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Friday, 7 October 2016

A niggle avoided

My new car allows me to check tyre pressures electronically at the steering wheel. And, if a tyre starts to deflate an icon lights up. This is a worthwhile step forward. I always carry a pressure gauge (several in fact) and will continue to do so, but its application seems rooted in the dark ages, slightly hit and miss, with consequent small loss of air.

In fact it requires a knack. Knacks are for men who reminisce about old cars, boasting about how their skills overcame a vehicle's shortcomings. In the twenty-first century there should be no shortcomings to overcome, and for this reason: even the feeblest modern car can exceed the motorway maximum speed. Often it takes a crash or a near-miss for an inert driver to realise just how much dangerous energy is involved in a ton at 70 mph.

Check, too, the local newspaper for road fatalities. They appear to be split between the very young and the very old. Reflect: the very young are probably too young to have picked up knacks, the very old are quite likely to have forgotten them.  Yes, I'm well aware which category I belong to.

I've switched from diesel to petrol for speculative reasons I won't go into. A veritable sea-change, whatever that is (Please don't explain; I too can use Google). With the diesel at slow speeds I used to loaf along, my right foot merely hovering over the loud pedal, torque being developed at tiny rpm figures. Now even the mildest acceleration requires conscious foot pressure; occasionally I forget.

“Start-stop” switches off the engine at traffic lights, saving fuel; re-starting is instantaneous and virtually unnoticeable. For Trump voters and other climate-change deniers there's a disabling switch. The car is thus politically neutral.

The auto/manual gearbox is seven speeds.


mikeM said...

What is the knack for using a pressure gauge if it's other than quick and clean off/on? I always pump a little extra air into my bicycle tires so that the unavoidable loss on chuck removal is compensated for. I used to always try to achieve the rated maximum pressure (often 130psi or more these days) but have lately been semi-convinced that a bit less pressure will offer more safety without upping rolling resistance, especially on rougher roads. (a harder tire bounces more, the vertical component detracting from speed). Not that I'm all that fast. A 104 mile ride yesterday took just over eight hours, half of it with a sore knee, but (because of?)a vertical mile of climbing.
I don't have much experience with diesel, but a friend has an old Mazda pick-up truck that he modified years ago (simply I think) to burn vegetable oil. Thus he makes occasional stops at restaurants where they happily give him their old (dirty, rancid) frying oil. The exhaust smells like french fries (chips?)
I'm not sure I like the idea of a car that starts "unnoticeably", but I guess if it had a tach or some other "now running" indicator I could adapt. I recently drove a new Subaru that had push button start ("uh...where is the key?) and was very quiet. Pressure indicator sensors, like all sensors, are fine when they work right. I've seen some false alarms.

Roderick Robinson said...

MikeM: Bike tyres are easy to check because the valves are installed radially and it's easy to achieve a right-angled connection between the gauge and the valve. Valves on car tyres are skewed outwards from the radius and sometimes if the wheel has come to a halt with the valve on 6 pm, the slidy bit in the gauge is fouled by terra firma when it is propelled outwards. (A digital gauge is even more awkward in my experience). Even when the valve's in a more convenient position aligning the gauge can be fiddly

My previous two cars were diesels and gave phenomenal mileage (47 mpg for the life of the car) even though the engines, at two litres, were largish by UK standards. Turbo-charging (ie, an impellor driven by exhaust gases) gave good acceleration.

With Start-Stop, the engine only re-starts when the car is stationary and the driver's foot is on the brake. And you can, if you wish, do a Trump.

The tyre pressure system doesn't measure pressure (BMW has such a system but it's incredibly expensive) but works via a calculation related to tyre circumference. I knew there'd be doubters but just imagine; suppose you didn't have this system and you started developing a puncture. It might take some time for you to recognise the gradual softening of the tyre, especially at the rear, and the first truly recognisable symptom might well be a loud bang and flames (perilously close to the gas tank) as happened in my Volvo traversing Indiana. If the system fails well you'd be no worse off but with a very good chance that it wouldn't fail.

mikeM said...

I'd have thought you'd have a dial gauge.

Roderick Robinson said...

MikeM: I tried several types of gauge, including one with a digital readout, but the most accurate turned out to be the oldest design (ie, whereby tyre pressure mechanically forces, in effect, a piston up a concentric tube). I think I ruled out the dial gauge because of its expense and the fact that the dial's accuracy is compromised by the smallness of its diameter.

If I sound obsessive on the subject blame the experience in Indiana and the fact that each year we drive down to southern France five up with a full boot (you'd say trunk) of luggage. For loads like that the owner's handbook recommends increasing tyre pressure quite substantially. Also the maximum speed on French autoroutes (you'd say thruway, expressway or Interstate) is 80 mph, thus enhancing the risks from a blowout.

I think you're right about reduced tyre pressure with bikes. During the Tour de France, if it's raining at the start, most teams reduce tyre pressure a little to give riders just a little more grip on corners.

Roderick Robinson said...

MikeM: Gauge accuracy is important especially if pressure is measured in bars, the comparatively new SI unit. On the sliding piston gauge the length of the bar is too small to separate into readable sub-units; the length for psi is much more generous and is always divided up.

Again, I must seem obsessive. But recommended differences in pressure (eg, between back and front wheels on some cars) may be only a couple of psi. And I for one can tell the difference when I'm driving.

Avus said...

I well understand the importance of tyre pressures as an aid to safety, tyre longevity and road holding, having ridden motorcycles all my life and towed caravans (where tyre pressures can mean the difference between smooth progression and the dreaded snake). It was also a continued mantra when training advanced drivers/motorcyclists.

I tend to agree about the "pop-up" gauges and always use psi.

Roderick Robinson said...

Avus: An interesting point - I'd forgotten about motorcycles where tyre pressures are arguably even more important.

Yet when I look back I can't remember any worries about motorcycle tyres despite the fact that the last bike I owned was in the late fifties when the more reliable and efficient radial tyre had yet to appear in any great numbers. I can only conclude that a defective tyre on a bike was so much more obvious (visually and via its effect on handling) than on a car, that it got rectified immediately without recourse to a tyre gauge.

Ironically the second blow-out I experienced (other than the one in the USA I mention to MikeM) occurred on a moped somewhere near your present residence. I was covering the Daily Mail London-Paris Air Race for the magazine Cycling (called Cycling and Mopeds in those days) and was following a woman competitor who was moped-ing towards the airport at Lympne. This was riskier that it sounds since she was much lighter and could go 2 or 3 mph faster. My back tyre (almost certainly under-inflated) shredded and I'm rather grateful that her support crew in a van picked up me and my stricken Paloma and I was able to see her off at Lympne.

Avus said...

Happy (?) days RR?