The front two tyres on my Citroen C3 are worn, so I need to change them.
I have read some old posts with fierce discussion over whether the new tyres should always be fitted to the back or not.
Is there any consensus? On this particular car, should I fit the new ones to the back and move the back ones to the front?
If the fitter doesn't swap them, is it just a case of jacking up the front and using an axle stand and then jacking up the rear and using another axle stand and then swapping the tyres? is it ok to have front and back propped up like this at once?
Current thinking is new on rear. (I disagree, and wouldn't buy from anywhere that wouldn't fit *my* tyres to *my* car where I wanted them!)
It's perfectly OK to support the whole car *properly* on axle stands.
Arguably more important than whether the new ones are on the front or back, if you or the fitter swap them, make sure the pressures are adjusted appropriately.
I have to say that, since I adopted the new-on-the-rear practice, the most noticeable thing for me is that my car's handling balance never changes from before the tyre fitting to after. I used to hate the light steering feeling I got just after renewing front tyres.
The theory must be that on front-drive cars, the rear tyres will last a lot longer than the front tyres. So if you always fitted the new tyres to the front, the rears could get quite aged before the tread ever wears down. By fitting the new ones to the rear and moving the old rears to the front, you'll get your money's worth from the tread before the sidewalls get all old and cracked.
Do you mean an axle stand on each of the four wheels? I think I've seen cars propped like that on four brick "axle stands" when the wheels have gone missing;)
That's part of the story. The other part is more directly safety-related, and concerns managing the car's handling balance between the tendency to oversteer and the tendency to understeer.
As an ex motor sport driver with around 45 years driving experience, I'm comfortable with oversteer. But that takes experience, mainly because controlling oversteer is initially counter-intuitive. It also tends to result in a side impact, such as hitting a tree with a door.
To inexperienced drivers especially, understeer is a lot more intuitive in its control. It's also more likely to result in a frontal-impact crash, where the forces can be safely absorbed.
Putting the deepest tread on the back decreases the liklihood of oversteer when traction is lost unexpectedly.
Thank you. I did read but the more I read, the more I got confused. All this talk about understeer and oversteer and skids went over my head; can anyone draw me a picture ;)
It isn't obvious that the news ones should not go on the front; before I had read all the posts I had expected that if the front was most worn it must be the front tyres doing the most work and needing the most grip, so I would have expected to put the new ones on the front. I am glad I came here to be educated ;)
I shall ask the fitters to rotate the tyres. Since they will have all four of I can get them to check they are balanced at the same time.
Oversteer happens on a corner when the back of the car starts to slide first, getting the car sideways. The back of the car can then quickly overtake the front. To correct oversteer and get the car back under control, you've got to steer against the direction of the corner.
Understeer happens when it's the front wheels which start to slide first, and the car tends to go straight ahead without turning (ignoring the fact that you're trying to steer it left or right). Natural reactions of inexperienced drivers are to steer even harder into the direction they want to turn, and braking. Both of these reactions tend to help in regaining control. At least they're less likely to make the situation much worse (as they do with oversteer).
If you don't want to risk using two axle stands you can use your spare temporarily to effect the changes. It gets a bit complicated but start by removing one front wheel and replace with the spare. Carry on swapping until you've changed all wheels to their required new positions and the spare is back on its carrier.
Understeer - this is when the car doesn't turn enough despite turning the wheel to where you want to go (ie. car goes in a straighter line than desired and you're pointing towards the outside of the turn). The cause is not enough grip on the front. One solution is to slow (lift off the accelerator, and/or brake slightly) - then grip returns to the front (both due to a slower speed, and due to the 'weight' transferring towards the front wheels as you brake/slow) and you start turning as expected. This is a more intuitive characteristic to correct. Also, if you do continue understeering, you come off the road 'headfirst' - a better situation.
Oversteer - this is when the car turns more than desired - due to lack of grip on the back. Typically, the nose will be where you want it, but the rear slides - so you're now pointing to the apex, or the inside of the corner. In this situation, the rear of the car can continue to slide, causing the car to spin and face the opposite direction. Additionally, if this happens at high speed, once you're at 90 degrees to the direction of travel, your rear wheels no longer rotate, and may 'dig in', which may cause the car to flip and roll. Correction of this oversteer requires un-intuitive (to many) correction - if you do what seems natural - slowing, turning harder into the turn etc - then you can shift weight forward (braking) - causing the rear wheels to get even less weight (and therefore grip) - and turning into the turn more would cause the back end to swing out even more - making the chance of a spin even greater. Correction involves steering the other way!
Now, this may not be a problem in the dry - after all, a tyre with just
1mm of tread has a similar amount of dry grip and surface area as a new tyre (some may say that a slick, no-tread tyre has even more grip) - but when you bring water into it, the situation changes drastically. The deeper the tread, the more water it can displace. The faster you go, the faster it has to clear the water too - that's why 3mm of tread the minimum recommended, even if the legal is just 1.6mm. If it cannot displace enough, then the tyre aquaplanes - sits on top of the water - and you have no grip at all. So, if you have deeper tread at the front, in the wet, your rear tyres will aquaplane first, causing oversteer and possibly a spin/roll etc. If the rear tyres have deeper tread, then it's the fronts which would aquaplane first (which seems scary as they're the ones which steer) - but it's an easier one to correct - and better to hit something going forward, than sideways, rearwards, upside down etc.
D
Understeer is when you go through a wall forwards. Oversteer is when you go through a wall backwards. BHP is how fast you hit the wall. Torque is how far you drag it with you.
Thank you for the very detailed replies. So if the you are turning right, an over steer will cause the rear of the car to swing out to the left and you correct by steering left? Is that right?
I have often thought it would be useful to go to a skid pan for a day but never looked any further into it. Are there many nationally? Are they expensive? Do you learn enough in one day or do you have to go for a few days or return every few years for a refresher?
I went to a F1autocentre to have the tyres fitted. At first they said they would fit the new tyres to the front, perhaps they were looking for the easy option: fit two tyres, not four? But I asked if they could fit them on the back. I asked them to balance all four tyres and I think they were more willing to do the extra work when they realised they could get four rather than two charges.
I was in a waiting room so could not see what happened. They said all four needed balancing. I understand new tyres would need balancing but should the old, already-balanced, wheels needed adjustment? They said that as the tread wears is alters the balance. Is that true or have they pulled a fast one? Surely it should wear evenly and not make a difference?
I was a bit grumpy that they said they had to charge extra because Citroen alloys will not fit their balancing machine because there is no hole in the centre. I had to pay extra to use a "precision machine" whatever that is. I know the lack of central hole has caused problems at other fitters in the past but I have never been charged for using an adaptor before!
The new tyres have 8mm of tread. Is that all? I was expecting more. So I now have 8mm on the back and 6mm on the front. Since there is only
2mm difference, would that have been significant if they had fitted them new on front?
They also charged me for tracking - yes, I got sucked into paying for everything going LOL - and they said that was 2mm out. Would 2mm make any difference? OTOH at least I know the tyres will wear evenly now.
It's a bit like learning to ride a bike. Some people pick it up very quickly. Others take longer. But once you've developed the reflexes they stay with you.
Even the best drivers keep a healthy respect for oversteer situations though. It's been the demise of quite a few.
They were likely correct. It's normal for tyres to progressively become unbalanced again as they wear. And it's also not unheard of for the odd balance weight to fall off.
Differences between tyre brands also come into play. But for the general picture see:
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Some difference, yes.
A quick and easy way to check your own front wheel alignment is to rub your hand backwards and forwards (in the direction the tyre rotates) over the tyre tread while feeling for any difference. Smoothness in one direction with sharp edges felt in the other indicates that it's time to get things checked more thoroughly. Obviously this applies only to tyres which have been run in their current position for a significant mileage.
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