Replacing both tyres?

[TripleS]

Hi Nick, but if you had grippies on the back, baldies on the front, then in same situation surely you'd understeer? My front wheel drive cars would plough straight on. Eeek!

I'm really confused; I'm going by personal experience of running rubbishy tyres in my 'youff', advice from garages, friends and tyre fitters...

The technical replies you're getting here are probably right in theory, but if you are working in accordance with your experience (which may have included the use of some less than perfect tyres) and you've got the hang of what works and what doesn't work, and you continue to drive in accordance with that, I would say you are unlikely to get into much trouble.

Best wishes all,
Dave.

[daz6215]

Thats it Im fitting a tail rotor on the back to counter that torque!

[jcochrane]

As Gareth said, understeer is more easily controllable. It's progressive, and you can do something about it - either reduce speed, or apply more lock. If the back end goes, often it takes a much better driver to catch it.

So true, and if the back end is not properly corrected/over corrected the consequences can disasterous.

[Gareth]

The issues of which end the grippiest tyres should be, and why, came up in a thread that was started near the end of last year. Interestingly, the OP mentioned that he'd changed the front tyres 3 times, with the new tyres being very soft and grippy, but the rear tyres were still those originally fitted by the manufacturer.

[Angus]

I confess that until recently, I'd always thought that the best tyres should be at the driven end. If the best tyres should be at the back, but for most people the fronts are replaced more often, is it laziness or ignorance by the tyre people that they don't swap tyres for you? (assuming the same size tyre all round)

[ScoobyChris]

I'd say laziness - all the tyre fitters are trained to put new tyres on the rear, but it takes longer and they don't get any extra pay for doing so. And you'd probably whinge at being charged an extra tenner to have it done for you.

And they also never bother adjusting the pressures when they do

Chris

[Gareth]

is it laziness or ignorance by the tyre people that they don't swap tyres for you?

Some places will do this, or at least make the recommendation, but as StressedDave said, in a busy period the tyre fitters are more interested in getting your car out to make room for the next one. When it comes to getting tyres fitted on my car, I make it very clear what I want done, especially if wheels need moving from the back onto the front.

As it happens, the front and rear tyres seem to be wearing at about the same rate on our front wheel drive car. The fronts still wear quicker than the rears, but often when we've got around to replacing the fronts, either the rears could do with replacing at the same time or only a few thousand miles later. I'd guess this is something to do with the way we drive.

[jont]

While we're on about tyre fitters inadequacies, I'd also suggest once you get home it's worth loosening the wheel nuts/bolts and then retightening properly with a torque wrench. Far too often I've seen the monkeys do the nuts up with the air gun, followed by a torque wrench clicking a couple of times. They don't seem to realise that it means they could be way beyond tolerance

[TripleS]

....you want your best tyres on the rear. All the other worries about understeer are minor - you never have it so bad that the car ploughs straight on. You might not get as much cornering as you like, but you still get most of what you want.

Now that last bit is interesting, and I find it slightly reassuring. My greatest worry has always been severe understeer at a LH bend, leading to a head-on shunt with an oncomer, so if having the best tyres on the front leaves me open to a bit more risk of oversteer, I've always been minded to accept that. In any case I feel (rightly or wrongly) that I'm unlikely to encounter a serious loss of grip at either end, so it's largely academic anyhow.

On that basis my preference is therefore still to have the best tyres on the front. I believe this was the best advice going back four or five decades, but I accept that more recent vehicle and tyre design considerations might now make it incorrect.

Best wishes all,
Dave.

[TripleS]

As Gareth said, understeer is more easily controllable. It's progressive, and you can do something about it - either reduce speed, or apply more lock. If the back end goes, often it takes a much better driver to catch it.

So true, and if the back end is not properly corrected/over corrected the consequences can disasterous.

Agreed. I found that out very early in my driving career, with a tank slapper that I thought would never end. When you start with one of those at 50 mph in the snow, exiting a bend onto a long straight section of road, it takes a long time before it's all over.

Best wishes all,
Dave.

[Gareth]

My greatest worry has always been severe understeer at a LH bend, leading to a head-on shunt with an oncomer, so if having the best tyres on the front leaves me open to a bit more risk of oversteer, I've always been minded to accept that.

Your style of driving, (unless it has drastically changed recently), is such that you're not ever likely to face the situation of dramatic loss of front end grip going into a corner. Your cornering speeds are quite low as you prefer to make progress between corners.

I think you are under-estimating the potential severity of that oversteer; my understanding is that when the rear tyres lose grip a sudden spin is the result, and this happens so rapidly it's beyond the ability of most motorists to catch. Certainly well beyond my capabilities.

My only (relatively) recent experience of this was when I went on a limit handling course. In that case, I suffered two instances of spinning at about 50 mph on dry concrete. A horrible, if safe, experience, and the cause was braking too much at the wrong time while on a bend.

Under the guidance of the coach, I was trying to improve my time around a short test track and each time had got to the point where I was going too fast around a tight bend leading to loss of confidence. I braked, enough to increase the grip on the front tyres but unfortunately decreasing the grip at the back. The resulting spins were unbelievably quick.

The coach then gave me an outline about how grip changes with the balance of the car, and how the changes in grip are non-linear. When braking, as grip increases in ever smaller amounts at the front, it decreases in ever larger amounts at the rear. This is why people talk about braking in a straight line, and although it is possible to brake on a bend, without some rather specific training to sensitize one to what happening, it is hard to detect when the back is getting close to the point where it will break away.

Getting back to the point about having the grippiest tyres at the back; I absolutely want more grip at the back so that there is less chance of that sort of thing happening on the road.

[jbsportstech]

I'd say laziness - all the tyre fitters are trained to put new tyres on the rear, but it takes longer and they don't get any extra pay for doing so. And you'd probably whinge at being charged an extra tenner to have it done for you.

I don't trust tyre fitters period. I watch them like a hawk and double check everything they do, torque pressures etc.

In 2003 I had 4 new conti's fitted to my mondeo mk1 and when I was washing the car later I noticed I had 3Nr 195/ 55 r15 and 1nr 195/ 65 r15 I was not happy !!! Thats from so called expert tyre fitters.

[TripleS]

My greatest worry has always been severe understeer at a LH bend, leading to a head-on shunt with an oncomer, so if having the best tyres on the front leaves me open to a bit more risk of oversteer, I've always been minded to accept that.

Your style of driving, (unless it has drastically changed recently), is such that you're not ever likely to face the situation of dramatic loss of front end grip going into a corner. Your cornering speeds are quite low as you prefer to make progress between corners.

I think you are under-estimating the potential severity of that oversteer; my understanding is that when the rear tyres lose grip a sudden spin is the result, and this happens so rapidly it's beyond the ability of most motorists to catch. Certainly well beyond my capabilities.

Gareth - many thanks for your reply, including your detailed explanation that I've snipped here. It is all interesting, but I just want to reply on three points:

1. I'm glad to have your reassurance that I'm unlikely to suffer a dramatic loss of front end grip going into a corner (or indeed elsewhere, I'd hope) although Mark C didn't seem to share your confidence. He complained about the car wallowing through the bends, and made some reference to feeling the front end washing out, which, to put it bluntly, was hogwash IMHO. As far as I'm concerned the car was cornering smoothly, with only modest demands being made of it and I therefore felt quite happy that there was no risk of instability or loss of grip. If my technique was as poor as he seemed to feel it was, I'd have been off the road a great deal more by this time, and there's been none of that since my very early years.

2. Quite often my cornering speeds are indeed quite low, but this is not always the case, as my style varies through quite a wide range, depending on the situation, and my mood at the time. To be honest I'm a bit mystified when I hear about people who have a driving style that applies throughout. Mine varies between something fairly chauffeur-like - or as near as I can get to that - and the sort of thing that some people may feel shouldn't be seen on public roads. Examples of the latter are largely to do with maximum speeds used, plus late and very firm braking associated with high approach speeds into bends. I'm not a low speed numpty all the time - or at least I try not to be.

3. With regard to our prospects of catching and controlling sudden oversteer, I'm making no particular claims about that, although apart from the tank slapper I mentioned in reply to JC, I've coped fairly well on the rare occasions it has happened - maybe partly aided by luck, but who knows. I do recall that when radial ply tyres first came into popular use we were warned that although they provided higher levels of grip than the cross ply tyres used previously, when radial tyres do finally lose grip they break away very suddenly and dramatically, and are much more difficult to catch and deal with safely - so they appeared to be a bit of a mixed blessing. Admittedly I'm talking about how I remember things from when radials like the Michelin X first appeared in the early 1960s. Quite possibly some years of development may have made their breakaway characteristics more progressive and manageable since then, but I really don't know, and I don't think I want to find out.

Best wishes all,
Dave.

[Renny]

Let's simplify things.

<snip>

Dave, thanks for that clear explaination. Next time I will fit the new tyres to the rear, unless I replace all 4.

[zadocbrown]

Good stuff StressedDave. A couple of questions:

1. Presumably manufacturers are aware that despite their advice, lots of people have the good tyres on the front. So are they not inclined to build in a safety margin to compensate?

2. If so, then does this mean the car is biased towards understeer, and that exaggerating this by having crap tyres on the front will make it very understeery indeed? Perhaps if you want really neutral handling the rears should be just slightly down on grip?