I have a 4WD Nissan Patrol 2.8 Turbo diesel.
I bought the car brand new.
:banghead:
When I changed the 5 tyres(spare) from BF Goodridge to the Coopers brand the car immediatly pulled to the left (Australia drives on the left side) seriously just as I was driving out of the tyre fitting shop.
To drive the Nissan GU I have to maintain a constant 9 to 10 lbs pressure on the steering wheel.
I measured the force needed on the steering wheel using a measuring fish spring-scale.

:banghead: Can any one explain to me why tyre affect the pull of the car?
My car was driving perfectly straight before changing to these type of tyres.
I believe the walls of the tyres are flexing too much and force the car on the left on curved road.

:banghead: Is that possible or am I dreaming?
Guy

You may have a tire that has lateral pull see more on this at:


http://www.tirerack.com/tires/tiretech/general/diagnosingtirepull.html



Cy@tirerack.com
Performance Specialist
Moderator www.automotiveforums.com. To place an order please call 888 541 1777 Ext. 622 or for internet orders through www.tirerack.com please mention my name in the previous contact field directly above the Place Order button on the Order Summary page for quick, efficient & professional service.

You may have a tire that has lateral pull see more on this at:


http://www.tirerack.com/tires/tiretech/general/diagnosingtirepull.html



Cy@tirerack.com
Performance Specialist
Moderator www.automotiveforums.com. To place an order please call 888 541 1777 Ext. 622 or for internet orders through www.tirerack.com please mention my name in the previous contact field directly above the Place Order button on the Order Summary page for quick, efficient & professional service.

Hello Cy

This is very interesting.
But I have done the tests mentionned in http://www.tirerack.com/tires/tiretech/general/diagnosingtirepull.html
about 12 months ago.

In the URL above the important thing is
>>A tire diagnosed as a pulling tire is a manufacturer's >>defect...caused by the belts being incorrectly aligned during >>manufacture.

Cy I am tallking of a pull of a constant 9 lbs, immaterial of the curvatur of the road. :rofl:
And this just happened after changing these tyres from one brand to the other brand.
Cy, I believe that every one of this tyre is faulty. This is a batch defect.
To be able to prove it I need more figures here. :grinno:

Cy with your experience on a 16 inches diameter tyre 7 inches wide for a 4WD Nissan GU, how much pull in kg or lbs would a faulty belt generate.

:banghead: PLEASE , PLEASE give me a good guess. I need to do some more precise tests. I have $1400 at stack here plus the extreme pain of driving like that.
Is it 1, 2, 4 , 8 or more lbs per faulty tyre.
Guy (Australia)

Normally, TireRack does a great job of explaining tire stuff, but this is one case where they didn't quite get it right (Sorry, Cy!)

Tires have a property called conicity (root word - cone). It comes from the idea that a cone will not roll straight, but rolls off to one side.. Conicity is similar in that it is a measure of how much side force a tire is generating. It is expressed in terms of force with a sign indicating which direction the force is pointed. When you put 2 tires on the vehicle, the vector difference of the concities results in a total side force. BTW this would be different than what you were measuring at the steering wheel, although related. I don't think I have ever heard that the rear tires contribute to this, but I don't want to discount the possibility.

Every vehicle has a certain sensitivity to conicity and there is a threshold beyond which a particular vehicle will pull. What is important is 1) The sensitivity of the vehicle (and there is a wide range of sensivities.) and 2) the vector sum of the conicities.

Example: You've got a vehicle that is sensitive beyond 15 pounds. Put on 2 tires: a + 10 and a - 10, that's a difference of 20,--> the vehicle pulls. Take one of the tires and remount it so what was the outside is now the inside. That changes the relative direction of the conicity for that tire. Result? --> Zero force, and no pull.

For our example, any combination that exceeds 15 will cause a pull. so a + 20 and a zero will also cause a pull.

Vehicle alignment can have a profound effect. Assuming the concities are the same for the 2 front tires, a difference in toe in, side to side, will result in a steering wheel that has to be turned slightly to get the vehicle to run straight. Obviously a difference in tire conicity would add or subtract from this situation. BTW, it is possible to wear conicity into a tire.

Camber can add to the force being generated. The term is called cross camber, and it is the difference between the 2 camber measurements. Again conicity would add or subtract to this situation.

So it isn't a defect per se, it's what the combination is. Because of the laws of statistics, most of the tires fall within a certain range and what usually happens is that there will be one tire on the high side. Changing it eliminates the problem, leaving folks to conclude THAT tire had a defect.

What the diagnostic procedures charts do is help find which tire is the "odd man out".

At this point, I should mention that vehicle manufacturers specify the concity limits for tires supplied as original equipment. Some specify that they always is the same sign. Tire manufacturers then mark the tires in such a way that the proper side is mounted out. Of course, this doesn't work on WSW tires.

Guy, You didn't say what the results of your diagnostic test were. The impression is that you couldn't isolate an individual tire. So it is still possible that it's vehicle alignment. Any idea how close to the vehicle specs the alignment is? IMHO, vehicle manufacturer's alignment tolerance is too wide by half. I'm not talking the target value - I'm talking about how far off the target the actual values are. I've seen some specs where the camber tolerances were such that the cross camber would result in a pull.

Hope this helps.

.....
Tires have a property called conicity (root word - cone).....
Every vehicle has a certain sensitivity to conicity.....
Example: You've got a vehicle that is sensitive beyond 15 pounds. Put on 2 tires: a + 10 and a - 10, that's a difference of 20,--> the vehicle pulls. Take one of the tires and remount it so what was the outside is now the inside. That changes the relative direction of the conicity for that tire. Result? --> Zero force, and no pull.

For our example, any combination that exceeds 15 will cause a pull. so a + 20 and a zero will also cause a pull.
......
Guy, You didn't say what the results of your diagnostic test were?
Hope this helps.
Hello CapriRacer
1) Your reply about CONICITY helped me. never heard it before so are a lot of tyre fitting shop here in Australia..
I am familiar with all the tests you mentioned because my Nissan Gu 2.8 Turbo diesel 4WD was brand new when I bought it in 99.

It's only after 2000 Kms that the original car tyres were swapped for the brand new Coopers.

2) You are right in saying that I could not isolate an individual tyre nor do the 3 different wheel alignement worksshop and tyre specialists.
15 minutes after driving out of the tyre shop my car was back in there having all sorts of tests.
All the tests were paid by Coopers and Nissan. These test lasted 3 months.
I was present at each test.
Nissan engineering claims that 20% of cars like the Nissan Gu diesel or petrol in Australia pull on the left buit do not know the reasons.

About 22 months later I know what the reasons are but how can I prove it?

Some Coopers tyres are weak in the side wall and change shape enormoulsy with a small difference of curve in the road.
Plus there is a serious weakeness of the Nissan Gu 4WD rim which crackd all the time.
I checked this with about 6 different car wreckers which confirm that.

3)The car was steeering perfectly correctly before entering the tyre shop and as soon as I drove off from the tyre shop, my car was pulling enormously on the left.
The car was OVER_following the contour of our roads because in Australia we drive on the left side of the road.

As the road curve left the tyre deformes right.

If I go on the right side of the road then the tyre deformes towards the left due to the weight and the tyre goes right.

As you were explaining with Conicity, there is so much tyre shape changing (too flexible on the side wall- increasing the pressure makes a difference).
The recommended pressure for these tyres are 65 PSI. May as well buy some concrete wheels ;-) :-)

4) Here some photos

Fig 1& 2 (http://home.dyson.brisnet.org.au/~aufempen/Tyres_Rim_problems/Tyre_Coopers_01&02.jpg)
Fig 3 (http://home.dyson.brisnet.org.au/~aufempen/Tyres_Rim_problems/Tyre_Coopers_03.jpg)
Fig 4 (http://home.dyson.brisnet.org.au/~aufempen/Tyres_Rim_problems/Tyre_Coopers_04.jpg)
Fig 5 (http://home.dyson.brisnet.org.au/~aufempen/Tyres_Rim_problems/Tyre_Coopers_05.jpg)
Fig 6 (http://home.dyson.brisnet.org.au/~aufempen/Tyres_Rim_problems/Tyre_Coopers_06.jpg)
Fig 7 (http://home.dyson.brisnet.org.au/~aufempen/Tyres_Rim_problems/Tyre_Coopers_07.jpg)
Fig 8 (http://home.dyson.brisnet.org.au/~aufempen/Tyres_Rim_problems/Tyre_Coopers_08.jpg)
Fig 9 (http://home.dyson.brisnet.org.au/~aufempen/Tyres_Rim_problems/Tyre_Coopers_09.jpg)
Fig 10 (http://home.dyson.brisnet.org.au/~aufempen/Tyres_Rim_problems/Tyre_Coopers_10.jpg)

You noticed that the tyre is wearing in a very strange way after 50 000 km.
A way that I have NEVER seen before.
The Cooper tyre wears inside on about 1 meter long.
Every one of my 5 tyre wear the same way.

Plus the tyre does not seem to be centered. There is more rubber in on side that the other.
I mean the belts inside are not centered.
Plus the tyre deforms enromously and far too much for an 8 plys tyre.
Look at the photos with 33 PSI..

I am NOT sure that I have been sold an 10 ply tyre_ a question for an other time.

5) Plus Nissan GU 2.8 liters turbo diesel have a faulty rim which cracks all the time.
This is my 3rd rim cracking after only 100 000 km
Fig 11 (http://home.dyson.brisnet.org.au/~aufempen/Tyres_Rim_problems/Tyre_Coopers_11.jpg)
Fig 12 (http://home.dyson.brisnet.org.au/~aufempen/Tyres_Rim_problems/Tyre_Coopers_12.jpg)
Fig 13 (http://home.dyson.brisnet.org.au/~aufempen/Tyres_Rim_problems/Tyre_Coopers_13.jpg)
A friend of mine and I have spoken to a few 4WDrive wreckers and we know that Coopers are problems and that the Nissan rims for the GU are problems.
But what I would like to know is what problems are they so I do not buy the same problem again?
Guy

I think we need to get back to basics:

What does the placard on your vehicle say for: Tire Size, Inflation pressure, Rim width, GAWR (front and rear)

What inflation pressure are you running?

A couple of comments:

Figure 7 shows a difference in sidewall bulging one side to the other. While this infers that there is something off center in the tire (perhaps the belts), it could also mean camber angle. The way to verify this is to swap the tire, inside becoming the outside.

There is a lot of cracking, but cracking can indicate a lot of things, including age, the amount of heat the tire has experienced, underinflation, but it doesn't have anything to do with the pull.

The photos showing the wear pattern: The wear pattern is obsured by the lines you drew, but it seems that you are indicating heel and toe wear (the edge of one lug is higher that the adjacent edge of the next lug, for every lug). I think this is what you were trying to show in fifure 8. Hele and toe wear is normal, if not excessive, (Yours appears excessive) and can become excessive if there is an alignment problem. Off center belts probably wouldn't cause this.

I can't read the scale to see how wide the wheel is, but wheel widths are measured between the flanges, not from the outermost edges of the flange. And it ought to be stamped somewhere on the wheel. An LT265/75R16 takes a maximum of an 8.5" wheel.

You refered to 10 ply. I hope you are not thinking that it ought to have 10 plies. "Ply Rating" is term that used to be used to describe the load rating of a tire. It's a simple way of saying "we could use 10 plies to build this tire if it was a bias ply tire, but we have a radial AND we used a stronger cord, but less of them to acheive the same strength". The term has been replaced by "Load Range", which is a better way of describing the situation and it avoids the confusion.

BTW, a Load Range D is equivalent to an 8 ply rating, but I don't hink that has anything to do with the pull.

The wheel cracking - I think you are off base on the reason for the wheel cracking. I have seen many of these types of wheels used successfully in many applications. The support you mentioned might help the situation, but increased thickness in the area of the crack, or even a different material, might also help.

Based on what I've seen, I suggest you look at the following:

Camber, especially cross camber.

Toe

Load vs inflation pressure. Be sure you are looking at the max loads

Wheel width vs tire size.

And I would take a real close look at the thrust angle. Remember what I said about alignment tolerances.

Be aware that with a change in tires, you might go from good to bad, but the real source of the problem could be the alignment.

Hope this helps.

I think we need to get back to basics:

What does the placard on your vehicle say for: Tire Size, Inflation pressure, Rim width, GAWR (front and rear)

What inflation pressure are you running?
..........
Hope this helps.
Thanks. you are giving some more clues which is great

What I've marked in white on the photos is not the wear of the tyre, but the roundness of the tyre.

This is were the tyre looses it's diameter by about 6 mm (roundness). Actually there is a lot less wear in this area.
This causes slight vibrations when driving.

This is were the tyre looses about 6 mm of "thickness". Like a "long hole" in the tyre. At that spot the rubber has not the same consistency. (What is wrong at that spot iI do not know).

The belts are off center by at least 10mm on each one of these tyres.

I am preparing a full webpage with photos and text and all the camber, toe etc data so it could be examined easely.

In 3 months I need to purchase $3000 of tyres and rims. So I need to get it exactly right. I need to buy the right tyres and right rims.

If I stuff up my diagnostic, like in the past the problem will still be there.
I'll be $3000 down the drain then it will not stop or will get worse as the car gets older.

This what happened before. We (Nissan + Tyres shops) looked at the camber, toe etc.. and all sort of figures and try swapping all sort of things but we forgot the obvious which are these Coopers in the first place.
At no time Coopers took ownership of their responsabilty. Nor did Nissan.
Both Nissan and Coopers told me a big story which confused me, so I could go away confused.

What I really want to know is "how tyres can affect a 3 tonnes 4WD and its steering".

I want to know how many tyres defects do exist?

What cause the tyre defect and what sort of consequence the tyre defect has on any 4WD?

S0 far I have not seen any Website listing 50 tyre defects and explaining how ONE tyre defect affects the steering or the drive or the braking etc... of a 3 tonnes 4WD on a perfectly straight road with a 8 degrees curvature.

Reading all the websites around the world , a person like me as the impression that tyres defect never exist. I do not buy this theory anymore that ALL BRANDS and EVERY TYRE is put on the market with perfect quality control and perfect batch control.
I am a chemical engineer and know better than that.
This is a Cinderella story.

I am sure you understand what I am talking about.
Guy

Guy,

Let's move this discussion off this web site, so post your email address or someother way to contact you. I'm sure someone will appreciate not using up the bandwidth.

For those that read this and want to know the conclusion, I'll post it when we get there.

But for those who can't wait:

I'm inclined to think this has something to do with alignment, rather than tires. Everything I know about tires says that if you swap tires arround, then the problem should change, but it hasn't. I suspect the problem is something that has yet to be touched on in this discussion.