Disco TD5 - New tyres which axle ?

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A

Andrew Mawson

Guest
OK - two brand new tyres (8mm tread), and two part worn (4mm tread).

Where do you put the new tyres - front axle or rear ?

Reason for question - tyre dealers suggestion runs contrary to what
I'd expect so what's your view and why?

AWEM



 
Andrew Mawson wrote:
> OK - two brand new tyres (8mm tread), and two part worn (4mm tread).
>
> Where do you put the new tyres - front axle or rear ?
>
> Reason for question - tyre dealers suggestion runs contrary to what
> I'd expect so what's your view and why?

My personal view is front - it's where your braking & steering come from
so you need the best grip there.

I'll bet their view is rear, and it's ostensibly safety related to
prevent massive oversteer due to loss of rear traction.


--
EMB
 
On Wed, 2 Nov 2005 23:51:10 +0000 (UTC), "Andrew Mawson"
<andrew@no_spam_please_mawson.org.uk> wrote:

>OK - two brand new tyres (8mm tread), and two part worn (4mm tread).
>
>Where do you put the new tyres - front axle or rear ?
>
>Reason for question - tyre dealers suggestion runs contrary to what
>I'd expect so what's your view and why?
>
>AWEM
>
>

Best tyres to the rear, for the reasons EMB states. It's the ROSPA
advice and also the advice of every car handbook I've seen.

Understeer is easier to cope with than oversteer (especially in
something the height and weight of a Discovery) and the fronts are
much less likely to aquaplane in the wet as all the weight transfers
there under braking.

Then again, in my view 4mm is not 'part worn', it's 'well worn'. Have
you really only got 8mm on the new tyres - sounds rather less than
most 4x4 tyres.






--

Tim Hobbs

'58 Series 2 88" aka "Stig"
'03 Volvo V70
 
On or around Thu, 03 Nov 2005 12:54:32 +1300, EMB <[email protected]>
enlightened us thusly:

>Andrew Mawson wrote:
>> OK - two brand new tyres (8mm tread), and two part worn (4mm tread).
>>
>> Where do you put the new tyres - front axle or rear ?
>>
>> Reason for question - tyre dealers suggestion runs contrary to what
>> I'd expect so what's your view and why?
>
>My personal view is front - it's where your braking & steering come from
>so you need the best grip there.
>
>I'll bet their view is rear, and it's ostensibly safety related to
>prevent massive oversteer due to loss of rear traction.

which ain't likely to happen on a disco... or not IME. The only time I've
seriously lost grip in a 4x4 LR product was in the 110 on a road which must
have had diesel or something under the water - it was way slippier than it
had any right to be. On that occasion it broke away at the front first and
then the back and went sideways.
--
Austin Shackles. www.ddol-las.net my opinions are just that
If all be true that I do think, There are five reasons we should drink;
Good wine, a friend, or being dry, Or lest we should be by and by;
Or any other reason why. - Henry Aldrich (1647 - 1710)
 

"Andrew Mawson" <andrew@no_spam_please_mawson.org.uk> wrote in message
news:[email protected]...
> OK - two brand new tyres (8mm tread), and two part worn (4mm tread).
>
> Where do you put the new tyres - front axle or rear ?
>
> Reason for question - tyre dealers suggestion runs contrary to what
> I'd expect so what's your view and why?
>
> AWEM
>
>
>
Land Rover stipulate rear for the Freelander.

Richard


 
In news:[email protected],
EMB <[email protected]> blithered:
> Andrew Mawson wrote:
>> OK - two brand new tyres (8mm tread), and two part worn (4mm tread).
>>
>> Where do you put the new tyres - front axle or rear ?
>>
>> Reason for question - tyre dealers suggestion runs contrary to what
>> I'd expect so what's your view and why?
>
> My personal view is front - it's where your braking & steering come
> from so you need the best grip there.
>
> I'll bet their view is rear, and it's ostensibly safety related to
> prevent massive oversteer due to loss of rear traction.

Most vehicles these days are FWD so have no traction at the rear, I think you
meant grip.

--
"He who says it cannot be done should not interrupt her doing it."

If at first you don't succeed,
maybe skydiving's not for you!


 
In news:[email protected],
Tim Hobbs <[email protected]> blithered:
> On Wed, 2 Nov 2005 23:51:10 +0000 (UTC), "Andrew Mawson"
> <andrew@no_spam_please_mawson.org.uk> wrote:
>
>> OK - two brand new tyres (8mm tread), and two part worn (4mm tread).
>>
>> Where do you put the new tyres - front axle or rear ?
>>
>> Reason for question - tyre dealers suggestion runs contrary to what
>> I'd expect so what's your view and why?
>>
>> AWEM
>>
>>
>
> Best tyres to the rear, for the reasons EMB states. It's the ROSPA
> advice and also the advice of every car handbook I've seen.
>
> Understeer is easier to cope with than oversteer (especially in
> something the height and weight of a Discovery) and the fronts are
> much less likely to aquaplane in the wet as all the weight transfers
> there under braking.

Only if the tyres are gripping which they ain't when aquaplaning!!

>
> Then again, in my view 4mm is not 'part worn', it's 'well worn'. Have
> you really only got 8mm on the new tyres - sounds rather less than
> most 4x4 tyres.



--
"He who says it cannot be done should not interrupt her doing it."

If at first you don't succeed,
maybe skydiving's not for you!


 
Richard wrote:

> Land Rover stipulate rear for the Freelander.

And if they were being sensible they'd stipulate replacing all 4 tyres
at the same time.

--
EMB
 
GbH wrote:

>
> Most vehicles these days are FWD so have no traction at the rear, I think you
> meant grip.
>
This was in a LR forum - which aren't FWD - so I meant traction.

But add FWD vehicles into the mix and I'd much rather have understeer in
a FWD vehicle as it's significasntly easier to control and normally
occurs more progressively.

--
EMB
 

"EMB" <[email protected]> wrote in message
news:[email protected]...
> Richard wrote:
>
>> Land Rover stipulate rear for the Freelander.
>
> And if they were being sensible they'd stipulate replacing all 4 tyres at
> the same time.
>
I recall the primary advice in the Land Rover handbook for the Freelander is
to change all 4.

Changing 2 is a secondary fallback position which, so not considered best
practice, _but_ if you go down that road the advice is to put the 2 new
tyres (which should be the same as those used on the front) on the rear
axle.

I also recall 'it' doesn't explain why ........ which would have been nice.

In passing (as you seem to know about these things) over the years I have
had cars with rear wheel drive only and front wheel drive only and don't
ever recall having all this bother. In fact people often rotated wheels
............ so why is the advice for 4 wheel drive cars so fussy.

Richard


 
Richard wrote:

> In passing (as you seem to know about these things) over the years I have
> had cars with rear wheel drive only and front wheel drive only and don't
> ever recall having all this bother. In fact people often rotated wheels
> ........... so why is the advice for 4 wheel drive cars so fussy.

As all 4 wheels are driven one wants to keep the tyre circumferences as
close to the same as possible on both axles so that the centre diff is
doing as little work as possible. In the case of some viscous coupled
units it doesn't take much prolonged use with mismatched tyres to cause
a total failure of the centre diff.

--
EMB
 
In news:[email protected],
EMB <[email protected]> blithered:
> GbH wrote:
>
>>
>> Most vehicles these days are FWD so have no traction at the rear, I
>> think you meant grip.
>>
> This was in a LR forum - which aren't FWD - so I meant traction.
>
> But add FWD vehicles into the mix and I'd much rather have understeer
> in a FWD vehicle as it's significasntly easier to control and normally
> occurs more progressively.

Think what I meant was traction is what the drive train gives you, grip is the
tyres. So under/oversteer is dependent on the grip of tyres on the terrain

--
"He who says it cannot be done should not interrupt her doing it."

If at first you don't succeed,
maybe skydiving's not for you!


 
GbH wrote:
>
> Think what I meant was traction is what the drive train gives you, grip is the
> tyres. So under/oversteer is dependent on the grip of tyres on the terrain

Let's leave the pedantry out - we both know what each other means, and
according to the Oxford Dictionary, traction is the grip of a tyre on
the road, so in fact we are talking about exactly the same thing.

--
EMB
 
On or around Fri, 04 Nov 2005 08:59:03 +1300, EMB <[email protected]>
enlightened us thusly:

>Richard wrote:
>
>> In passing (as you seem to know about these things) over the years I have
>> had cars with rear wheel drive only and front wheel drive only and don't
>> ever recall having all this bother. In fact people often rotated wheels
>> ........... so why is the advice for 4 wheel drive cars so fussy.
>
>As all 4 wheels are driven one wants to keep the tyre circumferences as
>close to the same as possible on both axles so that the centre diff is
>doing as little work as possible. In the case of some viscous coupled
>units it doesn't take much prolonged use with mismatched tyres to cause
>a total failure of the centre diff.

how much "slip" will viscous thing allow before it stiffens up? I can't
really see tyre mismatches going much over 2% in normal use, assuming you've
not mismatched tyre *sizes*, just worn and new ones. I'd have thought that
2% wasn't enough for a viscous thing. Might possibly trigger traction
control systems.
--
Austin Shackles. www.ddol-las.net my opinions are just that
In Touch: Get in touch with yourself by touching yourself.
If somebody is watching, stop touching yourself.
from the Little Book of Complete B***ocks by Alistair Beaton.
 

"Austin Shackles" <[email protected]> wrote in message
news:[email protected]...
> On or around Fri, 04 Nov 2005 08:59:03 +1300, EMB <[email protected]>
> enlightened us thusly:
>
>>Richard wrote:
>>
>>> In passing (as you seem to know about these things) over the years I
>>> have
>>> had cars with rear wheel drive only and front wheel drive only and don't
>>> ever recall having all this bother. In fact people often rotated wheels
>>> ........... so why is the advice for 4 wheel drive cars so fussy.
>>
>>As all 4 wheels are driven one wants to keep the tyre circumferences as
>>close to the same as possible on both axles so that the centre diff is
>>doing as little work as possible. In the case of some viscous coupled
>>units it doesn't take much prolonged use with mismatched tyres to cause
>>a total failure of the centre diff.
>
snip

So what actually constitutes mismatched on for example (a) the same axle and
(b) front and rear axles ...... is for example a difference of a couple of
mm tread depth for (a) and/or (b) really going to make any difference and if
not what difference in tread depth is?

Being new to 4X4 with perm. 4 wheel drive I would like to clarify all this.

Richard


 
Austin Shackles wrote:
>
> how much "slip" will viscous thing allow before it stiffens up? I can't
> really see tyre mismatches going much over 2% in normal use, assuming you've
> not mismatched tyre *sizes*, just worn and new ones. I'd have thought that
> 2% wasn't enough for a viscous thing. Might possibly trigger traction
> control systems.

A brand new 31" (eg a 750R16) tyre with 14mm tread cf the same tyre with
the legal minimum has a difference in diameter of 1" which is 3%.

I don't think that's enough to stiffen a viscous unit but it's probably
enough to heat it up and damage it.


--
EMB
 
On or around Thu, 3 Nov 2005 23:14:36 +0000 (UTC), "Richard"
<[email protected]> enlightened us thusly:

>snip
>
>So what actually constitutes mismatched on for example (a) the same axle and
>(b) front and rear axles ...... is for example a difference of a couple of
>mm tread depth for (a) and/or (b) really going to make any difference and if
>not what difference in tread depth is?

both...

On Range Rovers with the Borg Warner T-box you have a viscous coupling in
the middle diff - this is the one that might get upset by front/rear tyre
imbalance. Side-to-side is not a big issue except from the handling point
of view. The optimum from the handling POV is to have all 4 tyres the same
make, size and age. Within that, it's also possible to swap front/rear to
even out wear for example.

Most of the earlier LR permanent 4x4 models (i.e. not series LRs) have a
simple free diff in the centre but with the provision to lock it. On hard
surfaces, a tyre imbalance could put unacceptable loads on a locked diff.

a couple of mm difference is not going to affect anything. Your tyres are
something around 740mm overall diameter on a disco, say - more on a 110.
taking that 740mm, though, on good 4x4 tyres there may be 12mm of tread
depth, so the difference between a new one and a worn out one with only 2mm
left is going to be 20mm on the tyre diameter, (or rather, in fact,
circumference will be 20*pi mm different, but that complicates it
unnecessarily) which is a percentage difference of 20/740*100 = 2.7%. So
your worn tyres are going to rotate 2.7% faster at a given road speed than
the new ones.

Take for example that you're in top gear at 2000 rpm (in a range rover
5-speed, since that's what I have the figures to hand for) you have an
overall ratio of 3.25:1, which means that the wheels are doing about 615rpm
and you should be doing about 53 mph. The above-mentioned 2.7% will mean
that the worn-out-tyre wheel does 16.6 (approx) rpm more than the non-worn
one - a speed equivalent to about 1.4 mph.
--
Austin Shackles. www.ddol-las.net my opinions are just that
"My centre is giving way, my right is in retreat; situation excellent.
I shall attack. - Marshal Foch (1851 - 1929)
 

"Austin Shackles" <[email protected]> wrote in message
news:[email protected]...
> On or around Thu, 3 Nov 2005 23:14:36 +0000 (UTC), "Richard"
> <[email protected]> enlightened us thusly:
>
>>snip
>>
>>So what actually constitutes mismatched on for example (a) the same axle
>>and
>>(b) front and rear axles ...... is for example a difference of a couple of
>>mm tread depth for (a) and/or (b) really going to make any difference and
>>if
>>not what difference in tread depth is?
>
> both...
>
> On Range Rovers with the Borg Warner T-box you have a viscous coupling in
> the middle diff - this is the one that might get upset by front/rear tyre
> imbalance. Side-to-side is not a big issue except from the handling point
> of view. The optimum from the handling POV is to have all 4 tyres the
> same
> make, size and age. Within that, it's also possible to swap front/rear to
> even out wear for example.
>
> Most of the earlier LR permanent 4x4 models (i.e. not series LRs) have a
> simple free diff in the centre but with the provision to lock it. On hard
> surfaces, a tyre imbalance could put unacceptable loads on a locked diff.
>
> a couple of mm difference is not going to affect anything. Your tyres are
> something around 740mm overall diameter on a disco, say - more on a 110.
> taking that 740mm, though, on good 4x4 tyres there may be 12mm of tread
> depth, so the difference between a new one and a worn out one with only
> 2mm
> left is going to be 20mm on the tyre diameter, (or rather, in fact,
> circumference will be 20*pi mm different, but that complicates it
> unnecessarily) which is a percentage difference of 20/740*100 = 2.7%. So
> your worn tyres are going to rotate 2.7% faster at a given road speed than
> the new ones.
>
> Take for example that you're in top gear at 2000 rpm (in a range rover
> 5-speed, since that's what I have the figures to hand for) you have an
> overall ratio of 3.25:1, which means that the wheels are doing about
> 615rpm
> and you should be doing about 53 mph. The above-mentioned 2.7% will mean
> that the worn-out-tyre wheel does 16.6 (approx) rpm more than the non-worn
> one - a speed equivalent to about 1.4 mph.
> --
> Austin Shackles. www.ddol-las.net my opinions are just that
> "My centre is giving way, my right is in retreat; situation excellent.
> I shall attack. - Marshal Foch (1851 - 1929)

Cheers ............ interesting little thread ...... Richard


 
On Thu, 03 Nov 2005 12:54:32 +1300, EMB wrote:

> I'll bet their view is rear, and it's ostensibly safety related to
> prevent massive oversteer due to loss of rear traction.

This is the view I support after having new on the front suffering
massive oversteer, that I tried at least 3 times to correct, gave up,
hit a wall and rolled over.

When I got the DII that had the tyres with most tread on the front, it
had a tendancy to wander under light throttle conditions. Swapped
tyres front to back and the wander disappeared. So marked was the
change I could detect the improvement in handling within the first
200yds of driving after the swap around.

Up to you but I know which way round I'll fit tyres now.

--
Cheers [email protected]
Dave. pam is missing e-mail



 
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