Yeah but what did proving her wrong cost you? 
I couldn’t sleep much last night so I watched some youtube videos about how plugs, especially with rubber cement, can last the usual life of a tire even if they aren’t as good as inner patches (yet you can always go that way at some point).
A couple covered what sidewall damage/corrosion looks like using suds - something I’d not done as I was sure it was a tread puncture. Went back to sleep till first light and then mixed up some dishwashing liquid and water and, while covering the treads again, put a lot of attention to the rim. There was one area that seemed to be showing more bubble action than anywhere else. I even wiped the rim clean and moved the car several times just to see if this area was always different than the rest and it was. I had already arranged with my wife to do the whole test at 10:30 yet at 10AM - 2+ hours later - from two flights up I looked down and could see a softball sized bubble of soap. And that area, and it alone, was still fizzing. Told my wife 10:30 test was called off.
I know several of you mentioned the sidewall/rim area for the suds test. I’ve not had this problem before. In one of the videos the guy said, yeah tire has to come off yet some wire-brushing and perhaps some glue and it can be fixed. I’ll see if the guy at the shop can make it so. I reckon the tire itself might be okay and if the rim is a goner used “certified recycled” rims of this type cost from £30-£60 on eBay.
Heh. I’m a known cheapskate. My plug cost nothing (it was an ancient kit). I’ve never pointed out to her that the plug has lasted a decade, just knowing I was right is enough for me.
With an open differential, the torque is split more or less 50/50. There isn’t a drive and a non-drive tire. Where it goes wrong is when one tire has little or no traction while the other has good grip. That’s when the tire on the no traction side spins while the other tire does nothing. From Wiki…
An open (non-locking or otherwise traction-aided) differential always supplies close to equal torque to each side. To illustrate how this can limit torque applied to the driving wheels, imagine a simple rear-wheel drive vehicle, with one rear roadwheel on asphalt with good grip, and the other on a patch of slippery ice**. It takes very little torque to spin the side on slippery ice, and because a differential splits torque equally to each side, the torque that is applied to the side that is on asphalt is limited to this amount.**
Sometimes it is NOT the tyre. If the car has alloy rims the part that seals against the bead of the tyre can get corroded. The corrosion results in slow leaks difficult to detect with the usual spray bottle of soapy water. When this happens the tyre is removed and then the rim is wire-wheeled and then clear-coated before re-installing the tyre
Any bubbling is vastly too much. Mark the area, fill it up and take to the shop.
Hooray for finding the problem!! Now on to the fix. As you say, should be tolerably cheap.
Got a good 300mm stainless breaker bar today and went right at removing the wheel. The nuts that wouldn’t budge with the puny comes-with tire iron came off like butter. Maybe the bicycle lube had helped yet certainly the extra leverage and knowing I could safely put a lot of force if needed helped.
Carried it down to the shop and they called just before closing. Cost: £20! ($25)
Scheduled the MOT with them next Friday.
Of the four lug nuts their was an odd one I reckoned was the lock nut did not fit the key! I checked it on the back tires and it was fine. I asked the guy at the shop about that and he said it’s likely a security nut with the security bit removed. So that is a thing you can do.
The donut tire did a yeoman’s job of keeping the rotor off the ground yet won’t see any action.
Hooray for success and for cheap! on to MOT. May it also be easy and cheap!
The Coda:
So on Friday with the car in for MOT I get a call from the Tyre shop at 2PM: Needs some rear driver side underbody welding else-fall-apart may occur and “the seat belts” apparently weren’t retracting to the Royal Standards of Seat Belts as laid out by Pitt The Elder (or was it Lord Palmerston?)
I was flabbergasted, at the same time thinking “WTF they have some mechanism for seat belt retraction?” and did ask if this could be a short-term advisory, but nope, in case of fiery crash we won’t get out of the car, as well as “messing around with the seat belts might be an issue with the air bags”. I even said that on the phone and he had no estimate except junk dealers better than brand new (for a 2008 Toyota)
Something was lost in cross-Atlantic translation, namely the word “rear” seat belts to which I’d have said, “Nobody is ever going to sit in that car’s rear. Do the seats even need to be there?” but all I heard was seat belts.
I’ve never sat in the back of this car or any car I’ve owned and wondered, “In case of fiery crash are these seat belts safe?” And really, as long as the front ones click in I don’t worry they will prevent me from exiting a fiery crash after the air bags blow up in my face.
And last night I watched some youtube videos where the fix for cleaning the front seat belts is some soap - not unlike sudsing up the tyre’s to look for a leak. So then I’m thinking, “Parts? Labour? This is a DIY” and went to the UK MOT checking site to see if this was a “dangerous” thing that would prevent me from driving away and saw is was the rear seatbelts. And on eBay they ranged from £30-£40.
I went to the shop this morning at open with my toolbox. I would not need any tools as per youtube - there’s just some clips to pop the seats. But why not bring the tools - I even held up my Stanley box and said “Semper P” (paratus) i.e. “Always Ready” (I think the coast guard motto? Semper Fi(delis) “always loyal” is the Marines.) I then added, in proper American English, that I was going to remove the seats. No seats, no fail. I asked should I do it now, or promise I’ll do it or what? If you do the welding I can get the car today? No worries, yes and yes.
So late in the day I see on the site that the car passed - no phone call - and walk on down there. I wave my debit card (always check the Invoice!) and am halfway to finding my car and see a £32.50 charge for removing the back seats - and they also removed the seat backs which they didn’t need to do. 30 minute of labour for a 2 minute job I was all set to do 8 hours ago. He refunded the charge without argument.
£ damage = £20 (tyre rims) + £148.85 for MOT and welding. Also was not able to drive my wife to Heathrow yesterday with such a dangerous car.
5 star google review for the rim job (heh). Dunno about this. Had I not done a modicum of youtube research it could easily have been £200 more and done sometime later this week. And certainly £32.50 more if I’d just phoned in “no rear seats” rather than walked in with my toolbox ready to do it.
I’ll put the seat backs in - this ain’t a Corvette - and if those rear seat belts aren’t in shitty shape it’s a 2 star review only for the good will shown / no arguments.
Cheerios!
Front seat belts are often finicky high-tech gadgets, depending on vintage, including integration with the airbag system and even pyrotechnics. (Literally a low-grade explosive device that generates a burst of gas to yank your seatbelt tight, you unsafe comfort-loving slacker.) Not the kind of thing sane DIYers mess with. Because pyrotechnics and faces are not compatible.
But back seat belts are just hardware and fabric.
Yes, thanks for affirming what I thought about front seat belts. I can buy into them getting grimey and in need of cleaning, yet never quite bought into the failure of both of their re-tractability. Trying to clean them and checking their motion was something I was going to do anyways, rather than paying £80 for parts and probably 90 minutes or £100 labour.
And tomorrow in the light when I put the seat backs back in (the hell, I’ll put the rear seats in too) those seat belts ought to look like they’ve been clawed on by bears else I will be rightly pissed off.
Last Friday the “(!)” TPMS warning light came on; one tire was a dozen PSI low so I filled it up (in the rain); the next day, after a lot of driving it came on again so I filled it up & looked at it; a screw in the tread; had to be out stupid-early on Sun morning as well & fell asleep when I got home in the afternoon & it was stoopit winter dark when I awakened from my slumber so I took it to the tire store on Moanday & they patched it for me, inside, in the warmth for $30. Easy-peasy & much safer now.
Tires with PSI monitors that display on your dash. Wow. Even more amazing than run-flat tires.
I was fixated on finding some screw or puncture in the treads since I started noticing the tire was getting low (only on the bottom) until people here told me to check the rims and it was blowing bubbles from one area.
Thanks to all who pointed me in that direction. BTW, a quick inspection by torch and it looks like at least the driver side rear back seat belt doesn’t want to retract at all. It is not grimey and looks to be a rather time-consuming replacement job. As do the fronts (besides the powder-keg air-bag pyrotechnics). If the rear-passenger is also not retracting I’ll have questions for Toyota. And one more thing to check when buying a used car.
HAL 9000: “Dave, there is a screw lodged in the hull of this spacecraft”
Just a WAG, but am guessing this is because the rear seatbelts are rarely if ever used; a lot of mechanical mechanisms tend to get “gummed up” when not used.
Yaay! Coulda been real bad if it decided to finish deflating on you out in the boonies. Good to hear you had an easy save. Hooray for cheap too 
Required by law in every car sold in the USA since 2007, so the last 17 years. Very few US cars on the road today don’t have it.
The first US luxo cars with it were in the early 1990s so ~35 years ago.
The EU requires them on all new cars since 2014, so 10 years now.
I realize you’re not a new car kinda person, but your next used car will almost certainly have it.
Depends on what you mean by “PSI monitors”. My 2010 Honda has a single light that indicates that one or more tire is at low pressure. I believe it gets that info from the antilock brake system, which is seeing a difference in RPM from one or more tire.
See
Broadly speaking there are two sorts, those based on direct air pressure measurement in each tire and those based on second-order effects like vibration differences, RPM differences, etc.
Okay. I have the dumb kind but was imagining PSI monitors that report the numerical PSI for each tire separately.
Bah. I have a plow truck. It never leaves my property. Good, heavy duty tires. no cracks, no wear. They have… 10 miles on them.
Developed a small leak in one tire. Took it off the truck and drove 40 minutes one way to get it fixed.
They would not do it. The tire is 10 years old. It’s against the rules to touch it.
So ‘Fix-A-Flat’ here we come.