tires and a “proper job” the car was much better, unfortunately the wobble was still there, around 48mph; It also developed a slight tramlining at certain tire pressures.

At that point the Garage guy blamed the transmission pointing the finger to the U-joints as they were in, according to him, “not so good shape”

So, new UJs followed , shortly after, by the steering shock, all 4 corner shocks & bags.

The wobble moved down to 40-45mph and it was like flicking a switch, nothing up to 40 and nothing over 45.

I replaced, as an experiment, the front propshaft with a brand new one, but the wobble remained there still coupled with a noticeable tramlining.

Looking online I read about the tyre pressure, the fact that the 18” wheels gave tramlining and wobblying issues , etc, etc .

I made peace with the fact the the P38 was **** and had a very disappointing handling overs 40-50mph, I looked around for a Classic V8 but never managed to find the right one (or the courage to pull the trigger and part with severl K£s for a good one!!!)

I honestly started to hate the thing, but it was convenient for many reasons like the loading (is the only car I know you can stick 3 bicycles at the back and carry 3 people onboard), low insurance, 4x4 , big and confortable somewhat cheap to run…

For over 12 years & over 60K Miles the car had regular MOTS, no advisories, but the tramlining got much worse and the bloody wobblying was always present at 40-45 Mph.

Then it comes the time for new tyres so I decide to go back to the 16” wheels hoping at least I can solve the tramlining issue and since we were putting all new rubber around we bit the bullet and overhauled all ball-joints, front suspension, all silentblocks, front shocks and trackrods.


The car is completely trasformed to the point that every time I drive it I have this smile in my face.

I blamed the ball joints for the bloody death wobble….and I cursed all the MOT technicians (at least 5 from 3 different stations) who never ever spotted the suspensions where “moving around”.

Shortly after I decided I did not want to keep the 18” Hurricanes and while putting them on Ebay I discovered:

A) they are not Hurricanes but the L322 Vogue 18” wheels.

b) They are not 8” by 7.5”, not sure if that make a difference but maybe that explains the tramlining and the stupid handling with the 255/55R18

C) they need spigot rings otherwhise they WILL WOBBLE…


So after 12 years chasing the bloody issue, at least 4 different tire fitters and 3 mechanics doing the maintenance (one of which was a LR specialist and not counting the one that did the conversion) , 3 MOT stations, 5 technicians and 12 Mots and not a single one that noticed the wheels were off center and suspensions were literally moving around.….

I never ever took off a wheel from my RR (never had a puncture) , if I had I would have noticed that they were .... unusual…

the L322 nuts are “square” (not conical) so it IS the HUB the one centering the wheel… if you compare them with the original P38 nuts , the latter are conical and will keep the rim centered on the hub when you tighten them

as soon as I had the conical nuts in my hands and compared them with the ones fitted on the car, I immediatly saw where was the problem and I am just a weekend mechanic; I wonder how is possible that no-one noticed or came up with the idea the wheels could not be running true.

OK, I am partially to blame as I have never looked into the issue personally, I just relied on the "professionals " to sort the issue... But then who else could you rely on? professionals , yeah right...

Lesson one : leave the thing standard, it is the very best solution.

Lesson two: if you want to modify the thing, make sure you do a proper research.

Lesson three: never trust mods made by others

Lesson four: a car should not tramline and should not wobble… if something is not right, there must be a reason and it is not the "car's character"

Lesson five: never fully trust the professionals, always question them … you are paying for them good money and they must do their job properly.

 

[RRToadHall]

Re: tale about P38, 18" wheels, bad mechanics & Death Wobbl

WOW what a story. I have proper 18" P38 Hurricanes. Sadly many folks install L322 rims to go up a size. Sad that you spent so much money on things not needed. Ujoints usually get ignored but would not cause tramlining. Nothing EAS or shocks would cause vibrations.

So is she proper P38 with P38 rims and the magic carpet ride?

 

[angelix]

Re: tale about P38, 18" wheels, bad mechanics & Death Wobbl

WOW what a story. I have proper 18" P38 Hurricanes. Sadly many folks install L322 rims to go up a size. Sad that you spent so much money on things not needed. Ujoints usually get ignored but would not cause tramlining. Nothing EAS or shocks would cause vibrations.

So is she proper P38 with P38 rims and the magic carpet ride?

Let's say that all the work carried was somehow due anyway, the car is 23 years old , so most of the works had to be done anyway.

The only thing that was really un-necessary was the extra balancing and the propshaft replacement , but since it was cheap (85quid I think) I decided to do it anyway.

my guess is that the tramlining was sorted by the suspension overhauling and wheel size change , the wobblying was only due to the poor fitment of the rims; 1.5 mm is very little to be noticed be eye, but it is still 1.5 mm and with such big tires it could make a difference.

Now the car is a joy to drive , so much I am committed to keep it as long as I can find parts to maintain it :mrgreen:

on Thursday it goes to Autoglass for a new windscreen (I got a nasty Chip & crack on the motorway 10 days ago) and shortly after I will treat it with a nice new headliner (already got all the stuff).

 

[Richard_G]

Re: tale about P38, 18" wheels, bad mechanics & Death Wobbl

With the amount of weight on the wheels, it sounds like someone tried to balance them on the car. Not a bad idea sometimes, and that's the way they do truck wheels, but on a 4x4 with live axles? You can't entirely blame the mechanics as the flat nuts were right for the wheels, it would need someone really on the ball to spot they weren't the right wheels for the car.

 

[mad as]

Re: tale about P38, 18" wheels, bad mechanics & Death Wobbl

the reason I fix my vehicles today is because I would pay for them to be fixed and then have to fix it myself anyway . with the closure of Ford and Holden in Australia and the influx of European vehicles their is a lot of mechanics and auto electricians are scratching their heads because their avoided these vehicles like the plague, even the importers are scratching to fix them?
its a bit like panel beaters all they do is replace things no repairs just replacement . that's todays mechanics for you if something needs to be fixed its shipped out to a so called specialist. all they do is service work, oil and filters and charge you a fortune.

 

[Sitomagus]

Re: tale about P38, 18" wheels, bad mechanics & Death Wobbl

Right - confession time: I am a professional. Well not strictly a Range Rover professional but I am a Vintage car specialist involved with anything pre 1980 and I do design and manufacture steering modifications and rack conversions.
I see this sort of thing a lot.
The truth is that on average the trade aren't that well trained on steering and suspension geometry. What a tyre shop / small garage is about is maintaining an original and newish vehicle to manufacturer's limits. The training is about learning the basics and learning to use the equipment properly. Not only is it unlikely that anyone will spot wrong wheels it is even less likely that they will see a problem with them. The conclusion you have come to is the correct one but it is also sadly an unusual one and it is not in the interests of the aftermarket wheel business for it to be very well known either.

If you look at the front of a beam axle car made in the 1920s or 30s you may notice that it has a lot of positive camber: the wheels are angled outwards at the top. If you were to extend a line through the kingpin of one of these cars it would meet the road at the centre point of the tyre. This is called centre point steering and it is light and (at modest speeds) precise. It was quite desirable before power steering was invented because the action of the steering is mechanically efficient.

As independent suspension became more fashionable in the 1930s manufacturers were inspired to explore the benefits of negative camber where the wheels are angled inwards at the top. This gave better cornering abilities and more stability but it could produce uneven tyre wear. Most of these cars were built with unequal length wishbones so that camber became more negative with deflection of the suspension so that it was only applied when you needed it. Even as late as the 1960s a MK2 Jaguar had positive camber in the static position which became negative under cornering forces.

As negative camber became the norm manufacturers started to offset the wheel outwards from the steering axis. If you were to protract a line through the ball joints of a P38 that line would meet the road surface inside the centre point of the tyre. The distance between these two points is called the scrub radius. The scrub radius is literally the radius about the centre point which the tyre has to scrub when steered and is the single biggest reason why a modern car tracks nice and straight down the road and you feel that you could take your hands of the wheel whereas a vintage car always feels like it needs to be corrected. Death wobble too was a massive bug bear in the 1920s.

If you alter the offset of the wheel for a given diameter, of course you change the scrub radius. What is less appreciated is the fact that if you fit larger diameter wheels with the same offset you also decrease the scrub radius because you are moving the kingpin axis further away from the road. A jump from 16 inch wheels to 20 inch wheels with exactly the same offset can actually cause a negative scrub radius which gives the handling characteristics of a supermarket trolley!

Manufacturers invest enormous amounts of time finding the best scrub radius for a given suspension design. This includes long periods of time on banked circuits finding the "neutral steer speed" and bringing it within the design speed range of the car. The neutral steer speed is the speed at which you can take your hands off the wheel when driving around a banked circuit. You change this geometry either because you have a deep knowledge and are modifying the car extensively or else you do so at your peril... The difference can be quite small: When Peugeot introduced the 1.9 GTI with different wheels to the 1.6 model they changed the included angle between the strut and the stub axle by less than one degree. They obviously thought it necessary to go to the expense of manufacturing a new assembly!

Hope this helps explain the mechanics without too much of a waffle!