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Hi,
Owners manuals for 4x4s appear to suggest that tyres are rotated front to back every 7 or 8,000 miles. This is to balance out tyre wear, ensure tyres are similar thickness which assists the 4x4 system.
There is also the idea that best grip is afforded by having the deepest tread on the rear wheels.
Are these 2 ideas contradictory?
Should you rotate tyres on the 4x4, by doing so risking a loss of control as the rear end loses grip and goes its own way?
regards
Durelli
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If the tyres are so worn you "risk losing control" - the issue is buying new tyres, not which axle to fit the least knackered tyres on.
If the tyres aren't worn, stick to conventional 4x4 wisdom and rotate the tyres regularly replacing in a set of 4.
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What about the modern SUVs which are primarily FWD except in rare circumstances when they are 4x4.
I have one, there is the recommendation to rotate tyres, but after 10,000 miles, the fronts have 5mm and the rears about 8mm.
Obviously I can rotate these so in 10k miles time all should be on 5mm, but it would mean for the next few thousand, having more tread on the front which might see the back end slipping out.
Durelli.
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Handling very much depends on the action of the centre differential or whatever doles out the drive to the rear.
One has to assume the makers know what they are advising, and 5mm is after all plenty for most road conditions.
Unless of course you want to wear out the front tyres and replace them, but most four wheel drives respond and handle best with 4 matching tyres. When I was running a Land Rover, I always aimed to need 4 new tyres at the same time.
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It's the part-time 4wd cars that need the regular rotation most to ensure consistent tyre diameters and allow the electronics to operate as intended.
If you let any of the tyres go below about 3mm tread, you simply won't get the benefit of 4wd - you need more than that in wet, muddy, cold slippy conditions and in dry, grippy conditions you don't need 4wd.
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No 4WD for me, a humble Mondeo 2.0 TDCi, which I love.
Now on just over 30k on original tyres,and had them checked. Pretty much 3-ish all round. I said I would replace them gradually, and the tyre people said to do the rears first, which surprised me , because I thought with FWD cars the fronts took most of the wear.
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with FWD cars the fronts took most of the wear.
They do. But during braking, it is generally easier to control a front axle skid than a rear axle skid-hence the advice to put the best tyres on the back axle.
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with FWD cars the fronts took most of the wear.
They do. But during braking, it is generally easier to control a front axle skid than a rear axle skid-hence the advice to put the best tyres on the back axle.
Is not skid prevention the chief function of ABS, not to mention the stability control systems now commonly fitted?
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Is not skid prevention the chief function of ABS, not to mention the stability control systems now commonly fitted?
The namby pamby legislators have made ESP and ABS mandatory for new cars. However there are still a lot of cars on the road without these electronic aids. But computer controlled braking can't create traction-it can simply make better use of what traction is available.
Most cars are nose heavy to begin with-and this is amplified under braking. If you take a corner too quickly in slippery conditions (who hasn't?), ESP can't save you. Once the back end goes unexpectedly, it's quite hard to get it back under control. Understeer and difficulty wheelspin from standing starts are much easier to deal with.
It still seems counter inmtuitive to see shiny new tyres on the back though!
However, Costco didn't insist on putting the two new tyres on the back of my dad's car (which has all that ESPN ABC, FOX carp)-but they did on mine-which doesn't!
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''IOnce the back end goes unexpectedly, it's quite hard to get it back under control. Understeer and difficulty wheelspin from standing starts are much easier to deal with''.
I could not disagree more with both the above sentences, oversteer is normally recoverable for a reasonably competent driver, though such driver will feel through the seat of their pants that the quickly increasing light feeling of the car means it is reaching the limits of adhesion, usually associated with RWD.
Understeer is a horrible skid and requires run off room and/or the ability to reduce speed when adhesion has been lost or a combination of both usually associated with FWD, likely to end up in tears, again a competent driver should feel it before it starts, but once traction is lost then trouble looms even for very skilled drivers, swiftly corrected understeer can soon become violent oversteer as you well know.
Wheelspin is usually the perogative of FWD cars not stuffed to the gills with electronics to protect incompetent FWD drivers (or owners of automated manuals) from themselves.
As for tyre rotation and new tyres being fitted, i always rotate however many wheels are driven, and buy 4 quality replacements at a time.
Funny how new tyres being fitted to the rear of cars doesn't throw the car off the road during its first up to 200 miles (lot more on some bigger 4x4 tyres) before the releasing agent wears off.
One size fits all..is that an EU directive yet.
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Back in the snowy 1960s I had a couple of Ford Zephyrs, mkII and Mk III. Keeping them going in a straight line on snow was entertaining, but I had done 3 sessions on a skidpan in an Austin Westminster.
I therefoer am less concerned about the rear hanging out than sliding off teh road front first, so I put new ones on the front.
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Nick - no doubt you meant to say more but were stopped by the Great God Microsoft. Try using Google Chrome - or anything other than Internet Explorer!
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I've struggled
That just about sums up MS Explorer !!
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Back in the snowy 1960s I had a couple of Ford Zephyrs, mkII and Mk III. Keeping them going in a straight line on snow was entertaining, but I had done 3 sessions on a skidpan in an Austin Westminster.
I therefoer am less concerned about the rear hanging out than sliding off teh road front first, so I put new ones on the front.
The reason for running the new tyres on the rear is to prevent aqua-planing, modern FWD cars are nose-heavy with relatively wide tyres, hit a puddle at speed with worn tyres on the lightly loaded rear and the car will swap ends with the gentlist of provocation – driver skill or not. This is why the good rubber MUST go on the rear of (particularly small and/or light) FWD cars.
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The reason for running the new tyres on the rear is to prevent aqua-planing, modern FWD cars are nose-heavy with relatively wide tyres, hit a puddle at speed with worn tyres on the lightly loaded rear and the car will swap ends with the gentlist of provocation – driver skill or not. This is why the good rubber MUST go on the rear of (particularly small and/or light) FWD cars.
Steve, I always change tyres when down to 3 mm of tread, would you class that as "worn" to the point of aquaplaning? In my impoverished and naive youth (before minimum tread depths were legislated for) like many others I sometimes ran tyres worn completely smooth - and had a 180 degree spin as a result in the wet!
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I have Santa Fe part time 4x4 Auto. Hyudai recomend front to back every 12 mth. even wear preferable on all 4x4 as in extreme cases can cause transmision wind up--- so I was told years ago when I had Landrover. peg
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It only causes transmission wind-up on very old-style 4wd systems, like Landrovers.
It shouldn't occur on a part-time 4wd system because the central coupling is friction-based so a small amount of slip always occurs naturally.
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It only causes transmission wind-up on very old-style 4wd systems, like Landrovers.
It shouldn't occur on a part-time 4wd system because the central coupling is friction-based so a small amount of slip always occurs naturally.
Modern 4WD systems with viscous couplings with also suffer, the coupling will overheat destroying the slip properties of VCU permanently.
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It only causes transmission wind-up on very old-style 4wd systems, like Landrovers.
It shouldn't occur on a part-time 4wd system because the central coupling is friction-based so a small amount of slip always occurs naturally.
Modern 4WD systems with viscous couplings with also suffer, the coupling will overheat destroying the slip properties of VCU permanently.
That would require significant amounts of slip, indicating VERY mismatched tyre diameters - otherwise the speed difference between front-frear would wreck the coupling when going round corners.
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That would require significant amounts of slip, indicating VERY mismatched tyre diameters - otherwise the speed difference between front-frear would wreck the coupling when going round corners.
Correct. A back-of-a-fag-packet estimation shows that the difference in diameter between new and worn-out tyres is of the order of 2%. Not desirable but hardly disastrous. God knows what effect supermarket fuel would have on the drivetrain. I suspect the pinging would cause the diff to resonate and seizure would be the inevitable result.
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If i had a quid for every time i hear about aquaplaning from the rear tyres if they have less tread than the fronts etc, for crying out loud how fast do you people drive through monsoon deluges.
Unless you drive a very peculiar car the back wheels normally follow the front wheels, the front wheels displace almost every bit of water before the rear wheels follow in their path, if they can't clear it you are fording a river and need a Ural truck..
Why is it so difficult for people to simply rotate their tyres now and again so they wear out reasonably evenly and buy four new ones before they get anywhere near legal minimum, no calculations for differential compensation needed.
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and buy four new ones before they get anywhere near legal minimum
Because four new tyres is a sizeable outlay-and people don't like paying for rubber. They can usually find the dough for repeated depreciation hits though...
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Because four new tyres is a sizeable outlay-and people don't like paying for rubber. They can usually find the dough for repeated depreciation hits though...
Which works out the same in the medium term.
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I know. I know.
But some people don't like laying out for something that isn't new and different.
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