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Permanent 4WD and tyres


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I visited my friend who is an experienced mechanic and garage owner the other day. He was explaining to me about modern 4WD vehicles and replacing tyres.

He had a customer who had replaced two front tyres at a nationwide tyre depot, the disparity in tread between the new tyres on the front and the more worn tyres on the rear had caused the diff to fail due to the slightly increased diameter.

Has anyone else heard of this occurrence?

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1 hour ago, Ricko said:

I visited my friend who is an experienced mechanic and garage owner the other day. He was explaining to me about modern 4WD vehicles and replacing tyres.

He had a customer who had replaced two front tyres at a nationwide tyre depot, the disparity in tread between the new tyres on the front and the more worn tyres on the rear had caused the diff to fail due to the slightly increased diameter.

Has anyone else heard of this occurrence?

What kind of vehicle? I don't see that being a cause of a diff failure. Diff failure is usually down to poor servicing or the vehicle being used outside of the expected parameters of the diff. 

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I replaced 2 front tyres on an Outlander Phev, and was read a statement provided by Mitsubishi that all 4 should be changed at the same time. It did seem odd to me at the time , seeing as there is no physical connection  between the front and rear axles. Needless to say I ignored it, as it was a leaser going back in a few months..

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Never heard that before, but there's quite a difference between AWD and 4WD. Many people these days buy an AWD and think it's 4WD which causes problems throughout the vehicle. 

Certain tyres aren't to be rotated corner to corner anymore on certain vehicles, but this is usually model or vehicle specific.

As stated above a diff is usually broken due to extreme hard use, or in the case of a locking diff being kept locked and driving "normally".

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The Freelander 1 was the same if you were only changing two tyres, on my Freelander 2 I have the wheels changed around every service so the tyre wear is more even. 

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I wanted to change from General Grabber road tyres to General Grabber All Terrain on my Freelander 2 and was told to change all four at the same time. They said I would see warning messages due to the difference in diameter, if I only changed two.

Note:- General Grabber All Terrain are a bit noisy

Edited by martinj
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I've had 4 subarus over the years, as you may know they are permanent symmetrical all wheel drive. Never known any such problem, and I have probably covered over 100000 miles in these vehicles. I actually find the tyres wear fairly evenly front to back. I would be interested to know if anyone else has experienced anything different. Certainly no diff problems. 

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I have been alternating two for two for the last 12 yrs on my Land Rover. Have two new they go on th front and the front two go on the back. When the back get to the limit repeat.

Never had a problem but there again these are Land Rover diffs.

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2 hours ago, adzyvilla said:

I've had 4 subarus over the years, as you may know they are permanent symmetrical all wheel drive. Never known any such problem, and I have probably covered over 100000 miles in these vehicles. I actually find the tyres wear fairly evenly front to back. I would be interested to know if anyone else has experienced anything different. Certainly no diff problems. 

Does a Subaru not have a centre differential though ? That part makes all the difference!

Edited by matone
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I've heard off that a few times, not the diffs going but folk changing all 4 at same time.

1 story I heard ( friend of friend) some fancy Audi or something got a puncture and had to replace all 4 relatively new tyres.

And that's a local tyre bit which is quite trustworthy but that's wot they say.

Mibbee covering there own backsides thou atleast if they warn u it's ur problem and can't blame them for not telling u manufacters advice, wether an real issue or not

 

I know they said the same when they stuck some tyres off my old pick up on my new 1, but to be fair they are a bit wider.

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Sounds to me like a scam to sell more tyres.  I had a 50% rear tyre blow last week and consulted my supplier about should I put a new pair on the rear and he took a look at the remaining tyre shook his head and ordered one replacement.  He could very easily have said yes and been another fifty notes in pocket but he values his customers.

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How on earth, given the difference in suspension travel as you drive, differing road surfaces, camber and speeds, incline and declines can uneven tyre wear be any sort of factor in the health of the differential? 

Even if you had brand spanking new tyres versus totally bald you are talking a difference of what? 12-15mm max? 

I bet the camber on some of the roads here is a difference of more than that. 

Sounds like a marketing ploy to me. 

 

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4 hours ago, London Best said:

That is surely the PURPOSE of a differential!

The problem arises from transmission windup IF you don`t have a differential mechanism between two axles turning at different revolution .Something has to `give` to get rid of the windup,usually wheelslip allows it but if you  are on surfaced roads it puts a lot more load on the transmission components .This is why landrover fitted a centre diff to the Range rover ,as opposed to the Series Landrovers transmission.Hth.

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5 hours ago, ClemFandango said:

How on earth, given the difference in suspension travel as you drive, differing road surfaces, camber and speeds, incline and declines can uneven tyre wear be any sort of factor in the health of the differential? 

Even if you had brand spanking new tyres versus totally bald you are talking a difference of what? 12-15mm max? 

I bet the camber on some of the roads here is a difference of more than that. 

Sounds like a marketing ploy to me. 

 

Or it could just be the electronic gizmos and gadgetry that’s built into them 

along with the emission reduction computer programs 🤭

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29 minutes ago, matone said:

The problem arises from transmission windup IF you don`t have a differential mechanism between two axles turning at different revolution .Something has to `give` to get rid of the windup,usually wheelslip allows it but if you  are on surfaced roads it puts a lot more load on the transmission components .This is why landrover fitted a centre diff to the Range rover ,as opposed to the Series Landrovers transmission.Hth.

Thank you. I did actually realise all that. I’ve run nothing but Land Rover products for 44 years now. But thanks anyway.

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1 hour ago, Old farrier said:

Or it could just be the electronic gizmos and gadgetry that’s built into them 

along with the emission reduction computer programs 🤭

More than likely. 

Pull all that **** out and leave me with wheels and an engine. 

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5 hours ago, blackbird said:

What happens if you have a puncture on a 1/2 worn tyre that can’t be repaired  ? replace all 4 tyres ?

 

Allegedly. And know someone that done it

Is it not more to do with grip than the differing radius??

Think it's more cars with loads off fancy computers rather than normal manual diffs

 

Atleast that's wot been told, and to be fair there the local tyre shop that wouldn't fleece lcals, been using them all my life as have rest off family

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So long as there is less than a certain difference in rolling diameter they're fine.

I've only ever changed them on the same axle. 

In modern 4x4 they're not permanent four wheel drive so should never be a problem. Most are electronic diffs.

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Panda 4x4 is supplied with 175/65-R15 tyres and a 125/80-R15 space-saver spare, which has 5% smaller rolling radius.   Manufacturer obviously thinks that is OK, and we have run 50 miles or more on the space-saver a few times after punctures without experiencing any problems.

One of the big tyre suppliers (think it was either Costco or Kwik****, but not certain) told me they were not allowed to replace tyres on any 4wd vehicle except as a complete set of four.  I took my custom elsewhere.

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