Thanks for the info.
Still interested in this 4x4 thing if someone has the time to explain. Last Sunday at the scrapyard the guy was saying about a Subaru (?) owner who wanted 4 matching tyres. I thought the owner was taking the mickey or misguided.
Steve.
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Excuse me, but don't all tyres rotate?
Try running an Audi with quattro 4wd, the tyres wear out at roughly the same rate so swapping would be pretty pointless. Guess that's probably true of the Subaru too.
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My Subaru Outback used to wear all four tyres at exactly the same rate which due to only half the power going through each wheel (50:50 split front to rear) was low compared to the front tyres of a front wheel drive car.
Also the tyre wear was very even across the tread. The service manual recommended swapping tyres front to rear every 6 month oil change but NOT side to side.
regards
Ian L.
btw the subaru has a diff for each axle and one for front to rear so replacing a single tyre is not a problem. This is not true for at least the earlier versions of the Volvo XC V70 which can wreck the gearbox.
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>Still interested in this 4x4 thing if someone has the time to explain.
Since you have diffs, and at that perhaps either limited slip or locked depending on what you are doing, across all the wheels then all the tyres need to turn at the same speed.
If some of the tyres are different diameters, then either the tyre is going to get worn out as it tries to move at a different speed, or there will be undue pressure on a diff, the gearbox or else where on the drive.
This is worse than on a 2wd since then only the same axle matters, where as on a 4wd you have to consider front and back as well.
As it was explained to me, 4mm difference in tread across all the tyres is the maximum and pushing it even then - bearing in mind that the larger 4x4s have very deep tread on the tyres, and so quite some variance is possible.
And on a large 4x4 which can lock its hubs and diffs, then you would have a similar effect if cornering on tarmac - which is why you shouldn't do it. Although I've often wondered why someone would lock diffs and hubs on the road.
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I see thanks for that.
Just out of interest, is there any proven scientific facts here? I'm not saying that you don't know your stuff but the putting pressure on the diff sounds a little like scare tactics to me, if diffs are made to cope with cornering and all how can a tiny amount of variance cause ware?
Could it be the tyre companies cashing in on peoples fears?
Another reason for me to stay away from 4WD!
Steve.
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Just been thru this on my F-150 4WD at service time last week. Ford where I live is very pro-active and the tech when I checked the car in took a look all around before he made me sign the service order.
He picked up exactly that, the big fat Goodyear Wranglers are rounding on the edges of the front tires but remaining square on the back because of the differing differential (does that make sense?) activity. His comment was "we normally recommend at this mileage moving front to back on this model to maintain even wear" (his words). That's what I'm paying him for, and have always had the feeling Ford here are very "engaged" (to use current fashionable management-speak) with their customers, so I went with it.
I don't see any cause for worry if the dealer knows what he's doing. Besides those big mothers cost, so I'm in no hurry to lever open my daughter's inheritance to replace 'em.
Incidentally I do use 4WD now and then on hard surfaces. We have a lot of concrete road (as opposed to tarmac), which gets very slippery in the monsoon downpours after prolonged dry periods. You can find yourself losing the back end gunning up hills because of this,whereas engaging 4 X 4 H ratio stabilises the plot.
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First car: 3500S Snr is imparting his years of car ownership advice to 3500S Jnr (Me).
Checking oil, all fluids and tyre pressures every tank fill was his first piece of advice (did I get it in the neck when I managed to blow up a H23 engine for not doing this even at the age of 32).
His second was brim the petrol tank and check consumption for the first sign of any potential nasties.
His last was rotate the tyres.
This I do. I always ask for fronts to back and vice-versa every yearly service. I leave the spare alone except to check the pressure. I reckon I get about another 3-5,000 out of a set of tyres. The wear tends to be more even, I have the MOTs with tyre tread depths to prove it.
Only downside is usually all four tyres need replacing within a vrey short space of time.
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