Discussion
This interesting thread came up on the Audi page of this forum http://www.pistonheads.com/gassing/topic.asp?h=0&a... 2 new tyres, front or rear?
The gist is that on a front wd car if you have one pair of new tyres they should go on the back, not the front.
Interesting arguments, and with respect to those who've commented, but I can't get past the concept that in wet weather you'd want the best ones at the front because a) fwd cars are designed to understeer and b)less tread = less water dispersal = longer braking distance.
Setting aside a set of four tyres being best, I don't mind being wrong (you'd want to get it right in real life), but what's the view of those who've had additional training?
The gist is that on a front wd car if you have one pair of new tyres they should go on the back, not the front.
Interesting arguments, and with respect to those who've commented, but I can't get past the concept that in wet weather you'd want the best ones at the front because a) fwd cars are designed to understeer and b)less tread = less water dispersal = longer braking distance.
Setting aside a set of four tyres being best, I don't mind being wrong (you'd want to get it right in real life), but what's the view of those who've had additional training?
I agree with you Sticks - I want the tyres with most tread on the front. Apart from the points you mention, I reckon that in a straight line or slight curve, the rear wheels are tracking the fronts so will have less surface water to shift once the front tyres have done their job and are therefore less likely to aquaplane. Plus, 75% of the braking effort is done by the front tyres.
Also, if we're talking about losing grip then I much prefer to deal with a rear wheel slide than a front wheel slide. Total loss of front end grip equals total loss of steering and braking. At least with oversteer you have options.
Also, if we're talking about losing grip then I much prefer to deal with a rear wheel slide than a front wheel slide. Total loss of front end grip equals total loss of steering and braking. At least with oversteer you have options.
Edited by gdaybruce on Wednesday 16th December 13:45
That's not necessarily true - back in the day <insert wavy lines> I dealt with a fatal RTA where the car in question had reached it's critical speed for oversteer - that's the one where the steering angle required to negotiate any particular radius of corner is zero. Twasn't pretty and a dynamically unstable car (which is what you can get) generally goes to the scene of the accident - in this case a large post supporting a roundabout sign that ended up in the passenger footwell, via the driver's door and the two occupants of the car.
On a road with low grip, you want the grippiest tyres at the rear where they can stop the car from spinning.
On a road with low grip, you want the grippiest tyres at the rear where they can stop the car from spinning.
StressedDave said:
That's not necessarily true - back in the day <insert wavy lines> I dealt with a fatal RTA where the car in question had reached it's critical speed for oversteer - that's the one where the steering angle required to negotiate any particular radius of corner is zero. Twasn't pretty and a dynamically unstable car (which is what you can get) generally goes to the scene of the accident - in this case a large post supporting a roundabout sign that ended up in the passenger footwell, via the driver's door and the two occupants of the car.
On a road with low grip, you want the grippiest tyres at the rear where they can stop the car from spinning.
I certainly didn't mean to imply that you will never have a serious accident with oversteer - loss of control is loss of control, whichever end lets go. However, the situation where the front end, on worn tyres, aquaplanes and the driver fails to cope with the consequent total understeer (most likely with front wheels locked and full steering lock applied) must surely be as common as spinning - and the source of equally serious accidents?On a road with low grip, you want the grippiest tyres at the rear where they can stop the car from spinning.
I suppose a head on accident allows the crumple zones, airbags and seat belts to work as designed, so that might be one advantage, but I still think you're less likely to lose control in the first place with the least worn tyres on the front.
Thanks for that. I do see the argument for 'rear' in terms of balance, oversteer limits etc but isn't that about driving beyond the safe conditions of the road? Surely we should aim to be well within them.
But in this scenario, where would you want your best tyres?
At a safe speed but on a wet road a child runs out right in front of you and you have to brake very hard.
In the wet, what difference will tread depth make to your stopping distance?
But in this scenario, where would you want your best tyres?
At a safe speed but on a wet road a child runs out right in front of you and you have to brake very hard.
In the wet, what difference will tread depth make to your stopping distance?
Sticks. said:
Thanks for that. I do see the argument for 'rear' in terms of balance, oversteer limits etc but isn't that about driving beyond the safe conditions of the road? Surely we should aim to be well within them.
The problem usually arises when you believe you are well within the limits and road conditions conspire to mean you are notSticks. said:
But in this scenario, where would you want your best tyres?
At a safe speed but on a wet road a child runs out right in front of you and you have to brake very hard.
In the wet, what difference will tread depth make to your stopping distance?
In finest AI fashion, then answer depends on the relative difference in tread depth, the macro and microstructure of the road, the speed you're travelling at and a myriad of other factors, although the short summary is you really want more than 3mm of tread all round otherwise you might not get the outcome you want.At a safe speed but on a wet road a child runs out right in front of you and you have to brake very hard.
In the wet, what difference will tread depth make to your stopping distance?
StressedDave said:
...the short summary is you really want more than 3mm of tread all round otherwise you might not get the outcome you want.
And the more water there is to shift (combination of standing water depth and speed) the more tread you want on the tyres doing most of the breaking effort. And that would be the tyres at the front 
. (IMHO)I see and understand the arguements for new tyres to the rear. However, my missus is one of those drivers who only drives to and from work; suburban streets and straight dual carriageway. Her driving style is accelerate hard, tailgate, break hard & late and generally be totally distracted. On a given journey driving any of my cars she averages 40% more fuel consumption than I would. Where we live it is uusually wet particularly autum and winter. Come autumn I make a point of putting the best tyres on the front of her car in the hope that it might just give her the edge next time she nearly rear-ends someone. I hope this makes sense, though I would be happy to stand corrected.
Better grip on the front for me thanks...
I'd rather be able to decelerate as effectively as possible, and be able to take avoiding action rather than stamping on the brake pedal and becoming a passenger as the car ploughs into whatever stationary object is in front of me....
Obviously, the pedants will argue that if you can't stop in time, you're driving to close/fast for the conditions etc...
I'd rather be able to decelerate as effectively as possible, and be able to take avoiding action rather than stamping on the brake pedal and becoming a passenger as the car ploughs into whatever stationary object is in front of me....
Obviously, the pedants will argue that if you can't stop in time, you're driving to close/fast for the conditions etc...
This may be old now, but the principle is there....
http://www.youtube.com/watch?v=bQN3R4jy0xY
PS - watch to the end to see the difference in stopping distance between a car and an artic
http://www.youtube.com/watch?v=bQN3R4jy0xY
PS - watch to the end to see the difference in stopping distance between a car and an artic
Here's Michelin's take on the subject:
http://www.michelin.co.uk/michelinuk/en/car-4x4-va...
If you only ever drive in a straight line then you might just be able to make a case for having the grippier tyres at the front, but as you don't (and depending on the imbalance having grippier tyres on the front can make your car dynamically unstable even in a straight line), they go on the rear. Michelin had a video where they put new tyres on the front and then put the car on a relatively low grip surface with a group of motorway driving reps - it was effectively uncontrollable. With the tyres reversed it was the exact opposite.
http://www.michelin.co.uk/michelinuk/en/car-4x4-va...
If you only ever drive in a straight line then you might just be able to make a case for having the grippier tyres at the front, but as you don't (and depending on the imbalance having grippier tyres on the front can make your car dynamically unstable even in a straight line), they go on the rear. Michelin had a video where they put new tyres on the front and then put the car on a relatively low grip surface with a group of motorway driving reps - it was effectively uncontrollable. With the tyres reversed it was the exact opposite.
gdaybruce said:
StressedDave said:
...the short summary is you really want more than 3mm of tread all round otherwise you might not get the outcome you want.
And the more water there is to shift (combination of standing water depth and speed) the more tread you want on the tyres doing most of the breaking effort. And that would be the tyres at the front . (IMHO)When I had my Impreza I tended to favour the fronts because although 4wd, it was set up to handle much like a front driver. I now have am MX5 but having just put four new tyres on it, I can lose control at both ends equally
I was very interested to come across this thread. As Editor of Volkswagen Driver magazine, we recently had a couple of letters on this very topic in our technical forum pages ( www.volkswagendrivermag.co.uk )
A couple of thoughts / observations (no more, no less..)
A lot of comment on the subject comes from enthusiasts and experienced IAM or trackday-type drivers, guys who understand the dynamics of driving and how to control their cars proactively. But any blanket advice / general principle on where to fit new tyres, front or rear, has to be tailored to the vast majority of average drivers, people who know nothing of understeer/oversteer but who might just find themselves in an emergency situation, and suddenly outside of all their previous experience. Which (simplistic) scenario is better for them – plough-on understeer, in which case the instinctive reaction is to lift off and ameliorate the situation, or oversteer in which case the instinctive reaction is to lift off, and exacerbate the situation... ?!
It's still a moot point whether it's better to have fully treaded tyres on front (more resistant to aquaplaning) or rear (offering more grip at rear?) but that depends on the situation (wet or dry, cornering or braking, under control/out of control?)
A couple of other considerations come to mind, though:
Brand-new tyres, still fresh and shiney, can be very 'slippery' and need to be treated with great respect until they are bedded in. As such, new tyres on rear could actually be a liability for the first few hundred miles. But any good tyre fitter will give a warning about this and it shouldn't arise anyway, unless you drive aggressively away from the tyre centre, thinking that your brand-new tyres will actually provide more grip than the worn ones you just got taken off.
On many cars, particularly those driven conservatively, the wear rate on the rear can be very low and if they weren't forced on to the front of the car, to be worn out and used up, they could still be in use on the rear for a great many years, during which (although not actually worn out) they will have far exceeded their 'lifetime' and become dry and brittle/fatigued, perhaps even liable to sudden puncture or blow-out (the worst possible situation to deal with, particularly when cornering in wet). So best to bring them to the front and wear them out / use them up sooner rather than later...
Some cynics might even suggest that this advice is in the vested interest of the tyre industry, using up tyres sooner rather than later and effecting a new sale sooner rather than later..?!
Lots of considerations going on here, and many different individual schools of thought will arise based in individual personal experiences, and different possibilities in different situations, so let's not forget that this front/rear tyre thing is just a simple and general recommendation for the benefit of the masses. It can't possibly be a perfect answer.
A couple of thoughts / observations (no more, no less..)
A lot of comment on the subject comes from enthusiasts and experienced IAM or trackday-type drivers, guys who understand the dynamics of driving and how to control their cars proactively. But any blanket advice / general principle on where to fit new tyres, front or rear, has to be tailored to the vast majority of average drivers, people who know nothing of understeer/oversteer but who might just find themselves in an emergency situation, and suddenly outside of all their previous experience. Which (simplistic) scenario is better for them – plough-on understeer, in which case the instinctive reaction is to lift off and ameliorate the situation, or oversteer in which case the instinctive reaction is to lift off, and exacerbate the situation... ?!
It's still a moot point whether it's better to have fully treaded tyres on front (more resistant to aquaplaning) or rear (offering more grip at rear?) but that depends on the situation (wet or dry, cornering or braking, under control/out of control?)
A couple of other considerations come to mind, though:
Brand-new tyres, still fresh and shiney, can be very 'slippery' and need to be treated with great respect until they are bedded in. As such, new tyres on rear could actually be a liability for the first few hundred miles. But any good tyre fitter will give a warning about this and it shouldn't arise anyway, unless you drive aggressively away from the tyre centre, thinking that your brand-new tyres will actually provide more grip than the worn ones you just got taken off.
On many cars, particularly those driven conservatively, the wear rate on the rear can be very low and if they weren't forced on to the front of the car, to be worn out and used up, they could still be in use on the rear for a great many years, during which (although not actually worn out) they will have far exceeded their 'lifetime' and become dry and brittle/fatigued, perhaps even liable to sudden puncture or blow-out (the worst possible situation to deal with, particularly when cornering in wet). So best to bring them to the front and wear them out / use them up sooner rather than later...
Some cynics might even suggest that this advice is in the vested interest of the tyre industry, using up tyres sooner rather than later and effecting a new sale sooner rather than later..?!
Lots of considerations going on here, and many different individual schools of thought will arise based in individual personal experiences, and different possibilities in different situations, so let's not forget that this front/rear tyre thing is just a simple and general recommendation for the benefit of the masses. It can't possibly be a perfect answer.
Edited by NBirkitt on Wednesday 16th December 16:30
StressedDave said:
Here's Michelin's take on the subject:
http://www.michelin.co.uk/michelinuk/en/car-4x4-va...
If you only ever drive in a straight line then you might just be able to make a case for having the grippier tyres at the front, but as you don't (and depending on the imbalance having grippier tyres on the front can make your car dynamically unstable even in a straight line), they go on the rear. Michelin had a video where they put new tyres on the front and then put the car on a relatively low grip surface with a group of motorway driving reps - it was effectively uncontrollable. With the tyres reversed it was the exact opposite.
I guess what I'm saying is, if that's the case, but also the Top Gear video and this http://www.rospa.com/roadsafety/advice/motorvehicl... then it'd have to be four good ones then?http://www.michelin.co.uk/michelinuk/en/car-4x4-va...
If you only ever drive in a straight line then you might just be able to make a case for having the grippier tyres at the front, but as you don't (and depending on the imbalance having grippier tyres on the front can make your car dynamically unstable even in a straight line), they go on the rear. Michelin had a video where they put new tyres on the front and then put the car on a relatively low grip surface with a group of motorway driving reps - it was effectively uncontrollable. With the tyres reversed it was the exact opposite.
Btw, remember when TG was for grown ups? lol
This: http://www.tirerack.com/tires/tiretech/techpage.js...
seems a bit dangerous... especially to a complete novice...
7 different 'patterns' of rotaion...
seems a bit dangerous... especially to a complete novice...
7 different 'patterns' of rotaion...
Also, there's a 'Rotation Calculator' on the Civinfo forums, which calculates the exact mileage at which to rotate your tyres to avoid uneven wear...
Not sure I'd fancy having all four tyres with less than 3mm on them though...
So which would be worse, a pair of tyres near the limit (either front or back) and a pair of new (with a few hundred mile on them), or a full set of evenly worn but nearing the end of their usable life?
Not sure I'd fancy having all four tyres with less than 3mm on them though...
So which would be worse, a pair of tyres near the limit (either front or back) and a pair of new (with a few hundred mile on them), or a full set of evenly worn but nearing the end of their usable life?
New fronts also preferred by me. Fronts hit standing water first, they do most of the braking and I would prefer to control a slide with the rears breaking traction then understeer into the curb/tree/pedestrian.
Tyre company/official advise is new tyres on rear, for the same reason most new cars are designed to understeer - safer for most people, but we, as pistonheads readers are 'superior' drivers!
Tyre company/official advise is new tyres on rear, for the same reason most new cars are designed to understeer - safer for most people, but we, as pistonheads readers are 'superior' drivers!
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