The offside rear tyre (original) of my 32k Toledo TDi has developed a slow puncture (goes from 38 to 30 PSI in a week). With 4mm of tread remaining, it is uneconomical to repair it and I have therefore decided to replace it prior to driving to Cologne at the end of the month.
My question is this - my front tyres both have 5.5mm of tread at present. Should I switch the fronts to the rear and replace the fronts, or just replace the rear tyres and accept that the fronts will need replacing in the next 4k miles or so? I have never switched tyres front to back before.
PS current tyres are Pirelli P6000 - not a favourite choice I realise, but they seem to give a reasonably comfortable ride and are well priced in comparison with Michellins. They also last 18 - 20k miles on the front.
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Conventional wisdom, for front or rear-wheel drive, but not 4x4, is to fit the "worst" tyres on the front and the best on the rear.
However, modern cars with traction control and/or electronic brake force distribution probably need tyres rotating from front to back and vice versa, regularly, to avoid differences in tread depth which can upset the electronics as they use rotational speed to determine their action. Rotational speed is affected by the rolling radius of the tyre and tread depth does have an effect.
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Full load recommended pressures are 35psi at the front and 44psi at the back. As I find this very high I usually run the rears at 38 and the fronts at 34.
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Recommendned rear tyre pressures can vary a lot, it seems, depending on the load carried but front tyre pressures normally don't, so I find it strange if the car has a range of pressures suggested for the front tyres. There is usually a range of pressures given for rear tyres nowadays, so I usually select something in between. This seems to be a reasonably recent trend though, as our Xantia has fixed pressures for front and back, with no variation suggested for increased load.
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Manufacturers recommended tyre pressures don't just take variations in load into account, they are also used to alter the handling characteristics.
Increased load almost always means a large increase in rear load, as a proprtion of the total. Increasing the rear tyre pressures may be necessary because of the load but it may also be necessary to increase the front pressures to maintain the handling balance.
Since manufacturers don't publish their handling/tyre testing details it's impossible for any layman to "know better" than the manufacturer.
Just follow the recommendations for your particular car and load.
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Since manufacturers don't publish their handling/tyre testing details it's impossible for any layman to "know better" than the manufacturer. Just follow the recommendations for your particular car and load.
My point was that these recommended variations in tyre pressures seem to be a recent trend, they certainly were never recommended for any car I had before the C5. Even with the C5, the variable pressures only apply to the rear tyres.
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All tyre manufacturers reccommend that when fitting tyres in pairs, the new tyres should be fitted to the rear wheels regardless of wether the car is front or rear wheel drive. Michelin quote from their technical book as follows:- Contrary to popular belief, deflation of a rear tyre is potentially far more dangerous than on a front tyre. This is because it produces a severe oversteer effect that is far harder to control than the possible under steer that results from deflation of a front tyre.......
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I always replace all four together. And I found by lowering the psi a few points has massively improved the ride on my Renault.
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The notion of putting the best tyres onto the rear is new to me - and I believe it would be to my tyre supplier. On my front-wheel drive car, I had always assumed that a better tread on the front tyres would aid traction - and breaking, where the weight of the vehicle is thrown forward. The differential in the possibility for deflation hadn't entered my thinking.
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If this issue is really new to your tyre supplier, change him - he's totally incompetent.
There may be some debate in this issue but no-one in the tyre industry should be unaware of the recommendation to fit best rubber on the rear.
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Is the logic for this contained within another thread? Cheers
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The logic is very simple. Its the same reason car makers build in understeer to car handling. Loosing the rear (oversteer) is far more dangerous than understeer. Best tyres on the back.
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Loosing the rear (oversteer) is far more dangerous than understeer. Best tyres on the back.
While this is the general rule of thumb it depends on the condition of the rear tyres, good condition, say 25% worn, tyres of the same make, tread pattern etc are likely to grip better than brand new tyres in all circumstances other than standing water hence most tyre centres will happily fit new tyres to the front if the rears are v good.
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>>Loosing the rear (oversteer) is far more dangerous than understeer. Best tyres on the back.
While this is the general rule of thumb it depends on the condition of the rear tyres, good condition
>>say 25% worn, tyres of the same make, tread pattern etc are likely to grip better than brand new tyresin all circumstances other than standing water hence most tyre centres will happily fit new tyres to the front if the rears are v good.
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www.goodyear.co.uk/services/guides/faq_care.html
When you select a pair of replacement tyres in the same size and construction as those on the car, we recommend you put them on the rear axle. A single new tyre should be paired on the rear axle with the tyre having the most tread depth of the other three.
The following page also contains a diagram or two
www.michelin.co.uk/uk/auto/auto_cons_bib_pqr_neuf....N
Why put new or less worn tyres at the rear ?
Whether you have front or rear wheel drive, we recommend that you use newer tyres for the rear set, for extra safety in unforeseen or difficult situations (emergency braking, tight bends etc) particularly on wet surfaces.
Numerous tests have shown that it is easier to control the front wheels than those at the rear.
Front tyres generally wear quicker than those fitted at the rear, particularly on front wheel drive cars, which are currently in the majority.
New tyres fitted in front :
- The behavior of the car will change, because the front / rear balance will be reversed.
The driver, used to a car with less grip at the front, will therefore be taken unawares.
- On a slippery road, the rear will lose traction before the front of the vehicle.
The driver will have no chance of controlling the rear, and will be tempted to accelerate further, which will amplify the spin effect. Only an experienced driver will be able to recover from this dangerous situation...
New tyres fitted at the back :
- The handling of the vehicle will be similar to that known by the driver before the tyre change, because the traction balance will be the same.
- Rear traction will be better, and the driver will be able to control and steer their vehicle without a problem by decelerating and turning the steering wheel in the direction of the bend.
That's why Michelin advises you to reduce the risks you take by fitting new or less worn tyres at the rear of the vehicle for:
- better grip on bends
- extra safety.
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Er... last week when I had to take to a field entrance to give way to a lorry coming the other way, I was glad to have the best rubber on the front. What's wrong with the logic there? In my work, I spend alot of time negotiating country lanes and tracks and when I am on the open road I drive well within the car's, the road's and my limits.
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Follwing that argument, you shoudl put the best rubber on the L/H side. You know that dont make sense either.
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RF - are you, by any chance, from Norfolk?
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