A interesting one here with my mother-in-law's Corsa.
It's just had a service - at 3500, but due on calander as it's a year old. The local main dealer reported on their paperwork that the front tyres had 4mm and rears 3mm of tread remaining, and in a further note, state that " we advise replacing tyres at 3mm "
Now, I checked, and rears are at least 6mm, fronts 7mm - in fact I get 4mm+ with my tyre gauge on the wear indicators. The only way iI can get 3mm is by measuring right on the shoulder where the tread pattern falls away anyway ( we're talking almot right angles to the tyre here - not running surface )
So...... pulling a fast one on a (potentially) vunerable person, or has the dealer got a good line in part-worns going?
Replace the tyre(s) when they wear down level with the TW indicators. The law requires that there is at least 1.6mm tread across 3/4 of the width of the tyre, with no other defects such as bulges, splits or wearing down to the cords. It's usually good practice to replace tyres when they get down to about 2 or 3mm since although still legal, their ability to cut through water (or displace it), etc. is drastically reduced compared to a new one.
Take the car back to the service centre and ask them to quantify their report. Also advise them that you are directly contacting the Trading Standards dept as advised earlier by Paul. At the very least you will be offered a concise explanation, something for free and the knowledge that their little scam has been uncovered with the possibility that they may be prosecuted.
Sounds like they were trying it on, but something is wrong because there is no way the rears should be more worn than the fronts, what are the tyre pressures?
The LOWEST point of the CENTRE 3/4 width is the tread depth. Not in the middle of the tire.
If the tyres were wearing on the edges, then you could have 6mm in the centre of the tyre, but 1.6 mm on the edge of the centre 3/4 band. So, they would be knackered.
Also, outside the centre 3/4 band could be virtually bald, and I would replace them because when cornering, most of the weight of the car is on these edges. And it won't be long before it is down to canvas and cords.
I personally think it is crazy that the law isn't changed. It should be
1.6mm over the complete width of the tyre. No confusion then, and a safer car.
Also, it is not uncommon for manufactures recommending tyres at 3mm. Some say they are covering themselves, but I think that it is either money orientated, or service advisors not knowing what they are talking about. Replacing tyre valves with every tyre change is also a money orientated con!
In all honestly though, when my tyres get to 2.5mm and below, I can feel the difference in the wet. I never let them go below 2-2.5mm in the winter, but I drive down country roads all the time. Tyres are the only think holding you to the road!
I don't agree with that, when the fronts are worn, the rears should go on the front, and new ones be fitted to the rear. Stops you getting cracked walls and running on 5-10 (?) year old rear tyres, valves and balance. It also gives the new tyres a chance to "Run In" in a low stress situation.
I drive a FWD 'sports' hatch - when I recently fitted a pair of new tyres to the back of my car the changed (dodgy) handling scared the living daylights out of me. I've changed them to the front and now all is well.
Why is this that it is recommended that new tyres be put on the back of FWD cars? Does it usually help handling? Improve safety? Reduce spinning?
When the OP said the service at "3500", maybe it was 3500 miles since the last service (therefore several tyre changes previous)? Or maybe OP's mother-in-law drives like a demon and is onto her 2nd or 3rd set of tyres at 3500 miles?
No, the vehicle has only covered 3500 since new. If I had found the tyres worn to the extent that the dealer claimed, without any due reason such as incorrect pressures, then I would be straight onto head office of the tyre manufacturers.
As it is, I thought people may heve been interested in the dubious practices of some mainstream dealers
I'm surprised you've got more tread on the fronts than the rear after you measured them yourself. Name and shame this dealership I say. As someone else said - let Trading Standards know, although I doubt they'd do anything - although if enough people complain then they will...
I was charged £15 for changing a wheel (nail causing a slow puncture in tyre) with the spare by a dealership once - I refused to pay up and grassed them to Toyota :) I can change a wheel, but due to a "design fault" on the sideskirts on the car there was no space to put the jack onto the rear pinch welds, and I had mentioned this to them before I asked them to change the wheel.
What I was trying to say was wear on the rear tyres, properly inflated, on a FWD car should be negligible, where the fronts can wear quick - but 3mm left on a car with 3500 miles on the clock seems a bit excessive - as does 6mm on the back (Assuming the tyres came with 8 - 8.5 mm to start with)
For example - the projected wear on my Astra Estate (to change at 2mm depth) for the fronts is 42k miles, the rears 105k - mainly motorway driving. For around town I would expect the fronts to last between 35 - 15k depending on which side (assuming the wear patterns are the same as my old Cavalier i.e. the N/S wears quicker than the O/S - shorter drive shafts or some such).
What will happen at that rate is that I will get about 40k out of the fronts (the car will be about 2 years old by then), and about 65 - 70k out of the rears which wll go onto the front, if you see what I mean.
This is how it was explained to me by tyre engineers when I worked at Michelin. When a tyre is new all the cords in the rubber, and different rubbers used in manufacturing are working themselves in with each other. So all tyres should really be run in for a couple of hundred miles, by gentle use. If the tyre is put on the back of a FWD car, then everything is worked together under a low stress situation, on the front the tyre has to bear the heavier front end, steering, power and the majority of braking. According to these guys the difference in tyre mileage and grip was measurable.
That was back in the mid-70s, during the 80's I managed a couple of small independant tyre depots, and this was always advocated by all the big tyre company reps.
A couple of possibilities why your handling suffered....... New tyres have a preservative coating, this can make them slippy for a short while Increased grip making the back go at a higher speed and more suddenly, this has caught me out before, thinking the tyres are bad, then realising I'm doing 10mph faster than on the old ones. Tyre pressures? Tyre quality?
I deliberated over this when it came to changing ours. I knew that I'd be changing the rears, then the fronts within 3,000 miles, however, so I figured that if it went wrong I'd be back sooner rather than later.
But essentially, I went for the better (newer) tyre on the back so that the Ka's butt would be harder to unstick in the wet.
In fairness, understeer in the Ka is usually a discretionary slide, unless you're being especially foolish. ;) Oversteer is also usually only encountered when you're trying it on somewhat, _however_ that said if you do have to make an emergency manoeuvre, it's the back that'll _tend_ to swing wide first.
I'd imagine the above to be true of many, but not all, front wheel drive cars. Understeer is simply caused by going too fast, or silly use of the accelerator, and letting go of the throttle in these circumstances is often enough to correct the skid. Letting go of the power when it's tipped into oversteer can occasionally be just the _wrong_ thing to do.
I know it's tilting the handling towards dullness, i.e. understeer in the wet, but at least if I (or Charlie) screw up we'll see what we run in to. :)
Incidentally, immediately after I changed them, I had to take the lad on a
250 mile trip in the wet, and with the new rear tyres being absolutely brand spanking new, he was veeeery oversteery on roundabouts, but at very modest speeds until the protective coating wore off. This may be why the Alfa felt tail happy, perhaps? I stuck with it, after four hundred miles they were much better.
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