New tyres best on rear wheels?

I will be getting two new tyres for my 2000 A3, as the front wheels treads are wearing. A friend said that new tyres are best on the rear wheels (even irrespective of whether FWD or RWD). Is this true or a myth?

Cheers

it's true.

if you're running e.g. at 40mph on the freeway and your rear wheel breaks, ther is no way avoiding a serious accident. If It's the front wheel, you have at least a chanche handling with the new sitiation... so best wheels belong to the rear!

HTH Rainer

I guess I don't understand this. I've experienced a flat rear tire (on an American rear wheel drive car many years ago): the car started to "swim" (i.e. oversteer?). I guess it's like throwing an anchor out the back? However, if a front tire/wheel were to go I would think you would be in much more trouble? When the car slows down, it pitches forward. Wouldn't that cause the car to spin? Does FWD or AWD make it work differently?

I would agree with this. I've had blowouts on both front and rear tires, and the front-tire blowout was much more difficult to control. I'd say you want your best tires on the front with any kind of car, but

*especially* a front-wheel-drive.

-- Mike Smith

No way José. Losing traction on fronts may cause problems with direction, but you'll stay pointed roughly where you want to go. Losing grip on the rears can easily cause you to swap ends when trying to stop.

The positive side of this is that rally drivers exploit the phenomenon in order to corner faster - they set the brake bias more to the rear so that the back end becomes unstable under braking (and threatens to spin the car). This allows the car to be (quickly) pointed in the right direction much earlier in the corner than is usually possible with "consumer-type" brake balance. You have to be used to it, of course, if you want to keep the car on the road ;-)

/Robert

The precise opposite.

While I've only experienced one blow-out (FWD car, braking heavily at 60mph down a 1:6 hill on a tight right-hand bend, left front blew. Fun..), the whole idea of a car swapping-ends while I'm trying to work out what's going on is.. frightening.

Having had the equivalent happen to me (stuck brake bias valve in a new Citroen AX GT), I can confirm that wrestling a car with locked rear wheels (same as bald tyres, if you see what I mean!) while some part is doing a

720* in front of you is.. distracting, at best.

If you want a /really/ fun afternoon, add a throttle that stuck to the floor the first time that it was used in anger (I was still running/"breaking" in..)

Anyway.

In general, understeer (even unexpected) is easier to deal with than oversteer. If you fit grippy tyres to the front, and skates to the back, then you're going to get oversteer. Even in an [old] Mini, where the rear wheels are then solely to stop you scraping the chrome off of the bumper.

*Always* fit new tyres to the rear, then (as soon as money allows) replace the front. Particularly on FWD cars, where the weight transfer under braking will leave the rear *seriously* light.

What causes a spin is the rear wheels. Period. Doesn't matter if they're driven or not. If your front end slides, the front end stays in front. If the rear end slides, the rear end tries to pass the front (a spin). The real cause is, sliding friction is less than static friction, so the sliding wheels tend to go faster than the non-sliding wheels, but we're not going into all that. Just remember that the end where the wheels are sliding will go to the front in the direction of the slide.

None whatsoever.

The problem with both your analyses is that you're assuming the only time this matters is with a blowout. You can count the number of times you've experienced a blowout on one hand (I hope!). At least I can, in about 35 years of driving, including a number of teen years on 'Bald Eagles'.

Having less (or worse) traction at the rear of the car is something you have to deal with *every single time you reach the limits of traction*! For the average driver, that occurs most often in reduced traction conditions like rain, snow, or loose surfaces. It also happens whether you're turning or going straight. It can even happen under acceleration in a RWD or AWD car if the rear loses traction. Acceleration is the *only* condition under which it matters where the drive wheels are, and a FWD will have a natural directional advantage here that's not negated by having better tires on the rear.

Because of the tendency of the lower traction end of the car to lead in a slide, if the rears break traction under braking, the car can swap ends. If the rears break traction while cornering, they tend to slide off the outside of the turn in a perpendicular (to the tangent) line from the point at which they broke loose. Either way, you end up with the taillights leading the way. Most people think of this as a Bad Thing (TM).

That depends on whether you prefer sliding butt-end first or whether you want to *see* what you hit. Frankly, if it's raining, I want the back end of the car to stay back there, so *my* good tires are always on the rear, no matter what the drivetrain configuration happens to be.

-- C.R. Krieger (Been there; done that)

[I think there was some snippage here?]

Good explanations. Thanks!

FWIW, these days I'm driving an AWD Subaru (can't affort Quattro), so I'm buying new tires all round. They say that any mismatch in tire size causes the transmission to have problems ("blow up"?) so I'm not taking chances. I guess I'm avoiding bad rear traction problems as a freebie?

I have to say that driving AWD "feels different" from RWD or FWD. I guess that's obvious? What's not so obvious to me is how to "get the hang of it". Whenever there's some snow, I try to find some clear space to "practice" slides, and handling when various wheels are "breaking free".

Thinking some more about it, I guess having good tires all around does not prevent spins. As you brake, the car pitches forward and you get more braking action from the front tires, and less weight (and hence frictional force) on the back tires. If they break free, they can still spin the car.

I guess AWD driving technique is more like FWD? You should plan on braking early, then "powering though" turns: i.e. point in the direction you want to go and (gently) apply accelerator, not brakes? OTOH, I think I've experienced a sudden "oversteer" that resulted when the tires started to grip: the front wheels were pointed where I wanted to go and started to turn that way, but the rear wheels had some power applied towards the outside of the turn. Hmm, I think I'm going to have to work on this...

No, but that's one of the time that it matters *most*.

Well, twice, like I said.

This is all true. But then again, I don't make a habit of driving on bald tires!

-- Mike Smith

Not really. I didn't want to spend a whole lot of time explaining why a suddenly deflated tire is pretty much a 'non-event', but it with modern suspension systems, it really is. While it might *feel* pretty weird, your chances of actually losing control as a result are almost as slim as having it happen in the first place.

Out of how many *cars* you've driven? The strongest odds are that you

*won't* experience a blowout in a given car, so why would you sacrifice safer handling *all the time* for a supposedly extreme event that probably won't occur?

I'm not talking about bald tires. Frankly, in dry conditions, you

*want* bald tires because they actually offer the most traction. However the tradeoff, as any of the eight Speed GT Series drivers who ended up off the last turn at Watkins Glen a few weeks ago will tell you, is that slicks really suck in rain. Even full-treaded tires can lose traction depending on the circumstances. Therefore, the smartest thing is to have the 'best' ones on the rear all the time.

-- C.R. Krieger (Been there; done that)

You're welcome.

Not the transmission; the differential. Never actually heard of one blowing up, either, even as sorely abused as some of 'em must be. As long as your nominal tire size (outside circumference) is close to the same, I wouldn't worry about it too much.

You need to learn that you'll still have FWD-style understeer at low speeds and more neutral handling at higher ones.

Bingo!

The fastest way through turns with FWD is to add a touch of braking when the front starts to slide (understeer) to induce some oversteer. You can gently experiment with the handbrake on curves, if you're adventurous and you want to feel the transition from under- to oversteer. Rally drivers discovered this decades ago.

With AWD, you can lift off the throttle *if* you get understeer. You can also accelerate until it starts to slide and get onto the gas earlier because of the power distribution (which doesn't tend to overload either end of the car when you do it). It's simply much more forgiving.

Could happen ...

-- C.R. Krieger (Been there; done that)

When I took my motor vehicle C&G 381 I was told that the best treat goes on the front for many reasons, the most obvious would be they do the steering (& driving on most cars) & that you will more likely aquaplane with lower tread front tyres. However, I can see the reason for the rears to have the better tyres too for reason given. I ALWAYS have my best on the front.

I have always believed the above to be true. However I now have a Audi A4 3.0 Quattro sport manual tranny and have changed my mind. I have been driving the last 3 months with new tires up front and 2/3 worn tires on the rear. When it does get wet the handling is very twitchy and non-progressive on sweepers.

After a couple of close calls I have replaced the rears. Note, I have no problem with oversteer, and am able to use it to my advantage on wet/snowy roads, but the oversteer with worn tires on the rear was just too unpredictable.

I still prefer the newer tires on the front for my front-wheel-drive vehicles and have driven them that way in all sorts of conditions.

Scott