New/Old Tyre configuration

[Patty]

All,

I have recently had a big blow-out on my 80 series and naturally have to get new tyres. I was running 285/75/16 mud tyres (Maxxis Bighorns) @ 70-80% tread remaining and the spare was a new road tyre which i inherited from the previous owner.

I have bought two new tyres of the same make, model and size to replace the spare with the one of the 3 remaining older tyres.

As I know this is not ideal have new and old tyres on the car, figured given they are the same tyres, I shouldn't incur any driveline damage (forgive my ignorance if this is incorrect).

Where I have come to a stand still is deciding to put the new tyres on the front or the back. I would be inclined to put them on the front, but given I do predominately more driving on sand than through mud and didn't want to shell out for a whole new set of ATs I was thinking keeping the new tyres on the back so the muddies don't dig into the sand as much.

Thoughts?

 

[clivehorridge]

Hi Patty,

For asphalt driving, I'd always have the "better" tyres on the front. For offroad, or sand as you say, I don't think it matters too much, just keep the same tyres on the end of each axle (front left the same make and size as front right, and similarly on the back).

IMO, there shouldn't be any driveline issues, the wear differences will be small if they are all same make and size.

 

[frank rabbets]

They say for safety to put new rubber on rear as a puncture is easier to control if it happens on the front.

 

[chadr]

They say for safety to put new rubber on rear as a puncture is easier to control if it happens on the front.

Current advice is for the "better" tyres to go on the rear - reason being is that loosing front end grip usually means under steer, which is usually easy to control/stop - come off the gas (instinctive) and you're usually OK, whereas worn rear tyres usually mean over steer which can be much harder to control and can certainly catch you out.

 

[Patty]

thanks for the advise guys.

much appreciated.

 

[clivehorridge]

Only my opinion it seems, but the front tyres take most of the wear. Even on a full time 4x4, the fronts wear quicker than the rears proving they're under more stress.

New on the front and old on the back means that as time goes on your tyres will be more equally balanced. OK, OK! I know they should be rotated every 5k or so...

I also like to be able to stop in the wet.

Fresh tyre tread grips much better than half worn (again IMO) so I'd still put the newies on the front.

So there.

 

[Shayne]

I'm with you Clive fronts work harder and wear faster and when i was doing power slides down by one of your rivers Ram tried very hard to do the same but could not get the 80's rear end to step out at all .

 

[uHu]

One more for new ones up front. As Clive said.
And:
When you lock the central diff, it will be easier to unlock it with the (slightly) bigger tyres on the fronts. Whatever small the difference is, there will be binding between front and rear when locked, maybe not noticable, but still there. Then, with the bigger ones up front, you can just turn slightly left or right to undo the binding, as the fronts will have to travel a longer distance in curves.

 

[chadr]

To qualify my earlier response - it applies to FWD cars. For 4WD vehicles the "advice" is to change all 4 but I admit that that is not always possible.

Cut and pasted from elsewhere......

"..They should go on the rear, when the rear looses grip on a front wheel drive car it is usually on turn in or mid corner when the driver backs off (puts more weight on the front wheels) basically lift off oversteer, this can happen very very quickly the car snaps sideways, only way to save it is to floor the throttle, as driver has backed off for a reason is likely to be the last thing he will think of in the panic, car oversteers off the road, or spins in the face of oncoming traffic.

If the front wheels loose grip, it usually running wide on the exit of the corner. The driver can simply back off the throttle, and they will slowly and predictably regain grip and there is little drama. Because of this the best tyres should go on the rear.

Tiff Needell demonstrated this on 'old' Top Gear many years back and even he couldn't catch the back end of a FWD car with worn tyres on the back and new tyres on the front......And if Tiff Needell can't collect the rear end then you probably won't be able too.

Costco ran a Michelin campaign a few years ago and played the adverts in store. The European advert was on a Saab so its not even about the driven axles, the Saab was fishtailing violently at speed when grip started to go.
"

 

[clivehorridge]

There's no argument here, just a debate, and IMO on my 80, I'd put the newer rubber on the front.

I'm not Tiff Needell and never will be, but my 80 isn't a Saab either, and at the speed I drive, the thought of it fish-tailing just brings a big grin to my face.

Now despite what he posted, Shayne probably doesn't wear out front tyres at all, they spend most of their time in the air, from his wheelies

Good to hear both sides of the debate though

 

[frank rabbets]

Yes pros and cons Clive.

 

[Towpack]

+1 on the new fronts, for the same reasons as Clive posted above.
In response to Shayne's comments in post 7 regarding power slides, I've tried this in snow and found it MUCH easier to step the back end out with the CD locked than with it open. Not sure how big a part the VC is playing here but it seems counterintuitive to me.

 

[clivehorridge]

+1 on the new fronts, for the same reasons as Clive posted above.
In response to Shayne's comments in post 7 regarding power slides, I've tried this in snow and found it MUCH easier to step the back end out with the CD locked than with it open. Not sure how big a part the VC is playing here but it seems counterintuitive to me.

Whenever you lock any diff, you are forcing one of the wheels operated by that diff to skid, the whole reason for having a diff in the first place.

So if you lock the CD the front axle will rotate at the same speed as the rear which will induce a skid if the conditions call for a difference in the axle speeds.

IMO on snow, skidding is no bad thing as long as you are in control. Ken Block could explain this better I'm sure!

Again IMO, locking the CD in deep snow can give more control generally but I'd only use it when I'm losing traction on one or more wheels, or when you're just having some fun!

 

[Shayne]

I suppose it's far more noticeable in a much lighter shortie how locked diffs are detrimental to handling . On a flat wet muddy track open diffs and speed give you more control even if it's sloppy enough to be counter intuitive .

More than once I have wished I could use low range without locking the cd .

 

[clivehorridge]

I suppose it's far more noticeable in a much lighter shortie how locked diffs are detrimental to handling . On a flat wet muddy track open diffs and speed give you more control even if it's sloppy enough to be counter intuitive .

More than once I have wished I could use low range without locking the cd .

It's easy on the 80.

Pull the connector plug Shayne and fit a dash CDL switch.

I don't know the 90 set-up but there must be a way.

 

[Shayne]

I haven't given it any serious thought Clive but I think the 90 series cd is purely mechanical . It's one of those things that's forgotten almost as quick as it comes to mind because it's a rare need .

There's a steep winding track lots of loose stone on one of the routes you take us up the mountain which is one of the places a separate low range would be beneficial but it's not like I struggle with the climb it's just a choice of compromised handling v compromised handling . Consequence of my truck having more power than it needs I guess .

 

[clivehorridge]

I have given it any serious thought Clive but I think the 90 series cd is purely mechanical . It's one of those things that's forgotten almost as quick as it comes to mind because it's a rare need .

There's a steep winding track lots of loose stone on one of the routes you take us up the mountain which is one of the places a separate low range would be beneficial but it's not like I struggle with the climb it's just a choice of compromised handling v compromised handling . Consequence of my truck having more power than it needs I guess .

Yep, I recognize the track you mean on the way up to the ridge, and as I use low along almost the entire length of that run, having open diff in low is ideal.

It's such a simple mod on the 80, just roll under the truck, pull a plug, protect the ends against the elements and tuck the cable out of harm's way. I already had the dash CDL switch, so nothing to add.

 

[Shayne]

Never mind eh it gives me time to stop roll a cig and catch up before you reach the top

 

[Towpack]

Whenever you lock any diff, you are forcing one of the wheels operated by that diff to skid, the whole reason for having a diff in the first place.

So if you lock the CD the front axle will rotate at the same speed as the rear which will induce a skid if the conditions call for a difference in the axle speeds.

I understand diffs and the necessity for them but why does a locked CD induce a rear end slide as opposed to a 4 wheel drift which is what I would expect? If one or both rears lose traction and spin then at least one front should be spinning at the same speed with a locked CD causing traction loss at the front also?

 

[Shayne]

Because when you turn the the front wheels have further to travel than the rear so in effect the rear wheels are moving faster and the ass wants to over take .

Edit :- it can work both ways where the rear wheels will force you forward regardless of steering which is one of the things that slows me down on the stony ascent i mentioned earlier .