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why 12V?



 
 
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  #131  
Old March 23rd 17, 01:48 PM posted to uk.tech.digital-tv
NY
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Posts: 1,061
Default why 12V?

"Woody" wrote in message
news

"Andy Burns" wrote in message
...
Martin wrote:

Vir Campestris wrote:

NY wrote:

It should have the same tyre as the four running ones

I don't have the only car with different tyres front and back...

http://www.continental-tires.com/car...irelexikon-3-4


In other words, don't mix sizes, speed ratings and tread patterns, and
although we'd like to scare you into buying four of our identical tyres,
the law doesn't let us ...



In France it is illegal to have non-identical tyres on the same axle, so
don't go there Andy!


So two tyres of the same size, speed rating etc, are illegal if they are
different manufacturers and therefore tread pattern? What about the extreme
case of fitting a space-saver spare? Or is there a rule that says that you
must always fit the spare on the back axle and swap one of the tyres between
front and back if the puncture was on the front?

I presume it means that once you buy a set of tyres for your car, you must
always buy the same make from then on if one of them punctures (to allow for
front/rear swapping).

What are the rules about mixing tyres of the same make but different amounts
of wear - if your tyres are getting towards the end of their life (but are
still well within the legal limit) and one of them needs to be replaced, are
you allowed to have one with full tread on the same axle as an identical
make of tyre which is 3/4 worn? Or are you supposed to replace both tyres
even though only one is punctured?

I'm always surprised that steering tracking isn't noticeably affected by
this situation (assuming the dissimilar tyres are on the front) but I've
never found an increased tendency of the car to pull to one side or the
other after having a part-worn tyre replaced with a new one.

  #132  
Old March 23rd 17, 02:11 PM posted to uk.tech.digital-tv
Andy Burns[_12_]
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Posts: 276
Default why 12V?

Woody wrote:

In France it is illegal to have non-identical tyres on the same axle,


No cars fitted with space-saver tyres there, then?

so don't go there Andy!


The chances of me driving anything other than a hire car in $FOREIGN are
close to zero.

  #133  
Old March 23rd 17, 03:59 PM posted to uk.tech.digital-tv
NY
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Posts: 1,061
Default why 12V?

"Martin" wrote in message
...
On Thu, 23 Mar 2017 13:52:01 +0000, Andy Burns
wrote:

Martin wrote:

Vir Campestris wrote:

NY wrote:

It should have the same tyre as the four running ones

I don't have the only car with different tyres front and back...

http://www.continental-tires.com/car...irelexikon-3-4


In other words, don't mix sizes, speed ratings and tread patterns, and
although we'd like to scare you into buying four of our identical tyres,
the law doesn't let us ...


Is there a good reason why you shouldn't have four identical tyres?


Yes. You buy a car with the manufacturer's standard tyres. As they need
replacing (maybe front wear more quickly than back so need replacing sooner)
you fit the tyres that you prefer (maybe cheap budget one, maybe better ones
with better wet/snow grip). Later on you get an unrepairable puncture and
replace that tyre. By now you could have a mixtures of tyres of different
ages and types.

  #134  
Old March 23rd 17, 04:48 PM posted to uk.tech.digital-tv
Andy Burns[_12_]
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Default why 12V?

Huge wrote:

Huh?


I just meant they start off saying "have four identical" but then they
weaken it a bit by saying "actually they don't have to be identical,
just this and that need to be the same" much as they'd like everyone to
stick with their brand.

  #135  
Old March 23rd 17, 05:25 PM posted to uk.tech.digital-tv
Woody[_5_]
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Posts: 1,676
Default why 12V?

Don't ask me, I was only told about it when I needed a pair
(fortunately) of new tyres whilst on hols in France. I thought it
might be a selling pitch so checked up when I got home and it is true.

Try reading the first entry at tinyurl.com/kpqvexr

Per the comment about tyres, Michelin were always regarded as the
longest lasting tyres and giving the best ride as they have relatively
soft sidewalls, but they were never the best in the wet. The soft
sidewalls also caused them to scream on anything other than the very
gentlest cornering!

In the days when I had a Co. car and I couldn't get Michelin I always
went for Contis. Dunlop and Goodyear always banged too much going over
bumps, Pirellis frightened me under hard braking (lack of.) In the
latter days the cars (Vauxhall) came with Bridgestones which were also
proved to be a pretty good halway house.

Since Dunlop and Goodyear have merged they have vastly improved - my
last car had Eagle F1 AS2 on it and my present has AS3, both Passat
estates - and the ride and sure footedness is really noticeable, even
SWMBO obeyed commented on it without prompting! The earlier car had a
set of Michelin Primacy Sport and they lasted about 24K on the front:
the present car had two sets of Conti SportContact5P - which is the
self-sealing version - originals and French replacements, and both
pairs did 22K on the front. Compare that with a set of Michelin Energy
E3A that I had on a Xantia estate 20 years ago that did 74K on the
set - albeit they were being swapped front-back at each service by the
dealer without my knowledge, but nonetheless......... On my last Co
car I did 39K on one set of fronts and 47K on the second pair and the
lease Co had a real go at me both times as they considered tyres to be
worn out at 15K!!



--
Woody

harrogate3 at ntlworld dot com


  #136  
Old March 23rd 17, 05:42 PM posted to uk.tech.digital-tv
Andy Burns[_12_]
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Posts: 276
Default why 12V?

Huge wrote:

IMO, it depends on the car, too. I always used to put identical tyres on the
same axle on my RS3 (300bhp+)


I've had four identical tyres (from three manufacturers over time) on
this car for the last 6 years, even to the extent of buying a good
part-worn to replace one tyre when I couldn't get a new one of the same
model.

but I don't bother with the Q3.


I wouldn't bother owning a Qanything, ugly things.

  #137  
Old March 23rd 17, 06:22 PM posted to uk.tech.digital-tv
Indy Jess John
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Default why 12V?

On 23/03/2017 16:27, Martin wrote:

When did Continental become the best tyre in independent tests? For years it was
always Michelin.


I don't know about Continental because they don't make tyres of the size
I use now (I have an old car with 80 profile tyres).

However in the past I discovered that Michelins were very good on light
cars but on heavy cars, Michelins on the front wheels had very little
grip when cornering in the rain, and heavy cars handled best when shod
with Pirellis (which had very good grip but wore down fairly quickly).

Jim
  #138  
Old March 23rd 17, 07:57 PM posted to uk.tech.digital-tv
NY
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Posts: 1,061
Default why 12V?

"Indy Jess John" wrote in message
...
On 23/03/2017 16:27, Martin wrote:

When did Continental become the best tyre in independent tests? For years
it was
always Michelin.


I don't know about Continental because they don't make tyres of the size I
use now (I have an old car with 80 profile tyres).

However in the past I discovered that Michelins were very good on light
cars but on heavy cars, Michelins on the front wheels had very little grip
when cornering in the rain, and heavy cars handled best when shod with
Pirellis (which had very good grip but wore down fairly quickly).


I bought a second hand (ex-demonstrator) car and it had a three different
makes of tyres. I think it had two Michelins on the back and a Dunlop and a
brand I'd never heard of on the front. It handled reasonably well but it
felt a bit vague on cornering, and seemed to like right hand bends better
than left hand ones (more feedback, less feeling that the front end was
about to go straight on).

So I decided to swap front and back, given that front were more worn, as you
get with a FWD car especially with a heavier diesel engine, and since back
were both the same make.

It was an interesting exercise involving 6 wheel changes and spare wheel on
all four wheels in turn, but it was worth it: the car felt a lot more
sure-footed on corners afterwards. I remember that morning well: my
neighbour came out when he saw that I seemed to be taking along time to
change "a wheel", to see if I needed a hand, and was rather chastened when I
said "I'm swapping the wheels round - done five out of six, so only one more
to go" :-)

It's the only time that I've noticed a change of tyres making a difference
to the handling of a car: normally I can't tell much difference when one or
both worn tyres on an axle are replace with new ones. I almost always change
both tyres on the same axle at the same time, if only because they both wear
low at about the same time.

Since then I've gone for mid-range tyres of a brand that I can't remember
(not one of the big names, but not one of the exceptionally cheap brands) so
by now all the tyres are of the same make, though front and back are not the
same age or amount of wear.

Some cars and/or some brands of tyre are better or worse in poor adhesion.
My cars (Peugeot 306 and then later a 308) with average tyres had much
better grip on snow than my wife's Civic did with expensive Pirelli tyres.
Although all the cars are FWD, with more weight distribution on the rear
axle than the front when going up hill, my car could climb hills that hers
couldn't - she lost traction and the wheels spun even when letting the
clutch in very gently to set off as gradually as possible. On the other
hand, her car felt a lot more stable in the wet - if one side hit a puddle,
her car was more inclined to go in a straight line whereas I have to
compensate (I do it instinctively now) by steering slightly away from the
puddle (to compensate for drag). In the dry when cornering, her car was more
inclined to maintain the non-straight-ahead course that you steered whereas
mine is more inclined to straighten up unless you kept pressure on the
steering wheel. I'm more used to mine, so I had a couple of scary moments
with her car when it continued to steer right even though I relaxed pressure
on the wheel and expected the car to straighten of its own accord. Only a
slight difference, and just a matter of thinking it through - probably more
a *feeling* than actually about to go wrong.

Could have been differences in the car (eg amount of power-steering
assistance) or could have been differences in the tyres.

Power steering is one of those things that you don't notice until it fails.
I was driving on the motorway when my fanbelt broke which stopped PS
working. The car needed a lot more effort to turn the wheel - like trying to
stir cold treacle! It was quite a challenge to come off at the next junction
and drive to a garage nearby to wait for the RAC to tow me home. I'd have
driven all the way (I was almost home after a 200 mile journey) but I judged
that the car might not run for 20 miles on battery alone, since it was at
night so I had to have the headlights on.

I presume cars with PS have wider tyres or different steering geometry which
inherently cause heavier steering (maybe so as to give better feedback)
whereas car without PS have a few compromises to give lighter steering at
the expense of less feedback.

  #139  
Old March 23rd 17, 08:20 PM posted to uk.tech.digital-tv
charles[_2_]
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Posts: 538
Default why 12V?

In article ,
Andy Burns wrote:
Huge wrote:


IMO, it depends on the car, too. I always used to put identical tyres
on the same axle on my RS3 (300bhp+)


I've had four identical tyres (from three manufacturers over time) on
this car for the last 6 years, even to the extent of buying a good
part-worn to replace one tyre when I couldn't get a new one of the same
model.


[Snip]

I remember that you shouldn't have steel braced tyres and fabric braced
ones on the same "axle" because of their different behaviour.

--
from KT24 in Surrey, England
  #140  
Old March 23rd 17, 09:00 PM posted to uk.tech.digital-tv
NY
external usenet poster
 
Posts: 1,061
Default why 12V?

"charles" wrote in message
...
In article ,
Andy Burns wrote:
Huge wrote:


IMO, it depends on the car, too. I always used to put identical tyres
on the same axle on my RS3 (300bhp+)


I've had four identical tyres (from three manufacturers over time) on
this car for the last 6 years, even to the extent of buying a good
part-worn to replace one tyre when I couldn't get a new one of the same
model.


[Snip]

I remember that you shouldn't have steel braced tyres and fabric braced
ones on the same "axle" because of their different behaviour.


I didn't realise that any tyres *were* fabric braced.

 




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