Time for a new tyre?

[John Rumm]

Quite a range of prices on that depending on brand:

[Graham.]

I have had more than one free puncture repairs on leased Company cars at Kwik-Fit. It needs a a phone call and some paperwork to get the relatively small sum of money, and basically they CBA.

[Tim+]

Hard to believe that here could be enough stored energy in a car tyre to cause such mayhem. A truck tyre yes, but a car tyre? I wonder what actually injured her, just a bit of flying rubber?

Tim

[Graham.]

I have heard this before, but I need some convincing.

Front tyres always experience more wear than rear, so why dosn't it make sense to swap them round and extend the life of the set?

[John Williamson]

When I had a front wheel drive car, I used to buy tyres in pairs, putting the new ones on the front and transferring the old ones to the rear. I also made sure I had at least 3mm of tread on all the tyres when I did this. I was told this was a Bad Thing (tm), as it left me with less grip on the rear, which could lead to end swapping, similar to what used to happen on rear wheel drive cars with crossply tyres, which is the configuration I learnt to drive on after I'd passed my test.

Personally, I've always found oversteer easier to cope with than understeer.

[Bill Wright]

ATS Maltby always looked after us well until they closed due to too much competition.

Bill

[Dave Liquorice]

BMW X3 has big tyres compared to ordinary cars...

If I've got the maths right the rears on my Discovery hold about 20KJ of energy in the compressed air. 18" wheel 10" wide = torus 5" dia with a central radius of 23" volume = 0.185 m^3 inflated to 38 psi. If that compressed air is released it will want to occupy about 2.5 times the compressed volume.

A nasty and very rare accident but another reason why space savers are bad news.

[Andy Burns]

Fronts on mine 245/40R18 = 13.3 litres @ 42psi = 3.8kJ

Handy calculator here

[Tim+]

'twas an Z3, not an X3 so I would imagine they were smaller.

Which in the big scheme of things, not *that* much bigger (compared to a diving cylinder letting rip say).

Higher pressure but smaller volume so it would balance out surely (in terms of stored energy). Besides, hard to conceive of a situation where you might be carrying a dodgy space-saver wheel on your lap.

Tim

[fred]

That's been my practice too and I haven't experienced any of the Scary (tm) handling problems that have been commented on. In fact, when I have been tempted to exercise the full perf of my motor I have welcomed a bit of rain to reduce grip, it's a bit dull otherwise, and that's without overpriced, oversized zero profile tyres.

Well, it's not done Tiffany Dell much harm, has it?

[Dave Liquorice]

Hum, that calculator gives 21.37l, 0.02137 m^3, 0.75 cu ft or a 9" cube for my 255/55R18's. That just is not right, the tyres have a rolling circumference fo 7'+... A factor of ten out maybe? Giving 213.7l, 7.5 cu ft would be nearer the mark.

Assuming that new volume I get to 23KJ and yours becomes 17.5KJ.

Looking at the calculator code it uses:

v1 = document.forms[0].breite1.value * h1 * (dr1 + h1) / 1000000

to work out the volume where:

breite1.value is the width in mm h1 is the height of the tyre from width * aspect/100 in mm dr1 is the rim in mm4

Pi is notably missing but maybe I'm missing a shortcut? The width * height gives the area of a cross section but then you need to multiply that by the average circumference ie pi * (dr1 + h1). That gives me 67l (2.3 cu ft) for my tyres which still seems on the low side.

[Dave Liquorice]

You miss the point if the car hadn't had a space saver the buggered tyre would have been in the boot...

[F Murtz]

If it is like Australia, where if you can prove the council knew that the hole existed (from reports etc) you have a case.

[mogga]

them via that. I try to make the effort to remember where they are - our council is good at doing little ones but ones at busy junctions take more time to get done cos of presumably the extra organising it takes to bring lots of cones.

[fred]

ISTR receiving advice that regardless of the driven wheels best tyres shoul= d always be fitted to the front. Given the option you don't really want to = lose control of the steering. If you lose control due to the back end break= ing away then control may be recovered by use of the steering. If you lose = control of the steering then you are in real trouble, tyres on back are not= going to be of any assistance in getting out of that one.

Apart from all of this the majority of the braking force is applied via the= front wheels so sensibly thats where you want the maximum grip

[Brian Gaff]

I suggest some enterprising company starts making cars with caterpillar tracks, from what I read they will soon be needed. Round here they seem to spend a lot onf money on fixing cycle lanes and tracks but sod the motorist and the pedestrian. maybe they have been successfully sued by a cyclist or something.

Brian

[mogga]

It might be that they're the ones who report pot holes most?

[Paul D Smith]

I suggest some enterprising company starts making cars with caterpillar tracks, from what I read they will soon be needed. Round here they seem to spend a lot onf money on fixing cycle lanes and tracks but sod the motorist and the pedestrian. maybe they have been successfully sued by a cyclist or something.

Brian

[Dave Liquorice]

My personal experience tells me otherwise. In the case of the upside down Mondeo linked to previously I "steered into the skid" three probably four times in opposite directions but the back end refused to behave, it was flapping about like a fishes tail.

Good tyres or not on the front once they have truely broken away you are screwed. I do mean truely broken away, not just getting to the limit and sliding a bit. The back end in the above example had truely broken away there was very, very little friction from the road.

Having good on the back means that the front will start to complain first and you avoid the situation were the back completely lets go first.

[Tim+]

Ah, yep.

Tim