Tyres

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S

Simon Atkinson

Guest
Just managed to pick up a pair of 6 X 16 tyres for my SIII SWB.
Currently it's got some radials (205X16) on it. The fronts need
replacing before the MOT.

IIRC I can put the cross-ply 6X16's on the front - and leave the
radials on the back (short term) - is that the right way round?

Anyone know where I can pick up another pair of the 6X16's cheaply in
or near Northants? This SIII is being rebuilt on a shoe-string as
SWMBO thinks I have enough expensive hobbies already!

Cheers.

--
Simes
 
Simon Atkinson wrote:
> >
> IIRC I can put the cross-ply 6X16's on the front - and leave the
> radials on the back (short term) - is that the right way round?
>
>

Yes it is. According to the MoT tester's manual, reasons for rejection are:

* different types of tyre on the same axle
* crossply or bias-belted tyres on rear axle and radial tyres on front axle

http://www.motuk.co.uk/manual_410.htm

--

Rich

Series 2a
RR 4.6
V8 trialler
dog, wife, kids, whatever


 
On Fri, 20 Aug 2004 18:53:45 +0000 (UTC), "Richard Brookman"
<[email protected]> wrote:

>Simon Atkinson wrote:
>> >
>> IIRC I can put the cross-ply 6X16's on the front - and leave the
>> radials on the back (short term) - is that the right way round?
>>
>>
>
>Yes it is. According to the MoT tester's manual, reasons for rejection are:
>
>* different types of tyre on the same axle
>* crossply or bias-belted tyres on rear axle and radial tyres on front axle
>

Not only because the MOT manual says so. X-plys on the back and
Radials on the front is also dangerous.

Alex

 
Alex wrote:

> On Fri, 20 Aug 2004 18:53:45 +0000 (UTC), "Richard Brookman"
> <[email protected]> wrote:
>
> > Simon Atkinson wrote:
> >> >
> >> IIRC I can put the cross-ply 6X16's on the front - and leave the
> >> radials on the back (short term) - is that the right way round?
> > >
> > >
> >
> > Yes it is. According to the MoT tester's manual, reasons for
> > rejection are:
> >
> > * different types of tyre on the same axle
> > * crossply or bias-belted tyres on rear axle and radial tyres on
> > front axle
> >
>
> Not only because the MOT manual says so. X-plys on the back and
> Radials on the front is also dangerous.

Thanks for the assistance - she failed anyway on a worn swivel... Back
in for Retest on Monday.

--
Simes
 
Alex wrote:

> Not only because the MOT manual says so. X-plys on the back and
> Radials on the front is also dangerous.

Any idea why?
In a skid or something?

nigelH


 
Nigel Hewitt wrote:
> Alex wrote:
>
>> Not only because the MOT manual says so. X-plys on the back and
>> Radials on the front is also dangerous.
>
> Any idea why?
> In a skid or something?
>
> nigelH

Any car will be unpredictable with a mixture of tyre types, but that doesn't
explain why one combination is allowed for the MoT and the other is not. My
guess is this: radials grip better than x-plies. Therefore, a car with
radials on the front and x-plies on the back will tend to oversteer in a
corner and be liable to spin right round in an emergency stop, whereas a car
with radials on the back and x-plies on the front will tend to understeer in
a corner and remain relatively stable under heavy braking. But it's only a
guess. Anyone know better?

--

Rich

Series 2a
RR 4.6
V8 trialler
dog, wife, kids, whatever


 
On Sat, 21 Aug 2004 16:55:00 +0000 (UTC), "Nigel Hewitt"
<[email protected]> wrote:

>Alex wrote:
>
>> Not only because the MOT manual says so. X-plys on the back and
>> Radials on the front is also dangerous.
>
>Any idea why?
>In a skid or something?
>
>nigelH
>
"Tyre Types

It is illegal to mix tyres of a different construction (cross-ply;
bias belted or radial) on the same axle. Cross-ply and bias-belted
tyres are seldom used on production cars, and are not widely available
in the UK. Cross-ply and radial tyres should never be mixed on the
same vehicle. Where a mix is necessary, radial tyres MUST only ever be
used on the rear axle and cross-ply tyres on the front. This mix of
tyres will produce 'over steer' whereas the opposite will produce
'under-steer'. (Over-steer refers to the car turning more tightly into
a corner than it is steered; under-steer indicates that the vehicle
turns at less of an angle than it is steered). Of the two conditions,
over-steer is generally accepted to be easier to control. "

Taken from
http://www.rospa.com/cms/STORE/Road Safety/Tyrefacts_files/Tyrefacts.htm

I suspect this is also why manufacturers recommend keeping the best
(i.e. least worn) tyres on the rear axle.


--

Tim Hobbs

'58 Series 2 88" aka "Stig"
'77 101FC Ambulance aka "Burrt"
'95 Discovery V8i aka "The Disco" (FOR SALE)
'03 Volvo V70

My Landies? http://www.seriesii.co.uk
Barcoding? http://www.bartec-systems.com
Tony Luckwill web archive at http://www.luckwill.com
 
On Sat, 21 Aug 2004 19:17:14 +0100, Tim Hobbs
<[email protected]> wrote:

>On Sat, 21 Aug 2004 16:55:00 +0000 (UTC), "Nigel Hewitt"
><[email protected]> wrote:
>
>>Alex wrote:
>>
>>> Not only because the MOT manual says so. X-plys on the back and
>>> Radials on the front is also dangerous.
>>
>>Any idea why?
>>In a skid or something?
>>
>>nigelH
>>
> "Tyre Types
>
>It is illegal to mix tyres of a different construction (cross-ply;
>bias belted or radial) on the same axle. Cross-ply and bias-belted
>tyres are seldom used on production cars, and are not widely available
>in the UK. Cross-ply and radial tyres should never be mixed on the
>same vehicle. Where a mix is necessary, radial tyres MUST only ever be
>used on the rear axle and cross-ply tyres on the front. This mix of
>tyres will produce 'over steer' whereas the opposite will produce
>'under-steer'. (Over-steer refers to the car turning more tightly into
>a corner than it is steered; under-steer indicates that the vehicle
>turns at less of an angle than it is steered). Of the two conditions,
>over-steer is generally accepted to be easier to control. "
>
>Taken from
>http://www.rospa.com/cms/STORE/Road Safety/Tyrefacts_files/Tyrefacts.htm
>
>I suspect this is also why manufacturers recommend keeping the best
>(i.e. least worn) tyres on the rear axle.

Now I've read that properly, they must surely mean it the other way
around?


--

Tim Hobbs

'58 Series 2 88" aka "Stig"
'77 101FC Ambulance aka "Burrt"
'95 Discovery V8i aka "The Disco" (FOR SALE)
'03 Volvo V70

My Landies? http://www.seriesii.co.uk
Barcoding? http://www.bartec-systems.com
Tony Luckwill web archive at http://www.luckwill.com
 
>
>It is illegal to mix tyres of a different construction (cross-ply;
>bias belted or radial) on the same axle. Cross-ply and bias-belted
>tyres are seldom used on production cars, and are not widely available
>in the UK. Cross-ply and radial tyres should never be mixed on the
>same vehicle. Where a mix is necessary, radial tyres MUST only ever be
>used on the rear axle and cross-ply tyres on the front. This mix of
>tyres will produce 'over steer' whereas the opposite will produce
>'under-steer'. (Over-steer refers to the car turning more tightly into
>a corner than it is steered; under-steer indicates that the vehicle
>turns at less of an angle than it is steered). Of the two conditions,
>over-steer is generally accepted to be easier to control. "
>
>Taken from
>http://www.rospa.com/cms/STORE/Road Safety/Tyrefacts_files/Tyrefacts.htm
>
>I suspect this is also why manufacturers recommend keeping the best
>(i.e. least worn) tyres on the rear axle.

Always better to have the back end break out, than the front.

I like that bit about "Cross-ply and bias-belted tyres are seldom used
on production cars, and are not widely available in the UK"

Unless of course you have a landrover, in which case X-Ply tyres are
commonly available.

Alex

 
Tim Hobbs wrote:
> <snip>
>> "Where a mix is necessary, radial tyres
>> MUST only ever be used on the rear axle and cross-ply tyres on the
>> front. This mix of tyres will produce 'over steer' whereas the
>> opposite will produce 'under-steer'. (Over-steer refers to the car
>> turning more tightly into a corner than it is steered; under-steer
>> indicates that the vehicle turns at less of an angle than it is
>> steered). Of the two conditions, over-steer is generally accepted to
>> be easier to control. "

> Now I've read that properly, they must surely mean it the other way
> around?

Surely they must. I thought the opposite effect would be true, i.e. radials
on the back would make a car understeer due to the greater grip at the back
end. I'm prepared to be corrected on that one. But to say that "over-steer
is generally accepted to be easier to control" is total bollocks. It is if
you are Michael Schumacher [1]. But for the average driver, a mild
understeer is much the safer setup. If you overcook it into a corner, it
will gently run wide until you ease off. If you get it badly wrong, you are
still facing forward. An oversteering car will need opposite lock and a
delicate right foot, and has a tendency to bite back hard if you get it
wrong. This is why almost all "family" cars are designed with slight
understeer (and it's a characteristic of FWD as well, which is convenient).

If this is what ROSPA genuinely think, rather than just a copyist's error,
then they are a duller lot of arses than I gave them credit for.

[1] Top Gear, and MS track testing the new Ford Mustang (I think). Round a
long bend at over the ton, opposite lock all the way, controlled with one
hand on the wheel while looking over his shoulder and talking to the
cameraman in the back seat. I'm not a big fan of Schumi, but it was an
awesome bit of driving.

--

Rich

Series 2a
RR 4.6
V8 trialler
dog, wife, kids, whatever


 
Alex wrote:
>> >
> Always better to have the back end break out, than the front.
>

If we are talking about "involuntary" breaking out, then I don't agree.

Back end breaks out - car sideways, skill and experience required to
correct, danger of sideways slide into bus queue, risk of rollover if car
hits a kerb or ditch.

Front end breaks out - car facing forward, natural tendency to tighten
steering and ease off usually corrects problem, and if the worst happens,
you hit a wall with the bit of the car that was designed to handle it -
crumple zones, airbags etc.

What did Mercedes do when the new A-class kept failing the "moose test"?
Designed in a little mild understeer.

If we are talking about doing this on purpose, then I agree entirely. One
of my favourite cars was a 2.8 Capri (RWD, LSD*), which went in every way
but a straight line in the wet. Its favourite direction was sideways.

*The transmission, not the reality-enhancer.

--

Rich

Series 2a
RR 4.6
V8 trialler
dog, wife, kids, whatever


 
Richard Brookman vaguely muttered something like ...

> If we are talking about doing this on purpose, then I agree entirely. One
> of my favourite cars was a 2.8 Capri (RWD, LSD*), which went in every way
> but a straight line in the wet. Its favourite direction was sideways.
>
> *The transmission, not the reality-enhancer.

Heheheh, had a Triumph Dolomite that also liked it sideways a tad .. ;)

Very good manners though, and very, very easy to control ..

--
Paul ...

(8(|) ... Homer Rocks

"A tosser is a tosser, no matter what mode of transport they're using."


 
On Sat, 21 Aug 2004 20:23:49 +0000 (UTC), "Richard Brookman"
<[email protected]> wrote:

>Tim Hobbs wrote:
>> <snip>
>>> "Where a mix is necessary, radial tyres
>>> MUST only ever be used on the rear axle and cross-ply tyres on the
>>> front. This mix of tyres will produce 'over steer' whereas the
>>> opposite will produce 'under-steer'. (Over-steer refers to the car
>>> turning more tightly into a corner than it is steered; under-steer
>>> indicates that the vehicle turns at less of an angle than it is
>>> steered). Of the two conditions, over-steer is generally accepted to
>>> be easier to control. "
>
>> Now I've read that properly, they must surely mean it the other way
>> around?
>
>Surely they must. I thought the opposite effect would be true, i.e. radials
>on the back would make a car understeer due to the greater grip at the back
>end. I'm prepared to be corrected on that one. But to say that "over-steer
>is generally accepted to be easier to control" is total bollocks. It is if
>you are Michael Schumacher [1]. But for the average driver, a mild
>understeer is much the safer setup. If you overcook it into a corner, it
>will gently run wide until you ease off. If you get it badly wrong, you are
>still facing forward. An oversteering car will need opposite lock and a
>delicate right foot, and has a tendency to bite back hard if you get it
>wrong. This is why almost all "family" cars are designed with slight
>understeer (and it's a characteristic of FWD as well, which is convenient).
>

I think it's the other way around. People are so used to FWD cars
which understeer that they no longer know how to handle (RWD) cars
which oversteer.

With oversteer it is possible (with the correct skills) to recover the
situation, wheras if you are in an understeer position, and the car is
understeering into a brick wall at the side of the road, there is
absolutly nothing that can be done. You have to back off and hope that
the car will return to the desired line.

Just because people are not capable of handling oversteer doesn't mean
to say it's better to have understeer. But then I think that skid-pan
training and motorway driving are just some of the things should also
be included in the basic driving test, driving standards are far too
low these days.

Alex
 
In news:[email protected],
Alex <[email protected]> blithered:
>> It is illegal to mix tyres of a different construction (cross-ply;
>> bias belted or radial) on the same axle. Cross-ply and bias-belted
>> tyres are seldom used on production cars, and are not widely
>> available in the UK. Cross-ply and radial tyres should never be
>> mixed on the same vehicle. Where a mix is necessary, radial tyres
>> MUST only ever be used on the rear axle and cross-ply tyres on the
>> front. This mix of tyres will produce 'over steer' whereas the
>> opposite will produce 'under-steer'. (Over-steer refers to the car
>> turning more tightly into a corner than it is steered; under-steer
>> indicates that the vehicle turns at less of an angle than it is
>> steered). Of the two conditions, over-steer is generally accepted to
>> be easier to control. "
>>
>> Taken from
>> http://www.rospa.com/cms/STORE/Road Safety/Tyrefacts_files/Tyrefacts.htm
>>
>> I suspect this is also why manufacturers recommend keeping the best
>> (i.e. least worn) tyres on the rear axle.
>
> Always better to have the back end break out, than the front.
>
> I like that bit about "Cross-ply and bias-belted tyres are seldom used
> on production cars, and are not widely available in the UK"
>
> Unless of course you have a landrover, in which case X-Ply tyres are
> commonly available.
>
> Alex

If the back end goes it is probably recoverable if the front end you're gone!


--
If Your specification is vague or imprecise, you'll likely get what you
asked for not what you want


 
Alex wrote:
> >
> Just because people are not capable of handling oversteer doesn't mean
> to say it's better to have understeer. But then I think that skid-pan
> training and motorway driving are just some of the things should also
> be included in the basic driving test, driving standards are far too
> low these days.
>
Yebbut yebbut, that's the whole point. Cars are generally built for the
mass market, and the mass-market driver CBA to learn the skills necessary to
drive an oversteering car in safety. Understeer is usually gradual and
predictable, whereas oversteer usually happens quickly and is pretty
disastrous if allowed to develop beyond a mild tail-out posture. Hence the
mega-millions of small family hatches with FWD that will push out on a
corner if driven hard, but which react predictably and safely to the
driver's natural reaction to tighten up and back off. Remember the days of
the big old Ford Zephyrs and Austin Cambridges that would spin 180 deg and
carry on backwards at the first sign of hard braking in the wet? I even
managed it in a Morris Minor once, *and* I was expecting it! Modern cars
are much safer, even if less "fun".

I agree about the training - we let people onto the roads with only the most
basic skills. Given the number of accidents caused by aggression and/or
impatience (as opposed to lack of skill), psychometric testing might be a
useful addition too. To be fair, though, the roads are for everyone, not
just the elite, and we have to accept that some compromises have to be made.
--

Rich

Series 2a
RR 4.6
V8 trialler
dog, wife, kids, whatever


 
On Fri, 20 Aug 2004 18:53:45 +0000 (UTC), "Richard Brookman"
<[email protected]> wrote:

>Simon Atkinson wrote:
>> >
>> IIRC I can put the cross-ply 6X16's on the front - and leave the
>> radials on the back (short term) - is that the right way round?
>>
>>
>
>Yes it is. According to the MoT tester's manual, reasons for rejection are:
>
>* different types of tyre on the same axle
>* crossply or bias-belted tyres on rear axle and radial tyres on front axle
>

Not only because the MOT manual says so. X-plys on the back and
Radials on the front is also dangerous.

Alex

 
On Sat, 21 Aug 2004 16:55:00 +0000 (UTC), "Nigel Hewitt"
<[email protected]> wrote:

>Alex wrote:
>
>> Not only because the MOT manual says so. X-plys on the back and
>> Radials on the front is also dangerous.
>
>Any idea why?
>In a skid or something?
>
>nigelH
>
"Tyre Types

It is illegal to mix tyres of a different construction (cross-ply;
bias belted or radial) on the same axle. Cross-ply and bias-belted
tyres are seldom used on production cars, and are not widely available
in the UK. Cross-ply and radial tyres should never be mixed on the
same vehicle. Where a mix is necessary, radial tyres MUST only ever be
used on the rear axle and cross-ply tyres on the front. This mix of
tyres will produce 'over steer' whereas the opposite will produce
'under-steer'. (Over-steer refers to the car turning more tightly into
a corner than it is steered; under-steer indicates that the vehicle
turns at less of an angle than it is steered). Of the two conditions,
over-steer is generally accepted to be easier to control. "

Taken from
http://www.rospa.com/cms/STORE/Road Safety/Tyrefacts_files/Tyrefacts.htm

I suspect this is also why manufacturers recommend keeping the best
(i.e. least worn) tyres on the rear axle.


--

Tim Hobbs

'58 Series 2 88" aka "Stig"
'77 101FC Ambulance aka "Burrt"
'95 Discovery V8i aka "The Disco" (FOR SALE)
'03 Volvo V70

My Landies? http://www.seriesii.co.uk
Barcoding? http://www.bartec-systems.com
Tony Luckwill web archive at http://www.luckwill.com
 
Alex wrote:

> On Fri, 20 Aug 2004 18:53:45 +0000 (UTC), "Richard Brookman"
> <[email protected]> wrote:
>
> > Simon Atkinson wrote:
> >> >
> >> IIRC I can put the cross-ply 6X16's on the front - and leave the
> >> radials on the back (short term) - is that the right way round?
> > >
> > >
> >
> > Yes it is. According to the MoT tester's manual, reasons for
> > rejection are:
> >
> > * different types of tyre on the same axle
> > * crossply or bias-belted tyres on rear axle and radial tyres on
> > front axle
> >
>
> Not only because the MOT manual says so. X-plys on the back and
> Radials on the front is also dangerous.

Thanks for the assistance - she failed anyway on a worn swivel... Back
in for Retest on Monday.

--
Simes
 
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