My first Mini roadside service experience

It is just as true for an ICE car but the engine is so inefficient you don't really notice the difference.

1 gallon of gas is equivalent to 33.7kWh so an ICE cooper with an 11.6gal tank has the equivalent of a 391 kWh battery. The extra ~60Wh/mi used by run flats is negligible compared to the extra 897Wh/mi used by the combustion engine (vs the SE).

For ICE cars it makes much more sense to focus on improving fuel efficiency of the engine than the other miniscule things we notice with our super efficiency EVs

 

ICE cars have not put much effort into efficiency until the hybrids came along. See the first generation Insight. Speaking of which...

I've been wondering if adding wheel spats to the SE would be beneficial.

 

Reducing unsprung weight is far more important for handling than it is for acceleration and braking (but both are also affected.)
Lowering unsprung weight allows for much better contact with the road surface. When hitting a bump, the energy of the tire sidewall rebound needs to be countered/controlled by the shock absorber and springs of the suspension. Lower unsprung weight allows the damping to occur faster with less rebound.
Run Flat tyres typically are much heavier than conventional tyres. Wheel weight also comes into play when considering total weight of the combination.
As for de/acceleration, the heavier weight of a run-flat shifts the overall weight further from the axle. This shift means more torque needs to be applied to spin the wheel up. Think of the wheel/tyre combination like a flywheel. The further from the centre you place the weight, the harder it is to get it to turn - and harder it is to stop in.
The engineers, designers and bean counters have to make decisions and compromises when creating the package of mechanicals that make a MINI a MINI.


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Will you include the 5th tire in your regular tire rotation? Please send diagram.

 

Hmm, interesting cost/benefit analysis. Does it make sense to have an insurance tire, or do you decide the likelihood of a flat is small enough to take the risk. I had an issue with my Clubman earlier in the week (all four tires went low because of extreme cold), but figured worst case I had my summer wheels I could rely on. There is no right answer, but I find it a good intellectual problem to think about.

 

I, too, am counting on my off-season rims/tires to stand in should I have to wait for a replacement tire.

 

Wouldn't his tire rotation approach be exactly the same as if the (spare) tire were (as in the good ol' days) stored in the trunk instead of his garage? See the diagram from AutoZone as one from the good ol' days. (Of course, in the good ol' days spare tires in the trunk were mounted on an extra rim too. Hmmm. This is starting to sound expensive too.)

 

What if three or four people in a city timeshared a complete wheel and tire spare. I'd pay a breakdown co-op $100 for nearly immediate access to a full size spare.

Frankly, given the disappearance of spare tires in new cars, I don't know why dealers wouldn't keep a couple of loaner wheels around. In a world of diminishing dealer usefulness, that's low hanging fruit.

 

Wait this diagram doesn't make any sense! The wheels on the left are on full time but the ones on the right are on 2/3 of the time? I don't know about that.

 

I believe many (all?) tires can only be rotated front-to-back nowadays, can't swap sides (run in opposite direction) like in the early days of tires.

 

So you're saying you need two spares then?

It's definitely not all tires, as I haven't had directional tires in many years. I should check the OEM summer tires that came on my SE before putting them back on the car this spring.

 

If all 4 tyre pressures drop due to low temperature, why not just use the compressor in your boot to quickly pump them up?
I also have a nice bicycle pump I occasionally use to pump up a tire that has lost some pressure rather than bother with the compressor.
I am curious to know if there is anyone out there that thinks nitrogen is better than air. I think nitrogen is just a marketing thing to squeeze a little more profit.


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Michelin Man has all the rotation methods! Maybe I've always done front-to-back rotation for FWD vehicles. But then one wonders if that applies to vehicles like the SE, with near 50-50 weight distribution. Or is it because of wear due to steering, which is also not the same with EVs? Maybe everything I thought I knew is up in the air.

 

I did exactly that. My spouse drove around on them when low, and somehow one got really low (below 20 psi). They happen to be run-flats, and everything seems good now after inflating.

 

The 5 tire rotation pattern on that site makes way more sense to me (assuming you have bi-directional tires).

 

I think nitrogen in tires is great! I happen to prefer a special, hybrid mixture of 78% nitrogen, 21% oxygen, and 1% argon...

I've heard a lot of claims why N2 is supposed to be better than air in passenger cars. I'll list them with my rebuttal of each:

1. N2, with larger molecules, permeates tires slower, so N2-inflated tires don't deflate as fast. Rebuttal: If the O2 in compressed air leaks out while the N2 remains, then after one, 5-pound-low fill up with standard air, the tires would contain about 88% N2. After two such fill ups, they would contain 97% N2.

2. N2 is dry, so when it is heated it expands less than moist air. Rebuttal: I have never experienced nor heard of a passenger car on public roads having an issue with heat related expansion. Perhaps on a track, this is a thing, but we're not talking about track day setups or cars with red hot brakes.

3. The military puts nitrogen in its aircraft tires. Rebuttal: This is true. My Tomcat used it. But, we used it because nitrogen is also used in canopy systems, hook systems, and in all the other pneumatic systems, because it is clean and dry and plentiful. There is no compressed air on the flight deck; they use N2 bottles for everything, including tires. Also, aircraft brakes get red hot, often; see number 2, above.

4 . Dry means less corrosion to the inside. Of the wheel. No rebuttal.

 

DRY. That is the single reason I can accept ANY advantage to using N2. Unless the compressor being used has some effective drying method, water vapour from humid air is introduced. This vapour increases the rate of pressure reduction when temperatures fall below freezing.
In general, tire inflation pressure will fall by 1 psi for every 10°F drop. By this factor, if you set your cold tire pressure (35 psi front/32 psi rear) during the summer at 70°F, unadjusted, your cold tire pressure at 30°F will have dropped to 31 psi/28 psi - and that doesn’t take into account water vapour which will aggravate loss of pressure at colder temperatures in places like Alberta (or some days in Ontario)

As for interior corrosion, with alloy wheels, negligible. With steels wheels, minimal.

Track day heating from hot brakes may have some additional effect but we aren’t talking about F1 cars are we.

Oh and as for F14Scott’s special hybrid mixture, it is what I use. I use it for my bicycle and all my cars but I would note that the CO2 component has increased significantly since I was in high school - part of the reason I acquired Mike Wazowski, my MINI Cooper SE.



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And that's why I got four low tires at the same time on my Clubman when the temperature dropped to -5 ºF (btw, -25 ºF air temp for me this morning).

I believe @F14Scott is making a funny, it sounds like the mixture my regular compressor at home uses...