Would a differential iron-out the tendency for two wheels on the same axle with different diameters to want to steer in one direction, needing constant counter-steer to correct it?
Maybe it would. Obviously it allows them to rotate at different speeds when they are turning on different radii of curvature, but would a car that is going in a straight line tend to keep that line if the tyres were different sizes?
I *thought* that a spacesaver spare tyre was always (nominally) the same OD as the wheel that it is replacing, allowing for different amounts of tread wear, and that it was only the tyre *width* that was narrower. I agree that one wheel may be a different size to the other, but that is immaterial as long as the OD of the tyre is the same.
It's scary to think that vehicles that were capable of well over 100 mph could be sharing a lane with vehicles that were physically unable to reach even 50 or 60, or drivers that were unwilling to drive any faster even if the vehicle could do so.
At least nowadays just about all vehicles that are allowed to use a motorway are physically capable of reaching at least 56 mph / 80 km/hr and all cars capable of doing at least 70, so there's much less spread of speed than there used to be on unrestricted motorways (or still are on modern German autobahns *). I suppose on unrestricted roads, drivers are a lot more disciplined in only entering that lane if they can see that there really isn't anyone coming up behind them going a lot faster - which is not the case on your average British motorway where it's common to be doing 70 and find that someone doing 50 pulls out in front of you without caring.
(*) OK, I know it should be "autobahnen", but my rule is that if we borrow or steal a foreign word, we have the right to form its plural the English way ;-)
I thought racing on the public highway was already illegal. If the legislation is such that cycles slip though a loophole then that should be tightened up.
It used to be the case that a bike had to have a bell and working lights at all times. What happened to all of that? Or did some bollocks about exemptions for racing bikes slip through?
We need to get back to the notion that a bike is a mode of transport, and be much tougher about it.
Yes you could do it if the pulses were coming from a laser scanner pointing at the road so wear and pressure changes in the tyres didn't have any effect, or you could drag a fifth wheel speedo behind you to get an accurate speed.
I've not actually heard of that recommendation, though I can see that it makes sense. It does take a lot longer, because you have to make two manoeuvres instead of one:
- spare on back to free up a good tyre
- good tyre on front in place of punctured tyre
Mind you, a lot of the time of changing a wheel is initial stuff like removing stuff from the boot onto the back seat to lift the boot floor to get at the spare and the jack.
With modern scissor jacks (which have almost no ground clearance for the handle to turn without grazing your knuckles, it is a thankless task.
The last time I had to change a wheel was about 6 months ago when I caught the inside of a tyre (almost brand new) on the edge of the road surface that stood proud of a rut beside the road, when an oncoming tractor who should have given way to me bullied his way forward so I had to veer off the road to avoid a collision. The tyre held up for another half-mile till I got home and parked, but a few minutes later a neighbour said "do you know you've got a flat tyre". That was a waste of £40: there was a huge gash in the inside wall, a *long* way from the tread so no quibble: the tyre was unrepeatable.
And how much the car sags at one corner because one wheel is smaller. When I can be arsed, I'll go and measure my spare against a full-size wheel. They look the same OD and the car looks level, without a dip at one corner making the opposite corner high and hence less downward force on that wheel.
Certainly I've not felt any pulling to one side on the steering, with the spare on the front or the back - I was amazed at how little it affected the handling of the car, though I'd be more cautious on cornering and I'd restrict myself to the 50 mph and 50 miles limit that they always say.
Gone are the days when your spare is fully-interchangeable with the four running wheels and can be driven as far and as fast as you like without any limit. I really wish the UK would mandate cars to be designed so they can accommodate a full-side spare (steel rather than allow wheel, but otherwise normal tyre) as used to be the case until corner-cutting took over. Cars always had a recess in the boot floor or else a cage under the boot for the full size wheel - or on some cars like the Ford Zephyr and some small Renaults it was under the bonnet. Nowadays the boot doesn't seem any more capacious but there's allegedly no room for a full size wheel in boot - all the pain, but with no perceivable gain.
I think even our big Honda CRV has a space-saver spare, and that's got plenty of space below the boot floor to take a full-height spare.
Car manufacturers say "oh, it's not a problem - put the spare on and drive to a tyre place". Not at 10 PM on a Sunday when you're about to start on a long journey. I don't think I've ever in all the years I've been driving had a puncture that's happened during shop opening hours - it's always late at night or on a Sunday that I discover it. Until recently it was a minor nuisance which delays me setting off by 10 mins or so to fit the spare, and then take the dead tyre in to be repaired at a later date when I'm not in a rush to be somewhere. Now it's a show-stopper which means waiting till the following morning to set off after I've been to the garage - hoping that they actually have the right size in stock and I don't have to wait another
Hum, was down at Milton Keynes and Nottingham last year, thought the M1 driving was much better than the M6/M61 south of Preston. That's abit further north I think but the picture of a dragon obscures the map.
The M1 is mostly "smart motorway" and even without the variable speed limit in operation everyone one was doing 70 and reasonably well spaced out. Presumably because some of the VSL gantries also have ordinary speed cameras bolted on the side...
The M6/M61 is not "smart motorway" and no speed cameras. Any time near the rush and you'll have cars doing 80+ mph, two car lengths apart.
The M61 is only 20 miles long, time difference between *average* speeds of 65 and 75, is a mere 2' 27". Do people really time their commute so finely? Hitting a couple sets of lights on red instead of green will add that sort of time...
Think yourself lucky, they don't do a space saver in my car. But as its a motability car I might just ignore the flat and drive to a tyre place if its close or call them out if it isn't.
I suppose I could try the junk in the can first if I can get to the tyre without getting run down.
The last puncture I had I drove a couple of miles on the M^ roadworks to avoid stopping on a live lane, its fine as long as you can do at least
50 to keep the tyre up by centripetal forces. Then I had the RAC come and change it while I watched from behind the barriers.
So far I've been lucky and never had a puncture when I've been on a motorway. Changing a nearside wheel at least gives you a bit of protection from passing traffic, but I think I might break with a habit of a lifetime and call out RAC for one on the offside. The only time I ever needed to call them out for a puncture was when I couldn't unscrew the wire basket that held the spare under the boot floor because the thread had seized up. It took the RAC man about half an hour with applications of WD40, blowlamp (shielded from tyre) and a lot of cursing to get it free. It would have been easy if the bolt had had a proper hexagonal wheelnut head, but it was a circular head with a single U-shaped depression in which you were supposed to insert the flattened end of the wheelbrace - a really useless cack-handed design which meant that neither he nor I could get any purchase on the bolt to turn it.
About the only time I've broken down on a motorway was when the fan belt failed - and luckily it was only about a mile to the junction where I'd planned to come off anyway, and only another two miles to a garage where I know I could wait away from the traffic. I just had to allow for the steering being a *lot* heavier because the "fan belt" drives the power steering. Inevitably as with so many thing on a modern car, the RAC man couldn't fit a new belt (it's a major job even for a garage to do) so he just had to tow me home and I popped it round to my local garage afterwards.
I wouldn't have liked to wait half an hour in the cold and rain outside my car on the motorway - I judged that I'd have plenty of battery to drive the car (including lights) without an alternator without having to stop immediately.
Sadly the garage didn't notice *why* the fanbelt had failed: one of the pulleys had a distorted flange. So after shelling out about £400 for part and labour, the new belt failed a few hundred miles later - and the garage denied all liability for parts and labour, even when faced with a statement from the main-dealer garage where I took my car for the second belt. So I stopped using them after that, and mentioned my experience to as many locals as possible.
Do traffic cars still use those in preference to GPS? I presume nowadays if they do measure wheel rotations, everything is electronic, with no moving parts other than the object that rotates at (a proportion of) wheel speed, but now sensed by a Hall effect sensor and then rate of pulses (speed) determined electronically - so there's no spring in the gauge to need to be recalibrated as it loses its springiness. I wonder if they are recalibrated periodically as a car's tyres wear down.
I remember in the 1970s we were staying on a caravan site and the guy in the next caravan was a traffic policeman who described how they trained their pursuit drivers to drive at speed - on "live" roads with real traffic, with a "hare" driver (inevitably, in a Jag Mark II or S-type) that that "hound" had to follow. He said that their "best hare" was a tiny lass whose feet barely reached the pedals and who looked as if a strong wind would blow her away, but who was almost impossible for even the best pursuit drivers to keep up with as she weaved through traffic. Wouldn't be allowed nowadays. H&S and all that. Reminds me of that cracking episode "Stoppo Driver" of The Sweeney.
There are quite a few cars with different size (usually width) tyres front and rear. It's likely the rear wouldn't go on the front (these are normally RWD cars)
There is course a reason why you're limited to 90kph with spacesavers.
If you aren't careful you won't measure 0-60 times, you'll measure acceleration to 60 - 8%.
And you'll work out your fuel consumption at a steady 50, not a steady 56...
Win-win for the manufacturer...
I tend to use the tacho. 20MPH per 1000RPM in top, bang on the button, checked against GPS when straight, level and steady - and I've never noticed any effect from tyre wear.
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